H 2 O Deprotonation Promotes Hole Transfer at the Anatase TiO 2 (001)/Water Interface: First-Principles Molecular Dynamics

Photocatalytic water splitting represents a promising approach for solar energy utilization, but its performance is primarily constrained by the sluggish water oxidation reaction, where the hole transfer at the solid/liquid interface plays a significant role. Despite extensive experimental and theoretical efforts, the hole trapping mechanism of TiO2, a widely used photocatalyst, in the aqueous environment is still controversial. Here, using first-principles molecular dynamic simulations, we establish the hole trapping sites and the hole transfer mechanisms at the anatase TiO2(001)/water interface. Both molecular and dissociative H2O adsorptions are considered. We demonstrate that the holes at the adsorbed H2O and HO– species are unstable and migrate spontaneously to TiO2, whereas the deprotonated O2– ions can be oxidized and retain the holes forming stable structures. Further, bulk water facilitates hole localization at the TiO2/water interface, and in turn, the trapped holes regulate the interfacial water configuration. These findings provide fundamental insights into the photocatalytic performance and interfacial charge separation.