Polaron-Regulated Charge Utilization in Boron-Mediated VOx-Reconstructed BiVO4 Photoanodes for Photoelectrochemical Water Oxidation

Abstract Bismuth vanadate (BiVO4) has been extensively investigated as a promising candidate photoanode semiconductor for photoelectrochemical (PEC) water oxidation, yet its performance is severely restricted by the suboptimal charge utilization originating from local V–O coordination environment, with vanadium deficiency and near-surface lattice distortion interrupting polaron-mediated charge transfer. Herein, a boron-mediated hydrothermal reconstruction strategy is developed to construct modified BiVO4 photoanodes through the coupled introduction of vanadium oxide species, with borate-derived surface ligands. Electron paramagnetic resonance (EPR) analysis, temperature-dependent photoluminescence (Td-PL) spectra, and in situ Raman measurements collectively indicate that the formed thin B-VOx-rich surface layer drives the near-surface V/Bi ratio toward stoichiometry to mitigate V-deficiency-related surface states, modulates the V–O framework with higher symmetry in VO4 tetrahedron, and accelerates the water oxidation kinetics by a borate promoter. Thereby, the charge utilization efficiency is significantly improved by simultaneously enhanced photoinduced electron separation via activated polaron hopping and boosted photogenerated photohole injection. As a result, the optimized photoanode achieves photocurrent density up to 5.58 mA cm–2 at 1.23 VRHE under simulated one sun illumination, more than 4.85 times higher than that of pristine BiVO4, together with high separation and injection efficiencies of 85.18% and 87.83%, respectively. This work provides an innovative defect-interface reconstruction route for enhancing polaron-mediated charge utilization in metal oxide photoelectrodes.