Photocatalytic water splitting with near 100% efficiency

Using sunlight to split water is attractive for renewable hydrogen production, but challenging to carry out efficiently. Kazunari Domen and colleagues now show that a photocatalyst can be designed such that light-generated charges are transferred efficiently and then used to split water into hydrogen and oxygen. Critical are the separation of hydrogen and oxygen formation on separate photocatalyst facets and the use of highly active catalyst species. This suppresses losses due to charge recombination, and results in water splitting with almost 100% quantum efficiency. While the reported photocatalyst uses ultraviolet light, the design principles should also be applicable to materials able to use more abundant visible light, which could form the basis of a practically useful process for generating hydrogen using sunlight and water.