Ultrafast dynamics of solvated electrons at anatase TiO2/H2O interface

Abstract

Solvated electrons are known to be the lowest energy charge transfer pathways at oxide/aqueous interface and the understanding of the electron transfer dynamics at the interface is fundamental for photochemical and photocatalytic processes. Taking anatase TiO2/H2O interface as a prototypical system, we perform time-dependent ab initio nonadiabatic molecular dynamics calculations to study the charge transfer dynamics of solvated electrons. For the static electronic properties, we find that the dangling H atoms can stabilize solvated electrons. A solvated electron band can be formed with one monolayer H2O adsorption. The energies of the solvated electron band minimum (SEBM) decrease when H2O adsorbs dissociatively. Moreover, the surface oxygen vacancies are also helpful for stabilizing the solvated electron band. For the dynamics behaviour, we find that the ultrafast charge transfer from SEBM to anatase TiO2 (1 0 1) surface at 100 K is mainly contributed by nonadiabatic mechanism. Comparing with rutile TiO2 (1 1 0) surface, the lifetime of solvated electron on anatase TiO2 (1 0 1) surface is longer, suggesting a better photocatalytic properties. Our results provide essential insights into the understanding of the charge transfer dynamics and the possible photocatalytic mechanism at oxide/aqueous interface.