Achieving Free‐Electron Transfer Reversal and <i>dz</i> ^<i>2</i> ‐Orbital Occupancy Modulation on Core‐shell NiS@Au Cocatalysts for Highly Selective H ₂ O ₂ Photosynthesis

Abstract Spontaneous free‐electron migration usually occurs on the interface between host photocatalysts and cocatalysts, but the influences of the charge transfer direction on the two‐electron oxygen reduction reaction (2e − ‐ORR) of cocatalysts have not been taken seriously. Herein, an innovative electron‐transfer reversal is proposed to direct the free‐electron transfer in a way that enables highly selective 2e − ‐ORR on Au cocatalysts. To this end, metallic Au nanoparticles are originally loaded on NiS particles to fabricate novel core–shell NiS@Au cocatalysts on g‐C 3 N 4 surface by a directional photodeposition procedure. XAS spectra and DFT calculations disclose that the intergrated NiS induces a reversed free‐electron transfer from Au nanoparticles to NiS core, thus essentially modulating d z 2 ‐orbital occupancy of Au atoms to enhance O 2 adsorption and stabilize key *OOH intermediates, endowing core–shell NiS@Au cocatalysts with a highly selective 2e − ‐ORR process for efficient H 2 O 2 evolution. Consequently, the optimized g‐C 3 N 4 /NiS@Au photocatalyst achieves a remarkably promoted H 2 O 2 ‐production rate of 264.82 μmol/h/50 mg in the air environment, possessing a high apparent quantum efficiency of 8.07 % under visible light. This work provides novel insights on purposefully steering free‐electron transfer direction to engineer dz 2 ‐orbital occupancy, offering a feasible approach for designing highly active photocatalysts and beyond.