S-scheme photocatalyst

Solar light utilization has garnered the attention of both the scientific and engineering worlds. Solar fuel generation via photocatalysts has great potential. It has been accepted that semiconductor heterojunction photocatalysts are superior to their single component counterpart. This chapter starts with basic semiconductor physics, which aids to clarify the charge transfer mechanism in heterojunction photocatalysts. Then, the intrinsic reasons for constructing heterojunctions are discussed, which aims to overcome the shortcomings of single component photocatalysts via revisiting the Jablonski diagram and simple photochemistry theory. Next, the development of the state-of-the-art S-scheme heterojunction is thoroughly expounded. And, the problems confronted by the type-II, liquid-phase Z-scheme, and all-solid-state Z-scheme photocatalysts that prevailed in the past are elaborated. Besides, the classification of S-scheme heterojunctions is presented. Moreover, the advantages of S-scheme heterojunctions are summarized from the aspects of promoted spatial charge separation and maximized redox ability. Ultimately, a new understanding of the Fermi level alignment considering electron concentrations when forming S-scheme heterojunction is briefly introduced. Hopefully, this chapter will provide directions for the rational design of S-scheme heterojunctions.