Unlocking One‐Step Two‐Electron Oxygen Reduction via Metalloid Boron‐Modified Zn ₃ In ₂ S ₆ for Efficient H ₂ O ₂ Photosynthesis

Abstract The indirect two‐step two‐electron oxygen reduction reaction (2e − ORR) dominates photocatalytic H 2 O 2 synthesis but suffers from sluggish kinetics, •O 2 − ‐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 Zn 3 In 2 S 6 ( 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 2 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 2 activation pathway from indirect to direct 2e − ORR process, delivering an exceptional H 2 O 2 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 H 2 O 2 photosynthesis among inorganic semiconducting photocatalysts, and can continuously produce medical‐grade H 2 O 2 (3 wt%). This work provides insights for designing efficient H 2 O 2 photocatalysts and beyond.