Recent advances in BiVO4 semiconductor materials for hydrogen production using photoelectrochemical water splitting

Numerous efforts have been made to find, produce and utilize renewable energy to replace fossil fuels that have seriously degraded the environment. Photoelectrochemical (PEC) water splitting has been considered a promising route for the production of hydrogen (H2) applying for free solar energy. PEC systems to produce H2 have the great advantages of simple process steps and very low environmental burdens. However, many challenges must be overcome for commercial applications, particularly for fabricating the necessary materials for PEC water splitting. Among many candidate semiconductor materials for photoelectrode utilization, BiVO4 is a very promising semiconductor because it is an inexpensive n-type photocatalyst with a moderate bandgap of 2.37 eV for PEC water oxidation. BiVO4 as a photoanode can theoretically absorb almost 10% of the solar energy with an appropriate valence band (VB) position to drive water oxidation with an identified maximum photocurrent of 7.5 mA/cm2. Many bismuth vanadate (BiVO4)-based semiconductors that have been developed for PEC water splitting to produce H2 have been troubled by the easy recombination of the photoinduced electrons and holes. None of the numerous nanocomposites and nanostructures that have been developed are perfect materials capable of satisfying all the criteria necessary for practical photocatalysis with sufficient solar energy conversion efficiency. Most semiconductor materials with highly efficient PEC water splitting have used ultraviolet (UV) as a light source. However, UV has only a small fraction (2-3%) of the solar spectrum and is therefore not considered a sustainable energy source to provide sufficient PEC-based hydrogen production for industrial utilization. This review examines very recent progress of 11 Strategy for improving the photocurrent density and especially hydrogen production of BiVO4 semiconductors using PEC techniques, and also highlights the challenges faced in the design of visible light-active water splitting photocatalysts.