Typical strategies to facilitate charge transfer for enhanced oxygen evolution reaction: Case studies on hematite

Abstract

Hydrogen can be sustainably produced through photoelectrochemical (PEC) water splitting. The process of PEC water splitting is composed of two vital half-reactions: water oxidation to O2 on photoanode, and proton reduction to H2 on photocathode. Both in thermodynamics and kinetics, the oxidation of water on photoanode is much more challenging, because the formation of O2 involves the four-holes reaction process that is more difficult than the two-protons reduction. Accordingly, the oxidation of water into O2 is the rate-determining reaction for PEC water splitting, which is closely affected by the light harvesting, charge separation and transfer, as well as surface activity of photoanode. In principle, water oxidation is initiated by the photo-excited charge of photoanode. In this review, we took hematite photoanode as a typical example to illustrate the progress in modifying the charge separation and migration property of metal-oxide photoanodes for water oxidation. The typical strategies adopted to facilitate the charge transfer and separation of hematite photoanode were specifically summarized. In addition, the views designing and developing hematite photoanode with high-performance for water oxidation were presented. This review provides comprehensive information about the state-of-the-art progress of hematite-based photoanodes and forecast the developing directions of photoanode materials for solar water splitting.