Axial and Asymmetric Coordination Coupling Adjust the Electronic Structure of Single-Atom Zinc Sites for Efficient Electroreduction of Carbon Dioxide.

Breaking the symmetric structure of active centers to adjust their electronic structure is a promising strategy for improving the performance of single-atom catalysts (SACs) in electrocatalytic carbon dioxide (CO) reduction (ECR). However, it remains highly challenging to achieve precise regulation and fine-tuning of single-atom sites at the atomic level. Here, by introducing S and Cl atoms, a Zn-SAC (ZnNSCl/C) with coupled axial and asymmetric coordination is successfully constructed, thereby enhancing the ECR performance. In situ attenuated total reflection infrared spectroscopy demonstrates that ZnNSCl/C promotes the formation of COOH and the desorption of CO species. Theoretical calculations show that the asymmetric coordination of S and the axial coordination of Cl can lead to the electron redistribution near the single Zn sites, increasing the overlap between the Zn (3d) and COOH (2p) orbitals. This enhances the adsorption strength of COOH on the Zn site and reduces the desorption energy of CO, thus facilitating catalytic performance. Therefore, the ZnNSCl/C catalyst achieves a CO faradaic efficiency of ≈100% in an H-cell, with excellent long-term stability of 240 h. This work may pave the way for the development of efficient ECR catalysts via fine manipulation of asymmetric and electronic structures of single-atom metal sites.