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 VRHE. 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.