Novel Black BiVO4/TiO2−x Photoanode with Enhanced Photon Absorption and Charge Separation for Efficient and Stable Solar Water Splitting

Abstract Recent advances in solar water splitting by using BiVO 4 as a photoanode have greatly optimized charge carrier and reaction dynamics, but relatively wide bandgap and poor photostability are still bottlenecks. Here, an excellent photoanode of black BiVO 4 @amorphous TiO 2− x to tackle both problems is reported. Its applied bias photon‐to‐current efficiency for solar water splitting is up to 2.5%, which is a new record for a single oxide photon absorber. This unique core–shell structure is fabricated by coating amorphous TiO 2 on nanoporous BiVO 4 with the aid of atomic layer deposition and further hydrogen plasma treatment at room temperature. The black BiVO 4 with moderate oxygen vacancies reveals a bandgap reduction of ≈0.3 eV and significantly enhances solar utilization, charge transport and separation simultaneously, compared with conventional BiVO 4 . The amorphous layer of TiO 2− x acts as both oxygen‐evolution catalyst and protection layer, which suppresses anodic photocorrosion to stabilize black BiVO 4 . This configuration of black BiVO 4 @amorphous TiO 2− x may provide an effective strategy to prompt solar water splitting toward practical applications.