The adoption of additive manufacturing (also known as 3D printing) for electrochemically related applications is receiving increased attention from the research community, particularly for water electrolysis driven by renewable energy. Additive manufacturing has demonstrated its great potential in the structural design of complex geometry and customization. Given the recent development of several fast-prototyping materials and methods, examining the gaps of electrocatalytic electrode materials and apparatus between the lab scale and industrial scale is important. In this paper, we have summarized the state-of-art 3D printing technologies and 3D printing techniques used in water electrolysis systems—both electrodes and reaction cells. The suitability and advantages of 3D printing methods in developing and designing water-splitting reaction systems are thoroughly discussed. In addition, recent progress demonstrating 3D-printed electrodes and water-splitting cells is reviewed. Finally, future directions for this developing field of research are given along with current difficulties.

Increasing concerns over climate change and the energy crisis have put enormous pressure to reduce carbon emissions and achieve carbon neutrality, as well as adopt renewable energy and develop a sustainable economy.1–6 A kind of non-carbon emission and sustainable energy would be a solution to this problem. Hydrogen is one of the most promising sustainable energy carriers by virtue of its high gravimetric energy density (2.5 times more energy per unit mass of fuel than conventional energy sources), zero pollution by-products (only H2 and O2 generated during the process), and natural abundance.7–10 Water electrolysis powered with renewable energy sources (such as hydraulic energy, solar energy, wind, and tide,)11,12 is the most promising way to produce pure hydrogen without any by-products.13,14 The water-splitting reaction contains two simple half-reactions: the oxygen evolution reaction (OER) at the anode [(1) and (2)] and the hydrogen evolution reaction (HER) at the cathode [(3) and (4)],
2 H 2 O l O 2 g + 4 H + a q + 4 e , a c i d m e d i a ,
(1)
4 O H a q O 2 g + H 2 O l + 4 e , a l k a l i n e m e d i a ,
(2)
2 H + a q + 2 e H 2 g , a c i d m e d i a ,
(3)
4 H 2 O l + 4 e 2 H 2 g + 4 O H a q , a l k a l i n e m e d i a .
(4)
The overall reaction is 2 H 2 O l O 2 g + 2 H 2 g .15 

Electrochemical water-splitting is one of the most influential and ideal ways to generate high-purity hydrogen without any pollution. To enhance the electrochemical performance of water electrolysis, lower their cost, and broaden their use, great work has been invested in exploring new electrode materials16–20 and optimizing cell architectures.21–23 Electrode materials consist of metals,24 metal alloys,25 transition metal derivatives (such as oxides,18 hydroxides,26 chalcogenides,27 selenides,28 phosphides,29 nitrides,30 and carbides31), and heteroatom-doped nanocarbons.32 Although various electrode materials have been explored for water electrolysis, the industrial scale-up of water electrolysis still remains a challenge due to the laborious and dangerous synthesis process of electrode materials.33 Meanwhile, the performance and energy efficiency of water splitting generating hydrogen must be significantly improved before it can be commercialized.

An easy way to facilitate commercialized water electrolysis is by adopting 3D printing (i.e., additive manufacturing) techniques. Compared to conventional manufacturing techniques, which have been widely used for decades in all industries, 3D printing owns some irreplaceable advantages: cost, speed, quality, and innovation.34 Applying 3D printing in electrochemical water splitting is a promising strategy that has the potential to develop electrochemical cells more effectively and economically.23,35–37 The performance of water electrolysis was improved by well-designed 3D structures, and advancements in reactor engineering and catalytic applications were also documented. Additive manufacturing is a group of technologies consisting of different printing techniques based on the nature of printing—vat photopolymerization (VP), powder bed fusion, and material extrusion/jetting. The printing principles and processes will be carefully discussed in Sec. II. Various printing methods should be chosen out of careful thinking for different end-use requirements.38 

This paper covers the most widely adopted 3D printing technologies and their applications in fabricating electrodes and cells for water splitting. Each printing technique follows by at least one detailed example to elaborate on the application of the fabricated electrode in water electrolysis. The content of this paper is organized as follows (see Fig. 1—schematic illustration of the review): In Sec. II., we discuss the printing principles and processes of commonly used 3D printing techniques for fabricating water electrolysis electrodes and cells and 3D-printed electrodes via different kinds of printing techniques, including vat polymerization-based printing, powder-based, material extrusion-based printing, and ink jetting (IJ), followed by discussing the advantages and drawbacks of each technique and the features of various fabricated electrodes. Afterward, we summarize the state-of-art 3D printed electrodes for water electrolysis electrodes in Sec. III and the fabrication of the entire electrolysis device in Sec. IV, respectively. Finally, conclusions and outlook for 3D printing of water electrolysis are discussed in Sec. V.

FIG. 1.

Schematic illustration of the minireview for 3D printed electrochemical water-splitting systems: common 3D printing techniques for water electrolysis systems, electrode materials, and examples of water splitting cells. Examples of successfully printed water splitting electrodes and cells. The major 3D printing techniques for manufacturing water electrolysis systems include vat-polymerization (VP)-based 3D printing—DLP and SLA; powder-based 3D printing—SLM, SLS, BJ, and EBM; and material extrusion/jetting-based printing—FDM, DIW, and IJ. Printed electrode materials include metal, ceramic, polymer, and carbon-based materials.

FIG. 1.

Schematic illustration of the minireview for 3D printed electrochemical water-splitting systems: common 3D printing techniques for water electrolysis systems, electrode materials, and examples of water splitting cells. Examples of successfully printed water splitting electrodes and cells. The major 3D printing techniques for manufacturing water electrolysis systems include vat-polymerization (VP)-based 3D printing—DLP and SLA; powder-based 3D printing—SLM, SLS, BJ, and EBM; and material extrusion/jetting-based printing—FDM, DIW, and IJ. Printed electrode materials include metal, ceramic, polymer, and carbon-based materials.

Close modal

Contrary to subtractive manufacturing, additive manufacturing (i.e., 3D printing) is a group of technologies that build 3D objects layer by layer and can be used to process various of materials, including metals, ceramics, polymers, and carbonaceous materials. The 3D printing process begins with building 3D models by CAD (computer aid design) software (such as Fusion 360, 3D Max, and blender), and then, the 3D models are exported as STL (a file formatcreated by three-dimensional computer-aided design (3D CAD) software) files. Each 3D printer comes with a slicer software that can slice the 3D models into multiple 2D patterns for the 3D printer to process. Finally, the 3D models would be printed out layer by layer with different printing principles. 3D printing has been widely used in assorted industries, such as aerospace,39 automobile,40 energy,41 and biomedical.42 Herein, we summarize a number of mature 3D printing methods for fabricating electrochemical water splitting electrodes and cells, including vat polymerization (VP)-based printing—stereolithography (SLA)43 and digital light processing (DLP);44 powder-based printing—selective laser melting (SLM),45–47 selective laser sintering (SLS),48 binder jetting (BJ),49,50 and electron beam melting (EBM);51,52 and material extrusion/jetting-based printing—direct ink writing (DIW),53,54 fused deposition modeling (FDM),55,56 and ink jetting (IJ).57 A comparison of available materials, advantages, and limitations of these printing methods are listed in Table I. The printing mechanisms and processes are discussed below (Tables II and III).

TABLE I.

Comparison of different 3D printing techniques for fabricating electrodes and cells of water electrolysis in terms of available materials, advantages, and limitations.

3D printing process Technique Available materials Advantages Limitations
Polymerization  Stereolithography  Photopolymer (photo-  High resolution and  Limited materials choice 
  (SLA)  curable resin)  printing accuracy Ability  Low printing speed 
      to do color printing  Time consuming formula 
        development process 
  Digital light  Photopolymer (photo-  Higher printing speed  Limited materials 
  processing (DLP)  curable resin)  than SLA High resolution  Takes time to develop 
      and printing accuracy Ability  suitable formulas 
      to do color printing   
Powder-based  Selective laser  Metals (such as iron, nickel,  Ability to produce fully dense  Limited printing materials 
  melting (SLM)  and titanium). Ceramics (such as silica,  near-net-shape components  Low accuracy and cause printing 
    alumina, and zirconia) Composites  Suitable for mass production  part to dislocate sometimes 
  Selective laser  Polymers  High component complexity  High cost of machines and powders 
  sintering (SLS)  Some metal alloys (such  A wide range of raw materials  Long cooling down time 
    as aluminum alloy powder)  High material utilization rate   
  Binder jetting (BJ)  Ceramic powder,  Low cost  Relatively low resolution 
    metal powder.  High printing speed  Long post-processing time 
  Electron beam  Nobel metals and their alloys  Greater laser density than SLM  Expensive machine and 
  melting (EBM)  (such as titanium, niobium,  and SLS leading dense part  power source 
    tantalum, molybdenum, and tungsten)  with high mechanical property  Limited materials 
      Reduced printing time   
Material extrusion/  Direct ink writing (DIW)  Any materials that can form  Able to produce parts with  Laborious process to make 
jetting-based    a stable paste with a proper  various structures Low cost  rheological proper paste 
    rheological property etting-based  and reduced material waste   
  Fused deposition  Thermoplastics  Best for prototyping  Limited materials 
  modeling (FDM)    Low cost  Difficulty in printing intricate parts 
      Fast printing speed  Finished parts with low mechanical 
  Ink jetting (IJ)  Liquid photopolymers  Allows for the simultaneous  property Limited materials 
      deposit of multiple materials  Limited applications 
3D printing process Technique Available materials Advantages Limitations
Polymerization  Stereolithography  Photopolymer (photo-  High resolution and  Limited materials choice 
  (SLA)  curable resin)  printing accuracy Ability  Low printing speed 
      to do color printing  Time consuming formula 
        development process 
  Digital light  Photopolymer (photo-  Higher printing speed  Limited materials 
  processing (DLP)  curable resin)  than SLA High resolution  Takes time to develop 
      and printing accuracy Ability  suitable formulas 
      to do color printing   
Powder-based  Selective laser  Metals (such as iron, nickel,  Ability to produce fully dense  Limited printing materials 
  melting (SLM)  and titanium). Ceramics (such as silica,  near-net-shape components  Low accuracy and cause printing 
    alumina, and zirconia) Composites  Suitable for mass production  part to dislocate sometimes 
  Selective laser  Polymers  High component complexity  High cost of machines and powders 
  sintering (SLS)  Some metal alloys (such  A wide range of raw materials  Long cooling down time 
    as aluminum alloy powder)  High material utilization rate   
  Binder jetting (BJ)  Ceramic powder,  Low cost  Relatively low resolution 
    metal powder.  High printing speed  Long post-processing time 
  Electron beam  Nobel metals and their alloys  Greater laser density than SLM  Expensive machine and 
  melting (EBM)  (such as titanium, niobium,  and SLS leading dense part  power source 
    tantalum, molybdenum, and tungsten)  with high mechanical property  Limited materials 
      Reduced printing time   
Material extrusion/  Direct ink writing (DIW)  Any materials that can form  Able to produce parts with  Laborious process to make 
jetting-based    a stable paste with a proper  various structures Low cost  rheological proper paste 
    rheological property etting-based  and reduced material waste   
  Fused deposition  Thermoplastics  Best for prototyping  Limited materials 
  modeling (FDM)    Low cost  Difficulty in printing intricate parts 
      Fast printing speed  Finished parts with low mechanical 
  Ink jetting (IJ)  Liquid photopolymers  Allows for the simultaneous  property Limited materials 
      deposit of multiple materials  Limited applications 
TABLE II.

Summary and comparison of the 3D-printed electrodes with different materials for electrochemical water splitting.

Printing method Electrode material Main points Performance Reference
Digital light  Cu–NiFe  A new technique for  OER: 196 mV @ 10 mA/cm2  58  
processing (DLP)    producing pure metal (alloy)     
    with complicated structures     
  Nickel–iron-(oxo)  DLP printed complex geometries  OER: 197 mV @ 10 mA cm−2  59  
  hydroxide nanosheets  with subsequent deposition of     
    active catalytic materials     
Selective laser  Ti–TiO2 nanotube  Created a variety of electrodes  Photoelectrochemical  60  
melting (SLM)    with distinctive architectures on  water-splitting study   
    different metal substrates     
  Inconel 718 (with formed  In-situ remelting and in situ  OER: 261 mV @ 1500 mA cm−2  61  
  amorphous NiFe–OOH and  electrochemical activation to     
  nanocrystalline Ni3Nb)  incorporate nanocrystalline Ni3Nb     
    intermetallic into amorphous NiFe–OOH     
    matrix to dramatically increase     
    the catalytic performance     
  Ni/stainless steel  The printed porous electrode  Mass transport study  62  
    has better mass transport properties     
    than planar, mesh, and RVC electrodes,     
    which creates the possibility of     
    using various geometrically complicated     
    electrodes in flow reactors     
  NiCo2S4 nanoneedles/  By using SLM and nanofabrication,  OER: 226 mV @ 10 mA cm−2 63  
  stainless steel  the macro/micro/nano multiscale  277 mV @ 100 mA cm−2   
    hierarchical architecture was formed from     
    metal supports and catalyst coating. It shows     
    good OER performance and has tunable porosity,     
    surface area, and pore size     
  IrO2, Pt, or  Electrodeposition of IrO2 Hydrogen can be produced at a potential  64  
  Ni/stainless steel  Pt, or Ni on SLM-printed stainless  close to 0 V and OER occurs   
    steel support, reducing the cost and showing  at a potential   
    the potential for commercialization  close to 1.5 V (vs RHE)   
  Nickel–iron oxyhydroxides/  It has a significant  OER: 270 mV @ 10 mA cm−2  65  
  stainless steel  electrochemical surface area     
    as well as effective linked bubble     
    and ion transport routes     
Selective laser  Nylon-Cu-Ni  Electrode with tunable surface and  HER: 235 mV @ 10 mA cm−2  66  
sintering (SLS)    architecture was produced by combined     
    SLS printing and metal     
    deposition methods.     
Binder jetting (BJ)  Thermally reduced  First fabricated thick graphene-based  Gravimetric and areal capacitance  67  
  graphene oxide (TRGO)  electrodes via BJ. The electrodes  values of 260 F g-1 and 700 mF cm-2   
    showed a more porous microstructure,     
    resulting in a network of interconnected     
    pores that made ion transfer easier     
Electron beam  Titanium-based (Ti–6Al–4V)  Fabricated a titanium-based  The operating voltage decreased  68  
melting (EBM)    electrode with high corrosion resistance  from 2.49 to 2.18 V at 1.5 A/cm2   
    and tunable multi-functional parameters.     
    It has up to 8% higher performance and     
    efficiency at room temperature     
    because of lower ohmic loss     
Direct ink  NiMo-based  It has a homogenous chemical  HER: 45 mV @ 10 mA cm−2  69  
writing (DIW)    composition and complicated, multiscale  (flow configuration)   
    interior and surface structures, which,     
    especially at high operating current densities,     
    result in high roughness and large     
    electrochemically accessible surface areas     
  Graphene/CNT/NiFeP  The printed graphene/CNT electrode is  Serve as bi-functional electrode,  70  
    mechanically reliable and has high  a cell voltage of   
    flexural strength, high conductivity,  1.58 V at 30 mA cm−2   
    and hierarchical porous structure.     
    In addition, it has both high     
    HER and OER performance     
  Reduced graphene  It was printed without the  Areal and volumetric  71  
  oxide/CNT  use of polymer binders. Fast electron  capacitances of   
    and ion transport channels are present  4.56 F cm−2 and 10.28 F cm−3   
    in the printed electrodes with open and     
    hierarchical pores, which can improve     
    the electrochemical performance     
  Graphene/Cu/Cu2 Two steps of electrode fabrication:  Photoelectrode  72  
    DIW of graphene-based electrodes with pyramid     
    array design and electrodeposition of Cu     
    (current collector) and a p–n     
    homojunction Cu2O (photocatalyst)     
    onto the printed pyramids     
  NiFe-layered  The ECSA of the DIW-printed  OER: 258 mV @ 10 mA cm−2  26  
  double hydroxide  electrode with pyramid structure was     
    twice larger than that of the flat     
    electrode, and it has higher OER     
    performance than the planar electrode     
  Polypyrrole–  A suitable polypyrrole loading is a  Areal capacitance is 2 F cm−2  73  
  graphene  critical element for concurrent structure  and energy density   
    reinforcement and a notable increase in specific  is 0.78 m Wh cm−2   
    capacitance for graphene aerogel. The     
    hierarchical pore patterns serve as a generic     
    template onto which functional substances     
    such as metal oxides can be placed in a regulated     
    manner to enable multifunctionality and     
    expand the range of applications     
  Fe(single atom)-doped  The hierarchical structure and  OER: 175 mV @ 30 mA cm-2  74  
  Ni/Ni(OH)2 and Fe-doped  the proper position of the  HER: 108 mV @ 30 mA cm-2   
  carbon nanotubes (Fe-CNTs)  active center enabled the overpotentials     
    of 175 and 108 mV for OER and HER to     
    achieve 30 mA cm-2 in an alkaline     
    solution. As a result, a low voltage     
    of 1.51 V was needed for the     
    overall water splitting     
  MoSe2/C/PLA  Fabricated MoSe2/C/PLA  HER: Onset potential  75  
  and Pt/C/PLA  and Pt/C/PLA electrodes  of −0.8 V (vs RHE)   
    with fully tunable electrochemical  in 0.1 M KOH, and −0.24 V (vs RHE) 
    characteristics using FDM. The  in 0.5 M H2SO4 solution 
    electrochemical characteristics toward HER   
    and OER are considerably enhanced.   
    It shows the potential to simplify complicated   
    fabrication processes in the production   
    of prototype electrolyzer components   
Fused deposition  Ni/PLA  It showed a unique “clickable”  An attempt at a membrane-  76  
modeling (FDM)    electrode design achieved by  less electrolyzer   
    FDM printing. The printed electrodes     
    could be easily clicked in and     
    out of the gas collection manifold.     
    This enables a low resistance contact,     
    straightforward electrode maintenance,     
    and enhanced scalability     
  C, TiO2, or  The FDM-printed Cu/PLA electrodes  The anodic current of the  77  
  Al2O3/Cu/PLA  incorporated with three refractory  Al2O3/3DCu is less than   
    materials (C, TiO2, and Al2O3 0.1 mA at E = 1.5, while   
    were tested for their effects on  the current is 0.5 mA for   
    photoelectrochemical performance in water  the C/3DCu and the TiO2/3DCu   
    splitting. It was discovered that Al2O3    
    doped photoelectrodes demonstrated the highest     
    photoelectrochemical activity despite the     
    reduced area available for reactions,     
    indicating a critical role for Al2O3     
    in boosting the electrochemical activity     
Printing method Electrode material Main points Performance Reference
Digital light  Cu–NiFe  A new technique for  OER: 196 mV @ 10 mA/cm2  58  
processing (DLP)    producing pure metal (alloy)     
    with complicated structures     
  Nickel–iron-(oxo)  DLP printed complex geometries  OER: 197 mV @ 10 mA cm−2  59  
  hydroxide nanosheets  with subsequent deposition of     
    active catalytic materials     
Selective laser  Ti–TiO2 nanotube  Created a variety of electrodes  Photoelectrochemical  60  
melting (SLM)    with distinctive architectures on  water-splitting study   
    different metal substrates     
  Inconel 718 (with formed  In-situ remelting and in situ  OER: 261 mV @ 1500 mA cm−2  61  
  amorphous NiFe–OOH and  electrochemical activation to     
  nanocrystalline Ni3Nb)  incorporate nanocrystalline Ni3Nb     
    intermetallic into amorphous NiFe–OOH     
    matrix to dramatically increase     
    the catalytic performance     
  Ni/stainless steel  The printed porous electrode  Mass transport study  62  
    has better mass transport properties     
    than planar, mesh, and RVC electrodes,     
    which creates the possibility of     
    using various geometrically complicated     
    electrodes in flow reactors     
  NiCo2S4 nanoneedles/  By using SLM and nanofabrication,  OER: 226 mV @ 10 mA cm−2 63  
  stainless steel  the macro/micro/nano multiscale  277 mV @ 100 mA cm−2   
    hierarchical architecture was formed from     
    metal supports and catalyst coating. It shows     
    good OER performance and has tunable porosity,     
    surface area, and pore size     
  IrO2, Pt, or  Electrodeposition of IrO2 Hydrogen can be produced at a potential  64  
  Ni/stainless steel  Pt, or Ni on SLM-printed stainless  close to 0 V and OER occurs   
    steel support, reducing the cost and showing  at a potential   
    the potential for commercialization  close to 1.5 V (vs RHE)   
  Nickel–iron oxyhydroxides/  It has a significant  OER: 270 mV @ 10 mA cm−2  65  
  stainless steel  electrochemical surface area     
    as well as effective linked bubble     
    and ion transport routes     
Selective laser  Nylon-Cu-Ni  Electrode with tunable surface and  HER: 235 mV @ 10 mA cm−2  66  
sintering (SLS)    architecture was produced by combined     
    SLS printing and metal     
    deposition methods.     
Binder jetting (BJ)  Thermally reduced  First fabricated thick graphene-based  Gravimetric and areal capacitance  67  
  graphene oxide (TRGO)  electrodes via BJ. The electrodes  values of 260 F g-1 and 700 mF cm-2   
    showed a more porous microstructure,     
    resulting in a network of interconnected     
    pores that made ion transfer easier     
Electron beam  Titanium-based (Ti–6Al–4V)  Fabricated a titanium-based  The operating voltage decreased  68  
melting (EBM)    electrode with high corrosion resistance  from 2.49 to 2.18 V at 1.5 A/cm2   
    and tunable multi-functional parameters.     
    It has up to 8% higher performance and     
    efficiency at room temperature     
    because of lower ohmic loss     
Direct ink  NiMo-based  It has a homogenous chemical  HER: 45 mV @ 10 mA cm−2  69  
writing (DIW)    composition and complicated, multiscale  (flow configuration)   
    interior and surface structures, which,     
    especially at high operating current densities,     
    result in high roughness and large     
    electrochemically accessible surface areas     
  Graphene/CNT/NiFeP  The printed graphene/CNT electrode is  Serve as bi-functional electrode,  70  
    mechanically reliable and has high  a cell voltage of   
    flexural strength, high conductivity,  1.58 V at 30 mA cm−2   
    and hierarchical porous structure.     
    In addition, it has both high     
    HER and OER performance     
  Reduced graphene  It was printed without the  Areal and volumetric  71  
  oxide/CNT  use of polymer binders. Fast electron  capacitances of   
    and ion transport channels are present  4.56 F cm−2 and 10.28 F cm−3   
    in the printed electrodes with open and     
    hierarchical pores, which can improve     
    the electrochemical performance     
  Graphene/Cu/Cu2 Two steps of electrode fabrication:  Photoelectrode  72  
    DIW of graphene-based electrodes with pyramid     
    array design and electrodeposition of Cu     
    (current collector) and a p–n     
    homojunction Cu2O (photocatalyst)     
    onto the printed pyramids     
  NiFe-layered  The ECSA of the DIW-printed  OER: 258 mV @ 10 mA cm−2  26  
  double hydroxide  electrode with pyramid structure was     
    twice larger than that of the flat     
    electrode, and it has higher OER     
    performance than the planar electrode     
  Polypyrrole–  A suitable polypyrrole loading is a  Areal capacitance is 2 F cm−2  73  
  graphene  critical element for concurrent structure  and energy density   
    reinforcement and a notable increase in specific  is 0.78 m Wh cm−2   
    capacitance for graphene aerogel. The     
    hierarchical pore patterns serve as a generic     
    template onto which functional substances     
    such as metal oxides can be placed in a regulated     
    manner to enable multifunctionality and     
    expand the range of applications     
  Fe(single atom)-doped  The hierarchical structure and  OER: 175 mV @ 30 mA cm-2  74  
  Ni/Ni(OH)2 and Fe-doped  the proper position of the  HER: 108 mV @ 30 mA cm-2   
  carbon nanotubes (Fe-CNTs)  active center enabled the overpotentials     
    of 175 and 108 mV for OER and HER to     
    achieve 30 mA cm-2 in an alkaline     
    solution. As a result, a low voltage     
    of 1.51 V was needed for the     
    overall water splitting     
  MoSe2/C/PLA  Fabricated MoSe2/C/PLA  HER: Onset potential  75  
  and Pt/C/PLA  and Pt/C/PLA electrodes  of −0.8 V (vs RHE)   
    with fully tunable electrochemical  in 0.1 M KOH, and −0.24 V (vs RHE) 
    characteristics using FDM. The  in 0.5 M H2SO4 solution 
    electrochemical characteristics toward HER   
    and OER are considerably enhanced.   
    It shows the potential to simplify complicated   
    fabrication processes in the production   
    of prototype electrolyzer components   
Fused deposition  Ni/PLA  It showed a unique “clickable”  An attempt at a membrane-  76  
modeling (FDM)    electrode design achieved by  less electrolyzer   
    FDM printing. The printed electrodes     
    could be easily clicked in and     
    out of the gas collection manifold.     
    This enables a low resistance contact,     
    straightforward electrode maintenance,     
    and enhanced scalability     
  C, TiO2, or  The FDM-printed Cu/PLA electrodes  The anodic current of the  77  
  Al2O3/Cu/PLA  incorporated with three refractory  Al2O3/3DCu is less than   
    materials (C, TiO2, and Al2O3 0.1 mA at E = 1.5, while   
    were tested for their effects on  the current is 0.5 mA for   
    photoelectrochemical performance in water  the C/3DCu and the TiO2/3DCu   
    splitting. It was discovered that Al2O3    
    doped photoelectrodes demonstrated the highest     
    photoelectrochemical activity despite the     
    reduced area available for reactions,     
    indicating a critical role for Al2O3     
    in boosting the electrochemical activity     
TABLE III.

Summary of 3D printed electrochemical cells found in the literature, how their components printed, what materials they were printed from, and advantages of 3D printing manufacturing techniques.

Electrode Container or important components that acts as supports
Electrochemical Printing Materials Printing Materials    
cell design method printed method printed Advantages Reference
Electrolyzer flow  FDM  PLA (nickel-coated)  FDM  ABS  It can substitute for computerized  78  
field plates of OER          numerical-control milling   
          and enable rapid prototyping of   
          electrolyzer flow field plates   
Filter-press  ⋯  ⋯  FDM  Co-polyester  It exhibits remarkable  79  
electrochemical reactor        PETG/ABS  chemical stability to the majority   
for multipurpose          of the studied chemical agents   
Polarized liquid–liquid  ⋯  ⋯  FDM  Polyamide-12  Low processing temperature,  80  
interface research by          no moulds needed, direct   
electrochemical cell          laboratory production of complicated   
          structures at a low cost   
Monolithic microbial  FDM  Plain carbon veil/  FDM  Ceramic  It can optimize the  81  
fuel cell    Conductive PLA      design of each part and   
          reactor component for certain   
          applications and increase system   
          efficiency through straightforward   
          production and assembly procedures   
Water splitting cell  ⋯  Ni foam  FDM  ABS  It uses materials of  82  
          a high caliber and replicable   
PEMEC for water  ⋯  ⋯  FDM  Non-conductive PLA  Complex structures can be  83  
electrolysis          manufactured at very low cost   
          with minimal post-processing   
PEM electrolyzer  ⋯  ⋯  SLM  Stainless steel  A quick, cheap, and alternative  84  
cell        316L  method of creating equipment   
          for producing hydrogen   
          from renewable sources   
Fully printed  ⋯  ⋯  SLM  Stainless steel  Decrease the weight, volume,  85  
and integrated          and component quantity while   
electrolyzer cell          increasing energy efficiency   
Electrode Container or important components that acts as supports
Electrochemical Printing Materials Printing Materials    
cell design method printed method printed Advantages Reference
Electrolyzer flow  FDM  PLA (nickel-coated)  FDM  ABS  It can substitute for computerized  78  
field plates of OER          numerical-control milling   
          and enable rapid prototyping of   
          electrolyzer flow field plates   
Filter-press  ⋯  ⋯  FDM  Co-polyester  It exhibits remarkable  79  
electrochemical reactor        PETG/ABS  chemical stability to the majority   
for multipurpose          of the studied chemical agents   
Polarized liquid–liquid  ⋯  ⋯  FDM  Polyamide-12  Low processing temperature,  80  
interface research by          no moulds needed, direct   
electrochemical cell          laboratory production of complicated   
          structures at a low cost   
Monolithic microbial  FDM  Plain carbon veil/  FDM  Ceramic  It can optimize the  81  
fuel cell    Conductive PLA      design of each part and   
          reactor component for certain   
          applications and increase system   
          efficiency through straightforward   
          production and assembly procedures   
Water splitting cell  ⋯  Ni foam  FDM  ABS  It uses materials of  82  
          a high caliber and replicable   
PEMEC for water  ⋯  ⋯  FDM  Non-conductive PLA  Complex structures can be  83  
electrolysis          manufactured at very low cost   
          with minimal post-processing   
PEM electrolyzer  ⋯  ⋯  SLM  Stainless steel  A quick, cheap, and alternative  84  
cell        316L  method of creating equipment   
          for producing hydrogen   
          from renewable sources   
Fully printed  ⋯  ⋯  SLM  Stainless steel  Decrease the weight, volume,  85  
and integrated          and component quantity while   
electrolyzer cell          increasing energy efficiency   

Vat-photopolymerization (VP) is a printing process based on the UV/light processing technique. It can be categorized into SLA and DLP. The printing materials are usually acrylate and epoxy-based monomers and oligomers, which can be photocured via cationic and radical polymerization with the existence of a photo initiator, yielding thermosets. A build platform will be either raised or lowered according to the layer thickness, and a printed structure will be printed on the platform. In SLA, a UV laser or other coherent light source activates the photopolymerization of a liquid resin. There are two types of setup for SLA—bottom up and top down.86 The schematic diagrams are shown in Fig. 2(A-a). The resin solidifies and forms one layer as the laser beam traverses the surface. A three-dimensional thermoset product can be printed layer by layer by repeating this procedure. In relation to the size of the laser beam’s spot, SLA enables the 3D manufacturing of complex structures with great resolution and a low feature size (on the micrometer scale).87 The printing mechanism of DLP is similar to SLA [Fig. 2(A-b)]. The only difference is the light source—the UV light is projected from a projector for DLP, which means that it can generate a whole 2D pattern at one time rather than drawing the pattern by UV light. As a consequence, the printing speed of DLP is much faster than SLA. To be applied to fabricate water-splitting electrodes and cells, the mechanical properties and catalytic performance of the DLP-printed structure need to be improved, which can be realized by incorporating fillers and fibers and optimizing the polymetric resin.88–90 

FIG. 2.

Vat-polymerization-based 3D printed electrodes for water electrolysis. (A) (a) Schematic of the SLA printing mechanism. Reproduced with permission from Melchels et al., “A review on stereolithography and its applications in biomedical engineering,” Biomaterials 31(24), 6121–6130 (2010). Copyright 2010, Elsevier. (b) Schematic of DLP printing mechanism. Reproduced with permission from Kadry et al., “Digital light processing (DLP) 3D-printing technology and photoreactive polymers in fabrication of modified-release tablets,” Eur. J. Pharm. Sci. 135, 60–67 (2019). Copyright 2019, Elsevier.91 (B) (a) The fabrication process of the DLP-printed NiFe hydroxide@copper sample: printing, debinding, thermal decomposition, and reduction. (b) SEM image of different temperature sintered NiFe samples. (c) Pictures of the comparison of tensile strength between the DLP-printed NiFe electrode and Ni foam. (C) OER performance of commercial copper foam, DLP-printed copper with gyroid structure, and DLP-printed copper covered with NiFe hydroxide. (a) LSV and CV curves demonstrate that the DLP-printed copper electrode has noticeably lower overpotential than copper foam, which can be further enhanced by electrodeposition of NiFe hydroxide. (b) Comparison of different electrodes’ overpotentials at 10, 100, and 500 mA cm−2. (c) A brief summary of the comparison between this work’s OER performance and that of other studies. (d) Chrono potentiometric (CP) curves driven at 500 mA cm−2 over 20 h. (e) The Tafel slope for NiFe hydroxide-coated Cu demonstrates the reasonably quick electron transport rate. In (f), the ESCA curve shows that DLP-printed copper has a greater active surface area than copper foam. Reproduced with permission from Li et al., “Incorporating metal precursors towards a library of high-resolution metal parts by stereolithography,” Appl. Mater. Today 29, 101553 (2022). Copyright 2022, Elsevier.

FIG. 2.

Vat-polymerization-based 3D printed electrodes for water electrolysis. (A) (a) Schematic of the SLA printing mechanism. Reproduced with permission from Melchels et al., “A review on stereolithography and its applications in biomedical engineering,” Biomaterials 31(24), 6121–6130 (2010). Copyright 2010, Elsevier. (b) Schematic of DLP printing mechanism. Reproduced with permission from Kadry et al., “Digital light processing (DLP) 3D-printing technology and photoreactive polymers in fabrication of modified-release tablets,” Eur. J. Pharm. Sci. 135, 60–67 (2019). Copyright 2019, Elsevier.91 (B) (a) The fabrication process of the DLP-printed NiFe hydroxide@copper sample: printing, debinding, thermal decomposition, and reduction. (b) SEM image of different temperature sintered NiFe samples. (c) Pictures of the comparison of tensile strength between the DLP-printed NiFe electrode and Ni foam. (C) OER performance of commercial copper foam, DLP-printed copper with gyroid structure, and DLP-printed copper covered with NiFe hydroxide. (a) LSV and CV curves demonstrate that the DLP-printed copper electrode has noticeably lower overpotential than copper foam, which can be further enhanced by electrodeposition of NiFe hydroxide. (b) Comparison of different electrodes’ overpotentials at 10, 100, and 500 mA cm−2. (c) A brief summary of the comparison between this work’s OER performance and that of other studies. (d) Chrono potentiometric (CP) curves driven at 500 mA cm−2 over 20 h. (e) The Tafel slope for NiFe hydroxide-coated Cu demonstrates the reasonably quick electron transport rate. In (f), the ESCA curve shows that DLP-printed copper has a greater active surface area than copper foam. Reproduced with permission from Li et al., “Incorporating metal precursors towards a library of high-resolution metal parts by stereolithography,” Appl. Mater. Today 29, 101553 (2022). Copyright 2022, Elsevier.

Close modal
FIG. 3.

Powder-based 3D printed electrodes for water electrolysis. (A) Schematic illustration of powder-based 3D printing techniques. (a) SLM, Reproduced with permission from Chang et al., “Conductivity modulation of 3D‐printed shellular electrodes through embedding nanocrystalline intermetallics into amorphous matrix for ultrahigh-current oxygen evolution,” Adv. Energy Mater. 11(28), 2100968 (2021). Copyright 2021, John Wiley and Sons. (b) SLS, Reproduced with permission from Fina et al., “Selective laser sintering (SLS) 3D printing of medicines,” Int. J. Pharm. 529(1–2), 285–293 (2017). Copyright 2017, Elsevier. (c) BJ. (d) EBM, Reproduced with permission from Parthasarathy et al., “Mechanical evaluation of porous titanium (Ti6Al4V) structures with electron beam melting (EBM),” J. Mech. Behav. Biomed. Mater. 3(3), 249–259 (2010). Copyright 2010, Elsevier. (B) SLM-printed electrodes for electrochemical water splitting. (a) Illustration of the SLM printing mechanism. (b) Top (from left to right): side view of the optical picture of the printed Ti-based electrode with conical arrays consisting of 216 cones cm−1 with a cone separation of around 700 µm and the corresponding SEM images of the Ti-based electrode from the top and angled views, respectively. Bottom (from left to right): side view of the optical picture of printed conical arrays of Ti-based electrode consisting of 407 cones cm−1 with a cone separation of around 430 µm and the corresponding SEM images from the top and angled view angles, respectively. (c) Left: chopped-light photoelectrochemical reactions of the TiO2 electrode, in comparison to array electrodes made up of 216 (blue) and 407 (red) cones. Right: photocurrent response at 1.2 V (versus RHE). Reproduced with permission from Lee et al., “3D-printed conical arrays of TiO2 electrodes for enhanced photoelectrochemical water splitting,” Adv. Energy Mater. 7(21), 1701060 (2017). Copyright 2017, John Wiley and Sons. (d) Illustration of the electrochemical activated SLM-printed Inconel 718 electrode. (e) Left: LSV curve of the electrochemically activated electrode. Right: SEM image of NiFe–OOH nanosheets grown on the Inconel 718 electrode. (f) Electrochemical testing results of the SLM-printed Inconel 718 electrode. Reproduced with permission from Chang et al., “Conductivity modulation of 3D‐printed shellular electrodes through embedding nanocrystalline intermetallics into amorphous matrix for ultrahigh-current oxygen evolution,” Adv. Energy Mater. 11(28), 2100968 (2021). Copyright 2021, John Wiley and Sons. (C) Characterization and performance testing results of the SLS-printed electrode: (a) illustration of the SLS-printed electrode, (b) NCP, and (c) SEM images of the Ni-coated SLS-printed electrode, (d) polarization curves and stability of the SLS-printed Ni/Cu electrode for HER and OER, (e) Tafel slopes, (f) the Ni2+/3+ redox peak during OER of the SLS-printed Ni/Cu electrode, (g) overpotential at 50 mA·cm−2 and charge of the Ni2+/3+ redox peak during OER, and (h) SEM images of the SLS-printed Ni/Cu electrode during OER. Reproduced with permission from Márquez et al., “Tailoring 3D-printed electrodes for enhanced water splitting,” ACS Appl. Mater. Interfaces 14, 42153 (2022). Copyright 2022, American Chemical Society. (D) BJ-printed electrodes for electrochemical water splitting. (a) Illustration of the printing process of the TRGO series samples. (b) SEM images of the TRGO and TRGO9 disk samples. (c) CV curves of BJ-printed TRGO and TRGO (1, 3, 9) disks at different scan rates (4 graphs on the top), specific and areal capacitance of the disks (2 graphs on the bottom). Reproduced with permission from Azhari et al., “Binder-jet powder-bed additive manufacturing (3D printing) of thick graphene-based electrodes,” Carbon 119, 257–266 (2017). Copyright 2017, Elsevier. (E) (a) Schematic of PEMEC with LGDL of the EBM-printed Ti–6Al–4V anode. (b) SEM images of the Ti–6Al–4V electrode. (c) The voltage–current curve of the Ti–6Al–4V electrode at room temperature. (d) The voltage–current curve of the Ti–6Al–4V electrode at different temperatures. Reproduced with permission from Mo et al., “Additive manufacturing of liquid/gas diffusion layers for low-cost and high-efficiency hydrogen production,” Int. J. Hydrogen Energy 41(4), 3128–3135 (2016). Copyright 2016, Elsevier.

FIG. 3.

Powder-based 3D printed electrodes for water electrolysis. (A) Schematic illustration of powder-based 3D printing techniques. (a) SLM, Reproduced with permission from Chang et al., “Conductivity modulation of 3D‐printed shellular electrodes through embedding nanocrystalline intermetallics into amorphous matrix for ultrahigh-current oxygen evolution,” Adv. Energy Mater. 11(28), 2100968 (2021). Copyright 2021, John Wiley and Sons. (b) SLS, Reproduced with permission from Fina et al., “Selective laser sintering (SLS) 3D printing of medicines,” Int. J. Pharm. 529(1–2), 285–293 (2017). Copyright 2017, Elsevier. (c) BJ. (d) EBM, Reproduced with permission from Parthasarathy et al., “Mechanical evaluation of porous titanium (Ti6Al4V) structures with electron beam melting (EBM),” J. Mech. Behav. Biomed. Mater. 3(3), 249–259 (2010). Copyright 2010, Elsevier. (B) SLM-printed electrodes for electrochemical water splitting. (a) Illustration of the SLM printing mechanism. (b) Top (from left to right): side view of the optical picture of the printed Ti-based electrode with conical arrays consisting of 216 cones cm−1 with a cone separation of around 700 µm and the corresponding SEM images of the Ti-based electrode from the top and angled views, respectively. Bottom (from left to right): side view of the optical picture of printed conical arrays of Ti-based electrode consisting of 407 cones cm−1 with a cone separation of around 430 µm and the corresponding SEM images from the top and angled view angles, respectively. (c) Left: chopped-light photoelectrochemical reactions of the TiO2 electrode, in comparison to array electrodes made up of 216 (blue) and 407 (red) cones. Right: photocurrent response at 1.2 V (versus RHE). Reproduced with permission from Lee et al., “3D-printed conical arrays of TiO2 electrodes for enhanced photoelectrochemical water splitting,” Adv. Energy Mater. 7(21), 1701060 (2017). Copyright 2017, John Wiley and Sons. (d) Illustration of the electrochemical activated SLM-printed Inconel 718 electrode. (e) Left: LSV curve of the electrochemically activated electrode. Right: SEM image of NiFe–OOH nanosheets grown on the Inconel 718 electrode. (f) Electrochemical testing results of the SLM-printed Inconel 718 electrode. Reproduced with permission from Chang et al., “Conductivity modulation of 3D‐printed shellular electrodes through embedding nanocrystalline intermetallics into amorphous matrix for ultrahigh-current oxygen evolution,” Adv. Energy Mater. 11(28), 2100968 (2021). Copyright 2021, John Wiley and Sons. (C) Characterization and performance testing results of the SLS-printed electrode: (a) illustration of the SLS-printed electrode, (b) NCP, and (c) SEM images of the Ni-coated SLS-printed electrode, (d) polarization curves and stability of the SLS-printed Ni/Cu electrode for HER and OER, (e) Tafel slopes, (f) the Ni2+/3+ redox peak during OER of the SLS-printed Ni/Cu electrode, (g) overpotential at 50 mA·cm−2 and charge of the Ni2+/3+ redox peak during OER, and (h) SEM images of the SLS-printed Ni/Cu electrode during OER. Reproduced with permission from Márquez et al., “Tailoring 3D-printed electrodes for enhanced water splitting,” ACS Appl. Mater. Interfaces 14, 42153 (2022). Copyright 2022, American Chemical Society. (D) BJ-printed electrodes for electrochemical water splitting. (a) Illustration of the printing process of the TRGO series samples. (b) SEM images of the TRGO and TRGO9 disk samples. (c) CV curves of BJ-printed TRGO and TRGO (1, 3, 9) disks at different scan rates (4 graphs on the top), specific and areal capacitance of the disks (2 graphs on the bottom). Reproduced with permission from Azhari et al., “Binder-jet powder-bed additive manufacturing (3D printing) of thick graphene-based electrodes,” Carbon 119, 257–266 (2017). Copyright 2017, Elsevier. (E) (a) Schematic of PEMEC with LGDL of the EBM-printed Ti–6Al–4V anode. (b) SEM images of the Ti–6Al–4V electrode. (c) The voltage–current curve of the Ti–6Al–4V electrode at room temperature. (d) The voltage–current curve of the Ti–6Al–4V electrode at different temperatures. Reproduced with permission from Mo et al., “Additive manufacturing of liquid/gas diffusion layers for low-cost and high-efficiency hydrogen production,” Int. J. Hydrogen Energy 41(4), 3128–3135 (2016). Copyright 2016, Elsevier.

Close modal
FIG. 3.

(Continued.)

FIG. 3.

(Continued.)

FIG. 3.

(Continued.)

Among the various additive manufacturing (3D printing) techniques, due to its increased print resolution, higher efficiency, superior surface polish, adaptability, and printing accuracy, VP is regarded as the top of the art at this time.92 However, some drawbacks hinder VP’s further development, starting with the options of printable materials. The printing mechanism is to apply UV light to cure photopolymers, so the precursors must have a proper optical property, especially a proper refractive index—lower than 1.50 as a matter of experience. VP printing is unsuitable for materials with high refractive indices (such as metal powder, transparent materials, carbon, and other black color materials). Second, it is time-consuming to develop an applicable formula for certain materials; some parameters need to be considered, such as the shrinkage after post-processing, the slurry’s dispersity, and the slurry’s viscosity. Compared to DLP, the printing speed of SLA is much slower, which deters its possibility of application in industrial applications.

Powder-bed printing uses the material precursor in powder form. It is made up of tightly packed, thin layers of fine granules that are spread out on a platform. Each layer’s particles are joined or fused together using an electron or laser beam, a binder, or both. Up until a fully 3D structure is constructed, further layers of powder are rolled over to the build platform and fused/bound. Powder size, powder distribution, and packing, which determine the density of the printed part, are the most important elements in determining how well this strategy works. The four common powder-based printing techniques consist of SLM, SLS, BJ, and EBM.

SLM was first developed to produce metal components using metallic powders. Similar to VP-based 3D printing, SLM also uses CAD software to build a 3D model and print the model out layer by layer [Fig. 3(A-a)]. It adopts a high-intensity laser as the power source to melt/fuse the metallic powders in the powder bed.93 In a building chamber, a substrate plate is covered with a thin layer of metal powder to begin construction. A high-intensity laser is utilized to melt/fuse certain portions of the powder after it has been placed down, in accordance with the processed data. The construction platform is lowered, a new layer of powder is placed on top, and the laser scans a new layer when the laser scanning is finished. Once the necessary components are fully constructed, the process is repeated for additional powder layers. Process variables, such as laser power, layer thickness, scanning speed, and hatch spacing, are adjusted so that a single melt vector can fuse completely with the nearby melt vectors and the previous layer. SLM has been widely utilized in many industries, especially in the aerospace and automobile industries. The key advantage of SLM is that it can produce fully dense near-net-shape components, which means that it does not require any post-processing to remove supporting parts. In addition, SLM is suitable for mass production and the printing quality is stable once the proper printing parameters are applied. The limitations of SLM include the limitation of printing materials (only a few materials with good flow characterization are acceptable for SLM) and the high energy process causing the printing part to dislocate and compromising the structural integrity.

SLS is also an industrial 3D printing technique that builds up the 3D object on a powder bed.94 The printing mechanism is shown in Fig. 3(A-b). It employs a laser to bond the powder particles together rather than fuse the powder. The laser is instructed to trace a precise pattern onto the powder bed’s surface while printing. A roller applies a fresh layer of powder on top of the old one once the first layer has dried. Layer by layer, the item is constructed and then recovered from the powder bed. High component complexity, rapid manufacturing, a wide range of raw materials, and a high material utilization rate are the benefits of the SLS technique. It has been developed and applied to many industries, such as medicine, aerospace, and aviation. However, the high cost of machines and powders limits further application. Meanwhile, longer production time is caused by up to 12 h of a cool-down time of 50% of print time. The surfaces of the parts are gritty without any post-processing.

FIG. 4.

Material extrusion/jetting-based 3D printed electrodes for water electrolysis. (A) Schematic illustration of material extrusion/jetting-based 3D printing techniques. (a) FDM, Reproduced with permission from Ning et al., “Additive manufacturing of carbon fiber reinforced thermoplastic composites using fused deposition modeling,” Composites, Part B 80, 369–378 (2015). Copyright 2015, Elsevier.104 (b) DIW, Reproduced with permission from L. del-Mazo-Barbara and M.-P. Ginebra, “Rheological characterisation of ceramic inks for 3D direct ink writing: A review,” J. Eur. Ceram. Soc. 41(16), 18–33 (2021). Copyright 2021, Elsevier. (B) (a) CAD design and printed PLA-based 2D-MoSe2 electrode. (b) and (c) Images of water splitting system with an M/C-10%/15%-AME as the cathode and a Pt/C-25%-AME as the anode. (d) Image of the three-electrode system: M/C-10%/15% AME as the working electrode (cathode), a nickel mesh as the counter electrode, and an RHE as the reference electrode. (e) LSV of unmodified and various modified electrodes showing HER activity of a Pt electrode. (f) Tafel slopes correspond to the faradaic regions of the LSVs shown in (e). (g) Cyclic stability examination of an M/C-10%/15% AME via LSV (scan rate: 100 mV s−1) was performed between 0 and −1.5 V (vs RHE), repeated for 1000 cycles [inset: chronoamperometry for 10 h at −0.60 V (vs RHE)]. Reproduced with permission from Hughes et al., “Single step additive manufacturing (3D printing) of electrocatalytic anodes and cathodes for efficient water splitting,” Sustainable Energy Fuels 4(1), 302–311 (2020). Copyright 2020, The Royal Society of Chemistry. (C) (a) Schematic illustration of the printing process of the DIW-printed NiMo-based electrocatalysts (top) and SEM image and optical images of the NiMo electrocatalysts. (bottom). (b) From left to right: overpotential of the DIW-printed NiMo-based electrode at current density = 10 mA cm−2 as a function of ECSA and Mo content. Correlation between the overpotential at current density = 10 mA cm−2 and RF: 3D geometric (blue) and 2D projected (red). ECSA values before oxidation (blue) and after (red). (c) CP measurements of the DIW-printed NiMo electrode at current density = 10 mA cm−2 for 24 h and (d) the corresponding Faradaic efficiency for HER. Reproduced with permission from Sullivan et al., “3D printed nickel–molybdenum-based electrocatalysts for hydrogen evolution at low overpotentials in a flow-through configuration,” ACS Appl. Mater. Interfaces 13(17), 20260–20268 (2021). Copyright 2021, American Chemical Society. (D) (a)–(d) SEM images of YSZ pillars on the Ni-YSZ substrate. (e) Assembled planar CO2(−CO)|Ni-YSZ|YSZ|YSZ-LSM|LSM|O2 cell. (f) Cell potential differences vs applied current density of the CO2(−CO)|Ni-YSZ|YSZ|YSZ-LSM|LSM| air cell. Reproduced with permission from Farandos et al., “Three-dimensional inkjet printed solid oxide electrochemical reactors. I. Yttria-stabilized zirconia electrolyte,” Electrochim. Acta 213, 324–331 (2016). Copyright 2016, Elsevier.

FIG. 4.

Material extrusion/jetting-based 3D printed electrodes for water electrolysis. (A) Schematic illustration of material extrusion/jetting-based 3D printing techniques. (a) FDM, Reproduced with permission from Ning et al., “Additive manufacturing of carbon fiber reinforced thermoplastic composites using fused deposition modeling,” Composites, Part B 80, 369–378 (2015). Copyright 2015, Elsevier.104 (b) DIW, Reproduced with permission from L. del-Mazo-Barbara and M.-P. Ginebra, “Rheological characterisation of ceramic inks for 3D direct ink writing: A review,” J. Eur. Ceram. Soc. 41(16), 18–33 (2021). Copyright 2021, Elsevier. (B) (a) CAD design and printed PLA-based 2D-MoSe2 electrode. (b) and (c) Images of water splitting system with an M/C-10%/15%-AME as the cathode and a Pt/C-25%-AME as the anode. (d) Image of the three-electrode system: M/C-10%/15% AME as the working electrode (cathode), a nickel mesh as the counter electrode, and an RHE as the reference electrode. (e) LSV of unmodified and various modified electrodes showing HER activity of a Pt electrode. (f) Tafel slopes correspond to the faradaic regions of the LSVs shown in (e). (g) Cyclic stability examination of an M/C-10%/15% AME via LSV (scan rate: 100 mV s−1) was performed between 0 and −1.5 V (vs RHE), repeated for 1000 cycles [inset: chronoamperometry for 10 h at −0.60 V (vs RHE)]. Reproduced with permission from Hughes et al., “Single step additive manufacturing (3D printing) of electrocatalytic anodes and cathodes for efficient water splitting,” Sustainable Energy Fuels 4(1), 302–311 (2020). Copyright 2020, The Royal Society of Chemistry. (C) (a) Schematic illustration of the printing process of the DIW-printed NiMo-based electrocatalysts (top) and SEM image and optical images of the NiMo electrocatalysts. (bottom). (b) From left to right: overpotential of the DIW-printed NiMo-based electrode at current density = 10 mA cm−2 as a function of ECSA and Mo content. Correlation between the overpotential at current density = 10 mA cm−2 and RF: 3D geometric (blue) and 2D projected (red). ECSA values before oxidation (blue) and after (red). (c) CP measurements of the DIW-printed NiMo electrode at current density = 10 mA cm−2 for 24 h and (d) the corresponding Faradaic efficiency for HER. Reproduced with permission from Sullivan et al., “3D printed nickel–molybdenum-based electrocatalysts for hydrogen evolution at low overpotentials in a flow-through configuration,” ACS Appl. Mater. Interfaces 13(17), 20260–20268 (2021). Copyright 2021, American Chemical Society. (D) (a)–(d) SEM images of YSZ pillars on the Ni-YSZ substrate. (e) Assembled planar CO2(−CO)|Ni-YSZ|YSZ|YSZ-LSM|LSM|O2 cell. (f) Cell potential differences vs applied current density of the CO2(−CO)|Ni-YSZ|YSZ|YSZ-LSM|LSM| air cell. Reproduced with permission from Farandos et al., “Three-dimensional inkjet printed solid oxide electrochemical reactors. I. Yttria-stabilized zirconia electrolyte,” Electrochim. Acta 213, 324–331 (2016). Copyright 2016, Elsevier.

Close modal
FIG. 4.

(Continued.)

Figure 3(A-c) shows an example of a binder jet (BJ) system. A few review papers have discussed the printing mechanism and applications in detail.50,95 A layer of powder is distributed over each layer of the part, often with a counter-rotating roller. The liquid binding agent is then jetted into the powder bed by an inkjet printhead, producing the layer’s 2D pattern. Heat is not a fundamental process need, but some binder/powder systems may make use of heaters to help with moisture management and curing. After each layer, the construction platform is lowered to make room for the next layer, and the process is repeated. The delicate parts are usually post-processed to enhance their mechanical qualities. Powder and binder are the key points for BJ. The powder deposition and the binder choice are therefore crucial features in building parts rapidly and reliably. Depending on the particles’ size, shape, composition, and humidity, inter-particle forces might change, necessitating the use of several techniques to reliably build thick, flaw-free layers. The technique of deposition is determined by the properties of powder flow. The typical BJ powders (30 µm or bigger) are treated in dry conditions, although smaller particles have been successfully deposited and disseminated by more careful adjusting of the process parameters. Some powders may need special treatments. As an alternative, agglomerates can be created from tiny particles. The powder is frequently dissolved in a fluid for the smallest size ranges to increase packing density and consistency. A low-viscosity binder would be good since it would speed up the formation and separation of the stream of individual droplet beads from the printhead nozzles. Additionally, the binder must be stable against the significant shear stress that printing causes. Good powder interaction, complete and clean burn-out nature, good repeatability, and a manageable environmental risk are further requirements. BJ has a large potential for high-speed and low-cost manufacturing compared to other 3D printing techniques. The limitations of BJ consist of a rough finishing surface and a long binder evaporation time (up to 12 h).

The printing mechanism of EBM is similar to SLM [see Fig. 3(A-d)].96 A vacuum environment is created over the raw material (metal powder or wire), and an electron beam uses heat to fuse the material. The only difference is that the power source has higher energy density compared to SLM and SLS, which shortens build times and, as a result, lowers manufacturing costs. The metal powder is completely melted by the high energy available, creating dense components with superior control over the mechanical properties of the manufactured porous pieces. In addition to lowering printing time, successful implant fabrication will produce personalized characteristics for quicker rehabilitation, longer durability, better functionality, and improved cosmesis. However, it only works for certain metals and alloys, such as titanium, niobium, tantalum, molybdenum, and tungsten. The high cost of the machine and the power source limits its further application.

FDM is an extrusion-based printing technique. The diagram of the printing mechanism is shown in Fig. 4(A-a). It makes use of a spool of filaments produced from a substance with a low melting point. Extrusion of the filament onto the building platform or on top of formerly printed layers occurs once the filament is heated at the nozzle to be melted. The printed strut is fixed by the nozzle size, thus printing in a different dimension is rather expensive. Although the characteristics and process of solidification of the matrix polymer can be impacted by the addition of additional materials, the solidification of each layer is mostly dependent on the crystallization and chain entanglement of the polymer. FDM is the best way for prototyping because of the low cost of materials and machines and fast printing speed. A lot of electrodes used for water splitting were fabricated by FDM, and some of them were further modified to improve the catalytic performance.77,97–103 However, it is limited by the printing materials (only thermoplastics) and finished parts with low mechanical properties. In addition, it has difficulty printing fine and intricate parts.

DIW (also known as robocasting) employs a paste of ceramic or metal that is well blended with a binder, plasticizer, reactant, or rheology modifier depending on the method of fabrication.105,106 The printhead is made of a standard needle that can be purchased off the shelf. To an added advantage, robocasting is a printing system that can include an extrusion printhead and inkjet printhead in the same setup. The printing process is shown in Fig. 4(A-b). DIW is possible to produce structures with any geometry, lateral extension, and thickness as well as customizable compositions and physical characteristics for printed devices. However, it requires a proper rheological property of the paste to extrude the material using the principle of shear thinning. Ink jetting (IJ) is similar to DIW. It also uses a printhead to jet materials, but the material is liquid photopolymer, and the printing resolution is ∼20 µm. In recent progress, inkjet has been widely used to print intricate and sophisticated microscale structures for applications such as medical devices, tissue engineering scaffolds, and energy-related devices.57 

A recent paper published in Applied Materials Today demonstrated a Cu electrode fabricated by DLP, and the authors used it as the electrode for the oxygen evolution reaction (OER).58 They mixed copper sulfate pentahydrate (the precursor) and polymeric resin, then burned out the polymers in the printing resin, and decomposed the copper salt, subsequently reducing the sample in a tube furnace under a hydrogen/argon gas atmosphere [Fig. 2(B-a)]. Figure 2(B-b) shows that the porosity of the printed electrodes can be adjusted by different sintering temperatures. Figure 2(B-c) shows that the DLP-printed electrodes have much higher mechanical strength than traditional Ni foam. Afterward, they used a VMP3 electrochemical workstation (Biologic, Inc.) to investigate the electrochemical catalytic performance of the NiFe hydroxide-coated 3D-printed copper sample. The sample was used as the electrode of OER in an alkaline solution (1M KOH), and it can drive a current density of 100 mA cm−2 solidly with low energy input. According to Fig. 2(C-a), DLP-printed copper gyroid exhibits significantly superior linear sweep voltammetry (LSV) performance than commercial copper foam. This performance can be further enhanced by coating with NiFe hydroxide. With an overpotential of 196 mV, this NiFe hydroxide-coated Cu can drive 10 mA cm−2 current density. In addition, NiFe hydroxide-coated Cu exhibits a much reduced overpotential at the same current densities of 10, 100, and 500 mA cm−2 when compared to commercial metal foams and DLP-printed Cu, according to Fig. 2(C-b). According to Fig. 2(C-c), it exhibits practically the lowest overpotential when compared to prior studies on OER performance in an alkaline environment. Figure 2(C-d) shows NiFe hydroxide-coated Cu can reliably drive 500 mA cm−2 for 20 h. Additionally, showing in Figs. 2(C-e) and 2(C-f), the NiFe hydroxide-coated Cu has the lowest Tafel slopes and largest ECSA (Electrochemical Active Surface Area).

To obtain a lightweight and robust electrode, Xinran and coauthors developed the electrode of 3D complex octet-truss structure with NiP and nickel–iron-(oxo) hydroxides nanosheets (NFNS) coating (NFNS@NiP@Truss) and applied it to the oxygen evolution reaction (OER) at an alkaline solution (1M KOH).59 The electrode was fabricated by electroless plating of NiP on the 3D-printed octet-truss structure and subsequently deposited NFNS thin layer by electrodeposition. The coating of NiP made it conductive and the coating of NFNS dramatically increased the electrochemical catalysis performance of the NFNS@NiP@Truss sample. It achieved the overpotential of 197 mV at 10 mA cm−2 with a Tafel slope of 51 mV dec−1. The large specific surface area of the 3D-printed octet-truss structure and porous processing significantly improved the catalysis performance. In addition, the 3D structure helps with effective bubble removal, which also contributes to the improvement of the performance.

In a paper published in Advanced Energy Materials,60 Lee et al. used SLM to create a kind of Ti-based electrodes with a controllable conical arrays’ microstructure [see Fig. 3(B-a)]. To achieve a large photoelectrode with improved light absorption property and charge separation for high efficient water-splitting, they printed conical arrays of Ti-based electrodes, taking advantage of the simplicity of the 3D model design and manufacture of metal electrodes made possible by SLM printing. The optical and SEM images shown in Fig. 3(B-b) indicate the densities of the conical structure are 216 and 407/cm2, and the cone separations are around 700 and 430 µm, respectively. This kind of structure helps improve the catalytic performance dramatically. Figure 3(B-c) compares the current–potential cut photo responses of the simple flat electrode and conical array electrode. Comparing the simple flat electrode to the conical arrays, where the dark current starts at 1.0 V vs Reversible Hydrogen Electrode (RHE), a more constant baseline of dark current is shown. As compared to a nominally flat electrode, this figure shows a significant increase in photo response across the applied voltage when conical arrays are used. When contrasting the conical array electrodes with thick and sparse cones, the same trend is also present; however, the degree of the photo response rise decreased. The sliced photo-electrochemical response was acquired at a potential of 1.2 V vs RHE to further illustrate how the photo responses varied.

A more recent paper published in Advanced Energy Materials shows the potential of SLM-printed electrodes for high-current density electrochemical water splitting.61 Chang et al. used Inconel 718 alloy as the support material for electrodes out of its principal constituents—Fe and Ni—to promote the NiFe–OOH catalyst creation. Additionally is the possibility that its corrosion-resistant intermetallic Ni3Nb phase will persist after oxidation. In order to regulate the grain structure during SLM and enable the dispersive precipitation of small Ni3Nb nanoparticles in significant quantities, they employed a specially designed in situ laser remelting technique [see Fig. 3(B-d)]. Additionally, SLM created the linked Shellular 3D structure, which is inspired by nature and has a high specific surface area. Beyond that, it has good electrical conductivity, mechanical strength, and great kinetics for electrolyte/bubble diffusion. They also suggested a novel approach of integrating nanocrystalline Ni3Nb intermetallic into amorphous NiFe–OOH matrix to enhance the electrocatalytic activity and electronic conductivity of the SLM-printed Shellular supports. This tactic was created via controlled SLM printing and in situ electrochemical activation using NH4F/KOH as the growth-mode electrolyte. This method enables the in situ synthesis of nanocrystalline Ni3Nb intermetallic, which persist and are uniformly incorporated in the NiFe–OOH matrix to improve conductivity and large electrochemically active amorphous NiFe–OOH nanosheets [see Fig. 3(B-e)]. A greatly effective electrode for OER can produce large current densities (more than 1500 mA cm−2) at an incredibly low overpotential of 261 mV using this developed strategy, which can simultaneously inflect electronic structure and increase the number of active sites and electric conductivity [see Fig. 3(B-f)].

Márquez et al. used SLS to fabricate a Cu and Ni coated nylon electrode and published the work in ACS Appl. Mater. Interfaces in 2022.66 They adjusted the surface features and architecture of SLS-printed electrodes to examine the effects of extrinsic characteristics on the electrochemical catalytic performance of water splitting and bubble release behavior at an alkaline solution. The prepared electrodes were made of SLS-fabricated nylon substrates, and successive Cu and Ni layers were deposited on top of them. The printed sample is shown in Fig. 3(C-a). The porous electrode (referred to as 3D-Ni/Cu) has an exposed surface roughly six times larger than the planar electrode. A rough surface covered in many protrusions is visible in NCP and SEM images [Figs. 3(C-b) and 3(C-c)], demonstrating the applicability of the deposition approach to macroporous 3D electrodes. The catalytic performance of the 3D-Ni/Cu electrode was assessed using linear sweep voltammetry (LSV) scans at both cathodic and anodic potentials in 1.0M KOH solution [Fig. 3(C-d)]. For HER, the 3D-Ni/Cu electrode needed an overpotential of 133 mV to reach a current density of 10 mA cm−2 and 202 mV to reach 50 mA cm−2. At 10 and 50 mA cm−2 for OER, the electrode showed overpotentials of 400 and 512 mV, respectively. The Tafel slopes are 80 and 123 mV dec −1 for HER and OER, respectively [Fig. 3(C-e)]. Circulating the Ni/Cu electrode reduced the overpotential until it stabilized at ∼300 and 398 mV for the current density of 10 and 50 mA cm−2, respectively [Fig. 3(C-f)], which is brought on by the development of NiOOH sites. The electric charge connected to the Ni2+/3+ redox peak and the overpotential at 50 mA cm−2 were analyzed to assess oxidation and activity improvement more accurately. At about 8000 cycles, the overpotential and charge stabilized at 398 mV and 197 mC cm−2, respectively. Figure 3(C-g) demonstrates how the surface progressively smooths down after 8000 cycles, and how large protrusions and surface roughness are still present even after 20 000 cycles.

In the paper that Azhari and co-authors published in 2017, they showed how BJ could be used to create thick graphene-based 3D objects and described how these structures are used as electrodes in electrochemical water-splitting.67 They first processed graphene oxide using a rapid thermal expansion technique to obtain a high specific surface area. The thermally reduced graphene oxide (TRGO), which is composed of aggregated sheets, prevents the sheets from restacking and maintains a high specific surface area, thanks to folds and wrinkles caused by rapidly releasing gases during the fast decomposition and reduction of graphite oxide. Then, the powder is employed to the binder jetting (BJ) machine. The TRGO is constructed layer by layer using very little water. The printing process is shown in Fig. 3(D-a). This material is then evaporatively condensed to produce a powder with a higher bulk density, which is then used to layer-by-layer assemble the TRGO into electrodes that may be practically any shape or size that is mm scale thick. A small number of Pd nanoparticles (<9 wt. %) were added to the electrodes to increase the catalytic performance. Figure 3(D-b) shows the micro features of the printed electrodes. The electrochemical testing results are shown in Fig. 3(D-c). The constant voltage (CV) curves of the several BJ-printed electrodes with variable Pd nanoparticle contents were examined at a range of scan rates (5–500 mV s−1). All curves are rectangular, and no redox peaks are clearly connected to the pseudo-capacitance. Increased current density and more rectangular CVs are produced by increasing the palladium nanoparticle concentration from 0% to 9% in TRGO to TRGO9. This shape change is related to the electrodes’ decreased resistance. Comparatively, TRGO9 electrodes perform more capacitively than their TRGO counterparts, which may be explained by the palladium nanoparticles’ reduced impact on contact resistance. This effect is more prominent when scanning at greater scan rates—200 or 500 mV s−1. On top of that, they also tested the capacitance of the printed electrodes. The results are shown in Fig. 3(D-c) as well (bottom).

Mo et al. used EBM to fabricate a titanium anode electrode as the liquid/gas diffusion layer (LGDL) and assemble it into proton exchange membrane electrolyzer cells (PEMECs) [see Fig. 3(E-a)].68 The thickness of the printed titanium LGDL is 300 mm, and its square pores measure 1.5 mm in size and 500 mm in width. The used powder is Ti–6Al–4V, and the SEM images of the printed electrodes are shown in Fig. 3(E-b). The titanium powder is distinctly visible at the side walls of the pores in the high-resolution images. The interface between the catalyst layer and the LGDL is substantially improved by the top and bottom surfaces being smooth, flat, and uniformly thick, lowering the resistance between the two layers. For the electrochemical testing, as a benchmark, a titanium woven mesh was chosen because of its same wire thickness and porosity. Fabricated meshes were employed as the gas diffusion layer at the anode and tested under the same PEMEC and operating circumstances as EBM Ti–6Al–4V structures. At room temperature, the impact of the LGDL with various fabrication techniques and anode structures on the PEMEC performance is demonstrated in Fig. 3(E-c). The performance of both LGDLs is limited by ohmic losses, and the operating voltages increased linearly with the increasing current densities from 0.2 to 2.0 A cm−2. With EBM-printed Ti–6Al–4V LGDL, better performance (lower voltage) was attained. At 1.5 A cm−2, the operating voltage dropped from 2.49 to 2.18 V, resulting in an efficiency improvement of more than 12%. Figure 3(E-d) shows that the PEMEC performance improved much more at higher operating temperatures. The range of the cell temperature within the PEMEC system’s general operating temperature is 35–65 °C, with steps of 15 °C. The operating voltage required at 1.5 A cm−2 was 2.13, 2.02, and 1.91 V, respectively, indicating a considerable improvement in performance. Increased proton conductivity inside the membrane, enhanced kinetics, and improved interfacial contacts are all facilitated by higher temperatures in PEMECs. Additionally, increased reactant diffusion results in a smaller concentration differential.

For the first time, a simple method for creating highly repeatable polylactic acid (PLA)-based 2D-MoSe2 and Pt/C AM laminates was described in the paper published in 2020.75 The filament is polylactic acid (PLA) and the 2D-MoSe2 was incorporated into PLA. The PLA-based 2D-MoSe2 electrode was fabricated by FDM [Fig. 4(B-a)]. Then, without the need for any post-printing processing, the printed electrode was applied to the electrochemical measurement as a cathode [Figs. 4(B-b) and 4(B-c)]. The electrochemical performance was carried out in a typical three-electrode system, where the printed PLA-based 2D-MoSe2 served as the working electrode, the counter electrode was a large nickel mesh, and the reference electrode was a Reversible Hydrogen Electrode (RHE) [see Fig. 4(B-d)]. Figure 4(B-e) shows the LSV curve obtained for various electrodes with different fillers—different MoSe2 and C contents (M/C—10%/5%, M/C—10%/10%, M/C—10%/15%), C-15%, Pt/C-25%, and a Pt electrode. The corresponding Tafel slopes are shown in Fig. 4(B-f). As a representative example of the FDM printed electrodes, the electrode with the filler of M/C - 10%/15% was put through 1000 cyclic CV repeatedly and chronoamperometry (CP) for 10 h. The findings are shown in Fig. 4(B-g). Unfortunately, it did not show good stability. Although it does not remain stable for a long time, the demonstrated technology has the potential to simplify laborious fabrication processes of producing prototype electrolyzer components, enabling researchers, businesses, and anyone else with an interest to quickly transform desktop CAD into functional prototypes, cutting the price and time involved in conventional prototyping.

In 2021, Sullivan et al. reported a hierarchically porous NiMo-based electrocatalyst that was DIW printed, which significantly raised the ECSA and roughness factor and, thus, decreased the overpotentials for HER.69  Figure 4(C-a) shows the ink formulation, DIW printing process, sol–gel formation, and carbonization processes (top) and the flow-through configuration (bottom). The 3D hierarchically porous structure, which is responsible for the decreased overpotentials attained, made large ECSA and RF values available [Fig. 4(C-b)]. The flow-through arrangement was used to overcome mass transport constraints and effectively fasten bubble removal from the electrode’s surface, which increased overpotentials. The flowthrough structure greatly reduced the overpotentials needed for HER compared to a conventional planar, immobile electrode construction and enabled efficient hydrogen bubble removal from the electrode surface, particularly when operating at high current densities. An analytical model that considers the electro-kinetics of HER and mass transport with or without the flow-through configuration has been constructed to assess various reasons for the lowered over-potentials. At high working current densities, the majority of the voltage loss was caused by bubble-induced ohmic loss. Figure 4(C-c) displays the overpotential of the high-Mo content, oxidized porous electrode in a flow-through mode, which is 10 mA cm−2, as a function of time. The observed overpotential was 50 mV for the first 12 h; after 24 h, it increased steadily to 70 mV. An overpotential of around 45 mV was seen during this 24-h testing period. By using gas chromatography (GC), an average H2 Faradaic yield of 96% (5%) was determined throughout this time, proving that the only reaction taking place was HER with no side reactions (such as reduction of oxide) being noticed [Fig. 4(C-d)].

Microstructure engineering is another important technique to improve electrochemical catalysis performance. In 2016, Farandos et al. first reported a technique for creating aqueous yttria-stabilized zirconia (YSZ) particle dispersions resistant to aggregation over weeks and later used as inks to print repeatable planar and three-dimensional electrodes with microstructures for solid oxide electrolyzer (SOE) and solid oxide fuel cells (SOFCs).107 The authors changed the size of particles, the fraction of solids, the concentration of polymeric binder, and the viscosity of the ink formulation to test printed samples’ suitability for the electrolyte phase in SOFCs. The SEM images show the micro features of the IJ-printed electrodes [Figs. 4(D-a)4(D-d)]. In addition, they provided the first results for an SOE created by inkjet printing, which divided CO2 over a range of temperatures in a Ni-YSZ reactor [Fig. 4(D-e)] with an IJ-printed planar electrolyte. In the examined temperature range, current densities ranged between 0.35 and 0.78 A cm−2 at the thermo-neutral potential difference (∼1.5 V) [Fig. 4(D-f)].

Water electrolysis in the laboratory often takes place in glass beakers, and the distance between the individual electrodes is relatively constant in order to facilitate electrochemical tests. To enable the lab-to-fab transition and to meet the specific requirements of various reactions, 3D printing technology offers the possibility of customized reaction vessels.

To fabricate electrochemical systems using 3D printing technology, various non-conductive materials will need to be fabricated in addition to synthesizing containers for all kinds of reactions to integrate full cells. These non-conductive components will be used as anode compartments, cathode compartments, separators, gas collectors, liquid processors, etc., for the reactions to take place.23 If the additive manufacturing of each of these components can be achieved at a lower cost and in a more convenient way, it makes a significant contribution to the industrialization of this technology.

Using 3D printing methods, reaction tanks may be produced in a variety of sizes to match the size of the electrodes. Adriano and Martin built a self-contained electrochemical cell consisting of metal electrodes and a polymer body.64 In this work, as shown in Fig. 5(a), they fabricated gauze-shaped steel electrodes by the SLM method and then modified the surface to gain better electrocatalytic performance. In this case, they used cyclic voltammetry to electrodeposit IrO2 and galvanostatic time-controlled methods to deposit Pt by applying a fixed current and Ni by applying a fixed potential. After characterization, respectively, Pt-modified and IrO2-modified steel electrodes exhibit much better catalytic performance than bare electrodes or Ni-modified electrodes. Eventually, a proof-of-concept water electrolyzer was constructed with SLM-printed steel electrodes and an FDM-printed polymer cell body. As a high degree of precision is not required, this poly lactic acid (PLA) based container was obtained by FDM to accommodate different-sized electrodes.

FIG. 5.

Containers for 3D-printed electrochemical cells. (a) Electrochemical cells and electrodes of various sizes. Reproduced with permission from A. Ambrosi and M. Pumera, “Self-contained polymer/metal 3D printed electrochemical platform for tailored water splitting,” Adv. Funct. Mater. 28(27), 1700655 (2018). Copyright 2017, John Wiley and Sons.64 (b) Diagrams, features, and specifications of a WSFC. Reproduced with permission from Su et al., “Metallization of 3D printed polymers and their application as a fully functional water‐splitting system,” Adv. Sci. 6(6), 1801670 (2019). Copyright 2019, John Wiley and Sons.59 (c) Schematic and optical photos of an assembly 3D printed electrochemical water splitting cell. Reproduced with permission from Lee et al., “A 3D‐printed electrochemical water splitting cell,” Adv. Mater. Technol. 4(10), 1900433 (2019). Copyright 2019, John Wiley and Sons.108 (d) Top and side views of the electrolyzer parts. Reproduced with permission from A. Ambrosi and M. Pumera, “Multimaterial 3D-printed water electrolyzer with earth-abundant electrodeposited catalysts,” ACS Sustainable Chem. Eng. 6(12), 16968–16975 (2018). Copyright 2018, The Royal Society of Chemistry.109 (e) Structure of the electrolysis cell. Reproduced with permission from Chisholm et al., “3D printed flow plates for the electrolysis of water: An economic and adaptable approach to device manufacture,” Energy Environ. Sci. 7(9), 3026–3032 (2014). Copyright 2014, American Chemical Society.110 (f) The angled mesh flow-through electrode-based membrane-less electrochemical flow cell. (θ = the separation angle and L = electrode length). Reproduced with permission from O’Neil et al., “Hydrogen production with a simple and scalable membraneless electrolyzer,” J. Electrochem. Soc. 163(11), F3012–F3019 (2016). Copyright 2016, ECS.111 

FIG. 5.

Containers for 3D-printed electrochemical cells. (a) Electrochemical cells and electrodes of various sizes. Reproduced with permission from A. Ambrosi and M. Pumera, “Self-contained polymer/metal 3D printed electrochemical platform for tailored water splitting,” Adv. Funct. Mater. 28(27), 1700655 (2018). Copyright 2017, John Wiley and Sons.64 (b) Diagrams, features, and specifications of a WSFC. Reproduced with permission from Su et al., “Metallization of 3D printed polymers and their application as a fully functional water‐splitting system,” Adv. Sci. 6(6), 1801670 (2019). Copyright 2019, John Wiley and Sons.59 (c) Schematic and optical photos of an assembly 3D printed electrochemical water splitting cell. Reproduced with permission from Lee et al., “A 3D‐printed electrochemical water splitting cell,” Adv. Mater. Technol. 4(10), 1900433 (2019). Copyright 2019, John Wiley and Sons.108 (d) Top and side views of the electrolyzer parts. Reproduced with permission from A. Ambrosi and M. Pumera, “Multimaterial 3D-printed water electrolyzer with earth-abundant electrodeposited catalysts,” ACS Sustainable Chem. Eng. 6(12), 16968–16975 (2018). Copyright 2018, The Royal Society of Chemistry.109 (e) Structure of the electrolysis cell. Reproduced with permission from Chisholm et al., “3D printed flow plates for the electrolysis of water: An economic and adaptable approach to device manufacture,” Energy Environ. Sci. 7(9), 3026–3032 (2014). Copyright 2014, American Chemical Society.110 (f) The angled mesh flow-through electrode-based membrane-less electrochemical flow cell. (θ = the separation angle and L = electrode length). Reproduced with permission from O’Neil et al., “Hydrogen production with a simple and scalable membraneless electrolyzer,” J. Electrochem. Soc. 163(11), F3012–F3019 (2016). Copyright 2016, ECS.111 

Close modal

Employing 3D printing techniques, the relative arrangement of electrodes may be altered to enhance varied features of water electrolysis cells. Su et al. fabricated a fully functional water-splitting system integrated of 3D-printed components.59 In this work, as shown in Fig. 5(b), they printed a concentrically integration structure of good catalytic performances, which enables gas separation and collection. Bifunctional electrodes for both cathodic and anodic catalytic reactions with 3D printed polymers as precursors were first surface-metallized to nickel–iron-(oxo) hydroxide nanosheets (NFNS) by electroless deposition of NiP, followed by electrodeposition of the active layer. With such a concentric layout for the water-splitting full cell (WSFC), the distance between the OER and HER electrodes is kept to a minimum, reducing electrical resistance while making the most of the available space. At the same time, the semipermeable separating mesh that acts as a gas separator effectively separates the two gases, hydrogen and oxygen, so that they are collected with a high degree of purity.

Thanks to 3D printing technology, the materials used to create the different component pieces may be chosen based on how well they will serve their intended purpose.108 Lee et al. designed a water-splitting full cell that all components are printable as shown in Fig. 5(c). In this work, each aspect of the cell, including the metallic electrodes, the reaction tanks, and the base were manufactured by different 3D printing methods and materials. In order to increase electrochemical properties, the Ni-modified Ti electrodes with conical-array surfaces were first designed using the SLM method of fabrication and by simple electrodeposition to activate Ni. Then, to facilitate the collection of gases, the two electrolyte tanks were fabricated separately and also the electrodes were placed facing outward. It also provides the potential for using such a cell to photoelectrochemical water splitting by putting quartz glass at the port for the light source to illuminate the electrode. The anodic and cathodic chambers were printed by using the Proven PolyJet 3D Printing method using translucent photopolymer material to form a full electrochemical cell separated by a Nafion membrane as schematically shown. The main part is placed on the base, which was produced using the economical FDM printing platform by ABS (Polyacrylonitrile-Butadiene-Styrene) plastic. The base is made of a different material than the main body since it doesn’t need to be as precise and can be produced inexpensively and easily using 3D printing, but the main section comes in direct contact with the electrolyte and needs to be corrosion-resistant and leak-proof.

Using additive manufacturing technology, electrocatalytic cell devices may be created from scratch with highly advantageous for assembly due to the great printing precision. Ambrosi and Pumera exhibit the fabrication of a prototype water electrolyzer with electrodes and gas/liquid treatment equipment utilizing two distinct 3D printing processes.109 In this work, as HER electrodes, a Ni–MoS2 thin film was formed on the surface of the 3D-printed steel electrodes and NiFe double hydroxide was applied to deposit on the surface of OER electrodes. The cell case was accomplished by utilizing FDM technology and printed out of PLA thermoplastic material. As shown in Fig. 5(d), the two electrodes can be perfectly embedded in the space left by the housing during modeling, and the separation and collection of gases can be easily done.

3D printing can improve on some aspects of traditional manufacturing, making it possible to reduce costs, improve performance, and facilitate mass production. The structure of a conventional acid-mediated proton exchange membrane (PEM) electrolyzer is shown in Fig. 5(e) and consists of three main parts: the Nafion membrane, the porous gas diffusion layers (GDL), and the flow plates. Among these three parts, flow plates with a flow route for water circulation can separate each electrolyzer in the stack. Chisholm et al. invented a type of flow plate with a practical, affordable 3D printing manufacturing strategy.110 In this work, they show the creation and use of flow plates made of polypropylene by Bytes 3DTouch printer using a layer-by-layer deposition method and coated with silver. In terms of overall efficiency, internal resistances, and current–voltage responsiveness, they finally demonstrate that their gadget performs superbly.

Unusual designs for water electrolysis devices may be generated using fundamental physical principles, and 3D printing technology offers a fertile ground for innovators’ inventiveness. O’Neil et al. manufactured a simple, low-cost, electrolyzer without a membrane.111 Despite being extensively produced, electrolytic water systems with membranes based on acidic and alkaline electrolytes, respectively, nonetheless have expensive component prices. In this work, as shown in Fig. 5(f), angled mesh flow-through electrode-based membrane-less electrochemical flow cells are examined for the generation of gas from water electrolysis. As there is no ion exchange membrane in the system, the movement of ions in the electrolyte solution and the generation and separation of gases is achieved by means of the angled flow-through ramps set up in the device. They tested the performance of the electrolytic system by controlling the angle of the electrodes and obtained the highest efficiency of 61.9% and 72.5% for acidic and alkaline environments, respectively, at 100 mA·cm−2 of operation. In addition, hydrogen can be collected with an efficiency of ∼90%, and the resultant product is of high purity. The advantage of this device is that the number of components is greatly reduced compared to having a film system, requiring only three parts: the anode mesh, the cathode mesh, and the cell body, which saves on printing paste and greatly reduces costs without compromising effectiveness.

The fabrication of higher-performing electrochemical device components will undoubtedly benefit from the ongoing developments in additive manufacturing technologies. However, the rate of development may vary based on the requirement of different components and the materials used for manufacturing. As we have seen, electrochemical water splitting systems for H2 energy production typically need three components: conductive materials for electrodes (usually metallic materials and carbonaceous materials), which serve as current collectors and catalytic materials; suitable materials for membranes (usually polymeric materials); and insulating materials for reactor cells, which include the platform for handling liquids and the casing. Various 3D printing techniques have their advantages and limitations, which have been carefully discussed in Table I. For new electrode materials exploration at laboratory scale, SLA/DLP and DIW are more suitable compared to other techniques; for prototyping of water splitting cells, FDM owns the best advantage; for large scale production, BJ and SLM are the better choices; and to achieve high mechanical property of the electrodes, SLM and EBM show the favor.

A few challenges need to be met to employ 3D printing in actual industrial production further. First, transfer the novel materials from lab synthesis to industrial production. Loads of new and novel electrode materials have been explored at the laboratory, but few of them are applied to mass production because of the high cost, laborious synthesis process, unsatisfied mechanical properties, and poor stability. Hence, adopting earth-abundant materials, using a facile and easy synthesis method, enhancing the mechanical properties of the electrodes, and increasing the catalysts’ stability and durability are vital. Non-precious metals have been explored and achieved good catalytic performance by doping and other synthesis methods. 3D printing has provided a much easier way to fabricate self-supported electrodes and the whole reactor. However, increasing the mechanical properties and stability of the printed electrodes remains challenging. SLM, SLS, and EBM can produce relatively dense electrodes, yet obtaining dense electrodes requires long-time and high-temperature post-processing for other printing methods. Second, 3D printing makes it possible to design various patterns for electrodes, but there is no systematic study of the effect of different 3D patterns on catalytic performance. Many 3D patterns have been reported to be used as electrodes for electrochemical water-splitting, such as gyroid, honeycomb, needle-like structures, conical arrays, DIW-printed mesh structures, and so on. However, few studies were done to explore the most suitable 3D design for water-splitting use, and a proper design is required to employ 3D-printed electrodes in the industry. Finally, most research focus on electrode development, and only a few research focus on the full-cell design. It has been proven that effectively 3D-designed water-splitting cells can improve catalytic performance.112 Furthermore, gas separation and bubble removal are of vital importance in actual HER and OER, and efficient gas separation and bubble release need proper full-cell design. Therefore, 3D printing for full-cell design needs more attention, especially the full-cell design for large current-density water-splitting.

Our research work was financially supported by MOE Tier 1 (Grant No. A-8000215-01-00) and Saint-Gobain (Grant No. A-0005427-01-00).

The authors have no conflicts to disclose.

Yanran Xun: Conceptualization (equal); Data curation (equal); Formal analysis (equal); Investigation (equal); Methodology (equal); Validation (equal); Writing – original draft (equal); Writing – review & editing (equal). Kaixi Zhang: Conceptualization (equal); Data curation (equal); Formal analysis (equal); Writing – original draft (equal). Win Jonhson: Writing – review & editing (supporting). Jun Ding: Conceptualization (equal); Data curation (equal); Funding acquisition (equal); Supervision (equal); Writing – review & editing (equal).

The data that support the findings of this study are available from the corresponding author upon reasonable request.

1.
C.
Bataille
,
H.
Waisman
,
Y.
Briand
,
J.
Svensson
,
A.
Vogt-Schilb
,
M.
Jaramillo
,
R.
Delgado
,
R.
Arguello
,
L.
Clarke
,
T.
Wild
,
F.
Lallana
,
G.
Bravo
,
G.
Nadal
,
G.
Le Treut
,
G.
Godinez
,
J.
Quiros-Tortos
,
E.
Pereira
,
M.
Howells
,
D.
Buira
,
J.
Tovilla
,
J.
Farbes
,
J.
Ryan
,
D.
De La Torre Ugarte
,
M.
Collado
,
F.
Requejo
,
X.
Gomez
,
R.
Soria
,
D.
Villamar
,
P.
Rochedo
, and
M.
Imperio
, “
Net-zero deep decarbonization pathways in Latin America: Challenges and opportunities
,”
Energy Strategy Rev.
30
,
100510
(
2020
).
2.
M.
Bohra
and
N.
Shah
, “
Optimizing Qatar’s energy system for a post-carbon future
,”
Energy Transitions
4
(
1
),
11
29
(
2020
).
3.
M. T.
Brozynski
and
B. D.
Leibowicz
, “
Decarbonizing power and transportation at the urban scale: An analysis of the Austin, Texas Community Climate Plan
,”
Sustainable Cities Soc.
43
,
41
54
(
2018
).
4.
T.
Burandt
,
B.
Xiong
,
K.
Löffler
, and
P.-Y.
Oei
, “
Decarbonizing China’s energy system—Modeling the transformation of the electricity, transportation, heat, and industrial sectors
,”
Appl. Energy
255
,
113820
(
2019
).
5.
M.
Gebler
,
J. F.
Cerdas
,
S.
Thiede
, and
C.
Herrmann
, “
Life cycle assessment of an automotive factory: Identifying challenges for the decarbonization of automotive production—A case study
,”
J. Cleaner Prod.
270
,
122330
(
2020
).
6.
M.
Golden
,
A.
Scheer
, and
C.
Best
, “
Decarbonization of electricity requires market-based demand flexibility
,”
Electr. J.
32
(
7
),
106621
(
2019
).
7.
F.
Dawood
,
M.
Anda
, and
G. M.
Shafiullah
, “
Hydrogen production for energy: An overview
,”
Int. J. Hydrogen Energy
45
(
7
),
3847
3869
(
2020
).
8.
N.
Muradov
, “
Low to near-zero CO2 production of hydrogen from fossil fuels: Status and perspectives
,”
Int. J. Hydrogen Energy
42
(
20
),
14058
14088
(
2017
).
9.
A.
Kovač
,
M.
Paranos
, and
D.
Marciuš
, “
Hydrogen in energy transition: A review
,”
Int. J. Hydrogen Energy
46
(
16
),
10016
10035
(
2021
).
10.
A.
Midilli
and
I.
Dincer
, “
Key strategies of hydrogen energy systems for sustainability
,”
Int. J. Hydrogen Energy
32
(
5
),
511
524
(
2007
).
11.
Z.
Yan
,
J. L.
Hitt
,
J. A.
Turner
, and
T. E.
Mallouk
, “
Renewable electricity storage using electrolysis
,”
Proc. Natl. Acad. Sci. U. S. A.
117
(
23
),
12558
12563
(
2020
).
12.
J. I.
Levene
,
M. K.
Mann
,
R. M.
Margolis
, and
A.
Milbrandt
, “
An analysis of hydrogen production from renewable electricity sources
,”
Sol. Energy
81
(
6
),
773
780
(
2007
).
13.
L.
Sun
, “
Material libraries for electrocatalytic overall water splitting
,”
Coord. Chem. Rev.
444
,
214049
(
2021
).
14.
S.
Sharma
and
S. K.
Ghoshal
, “
Hydrogen the future transportation fuel: From production to applications
,”
Renewable Sustainable Energy Rev.
43
,
1151
1158
(
2015
).
15.
Y.
Yan
,
B. Y.
Xia
,
B.
Zhao
, and
X.
Wang
, “
A review on noble-metal-free bifunctional heterogeneous catalysts for overall electrochemical water splitting
,”
J. Mater. Chem. A
4
(
45
),
17587
17603
(
2016
).
16.
A.
Eftekhari
, “
Electrocatalysts for hydrogen evolution reaction
,”
Int. J. Hydrogen Energy
42
(
16
),
11053
11077
(
2017
).
17.
I.
Roger
,
M. A.
Shipman
, and
M. D.
Symes
, “
Earth-abundant catalysts for electrochemical and photoelectrochemical water splitting
,”
Nat. Rev. Chem.
1
(
1
),
0003
(
2017
).
18.
X.
Liu
,
M.
Gong
,
S.
Deng
,
T.
Zhao
,
J.
Zhang
, and
D.
Wang
, “
Recent advances on metal alkoxide-based electrocatalysts for water splitting
,”
J. Mater. Chem. A
8
(
20
),
10130
10149
(
2020
).
19.
Y.
Peng
,
C. H.
Mak
,
J.-J.
Kai
,
M.
Du
,
L.
Ji
,
M.
Yuan
,
X.
Zou
,
H.-H.
Shen
,
S. P.
Santoso
,
J. C.
Colmenares
, and
H.-Y.
Hsu
, “
Recent progress on post-synthetic treatments of photoelectrodes for photoelectrochemical water splitting
,”
J. Mater. Chem. A
9
(
47
),
26628
26649
(
2021
).
20.
X.
Shang
,
B.
Dong
,
Y.-M.
Chai
, and
C.-G.
Liu
, “
In-situ electrochemical activation designed hybrid electrocatalysts for water electrolysis
,”
Sci. Bull.
63
(
13
),
853
876
(
2018
).
21.
P.
Chandran
, “
Study on the characteristics of hydrogen bubble formation and its transport during electrolysis of water
,”
Chem. Eng. Sci.
138
,
99
(
2015
).
22.
Y.
Luo
,
Z.
Zhang
,
M.
Chhowalla
, and
B.
Liu
, “
Recent advances in design of electrocatalysts for high‐current‐density water splitting
,”
Adv. Mater.
34
(
16
),
2108133
(
2022
).
23.
A.
Ambrosi
,
R. R. S.
Shi
, and
R. D.
Webster
, “
3D-printing for electrolytic processes and electrochemical flow systems
,”
J. Mater. Chem. A
8
(
42
),
21902
21929
(
2020
).
24.
L.
Jiao
,
Y.-X.
Zhou
, and
H.-L.
Jiang
, “
Metal–organic framework-based CoP/reduced graphene oxide: High-performance bifunctional electrocatalyst for overall water splitting
,”
Chem. Sci.
7
(
3
),
1690
1695
(
2016
).
25.
Q.
Zhang
,
P.
Li
,
D.
Zhou
,
Z.
Chang
,
Y.
Kuang
, and
X.
Sun
, “
Superaerophobic ultrathin Ni-MO alloy nanosheet array from in situ topotactic reduction for hydrogen evolution reaction
,”
Small
13
(
41
),
1701648
(
2017
).
26.
J.
Ahn
,
Y. S.
Park
,
S.
Lee
,
J.
Yang
,
J.
Pyo
,
J.
Lee
,
G. H.
Kim
,
S. M.
Choi
, and
S. K.
Seol
, “
3D-printed NiFe-layered double hydroxide pyramid electrodes for enhanced electrocatalytic oxygen evolution reaction
,”
Sci. Rep.
12
(
1
),
346
(
2022
).
27.
A.
Sivanantham
,
P.
Ganesan
, and
S.
Shanmugam
, “
Hierarchical NiCo2S4 nanowire arrays supported on Ni foam: An efficient and durable bifunctional electrocatalyst for oxygen and hydrogen evolution reactions
,”
Adv. Funct. Mater.
26
(
26
),
4661
4672
(
2016
).
28.
J.
Huang
,
S.
Wang
,
J.
Nie
,
C.
Huang
,
X.
Zhang
,
B.
Wang
,
J.
Tang
,
C.
Du
,
Z.
Liu
, and
J.
Chen
, “
Active site and intermediate modulation of 3D CoSe2 nanosheet array on Ni foam by MO doping for high-efficiency overall water splitting in alkaline media
,”
Chem. Eng. J.
417
,
128055
(
2021
).
29.
T. H.
Lee
,
S. A.
Lee
,
H.
Park
,
M.-J.
Choi
,
D.
Lee
, and
H. W.
Jang
, “
Understanding the enhancement of the catalytic properties of goethite by transition metal doping: Critical role of O* formation energy relative to OH* and OOH*
,”
ACS Appl. Energy Mater.
3
(
2
),
1634
1643
(
2020
).
30.
Z.
Chen
,
Y.
Ha
,
Y.
Liu
,
H.
Wang
,
H.
Yang
,
H.
Xu
,
Y.
Li
, and
R.
Wu
, “
In situ formation of cobalt nitrides/graphitic carbon composites as efficient bifunctional electrocatalysts for overall water splitting
,”
ACS Appl. Mater. Interfaces
10
(
8
),
7134
7144
(
2018
).
31.
Z.-Y.
Yu
,
Y.
Duan
,
M.-R.
Gao
,
C.-C.
Lang
,
Y.-R.
Zheng
, and
S.-H.
Yu
, “
A one-dimensional porous carbon-supported Ni/MO2C dual catalyst for efficient water splitting
,”
Chem. Sci.
8
(
2
),
968
973
(
2017
).
32.
C. N. R.
Rao
and
M.
Chhetri
, “
Borocarbonitrides as metal-free catalysts for the hydrogen evolution reaction
,”
Adv. Mater.
31
(
13
),
1803668
(
2019
).
33.
Z. Y.
Yu
,
Y.
Duan
,
X. Y.
Feng
,
X.
Yu
,
M. R.
Gao
, and
S. H.
Yu
, “
Clean and affordable hydrogen fuel from alkaline water splitting: Past, recent progress, and future prospects
,”
Adv. Mater.
33
(
31
),
2007100
(
2021
).
34.
M.
Attaran
, “
The rise of 3-D printing: The advantages of additive manufacturing over traditional manufacturing
,”
Bus. Horiz.
60
(
5
),
677
688
(
2017
).
35.
C.-Y.
Lee
,
A. C.
Taylor
,
A.
Nattestad
,
S.
Beirne
, and
G. G.
Wallace
, “
3D printing for electrocatalytic applications
,”
Joule
3
(
8
),
1835
1849
(
2019
).
36.
A.
Ambrosi
and
M.
Pumera
, “
3D-printing technologies for electrochemical applications
,”
Chem. Soc. Rev.
45
(
10
),
2740
2755
(
2016
).
37.
M. P.
Browne
,
E.
Redondo
, and
M.
Pumera
, “
3D printing for electrochemical energy applications
,”
Chem. Rev.
120
(
5
),
2783
2810
(
2020
).
38.
J.
Fan
,
L.
Zhang
,
S.
Wei
,
Z.
Zhang
,
S.-K.
Choi
,
B.
Song
, and
Y.
Shi
, “
A review of additive manufacturing of metamaterials and developing trends
,”
Mater. Today
50
,
303
328
(
2021
).
39.
M.
Khorasani
,
J.
Loy
,
A. H.
Ghasemi
,
E.
Sharabian
,
M.
Leary
,
H.
Mirafzal
,
P.
Cochrane
,
B.
Rolfe
, and
I.
Gibson
, “
A review of industry 4.0 and additive manufacturing synergy
,”
Rapid Prototyping J.
28
(
8
),
1462
1475
(
2022
).
40.
Z.
Liu
,
D.
Zhao
,
P.
Wang
,
M.
Yan
,
C.
Yang
,
Z.
Chen
,
J.
Lu
, and
Z.
Lu
, “
Additive manufacturing of metals: Microstructure evolution and multistage control
,”
J. Mater. Sci. Technol.
100
,
224
236
(
2022
).
41.
A.
Zhakeyev
,
P.
Wang
,
L.
Zhang
,
W.
Shu
,
H.
Wang
, and
J.
Xuan
, “
Additive manufacturing: Unlocking the evolution of energy materials
,”
Adv. Sci.
4
(
10
),
1700187
(
2017
).
42.
C.
Culmone
,
G.
Smit
, and
P.
Breedveld
, “
Additive manufacturing of medical instruments: A state-of-the-art review
,”
Addit. Manuf.
27
,
461
473
(
2019
).
43.
E. M.
Maines
,
M. K.
Porwal
,
C. J.
Ellison
, and
T. M.
Reineke
, “
Sustainable advances in SLA/DLP 3D printing materials and processes
,”
Green Chem.
23
(
18
),
6863
6897
(
2021
).
44.
G.
Le Fer
and
M. L.
Becker
, “
4D printing of resorbable complex shape-memory poly(propylene fumarate) star scaffolds
,”
ACS Appl. Mater. Interfaces
12
(
20
),
22444
22452
(
2020
).
45.
I.
Tolosa
,
F.
Garciandía
,
F.
Zubiri
,
F.
Zapirain
, and
A.
Esnaola
, “
Study of mechanical properties of AISI 316 stainless steel processed by ‘selective laser melting’, following different manufacturing strategies
,”
Int. J. Adv. Manuf. Technol.
51
(
5–8
),
639
647
(
2010
).
46.
J.
Wilkes
,
Y. C.
Hagedorn
,
W.
Meiners
, and
K.
Wissenbach
, “
Additive manufacturing of ZrO2‐Al2O3 ceramic components by selective laser melting
,”
Rapid Prototyping J.
19
(
1
),
51
57
(
2013
).
47.
H.
Attar
,
M.
Bönisch
,
M.
Calin
,
L.-C.
Zhang
,
S.
Scudino
, and
J.
Eckert
, “
Selective laser melting of in situ titanium–titanium boride composites: Processing, microstructure and mechanical properties
,”
Acta Mater.
76
,
13
22
(
2014
).
48.
E. O.
Olakanmi
,
R. F.
Cochrane
, and
K. W.
Dalgarno
, “
A review on selective laser sintering/melting (SLS/SLM) of aluminium alloy powders: Processing, microstructure, and properties
,”
Prog. Mater. Sci.
74
,
401
477
(
2015
).
49.
M.
Li
,
W.
Du
,
A.
Elwany
,
Z.
Pei
, and
C.
Ma
, “
Metal binder jetting additive manufacturing: A literature review
,”
J. Manuf. Sci. Eng.
142
(
9
),
090801
(
2020
).
50.
M.
Ziaee
and
N. B.
Crane
, “
Binder jetting: A review of process, materials, and methods
,”
Addit. Manuf.
28
,
781
801
(
2019
).
51.
M.
Galati
,
L.
Iuliano
,
A.
Salmi
, and
E.
Atzeni
, “
Modelling energy source and powder properties for the development of a thermal FE model of the EBM additive manufacturing process
,”
Addit. Manuf.
14
,
49
59
(
2017
).
52.
L.-C.
Zhang
,
Y.
Liu
,
S.
Li
, and
Y.
Hao
, “
Additive manufacturing of titanium alloys by electron beam melting: A review
,”
Adv. Eng. Mater.
20
(
5
),
1700842
(
2018
).
53.
X.
Peng
,
X.
Kuang
,
D. J.
Roach
,
Y.
Wang
,
C. M.
Hamel
,
C.
Lu
, and
H. J.
Qi
, “
Integrating digital light processing with direct ink writing for hybrid 3D printing of functional structures and devices
,”
Addit. Manuf.
40
,
101911
(
2021
).
54.
S.
Chandrasekaran
,
B.
Yao
,
T.
Liu
,
W.
Xiao
,
Y.
Song
,
F.
Qian
,
C.
Zhu
,
E. B.
Duoss
,
C. M.
Spadaccini
,
Y.
Li
, and
M. A.
Worsley
, “
Direct ink writing of organic and carbon aerogels
,”
Mater. Horiz.
5
(
6
),
1166
1175
(
2018
).
55.
H.
Gong
,
D.
Snelling
,
K.
Kardel
, and
A.
Carrano
, “
Comparison of stainless steel 316L parts made by FDM- and SLM-based additive manufacturing processes
,”
JOM
71
(
3
),
880
885
(
2019
).
56.
T. J.
Gordelier
,
P. R.
Thies
,
L.
Turner
, and
L.
Johanning
, “
Optimising the FDM additive manufacturing process to achieve maximum tensile strength: A state-of-the-art review
,”
Rapid Prototyping J.
25
(
6
),
953
971
(
2019
).
57.
D.
Behera
and
M.
Cullinan
, “
Current challenges and potential directions towards precision microscale additive manufacturing—Part I: Direct ink writing/jetting processes
,”
Precis. Eng.
68
,
326
337
(
2021
).
58.
Y.
Li
,
C.
Li
,
X.
Zhang
,
Y.
Wang
,
Y.
Tan
,
S.
Chang
,
Z.
Chen
,
G.
Fu
,
Z.
Kou
,
A.
Stefan
,
X.
Xu
, and
J.
Ding
, “
Incorporating metal precursors towards a library of high-resolution metal parts by stereolithography
,”
Appl. Mater. Today
29
,
101553
(
2022
).
59.
X.
Su
,
X.
Li
,
C. Y. A.
Ong
,
T. S.
Herng
,
Y.
Wang
,
E.
Peng
, and
J.
Ding
, “
Metallization of 3D printed polymers and their application as a fully functional water-splitting system
,”
Adv. Sci.
6
(
6
),
1801670
(
2019
).
60.
C.-Y.
Lee
,
A. C.
Taylor
,
S.
Beirne
, and
G. G.
Wallace
, “
3D-printed conical arrays of TiO2 electrodes for enhanced photoelectrochemical water splitting
,”
Adv. Energy Mater.
7
(
21
),
1701060
(
2017
).
61.
S.
Chang
,
Y.
Zhang
,
B.
Zhang
,
X.
Cao
,
L.
Zhang
,
X.
Huang
,
W.
Lu
,
C. Y. A.
Ong
,
S.
Yuan
,
C.
Li
,
Y.
Huang
,
K.
Zeng
,
L.
Li
,
W.
Yan
, and
J.
Ding
, “
Conductivity modulation of 3D‐printed shellular electrodes through embedding nanocrystalline intermetallics into amorphous matrix for ultrahigh-current oxygen evolution
,”
Adv. Energy Mater.
11
(
28
),
2100968
(
2021
).
62.
L. F.
Arenas
,
C.
Ponce de León
, and
F. C.
Walsh
, “
3D-printed porous electrodes for advanced electrochemical flow reactors: A Ni/stainless steel electrode and its mass transport characteristics
,”
Electrochem. Commun.
77
,
133
137
(
2017
).
63.
S.
Chang
,
X.
Huang
,
C. Y.
Aaron Ong
,
L.
Zhao
,
L.
Li
,
X.
Wang
, and
J.
Ding
, “
High loading accessible active sites via designable 3D-printed metal architecture towards promoting electrocatalytic performance
,”
J. Mater. Chem. A
7
(
31
),
18338
18347
(
2019
).
64.
A.
Ambrosi
and
M.
Pumera
, “
Self-contained polymer/metal 3D printed electrochemical platform for tailored water splitting
,”
Adv. Funct. Mater.
28
(
27
),
1700655
(
2018
).
65.
X.
Huang
,
S.
Chang
,
W. S. V.
Lee
,
J.
Ding
, and
J. M.
Xue
, “
Three-dimensional printed cellular stainless steel as a high-activity catalytic electrode for oxygen evolution
,”
J. Mater. Chem. A
5
(
34
),
18176
18182
(
2017
).
66.
R. A.
Márquez
,
K.
Kawashima
,
Y. J.
Son
,
R.
Rose
,
L. A.
Smith
,
N.
Miller
,
O. A.
Carrasco Jaim
,
H.
Celio
, and
C. B.
Mullins
, “
Tailoring 3D-printed electrodes for enhanced water splitting
,”
ACS Appl. Mater. Interfaces
14
,
42153
(
2022
).
67.
A.
Azhari
,
E.
Marzbanrad
,
D.
Yilman
,
E.
Toyserkani
, and
M. A.
Pope
, “
Binder-jet powder-bed additive manufacturing (3D printing) of thick graphene-based electrodes
,”
Carbon
119
,
257
266
(
2017
).
68.
J.
Mo
,
R. R.
Dehoff
,
W. H.
Peter
,
T. J.
Toops
,
J. B.
Green
, and
F.-Y.
Zhang
, “
Additive manufacturing of liquid/gas diffusion layers for low-cost and high-efficiency hydrogen production
,”
Int. J. Hydrogen Energy
41
(
4
),
3128
3135
(
2016
).
69.
I.
Sullivan
,
H.
Zhang
,
C.
Zhu
,
M.
Wood
,
A. J.
Nelson
,
S. E.
Baker
,
C. M.
Spadaccini
,
T.
Van Buuren
,
M.
Lin
,
E. B.
Duoss
,
S.
Liang
, and
C.
Xiang
, “
3D printed nickel–molybdenum-based electrocatalysts for hydrogen evolution at low overpotentials in a flow-through configuration
,”
ACS Appl. Mater. Interfaces
13
(
17
),
20260
20268
(
2021
).
70.
M.
Peng
,
D.
Shi
,
Y.
Sun
,
J.
Cheng
,
B.
Zhao
,
Y.
Xie
,
J.
Zhang
,
W.
Guo
,
Z.
Jia
,
Z.
Liang
, and
L.
Jiang
, “
3D printed mechanically robust graphene/CNT electrodes for highly efficient overall water splitting
,”
Adv. Mater.
32
(
23
),
1908201
(
2020
).
71.
T.
Gao
,
Z.
Zhou
,
J.
Yu
,
J.
Zhao
,
G.
Wang
,
D.
Cao
,
B.
Ding
, and
Y.
Li
, “
3D printing of tunable energy storage devices with both high areal and volumetric energy densities
,”
Adv. Energy Mater.
9
(
8
),
1802578
(
2019
).
72.
J.
Ahn
,
S.
Lee
,
J. H.
Kim
,
M.
Wajahat
,
H. H.
Sim
,
J.
Bae
,
J.
Pyo
,
M.
Jahandar
,
D. C.
Lim
, and
S. K.
Seol
, “
3D-printed Cu2O photoelectrodes for photoelectrochemical water splitting
,”
Nanoscale Adv.
2
(
12
),
5600
5606
(
2020
).
73.
Z.
Qi
,
J.
Ye
,
W.
Chen
,
J.
Biener
,
E. B.
Duoss
,
C. M.
Spadaccini
,
M. A.
Worsley
, and
C.
Zhu
, “
3D-printed, superelastic polypyrrole–graphene electrodes with ultrahigh areal capacitance for electrochemical energy storage
,”
Adv. Mater. Technol.
3
(
7
),
1800053
(
2018
).
74.
Y.
Chen
,
Y.
Cai
,
R.
Yu
,
X.
Pan
,
J.
Zhang
,
Z.
Wang
,
X.
Xiao
,
J.
Wu
,
L.
Xu
, and
L.
Mai
, “
Submerged-plant-inspired five-level-synergetic hierarchical single-Fe-atom-doped micro-electrodes for high-performance multifunctional electrocatalysis
,”
Chem. Eng. J.
446
,
136804
(
2022
).
75.
J. P.
Hughes
,
P. L.
dos Santos
,
M. P.
Down
,
C. W.
Foster
,
J. A.
Bonacin
,
E. M.
Keefe
,
S. J.
Rowley-Neale
, and
C. E.
Banks
, “
Single step additive manufacturing (3D printing) of electrocatalytic anodes and cathodes for efficient water splitting
,”
Sustainable Energy Fuels
4
(
1
),
302
311
(
2020
).
76.
J. C.
Bui
,
J. T.
Davis
, and
D. V.
Esposito
, “
3D-printed electrodes for membraneless water electrolysis
,”
Sustainable Energy Fuels
4
(
1
),
213
225
(
2020
).
77.
C.
Iffelsberger
,
D.
Rojas
, and
M.
Pumera
, “
Photo-responsive doped 3D-printed copper electrodes for water splitting: Refractory one-pot doping dramatically enhances the performance
,”
J. Phys. Chem. C
126
(
21
),
9016
9026
(
2022
).
78.
J. R.
Hudkins
,
D. G.
Wheeler
,
B.
Peña
, and
C. P.
Berlinguette
, “
Rapid prototyping of electrolyzer flow field plates
,”
Energy Environ. Sci.
9
(
11
),
3417
3423
(
2016
).
79.
R. A.
Márquez-Montes
,
V. H.
Collins-Martínez
,
I.
Pérez-Reyes
,
D.
Chávez-Flores
,
O. A.
Graeve
, and
V. H.
Ramos-Sánchez
, “
Electrochemical engineering assessment of a novel 3D-printed filter-press electrochemical reactor for multipurpose laboratory applications
,”
ACS Sustainable Chem. Eng.
8
(
9
),
3896
3905
(
2020
).
80.
L.
Poltorak
,
K.
Rudnicki
,
V.
Kolivoška
,
T.
Sebechlebská
,
P.
Krzyczmonik
, and
S.
Skrzypek
, “
Electrochemical study of ephedrine at the polarized liquid-liquid interface supported with a 3D printed cell
,”
J. Hazard Mater.
402
,
123411
(
2021
).
81.
J.
You
,
R. J.
Preen
,
L.
Bull
,
J.
Greenman
, and
I.
Ieropoulos
, “
3D printed components of microbial fuel cells: Towards monolithic microbial fuel cell fabrication using additive layer manufacturing
,”
Sustainable Energy Technol. Assess.
19
,
94
101
(
2017
).
82.
R. A.
Marquez-Montes
,
K.
Kawashima
,
Y. J.
Son
,
J. A.
Weeks
,
H. H.
Sun
,
H.
Celio
,
V. H.
Ramos-Sánchez
, and
C. B.
Mullins
, “
Mass transport-enhanced electrodeposition of Ni–S–P–O films on nickel foam for electrochemical water splitting
,”
J. Mater. Chem. A
9
(
12
),
7736
7749
(
2021
).
83.
G.
Yang
,
S.
Yu
,
Z.
Kang
,
Y.
Dohrmann
,
G.
Bender
,
B. S.
Pivovar
,
J. B.
Green
,
S. T.
Retterer
,
D. A.
Cullen
, and
F.-Y.
Zhang
, “
A novel PEMEC with 3D printed non-conductive bipolar plate for low-cost hydrogen production from water electrolysis
,”
Energy Convers. Manag.
182
,
108
116
(
2019
).
84.
G.
Yang
,
J.
Mo
,
Z.
Kang
,
F. A.
List
,
J. B.
Green
,
S. S.
Babu
, and
F.-Y.
Zhang
, “
Additive manufactured bipolar plate for high-efficiency hydrogen production in proton exchange membrane electrolyzer cells
,”
Int. J. Hydrogen Energy
42
(
21
),
14734
14740
(
2017
).
85.
G.
Yang
,
J.
Mo
,
Z.
Kang
,
Y.
Dohrmann
,
F. A.
List
,
J. B.
Green
,
S. S.
Babu
, and
F.-Y.
Zhang
, “
Fully printed and integrated electrolyzer cells with additive manufacturing for high-efficiency water splitting
,”
Appl. Energy
215
,
202
210
(
2018
).
86.
F. P. W.
Melchels
,
J.
Feijen
, and
D. W.
Grijpma
, “
A review on stereolithography and its applications in biomedical engineering
,”
Biomaterials
31
(
24
),
6121
6130
(
2010
).
87.
G. A.
Appuhamillage
,
N.
Chartrain
,
V.
Meenakshisundaram
,
K. D.
Feller
,
C. B.
Williams
, and
T. E.
Long
, “
110th anniversary: Vat photopolymerization-based additive manufacturing: Current trends and future directions in materials design
,”
IN Eng. Chem. Res.
58
(
33
),
15109
15118
(
2019
).
88.
Y.
Sano
,
R.
Matsuzaki
,
M.
Ueda
,
A.
Todoroki
, and
Y.
Hirano
, “
3D printing of discontinuous and continuous fibre composites using stereolithography
,”
Addit. Manuf.
24
,
521
527
(
2018
).
89.
M. M.
Hanon
,
A.
Ghaly
,
L.
Zsidai
,
Z.
Szakál
,
I.
Szabó
, and
L.
Kátai
, “
Investigations of the mechanical properties of DLP 3D printed graphene/resin composites
,”
Acta Polytech. Hung.
18
(
8
),
143
161
(
2021
).
90.
H.
Zhang
,
Y.
Xiong
,
L.
Dong
,
Y.
Shen
,
H.
Hu
,
H.
Gao
,
S.
Zhao
, and
X.
Li
, “
Microstructural, mechanical properties and strengthening mechanism of DLP produced β-tricalcium phosphate scaffolds by incorporation of MgO/ZnO/58S bioglass
,”
Ceram. Int.
47
(
18
),
25863
25874
(
2021
).
91.
H.
Kadry
,
S.
Wadnap
,
C.
Xu
, and
F.
Ahsan
, “
Digital light processing (DLP) 3D-printing technology and photoreactive polymers in fabrication of modified-release tablets
,”
Eur. J. Pharm. Sci.
135
,
60
67
(
2019
).
92.
J. Z.
Manapat
,
Q.
Chen
,
P.
Ye
, and
R. C.
Advincula
, “
3D printing of polymer nanocomposites via stereolithography
,”
Macromol. Mater. Eng.
302
(
9
),
1600553
(
2017
).
93.
C. Y.
Yap
,
C. K.
Chua
,
Z. L.
Dong
,
Z. H.
Liu
,
D. Q.
Zhang
,
L. E.
Loh
, and
S. L.
Sing
, “
Review of selective laser melting: Materials and applications
,”
Appl. Phys. Rev.
2
(
4
),
041101
(
2015
).
94.
F.
Fina
,
A.
Goyanes
,
S.
Gaisford
, and
A. W.
Basit
, “
Selective laser sintering (SLS) 3D printing of medicines
,”
Int. J. Pharm.
529
(
1–2
),
285
293
(
2017
).
95.
A.
Lores
,
N.
Azurmendi
,
I.
Agote
, and
E.
Zuza
, “
A review on recent developments in binder jetting metal additive manufacturing: Materials and process characteristics
,”
Powder Metall.
62
(
5
),
267
296
(
2019
).
96.
J.
Parthasarathy
,
B.
Starly
,
S.
Raman
, and
A.
Christensen
, “
Mechanical evaluation of porous titanium (Ti6Al4V) structures with electron beam melting (EBM)
,”
J. Mech. Behav. Biomed. Mater.
3
(
3
),
249
259
(
2010
).
97.
S.
Ng
,
R.
Zazpe
,
J.
Rodriguez-Pereira
,
J.
Michalička
,
J. M.
Macak
, and
M.
Pumera
, “
Atomic layer deposition of photoelectrocatalytic material on 3D-printed nanocarbon structures
,”
J. Mater. Chem. A
9
(
18
),
11405
11414
(
2021
).
98.
K. A.
Novčić
,
C.
Iffelsberger
,
S.
Ng
, and
M.
Pumera
, “
Local electrochemical activity of transition metal dichalcogenides and their heterojunctions on 3D-printed nanocarbon surfaces
,”
Nanoscale
13
(
10
),
5324
5332
(
2021
).
99.
C.
Iffelsberger
,
C. W.
Jellett
, and
M.
Pumera
, “
3D printing temperature tailors electrical and electrochemical properties through changing inner distribution of graphite/polymer
,”
Small
17
(
24
),
2101233
(
2021
).
100.
K.
Ghosh
,
S.
Ng
,
C.
Iffelsberger
, and
M.
Pumera
, “
2D MoS2/carbon/polylactic acid filament for 3D printing: Photo and electrochemical energy conversion and storage
,”
Appl. Mater. Today
26
,
101301
(
2022
).
101.
J.
Muñoz
,
C.
Iffelsberger
,
E.
Redondo
, and
M.
Pumera
, “
Design of bimetallic 3D-printed electrocatalysts via galvanic replacement to enhance energy conversion systems
,”
Appl. Catal., B
316
,
121609
(
2022
).
102.
M. P.
Browne
,
V.
Urbanova
,
J.
Plutnar
,
F.
Novotný
, and
M.
Pumera
, “
Inherent impurities in 3D-printed electrodes are responsible for catalysis towards water splitting
,”
J. Mater. Chem. A
8
(
3
),
1120
1126
(
2020
).
103.
M. P.
Browne
and
M.
Pumera
, “
Impurities in graphene/PLA 3D-printing filaments dramatically influence the electrochemical properties of the devices
,”
Chem. Commun.
55
(
58
),
8374
8377
(
2019
).
104.
F.
Ning
,
W.
Cong
,
J.
Qiu
,
J.
Wei
, and
S.
Wang
, “
Additive manufacturing of carbon fiber reinforced thermoplastic composites using fused deposition modeling
,”
Composites, Part B
80
,
369
378
(
2015
).
105.
L.
del-Mazo-Barbara
and
M.-P.
Ginebra
, “
Rheological characterisation of ceramic inks for 3D direct ink writing: A review
,”
J. Eur. Ceram. Soc.
41
(
16
),
18
33
(
2021
).
106.
H.
Chen
,
X.
Wang
,
F.
Xue
,
Y.
Huang
,
K.
Zhou
, and
D.
Zhang
, “
3D printing of SiC ceramic: Direct ink writing with a solution of preceramic polymers
,”
J. Eur. Ceram. Soc.
38
(
16
),
5294
5300
(
2018
).
107.
N. M.
Farandos
,
L.
Kleiminger
,
T.
Li
,
A.
Hankin
, and
G. H.
Kelsall
, “
Three-dimensional inkjet printed solid oxide electrochemical reactors. I. Yttria-stabilized zirconia electrolyte
,”
Electrochim. Acta
213
,
324
331
(
2016
).
108.
C.-Y.
Lee
,
A. C.
Taylor
,
S.
Beirne
, and
G. G.
Wallace
, “
A 3D-printed electrochemical water splitting cell
,”
Adv. Mater. Technol.
4
(
10
),
1900433
(
2019
).
109.
A.
Ambrosi
and
M.
Pumera
, “
Multimaterial 3D-printed water electrolyzer with earth-abundant electrodeposited catalysts
,”
ACS Sustainable Chem. Eng.
6
(
12
),
16968
16975
(
2018
).
110.
G.
Chisholm
,
P. J.
Kitson
,
N. D.
Kirkaldy
,
L. G.
Bloor
, and
L.
Cronin
, “
3D printed flow plates for the electrolysis of water: An economic and adaptable approach to device manufacture
,”
Energy Environ. Sci.
7
(
9
),
3026
3032
(
2014
).
111.
G. D.
O’Neil
,
C. D.
Christian
,
D. E.
Brown
, and
D. V.
Esposito
, “
Hydrogen production with a simple and scalable membraneless electrolyzer
,”
J. Electrochem. Soc.
163
(
11
),
F3012
F3019
(
2016
).
112.
M. P.
Browne
,
J.
Dodwell
,
F.
Novotny
,
S.
Jaśkaniec
,
P. R.
Shearing
,
V.
Nicolosi
,
D. J. L.
Brett
, and
M.
Pumera
, “
Oxygen evolution catalysts under proton exchange membrane conditions in a conventional three electrode cell vs. electrolyser device: A comparison study and a 3D-printed electrolyser for academic labs
,”
J. Mater. Chem. A
9
(
14
),
9113
9123
(
2021
).