Unbiased Photoelectrochemical H ₂ O ₂ Production Using Boron Nitride for Both Photogenerated Hole Extraction and Oxygen Reduction Selectivity Regulation

Unbiased photoelectrochemical (PEC) H₂O₂ production offers a sustainable alternative to the energy-intensive anthraquinone process, yet faces critical bottlenecks: inefficient charge separation, uncontrolled two-electron oxygen reduction reaction (2e^- ORR) pathways, and high-purity O₂ requirements. Herein, we report an efficient unbiased PEC system for H₂O₂ production under ambient air. The key innovation involves the strategic implementation of boron nitride (BN) serves a dual role as a charge transfer mediator and ORR pathway modulator. At the photoanode, BN functions as a hole-extraction layer, because of elevating the valence band position of BiVO₄ (BVO), effectively suppressing interfacial charge recombination between the BVO photoanode and the FeNiOOH cocatalyst, resulting in a photocurrent density achieving 6.08 mA cm^-2 at 1.23 V_RHE. At the cathode, BN acts as a "reaction helmsman", tuning the binding energy of the *OOH intermediate and enabling the CoPc + BN to achieve 97% 2e^- ORR selectivity at -0.3 V_Ag/AgCl. As a result, the integrated system delivers a sustained H₂O₂ production rate of 1.22 ± 0.14 mM cm^-2 h^-1 over 16 consecutive cycles. This study provides an innovative solution to address the key challenges in bias-free H₂O₂ production.