Photocatalytic Systems by Design: Materials, Mechanisms and Applications explores various aspects of photocatalysis, including the photocatalytic phenomenon and process, applications, and the design of photocatalysts via band gap engineering. The book also covers band edge position engineering for multiple photocatalytic applications, such as pollutant degradations, hydrogen production, CO2 reduction into hydrocarbon fuels, antimicrobial disinfections, organic synthesis, N2 fixation, and more. This book is designed to enable beginners to learn the concepts and applications of photocatalysis. Unlike conventional books on photocatalysis, the book provides a 360 Degrees perspective into the field of photocatalysis and serves as an informative handbook for all audiences.