Single Zn Atoms with Acetate-Anion-Enabled Asymmetric Coordination for Efficient H₂ O₂ Photosynthesis

Exploring unique single-atom sites capable of efficiently reducing O₂ to H₂ O₂ while being inert to H₂ O₂ decomposition under light conditions is significant for H₂ O₂ 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-N₃ O 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-N₃ O moiety exhibits higher intrinsic activity for O₂ reduction to H₂ O₂ 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 H₂ O₂ decomposition under both dark and light conditions. As a result, the optimized CN/Zn-OAc catalyst exhibits significantly improved photocatalytic H₂ O₂ production activity under visible light irradiation.