A review on tungsten-trioxide-based photoanodes for water oxidation

Photoelectrochemical (PEC) water splitting capable of reducing and oxidizing water into hydrogen and oxygen in a generation mode of spatial separation has gained extensive popularity. In order to effectively produce hydrogen at the photocathode of a PEC cell, the photoanode, where the oxygen evolution reaction occurs, should be systematically developed on priority. In particular, WO3 has been identified as one of the most promising photoanode materials owing to its narrow band gap and high valence band position. Its practical implementation, however, is still limited by excessive electron–hole recombination and poor water oxidation kinetics. This review presents the various strategies that have been studied for enhancing the PEC water oxidation performance of WO3, such as controlling the morphology, introducing defects, constructing a heterojunction, loading a cocatalyst, and exploiting the plasmonic effect. In addition, the possible future research directions are presented.