This book presents the fundamentals of photocatalysis in nanostructured TiO2. The factors affecting photocatalytic activity, design, and preparation procedures of various forms of nanostructured TiO2 are described together with their numerous applications in the fields of energy and environment. It highlights the use of ion-doping and inert-atmosphere annealing to extend the light-absorption range of photocatalysts and reduce recombination between electrons and holes. It discusses promising applications, such as water purification, gas sensing, storage and delivery, and energy generation, and is an invaluable resource and useful guide for a broad readership in various fields of catalysis, material sciences, environment, and energy.