This book highlights sustainable methods with photocatalytic activities to remediate environment and for energy conversion. The related photocatalytic materials are discussed in detail. Some significant photocatalytic applications in degrading industrial pollutants that include different organic dyes, purifying the polluted air, converting CO2 to alcohol fuels, storing energy from sunlight as ammonia by converting N2 to NH3, and splitting water by optimizing the oxygen evolution process are thoroughly elucidated. The chapters introduce the necessary materials and results, leading to a better conceptualization in order to work in the field of photocatalysis. Some related perspectives and outlooks are discussed in the last chapter for possible future developments.