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

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-VO x -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.