Role of oxygen vacancy in metal oxides for photocatalytic CO2 reduction

Photocatalytic conversion of greenhouse gas CO2 into valuable solar fuels represents a promising technology for addressing the global energy crisis and environmental issues simultaneously. In such a technology, the development of efficient photocatalysts is a central task for pushing forward the practical application of photocatalytic CO2 reduction. Due to their low cost, high redox capability, and environmental friendliness, metal oxide-based photocatalysts have been extensively employed for CO2 reduction. Moreover, oxygen vacancy engineering in metal oxides has gradually emerged as a versatile approach to enhancing their photocatalytic performance for CO2 reduction. In this article, the state-of-the-art progress in oxygen vacancy engineering, including its synthesis, characterization, and recent advancement in photocatalytic CO2 reduction, is reviewed. In particular, the roles of oxygen vacancy in promoting the three basic steps in photocatalytic CO2 reduction, i.e., light absorption, charge separation, and surface CO2 conversion, are discussed in detail. The current challenges and future opportunities of engineering oxygen vacancy in metal oxide-based photocatalysts for efficient CO2 reduction are also addressed. This review aims to inspire more creative works on the rational design of oxygen vacancy that maximizes its function, hence accelerating the discovery of high-performance photocatalysts for CO2 reduction.