Single Zn Atoms with Acetate-Anion-Enabled Asymmetric Coordination for Efficient H 2 O 2 Photosynthesis.

Exploring unique single-atom sites capable of efficiently reducing O 2 to H 2 O 2 while being inert to H 2 O 2 decomposition under light conditions is significant for H 2 O 2 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-N 3 O moiety on CN (denoted as CN/Zn-OAc), in contrast to the obtained Zn-N 4 sites when sulfate (SO 4 ) is adopted (CN/Zn-SO 4 ). Both experimental and theoretical investigations demonstrate that the Zn-N 3 O moiety exhibits higher intrinsic activity for O 2 reduction to H 2 O 2 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 H 2 O 2 decomposition under both dark and light conditions. As a result, the optimized CN/Zn-OAc catalyst exhibits significantly improved photocatalytic H 2 O 2 production activity under visible light irradiation.