The possibility of controlling electrokinetic transport through carbon and hexagonal boron nitride (hBN) nanotubes has recently opened new avenues for nanofluidic approaches to face outstanding challenges such as energy production and conversion or water desalination. The pH-dependence of experimental transport coefficients points to the sorption of hydroxide ions as the microscopic origin of the surface charge and recent ab initio calculations suggest that these ions behave differently on carbon and hBN, with only physisorption on the former and both physisorption and chemisorption on the latter. Using classical non-equilibrium molecular dynamics simulations of interfaces between an aqueous electrolyte and three models of hBN and graphite surfaces, we demonstrate the major influence of the sorption mode of hydroxide ions on the interfacial transport properties. Physisorbed surface charge leads to a considerable enhancement of the surface conductivity as compared to its chemisorbed counterpart, while values of the ζ-potential are less affected. The analysis of the MD results for the surface conductivity and ζ-potential in the framework of Poisson–Boltzmann–Stokes theory, as is usually done to analyze experimental data, further confirms the importance of taking into account both the mobility of surface hydroxide ions and the decrease in the slip length with increasing titratable surface charge density.
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28 January 2022
Research Article|
January 24 2022
Chemisorbed vs physisorbed surface charge and its impact on electrokinetic transport: Carbon vs boron nitride surface
Etienne Mangaud
;
Etienne Mangaud
1
Univ Gustave Eiffel, Univ Paris Est Creteil, CNRS, UMR 8208, MSME
, F-77454 Marne-la-Vallée, France
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Marie-Laure Bocquet
;
Marie-Laure Bocquet
2
PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS
, 75005 Paris, France
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Lydéric Bocquet
;
Lydéric Bocquet
3
Laboratoire de Physique de l’Ecole normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris
, 75005 Paris, France
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Benjamin Rotenberg
Benjamin Rotenberg
a)
4
Sorbonne Université, CNRS, Physicochimie des électrolytes et Nanosystèmes Interfaciaux
, F-75005 Paris, France
a)Author to whom correspondence should be addressed: benjamin.rotenberg@sorbonne-universite.fr
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a)Author to whom correspondence should be addressed: benjamin.rotenberg@sorbonne-universite.fr
J. Chem. Phys. 156, 044703 (2022)
Article history
Received:
October 11 2021
Accepted:
January 04 2022
Citation
Etienne Mangaud, Marie-Laure Bocquet, Lydéric Bocquet, Benjamin Rotenberg; Chemisorbed vs physisorbed surface charge and its impact on electrokinetic transport: Carbon vs boron nitride surface. J. Chem. Phys. 28 January 2022; 156 (4): 044703. https://doi.org/10.1063/5.0074808
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