This book presents photocatalysis as a state-of-art technology in energy production and conversion. The ever increasing demand for energy with growing economies has led to a dearth of energy sources. The exhaustive dependability on non-renewable resources of energy has not just depleted them but also lead to the birth of secondary problems such as pollution and climate change. The photoactive processes have opened a new window for the production of green energy and helped in environmental sustainability. The harnessing of renewable sources especially sun and water for fuel production and noxious gases reduction solve both the issues of pollution mitigation and energy crisis.