Unlocking One-Step Two-Electron Oxygen Reduction via Metalloid Boron-Modified Zn3In2S6 for Efficient H2O2 Photosynthesis

The indirect two-step two-electron oxygen reduction reaction (2e⁻ ORR) dominates photocatalytic H₂O₂ synthesis but suffers from sluggish kinetics, •O₂⁻-induced catalyst degradation, and spatiotemporal carrier-intermediate mismatch. Herein, we pioneer a metal-metalloid dual-site strategy to unlock the direct one-step 2e⁻ ORR pathway, demonstrated through boron-engineered Zn₃In₂S₆ (B-ZnInS) photocatalyst with In-B dual-active sites. The In-B dual-site configuration creates a charge-balanced electron reservoir by charge complementation, which achieves moderate O₂ adsorption via bidentate coordination and dual-channel electron transfer, preventing excessive O─O bond activation. Simultaneously, boron doping induces lattice polarization to establish a built-in electric field, quintupling photogenerated carrier lifetimes versus pristine ZnInS. These synergies redirect the O₂ activation pathway from indirect to direct 2e⁻ ORR process, delivering an exceptional H₂O₂ production rate of 3121 µmol g⁻¹ h⁻¹ in pure water under simulated AM 1.5G illumination (100 mW cm⁻²)—an 11-fold enhancement over ZnInS. The system achieves an unprecedented apparent quantum yield of 49.8% at 365 nm for H₂O₂ photosynthesis among inorganic semiconducting photocatalysts, and can continuously produce medical-grade H₂O₂ (3 wt%). This work provides insights for designing efficient H₂O₂ photocatalysts and beyond.