Photo- and mechano-catalytic overall water splitting reactions to form hydrogen and oxygen on heterogeneous catalysts

Recent progress of overall water splitting by photocatalysts and mechanocatalysts is briefly reviewed. In photocatalytic reactions, several new materials have been introduced, and the catalyst preparation has also been improved. As a result, a high quantum efficiency for overall water splitting of about 30% has been accomplished. In addition, recent progress in the understanding of the reaction mechanism is briefly introduced. On the other hand, mechano-catalytic overall water splitting reaction has been recently discovered by the authors. The phenomenological aspects of this novel reaction are summarized, and some implications of the reaction mechanism are also described.