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Viscous interfacial layer formation causes electroosmotic mobility reversal in monovalent electrolytes
Majid Rezaei1, Ahmad Reza Azimian, Ahmad Reza Pishevar
1Department of Mechanical Engineering, Isfahan University of Technology, 8415683111 Isfahan, Iran. Majid-rezaei@me.iut.ac.ir.
Physical Chemistry Chemical Physics : PCCP
|August 25, 2018
Summary
Molecular dynamics simulations reveal how ion redistribution near charged surfaces alters viscosity and electroosmotic mobility. Increased surface charge leads to charge inversion and mobility reversal, crucial for understanding interfacial phenomena.
Area of Science:
- Physical Chemistry
- Surface Science
- Computational Nanoscience
Background:
- Understanding ion behavior at charged interfaces is critical for electrochemical systems.
- Interfacial hydrodynamics significantly influence phenomena like electroosmosis.
Purpose of the Study:
- To investigate ion density, shear viscosity, and electroosmotic mobility at a charged solid-liquid interface.
- To elucidate the relationship between surface charge density and interfacial properties.
Main Methods:
- Utilized molecular dynamics simulations for an aqueous monovalent electrolyte near a charged surface.
- Analyzed ion distribution, viscosity, and electroosmotic mobility as a function of surface charge density.
Main Results:
- Increased surface charge density causes ion displacement, increasing viscosity in the outer Helmholtz layer and leading to charge inversion.
- Ion redistribution results in reversal of electroosmotic mobility, occurring at a different surface charge density than charge inversion.
- Interfacial viscosity's spatial dependence is essential for describing mobility reversal, not just slip boundary conditions.
Conclusions:
- Surface-charge-dependent interfacial hydrodynamics dictate electroosmotic mobility reversal.
- Accurate modeling requires considering the spatial variation of viscosity at charged interfaces.
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