Single Zn Atoms with Acetate-Anion-Enabled Asymmetric Coordination for Efficient H₂O₂ Photosynthesis

Exploring unique single-atom sites capable of efficiently reducing O₂ to H₂O₂ while being inert to H₂O₂ decomposition under light conditions is significant for H₂O₂ photosynthesis, but it remains challenging. Herein, we report the facile design and fabrication of polymeric carbon nitride (CN) decorated with single-Zn sites that have tailorable local coordination environments, which is enabled by utilizing different Zn salt anions. Specifically, the O atom from acetate (OAc) anion participates in the coordination of single-Zn sites on CN, forming asymmetric Zn−N₃O moiety on CN (denoted as CN/Zn−OAc), in contrast to the obtained Zn−N₄ sites when sulfate (SO₄) is adopted (CN/Zn−SO₄). Both experimental and theoretical investigations demonstrate that the Zn−N₃O moiety exhibits higher intrinsic activity for O₂ reduction to H₂O₂ than the Zn−N₄ moiety. This is attributed to the asymmetric N/O coordination, which promotes the adsorption of O₂ and the formation of the key intermediate *OOH on Zn sites due to their modulated electronic structure. Moreover, it is inactive for H₂O₂ decomposition under both dark and light conditions. As a result, the optimized CN/Zn−OAc catalyst exhibits significantly improved photocatalytic H₂O₂ production activity under visible light irradiation. © 2023 Wiley-VCH GmbH.