Photocatalysis is the acceleration of a photoreaction in the presence of a catalyst. Light is absorbed by an adsorbed substance in catalyzed photolysis. However, in photogenerated catalysis, the photocatalytic activity is based on the ability of the catalyst to generate electron-hole pairs which create free radicals. Homogeneous photocatalysis and heterogeneous photocatalysis are the two primary categories of photocatalysis. In homogeneous photocatalysis, the photocatalysts and the reactants exist in the same phase. Whereas, in heterogeneous photocatalysis reactants are in a different phase. Heterogeneous photocatalysis includes a large variety of reactions, such as mild or total oxidations, dehydrogenation, hydrogen transfer, and deuterium-alkane isotopic exchange, etc. This book brings forth some of the most innovative concepts and elucidates the unexplored aspects of photocatalysis. Different approaches, evaluations, methodologies and advanced studies on photocatalysis have been included in this book. This book is appropriate for students seeking detailed information in this area as well as for experts.