Controllable construction of oxygen vacancies by anaerobic catalytic combustion of dichloromethane over metal oxides for enhanced solar-to-hydrogen conversion

Abstract

Defect engineering is an effective strategy to modify metal oxide semiconductor photocatalysts, but the general strategy for controllable construction of defects remains a great challenge. Herein, we report a facile anaerobic catalytic combustion method using a volatile organic compound (CH₂Cl₂) as a reactant for controllable construction of oxygen vacancies (V_O) in TiO₂ for enhanced solar-to-hydrogen conversion. This strategy has the general applicability for the preparation of V_O enriched metal oxides including TiO₂ (001), rutile TiO₂, MoO₃, ZnO, and WO₃. The results of photocatalytic tests show V_O-dependent photocatalytic H₂ production activities under both visible light and solar light irradiation. The surface V_O on TiO₂ enable the visible light harvesting of TiO₂ and provide adsorption sites for H₂ evolution, and most importantly, they as charge carrier traps facilitate the separation of the photogenerated charges by intrinsic excitation with UV light irradiation, leading to greatly enhanced overall solar light activity of TiO₂. However, bulk V_O as the recombination centers hamper the photogenerated charge separation process, causing significantly decreased visible light and solar light photocatalytic activities. Moreover, we find that the synergistic effects of Pt cocatalysts and V_O further enhance the solar-to-hydrogen conversion over TiO₂. This work provides a general guide for constructing V_O on various metal oxide semiconductors and offers scope for the future development of V_O enriched metal oxide photocatalysts for efficient solar energy conversion.