Twin Structure in BiVO4 Photoanodes Boosting Water Oxidation Performance through Enhanced Charge Separation and Transport

Abstract The homojunction induced by twin structure in semiconductors is found to be highly effective in decreasing the bulk recombination. Theoretical and experimental results have demonstrated the “back to back” potentials and directional diffusion that originate from the homojunction could facilitate the charge separation and transport of BiVO 4 (BVO) single crystals. As expected, the resultant homojunction can lead to significantly enhanced photocatalytic activity. To eliminate the significant reduction of performance caused by solution mediated interface recombination on exposed fluorine‐doped tin oxide (FTO), a strategy for improving substrate coverage by a new “ n ‐step” method is applied. The BVO photoanode with preferable twin structure and high substrate coverage ratio reaches a photocurrent density of ≈3.1 mA cm −2 at 1.23 V versus reversible hydrogen electrode (RHE) and exhibits over 1.35% half‐cell solar‐to‐hydrogen conversion efficiency at 0.6 V versus RHE. This finding offers a new and effective way of fabricating twin structures to reduce bulk recombination of BVO photoanodes, which can also be applied to other semiconductors.