This book presents state-of-the-art coverage of the basic concept, new materials for photocatalysis and their applications. The contents cover types of photocatalysis, homogeneous photocatalysis, heterogeneous photocatalysis, photoelectrochemistry, basic principles of photocatalytic water splitting, theoretical models, UV-light-active photocatalysis, visible-light-active photocatalysis, NIR-lighter-active photocatalysis, various synthesis methods, solar energy conversion, photo-reductive process for trace metal ions, and theoretical design of novel photocatalyst for H2 generation under sunlight. Various semiconductors such as BiFeO3, BiVO4, titanate perovskites (ATiO3), nitrides, oxynitides, metal chalcogenides, graphenes, G-C3N4 based core-shells, transition metals based complexes, transition metal selenides, metal oxides like TiO2, ZnO, SnO2, NiO, CuO and MgO and their various nanocomposites, layered double hydroxides (LDHs), plasmonic semiconductor heterostructures, 2D-layered nanostructures, perovskite-oxide based nanostructures, semiconductors heterostructures, rare-earth ions doped nanomaterials, role of co-catalyst, and band gap engineering are also elaborated. The contents of this book are useful for researchers and professionals working in the areas of materials science, especially photocatalytic materials.