Modeling the aqueous interface of amorphous TiO2 using deep potential molecular dynamics

ZT Ding and A Selloni, JOURNAL OF CHEMICAL PHYSICS, 159, 024706 (2023).

DOI: 10.1063/5.0157188

Amorphous titanium dioxide (a-TiO2) is widely used as a coating material in applications such as electrochemistry and self-cleaning surfaces where its interface with water has a central role. However, little is known about the structures of the a-TiO2 surface and aqueous interface, particularly at the microscopic level. In this work, we construct a model of the a-TiO2 surface via a cut-melt-and-quench procedure based on molecular dynamics simulations with deep neural network potentials (DPs) trained on density functional theory data. After interfacing the a-TiO2 surface with water, we investigate the structure and dynamics of the resulting system using a combination of DP-based molecular dynamics (DPMD) and ab initio molecular dynamics (AIMD) simulations. Both AIMD and DPMD simulations reveal that the distribution of water on the a-TiO2 surface lacks distinct layers normally found at the aqueous interface of crystalline TiO2, leading to an & SIM;10 times faster diffusion of water at the interface. Bridging hydroxyls (Ti-2-ObH) resulting from water dissociation decay several times more slowly than terminal hydroxyls (Ti-OwH) due to fast Ti-OwH2 ? Ti-OwH proton exchange events. These results provide a basis for a detailed understanding of the properties of a-TiO2 in electrochemical environments. Moreover, the procedure of generating the a-TiO2-interface employed here is generally applicable to studying the aqueous interfaces of amorphous metal oxides.

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