Principles of photocatalysis

Photocatalysis is an important ramification of catalysis which generates charge carriers under light irradiation to catalyze chemical reactions. Photocatalysis mimics the natural photosynthesis process, which is driven by the clean and inexhaustible sunlight. Besides, photocatalytic reactions operate at ambient temperatures and pressures, greatly reducing the requirements for reaction facilities as well as the operating cost. Owing to these unique advantages, photocatalysis powered by the renewable solar energy is deemed as an ideal pathway for industrial production, which can greatly decrease the reliance on fossil fuels to alleviate energy crisis and the greenhouse effect. As a result, photocatalysis has been applied in many crucial reactions, such as H2 production via water splitting, CO2 photoreduction to renewable chemical fuels, photodegradation of pollutants, N2 fixation, H2O2 production, sterilization, organic synthesis, etc. However, photocatalysis suffers from low product yields due to the rapid recombination of photogenerated charge carriers and lack of redox abilities. Thus, the design and development of novel photocatalysts are paramount to address these issues and improve the photocatalytic performance. In this chapter, we will systematically introduce the fundamentals of photocatalysis, including the historical evolvement, the principles of a photocatalytic process, different classes of photocatalysts, and the application of photocatalysis in various reactions. We anticipate that readers will grasp basic understanding of photocatalysis and photocatalysts.