Solar energy as green and renewable energy source shows great application potential in the near future. This article reviews the development of photocatalysis for water detoxification to convert polluted water into fresh water and water splitting for hydrogen generation. Oxide semiconductors, especially titania TiO2, can be modified gradually according to their electronic structures, charge transport, and surface decoration treatment to fabricate high solar energy conversion efficiency photocatalysts for water purification/disinfection and water splitting. The basic photocatalytic process was reviewed based on the interaction of the photocatalysts and their environments. The influences of intrinsic semiconducting properties and surface states on the photocatalytic process were assessed based on the recent research outcomes. The importance of free radicals in the photocatalytic process was also emphasized because the free radicals show strong redox potential.
