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

Exploring unique single-atom sites capable of efficiently reducing O-2 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-N-4 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 O-2 reduction to H2O2 than the Zn-N-4 moiety. This is attributed to the asymmetric N/O coordination, which promotes the adsorption of O-2 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.