d ‐Orbital Single Electron Filling O─O π * Bonds on WO ₃ S ₁ Sites for Highly Selective Generation of Hydroxyl Radicals

Abstract Hydroxyl radical (•OH) stemming from dissolved oxygen (O ₂ ) via photocatalysis is very attractive, but its poor selectivity and generation efficiency greatly limit its application. Herein, a kind of tungsten single site co‐coordinated with O and S atoms (WO ₃ S ₁ ) is established on ZnIn ₂ S ₄ (W‐ZIS). The strong interactions in WO ₃ S ₁ shift the d ‐band center toward the Fermi level, enhancing the adsorption of O ₂ . These interactions improve the accumulation of photo‐generated electrons on WO ₃ S ₁ , facilitating the dissociation of O─O bonds in crucial intermediates and promoting the selective conversion from O ₂ into •OH. This brings a state‐of‐the‐art selectivity (40.2%) and generation efficiency (1668.90 mmol. g ⁻¹ . L ⁻¹ . h ⁻¹ ) of •OH production. Experimental results and theoretical simulations have elucidated that O ₂ can be reduced by d ‐orbitals single electron ( ↑ , _, _, _, _, _) of WO ₃ S ₁ transfer to 2 p ‐orbital O─O pi anti‐bonding ( π* : p _x and p _y ), initially activating O ₂ . Additionally, WO ₃ S ₁ sites facilitate the cleavage of H ₂ O, optimizing proton adsorption through W─O orbital coupling in WO ₃ S ₁ and promoting the transformation of oxygen‐containing intermediates. More importantly, d ‐orbitals single electron can fill O─O π* bond in •OOH intermediate, weakening the covalency of the O─O bond, mitigating the formation of H ₂ O ₂ and shortening the pathway for •OH generation.).