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arXiv · 2201.11029

Charging of dielectric surfaces in contact with aqueous electrolyte -- the influence of CO$_2$

Peter Vogel·Nadir Möller·Muhammad Nawaz Qaisrani·Pravash Bista·Stefan Weber·Hans-Jürgen Butt·Benno Liebchen·Marialore Sulpizi·Thomas Palberg
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Abstract

The charge state of dielectric surfaces in aqueous environments is of fundamental and technological importance. Here, we study the influence of dissolved molecular CO$_2$ on the charging of three, chemically different surfaces (SiO$_2$, Polystyrene, Perfluorooctadecyltrichlorosilane). We determine their charge state from electrokinetic experiments. We compare an ideal, CO$_2$-free reference system to a system equilibrated against ambient CO$_2$ conditions. In the reference system, the salt-dependence is weakened for SiO$_2$ and inverted for the organic surfaces. We show that screening and pH-driven charge regulation alone cannot explain the observed effects. As additional cause, we tentatively suggest dielectric regulation of surface charges due to a diffusively adsorbed thin layer of molecular CO$_2$. The formation of such a dynamic layer even at the hydrophilic and partially ionized silica surfaces is supported by a minimal theoretical model and results from molecular simulations.

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Peter Vogel, Nadir Möller, Muhammad Nawaz Qaisrani, Pravash Bista, Stefan Weber, Hans-Jürgen Butt, Benno Liebchen, Marialore Sulpizi, Thomas Palberg. 2022-01-26. Charging of dielectric surfaces in contact with aqueous electrolyte -- the influence of CO$_2$. https://doi.org/10.1021/jacs.2c06793

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