Correlated electron–nuclear dynamics of photoinduced water dissociation on rutile TiO2

Abstract

Elucidating the mechanism of photoinduced water splitting on TiO2 is important for advancing the understanding of photocatalysis and the ability to control photocatalytic surface reactions. However, incomplete experimental information and complex coupled electron–nuclear motion make the microscopic understanding challenging. Here we analyse the atomic-scale pathways of photogenerated charge carrier transport and photoinduced water dissociation at the prototypical water–rutile TiO2(110) interface using first-principles dynamics simulations. Two distinct mechanisms are observed. Field-initiated electron migration leads to adsorbed water dissociation via proton transfer to a surface bridging oxygen. In the other pathway, adsorbed water dissociation occurs via proton donation to a second-layer water molecule coupled to photoexcited-hole transfer promoted by in-plane surface lattice distortions. Two stages of non-adiabatic in-plane lattice motion—expansion and recovery—are observed, which are closely associated with population changes in Ti3d orbitals. Controlling such highly correlated electron–nuclear dynamics may provide opportunities for boosting the performance of photocatalytic materials. Understanding the origin of photoinduced water splitting on TiO2 is crucial to control photocatalytic surface reactions. A photoexcited-hole-transfer-driven mechanism now shows that water dissociation is strongly coupled with dynamic lattice distortion (photoexcited phonons) on TiO2 surfaces.