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 form 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.