Progress in bismuth vanadate photoanodes for use in solar water oxidation

Harvesting energy directly from sunlight as nature accomplishes through photosynthesis is a very attractive and desirable way to solve the energy challenge. Many efforts have been made to find appropriate materials and systems that can utilize solar energy to produce chemical fuels. One of the most viable options is the construction of a photoelectrochemical cell that can reduce water to H-2 or CO2 to carbon-based molecules. Bismuth vanadate (BiVO4) has recently emerged as a promising material for use as a photoanode that oxidizes water to O-2 in these cells. Significant advancement in the understanding and construction of efficient BiVO4-based photoanode systems has been made within a short period of time owing to various newly developed ideas and approaches. In this review, the crystal and electronic structures that are closely related to the photoelectrochemical properties of BiVO4 are described first, and the photoelectrochemical properties and limitations of BiVO4 are examined. Subsequently, the latest efforts toward addressing these limitations in order to improve the performances of BiVO4-based photoanodes are discussed. These efforts include morphology control, formation of composite structures, composition tuning, and coupling oxygen evolution catalysts. The discussions and insights provided in this review reflect the most recent approaches and directions for general photoelectrode developments and they will be directly applicable for the understanding and improvement of other photoelectrode systems.