PHOTOASSISTED ELECTROLYSIS OF WATER: CONVERSION OF OPTICAL TO CHEMICAL ENERGY.

Photoelectrochemical cells for the photoelectrolysis of H//2O to H//2 and O//2 are described. Such cells can, in principle, be used to efficiently convert solar energy to chemical energy in the form of the electrolysis products. The basic principles, potential advantages, and current problems associated with photoelectrochemical cells as energy conversion devices are outlined. The current state of the research in this area is briefly reviewed, and work carried out in the authors' laboratory on TiO//2-, SnO//2-, SrTiO//3-, KTaO//3-, and KTa//0//. //7//7Nb//0//. //2//3O//3-based cells is highlighted. For the perovskite based cells the highest efficiencies obtain, and conversion of solar to chemical energy for SrTiO//3 has been observed to be as efficient as about 1%. However, all of the metal oxide photoelectrodes listed above respond only to ultraviolet light which is a small fraction of the solar spectrum. Approaches to developing visible light responding cells are discussed.