This book comprises the fabrication of nanocomposites synthesized by a simple hydrothermal method and characterized by UV-visible, DRS, SEM, and TEM analysis. The photocatalytic activity of the synthesized nanocomposites was evaluated for the degradation of phenol. The photo-induced electron hole pair recombination retards the photocatalytic reaction, which was confirmed by the PL analysis. The improved photocatalytic activities were attributed to the formation of a heterojunction between Ag and SnO2. The photocatalytic mechanism was found through a trapping experiment. The stability of the photocatalyst was evaluated by a reusability experiment. Moreover, both hydroxyl radicals and superoxide radical anions were the key active species in the photodegradation of organic contaminants under visible light illumination.