Understanding oxygen vacancies in disorder-engineered surface and subsurface of CaTiO3 nanosheets on photocatalytic hydrogen evolution

Hydrogenation-induced surface disorder on semiconductors has been proved an efficient strategy in photocatalysis, but identification and understanding of surface and subsurface disordered layers from molecular level viewpoints are still unclear. Herein, we fabricate efficient disorder-engineered CaTiO3 nanosheets photocatalysts and illustrate functions of surface and subsurface oxygen vacancies on photocatalytic hydrogen evolution. Our experimental and theoretical results reveal that subsurface oxygen vacancies can change energy band structure of CaTiO3 to form band tail states, improving charge separation; and surface oxygen vacancies can act as active centers to facilitate H-2 formation. Both merits promote similar to 49 times of the hydrogen evolution rate than pristine CaTiO3. In addition, we discover that improving charge separation with subsurface oxygen vacancies is more important than promoting surface reactions with surface oxygen vacancies in defect-engineered photocatalysts. Our work provides new insights into the hydrogenated disordered surface layer, as well as the rational design of photocatalysts with defect-engineering strategies.