We present the coupling of two frameworks—the pseudo-open boundary simulation method known as constant potential molecular dynamics simulations (CμMD), combined with quantum mechanics/molecular dynamics (QMMD) calculations—to describe the properties of graphene electrodes in contact with electrolytes. The resulting CμQMMD model was then applied to three ionic solutions (LiCl, NaCl, and KCl in water) at bulk solution concentrations ranging from 0.5 M to 6 M in contact with a charged graphene electrode. The new approach we are describing here provides a simulation protocol to control the concentration of electrolyte solutions while including the effects of a fully polarizable electrode surface. Thanks to this coupling, we are able to accurately model both the electrode and solution side of the double layer and provide a thorough analysis of the properties of electrolytes at charged interfaces, such as the screening ability of the electrolyte and the electrostatic potential profile. We also report the calculation of the integral electrochemical double layer capacitance in the whole range of concentrations analyzed for each ionic species, while the quantum mechanical simulations provide access to the differential and integral quantum capacitance. We highlight how subtle features, such as the adsorption of potassium graphene or the tendency of the ions to form clusters contribute to the ability of graphene to store charge, and suggest implications for desalination.
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7 April 2023
Research Article|
April 04 2023
Constant chemical potential–quantum mechanical–molecular dynamics simulations of the graphene–electrolyte double layer
Special Collection:
Chemical Physics of Electrochemical Energy Materials
Nicodemo Di Pasquale
;
Nicodemo Di Pasquale
a)
(Conceptualization, Formal analysis, Funding acquisition, Investigation, Methodology, Supervision, Writing – original draft, Writing – review & editing)
1
Department of Chemical Engineering, Brunel University London
, Uxbridge UB8 3PH, United Kingdom
a)Author to whom correspondence should be addressed: nicodemo.dipasquale@brunel.ac.uk
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Aaron R. Finney
;
Aaron R. Finney
(Conceptualization, Data curation, Investigation, Methodology, Software, Writing – original draft, Writing – review & editing)
2
Department of Chemical Engineering, University College London
, London WC1E 7JE, United Kingdom
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Joshua D. Elliott
;
Joshua D. Elliott
(Conceptualization, Data curation, Investigation, Methodology, Software, Writing – original draft, Writing – review & editing)
3
Department of Chemical Engineering, University of Manchester
, Manchester M13 9PL, United Kingdom
4
Diamond Light Source, Harwell Science and Innovation Park
, Didcot, Oxfordshire OX11 8UQ, United Kingdom
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Paola Carbone
;
Paola Carbone
(Conceptualization, Formal analysis, Methodology, Resources, Writing – original draft, Writing – review & editing)
3
Department of Chemical Engineering, University of Manchester
, Manchester M13 9PL, United Kingdom
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Matteo Salvalaglio
Matteo Salvalaglio
(Conceptualization, Investigation, Methodology, Resources, Writing – original draft, Writing – review & editing)
2
Department of Chemical Engineering, University College London
, London WC1E 7JE, United Kingdom
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a)Author to whom correspondence should be addressed: nicodemo.dipasquale@brunel.ac.uk
Note: This paper is part of the JCP Special Topic on Chemical Physics of Electrochemical Energy Materials.
J. Chem. Phys. 158, 134714 (2023)
Article history
Received:
December 09 2022
Accepted:
March 13 2023
Citation
Nicodemo Di Pasquale, Aaron R. Finney, Joshua D. Elliott, Paola Carbone, Matteo Salvalaglio; Constant chemical potential–quantum mechanical–molecular dynamics simulations of the graphene–electrolyte double layer. J. Chem. Phys. 7 April 2023; 158 (13): 134714. https://doi.org/10.1063/5.0138267
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