Free Energy of Water Dissociation at the Water - TiO2 Interface from Ab Initio Deep Potential Molecular Dynamics*

TiO2 is a widely used photocatalyst in science and technology and its interface with water is important in fields ranging from geochemistry to biomedicine. Yet, it is still unclear whether water adsorbs in molecular or dissociated form on TiO2 even for the case of well-defined crystalline surfaces. To address this issue, we simulated the TiO2-water interface using molecular dynamics with an ab initio-based deep neural network potential. Our simulations show a 6% equilibrium fraction of water dissociation at room temperature, in agreement with enhanced sampling estimates of the dissociation free energy [1]. Due to the relevance of surface hydroxyl groups to the surface chemistry of TiO2, our model might be key to understanding phenomena ranging from surface functionalization to photocatalytic mechanisms.
Refs: [1] Marcos F. Calegari Andrade, Hsin-Yu Ko, Linfeng Zhang, Roberto Car and Annabella Selloni, submitted.