Unassisted bipolar photoelectrochemical synthesis of H₂O₂

Photoelectrochemical bipolar systems enable bias-free H₂O₂ synthesis by integrating light harvesting, water oxidation and oxygen reduction. However, poor selectivity due to competing 4e^- pathways, slow charge transfer, and inferior stability severely limit their practical application. Herein, we present a bias-free photoelectrochemical bipolar system for H₂O₂ production, which integrates a Zn-TiO₂/BVO/WO₃ photoanode for the 2e^- water oxidation reaction and a Ru:CuO/Nb-CBO photocathode for the 2e^- oxygen reduction reaction. The photoanode suppresses *OOH intermediates to favor H₂O₂ formation, achieving a Faradaic efficiency (FE) of 90.2% at 0.6 V_RHE. The photocathode stabilizes *OOH intermediates and delivers an FE of 91.9% under the same conditions while maintaining performance for over 50 h. Practical testing under natural sunlight with 36 cm² electrodes achieves an FE of 163.37% and a yield of 11.44 mmol L^-1. In situ generated H₂O₂ achieves over 99% bacterial inactivation within 60 min. This work provides an adaptive platform for solar-driven H₂O₂ synthesis and energy conversion.