Photocatalysis has received much attention as a potential solution to the worldwide energy shortage and for counteracting environmental degradation. However, the traditional photocatalyst, TiO2, cannot make use of visible light that accounts for 45% of solar spectrum because of a large bandgap (3.2 eV). Therefore, it is urgent to develop visible-light-driven photocatalysts. On the one hand, some modification technologies were explored to extend the light absorption of TiO2 to visible-light region, such as doping of metal and non-metal elements, dye sensitization, and so on. On the other hand, much effort has been directed toward the development of new visible-light photocatalysts. The good news is, some novel and efficient non-TiO2-based photocatalysts have been discovered, such as WO3, Ag3PO4, BiVO4, g-C3N4. In this chapter, these four typical visible light–driven semiconductor photocatalysts were highlighted. WO3 is a visible light–responsive photocatalyst that absorbs light up to ca. 480 nm. Besides that, WO3 has some advantages, such as low cost, harmlessness, and stability in acidic and oxidative conditions. Preparation of WO3 films with the deposition of noble metal is considered to be a promising approach for the photocatalytic applications. In addition, the characteristic morphology and improved photocatalytic performance of Ag3PO4-based and BiVO4-based have been raised up. New methods for fabrication Ag3PO4 with exposed high-energy facets and novel heterogeneous Ag3PO4 co-catalysts have been developed. Monoclinic BiVO4 is a promising photo-anode material for photocatalytic water splitting to produce hydrogen. Co-catalysts loaded on BiVO4 could improve the surface charge transfer efficiency. Furthermore, g-C3N4 is a promising visible-light photocatalyst due to its unique electronic structure. To date, g-C3N4-based photocatalysis has become a very hot research topic. The synthesis, bandgap engineering, and semiconductor composites of g-C3N4-based photocatalysts are highlighted.
Part of the book: Semiconductor Photocatalysis