Combining High Photocatalytic Activity and Stability via Subsurface Defects in TiO2

Surface defects consisting of oxygen vacancy in TiO2 provide sites with high photocatalytic activity, while their photocatalytic stability is often undermined because of the trapping of oxygen species. Here, we conducted a theoretic study to propose the use of subsurface oxygen vacancies in anatase TiO2(101) for photocatalytic water-splitting, aiming to combine both high activity and stability. This study demonstrates that subsurface defects expand light-harvesting ability of TiO2 to the visible light region and facilitate photogenerated charge separation, and these results were then verified by experiments. These vacancies also bestow high catalytic activity on sites of water adsorption and oxidation above them on the defect-free surface. Importantly, subsurface defects are inert toward reactive oxygen species, ensuring high stability for the nearby surface catalytic sites. These results demonstrate the role of subsurface oxygen vacancies in catalyzing oxygen evolution reaction, leading to a new design strategy for photocatalytic or catalytic oxide materials.