Unlocking One-Step Two-Electron Oxygen Reduction via Metalloid Boron-Modified ZnInS for Efficient HO Photosynthesis.

The indirect two-step two-electron oxygen reduction reaction (2e ORR) dominates photocatalytic HO synthesis but suffers from sluggish kinetics, •O -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 ZnInS (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 O 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 O activation pathway from indirect to direct 2e ORR process, delivering an exceptional HO production rate of 3121 µmol g h in pure water under simulated AM 1.5G illumination (100 mW cm)-an 11-fold enhancement over ZnInS. The system achieves an unprecedented apparent quantum yield of 49.8% at 365 nm for HO photosynthesis among inorganic semiconducting photocatalysts, and can continuously produce medical-grade HO (3 wt%). This work provides insights for designing efficient HO photocatalysts and beyond.