Synergistic Solute Engineering and Cocatalyst Modification toward Efficient BiVO ₄ Photocatalysts for Solar H ₂ O ₂ Production

Solar-driven hydrogen peroxide (H 2 O 2 ) production from earth-abundant water and oxygen represents a promising route toward sustainable solar fuels. Yet, achieving selective two-electron water oxidation remains limited by a substantial thermodynamic barrier. Here, we demonstrate overall H 2 O 2 photosynthesis on particulate BiVO 4 photocatalysts through solution-phase engineering using potassium bicarbonate (KHCO 3 ) and dipotassium phosphate (K 2 HPO 4 ), together with cocatalyst modification. Time-resolved spectroscopy indicates that solute modification extends the photocarrier lifetimes in BiVO 4, whereas combined theoretical and experimental analyses reveal that the coexistence of HCO 3 – and HPO 4 2– enhances oxidative H 2 O 2 formation by tuning the adsorption of *OH intermediates. Further deposition of Ag nanoparticles boosts charge separation, as confirmed by transient photovoltage (TPV) spectroscopy, leading to an apparent quantum yield of 4.9% at 365 nm. These insights highlight the synergy of solute engineering and cocatalyst deposition as a viable strategy for molecular-level design of efficient photocatalytic systems for solar H 2 O 2 production.