A review of step-scheme photocatalysts

The meticulous design of semiconductor photocatalysts has been known as the key to achieve a highly efficient and selective photocatalytic reaction toward solving the current environmental pollution and energy crisis. Recently, the combination of two or more semiconductors to form step-scheme (S-scheme) heterojunction photocatalysts has emerged as a rising star in photocatalysis due to their capability for optimizing the photogenerated charge carrier utilization and maximizing the reduction-oxidation potential of the photocatalytic system. Herein, this review summarizes and highlights the recent development of the S-scheme heterojunction photocatalysts. We first concisely compile the working mechanism of S-scheme photocatalysts, followed by discussing their characterization techniques. Then, we discuss and overview the applications of the S-scheme photocatalysts in water splitting, CO2 conversion, wastewater purification, H2O2 production, N2 fixation and so on. Finally, we conclude this review with a brief discussion of significant challenges and future prospects in the development of S-scheme photocatalytic systems.