Recent developments in photocatalytic solar water splitting

The generation of hydrogen through photocatalytic water splitting is a clean and sustainable technique to produce renewable fuels. Compared with photovoltaics, solar water splitting does not suffer from electricity storage problem, moreover, it can provide an important feedstock – hydrogen for the chemical industry. However, the energy conversion efficiency has remained much lower than that of photovoltaics. The solar water splitting process has two more steps than photovoltaics: hydrogen evolution and oxygen evolution. Thus, the improvement of efficiency relies on new materials for efficient solar energy harvesting as well as active co-catalysts for hydrogen and oxygen evolutions. In recent years the world has witnessed the emergence of many new materials and approaches with increased water splitting efficiency, in the Comment we look at some representative examples. The most important step in improving efficiency is to develop lower bandgap photocatalysts. The main effort has focused on reducing the bandgaps of wider semiconductors through doping or alloying. These engineered materials are solid solutions containing four or more elements. (Ga1 xZnx)(N1 xOx) and Ta-based semiconductors are two well-known examples of such semiconductor