Recent advances in the use of metal oxide-based photocathodes for solar fuel production

Harvesting solar energy for the production of clean fuel by a photoelectrochemical system is a very attractive, yet a challenging task. This review focuses on the recent efforts done to tailor metal oxide-based photocathode materials for the solar-driven hydrogen production. The materials are classified into three categories: simple oxides, complex oxides, and photocathodes used in p-n self-biased heterojunction cells. Generally, three strategies have been recommended to tailor p-type metal oxide semiconductors to meet the requirements for efficient solar-driven water splitting, namely (1) coating the p-type metal oxide either with a protective layer or a dye, (2) using co-catalyst, and (3) merging the p-type material with an n-type photoanode with the proper optical and electrical properties. In the light of those strategies, the optical, structural, and photoelectrochemical characteristics of such assemblies are discussed.