(387e) Dynamics Of Water And Adsorbed Ions At Oxide Surfaces: Simulation And Experimental Study

Molecular dynamics simulations were used to model the interface between oxide (TiO₂, SnO₂, SiO₂) surfaces and aqueous solutions, and interpret experimental data from quasi-elastic neutron scattering (QENS). Water diffusivity was studied in relation to various theoretical models and compared to available QENS data. It was found that there are three distinct layers of adsorbed water, whose dynamics are clearly reflected in the experimental results. Various diffusion modes were related to the properties of the hydrogen bond networks in the interfacial region. Ion adsorption and diffusion in the interface are closely connected to the formation of surface complexes and competition with water for available surface oxygens. Different ions included in our study (Li, Na, Rb, Ca, Sr, and Zn) prefer different surface complexes depending on their size and charge, and these complexes then determine ion diffusion. Analysis of these relations was performed. Viscosity in the interfacial region and its dependence on surface complexation was studied by the non-equilibrium molecular dynamics of Poisson and Couette flows between parallel plates of metal oxides.