Modeling electron storage at the interface between Au and anatase-TiO2 under ambient conditions

Au supported on TiO₂ is a promising photocatalyst due to its ability to catalyze reactions under illumination and store electrons for sustained reactivity in the dark. Using density functional theory (DFT), we investigate the structural evolution and reactivity of the Au/anatase-TiO₂(001) interface under realistic conditions. Phase diagrams and charge analysis reveal that the Au nanoparticles supported on TiO₂ (Au/TiO₂) interface can reversibly store electrons by transitioning between different charge states and structures via oxidation and reduction. This electron storage and the associated reducing potential, along with the atomic arrangement, promote key photoelectrochemical reactions, such as the oxygen reduction reaction (ORR) and the CO₂ reduction reaction (CO₂RR). Lattice titanium and oxygen vacancies act as active sites, with the two-electron (2e)-ORR pathway (H₂O₂ formation) kinetically favored due to a lower proton-coupled electron transfer barrier. The interface also facilitates CO₂ activation, which is challenging on bare Au. These findings provide a foundation for optimizing Au/TiO₂ composites for energy storage and conversion.