A COMPREHENSIVE REVIEW OF PHOTOCATALYTIC MATERIALS: FROM FUNDAMENTALS TO EMERGING FRONTIERS

Photocatalysis is an environmentally friendly, sunlight-powered method of addressing two global crises: the crisis of energy scarcity and the environmental pollution crisis. In this chapter we have reviewed all photocatalytic material developments from the first reported use of titanium dioxide (TiO2) to current multi- component photocatalysts. The basic photochemistry of photocatalytic reactions are described in detail by explaining how light is absorbed by the photocatalyst, how electrons move through the semiconductor, and where chemical changes occur at the surface of the photocatalyst. We have also analyzed the limitations of traditional semiconductors (TiO2 and ZnO) based on their inability to activate photons using wavelengths corresponding to visible light and their tendency to undergo photocorrosion. We have also explored the engineering of photocatalytic materials including the modification of band gaps using dopants made of metals and nonmetals, and the addition of graphene or carbon nanotubes (CNTS). Additionally, we have explored the use of plasmon and magnetically active photocatalysts. The chapter also discusses the transition from the use of single-component photocatalysts to the use of more complex heterojunction structures (Type-II, Z-scheme, and S-scheme) that provide improved charge separation efficiency while providing high redox potential. The chapter concludes by highlighting new photocatalytic materials that have been developed recently such as g-C3N4, MOFs, and perovskites. The synthesis of these materials and the future of scaling up the production of these materials for industry are discussed in the final section of the chapter.