Photocatalytic H_<b>2</b>O_<b>2</b> Production with &gt;30% Quantum Efficiency via Monovalent Copper Dynamics

Photocatalytic O₂ reduction to H₂O₂ is a green and promising technology with advantages in cost-effectiveness, sustainability, and environmental friendliness, but its efficiency is constrained by limited selectivity for the two-electron oxygen reduction reaction (ORR) pathway. Here, we anchored isolated Cu atoms with tunable oxidation states onto WO₃ as effective active centers to enhance photocatalytic H₂O₂ production. Due to the charge compensation between single atoms and the support, the oxidation state of Cu species exhibited a loading-dependent transition between +2 and +1 valence. Experimental and theoretical analyses indicate that Cu(I) sites exhibit outstanding O₂ adsorption and activation capabilities, transforming the thermodynamically unfavorable hydrogenation of the *OOH intermediate (the rate-determining step in the two-electron ORR pathway) into an exothermic process, thereby significantly improving selectivity and efficiency. The Cu(I)-SA/WO₃ photocatalyst exhibited a H₂O₂ production rate of 102 μmol h^-1 under visible light irradiation, much higher than other reported photocatalysts. More importantly, it achieves an impressive apparent quantum efficiency of 30% at 420 nm, making a significant breakthrough in this field. This work provides novel perspectives for designing single-atom catalysts for efficient H₂O₂ synthesis via electronic state modulation.