d-Orbital Single Electron Filling O─O π* Bonds on WO3S1 Sites for Highly Selective Generation of Hydroxyl Radicals

Hydroxyl radical (•OH) stemming from dissolved oxygen (O₂) 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 (WO₃S₁) is established on ZnIn₂S₄ (W-ZIS). The strong interactions in WO₃S₁ shift the d-band center toward the Fermi level, enhancing the adsorption of O₂. These interactions improve the accumulation of photo-generated electrons on WO₃S₁, facilitating the dissociation of O─O bonds in crucial intermediates and promoting the selective conversion from O₂ 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 O₂ can be reduced by d-orbitals single electron (↑, _, _, _, _, _) of WO₃S₁ transfer to 2p-orbital O─O pi anti-bonding (π*: p_x and p_y), initially activating O₂. Additionally, WO₃S₁ sites facilitate the cleavage of H₂O, optimizing proton adsorption through W─O orbital coupling in WO₃S₁ 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 H₂O₂ and shortening the pathway for •OH generation.).