Chemi-sorbed versus physi-sorbed surface charge and its impact on electrokinetic transport: carbon versus boron-nitride surface

Abstract

The possibility to control 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 $p$H-dependence of experimental transport coefficients point 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 physi- 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 $\zeta$-potential are less affected . The analysis of the MD results for the surface conductivity and $\zeta$-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 of the slip length with increasing titratable surface charge density.

References in corpus (6)

• Friction of Water on Graphene and Hexagonal Boron Nitride from ab initio Methods: Very Different Slippage Despite Very Similar Interface Structures
• Fluids at the Nanoscale: from continuum to sub-continuum transport
• Molecular streaming and its voltage control in ångström scale channels
• Liquid friction on charged surfaces: from hydrodynamic slippage to electrokinetics
• Electro-hydrodynamics near Hydrophobic Surfaces
• Interfacial transport with mobile surface charges and consequences for ionic transport in carbon nanotubes

Cited by in corpus (6)

• In-plane dielectric constant and conductivity of confined water
• Transport of ions in hydrophobic nanotubes
• Complex coupling between surface charge and thermo-osmotic phenomena
• Slippery and mobile hydrophobic electrokinetics: from single walls to nanochannels
• Donnan equilibrium in charged slit-pores from a hybrid nonequilibrium Molecular Dynamics / Monte Carlo method with ions and solvent exchange
• Enhanced zeta potentials caused by surface ion mobilities