Breaking Coordination Symmetry in Nickel Single-Atom Catalysts via Cl Modulation for Efficient CO2 Electroreduction and Zn-CO2 Batteries

Asymmetric Ni-N-Cl sites are built by NH 4 Cl vaporization. • Ni-N-Cl overcomes the kinetic challenges and delivers excellent CO 2 reduction performance. • XAFS, DFT and CW-ODMR reveal the asymmetric coordination mechanism. • Cl coordination creates electron-rich Ni centers with shifted d-band. • Ni-N-Cl achieves 86.2% CO Faradaic efficiency and enables durable Zn-CO 2 batteries for 53   h operation. Electrocatalytic CO 2 reduction reaction to value-added chemicals represents a promising pathway for sustainable carbon utilization. However, the symmetric coordination environment of conventional M-N 4 single atom sites restricts electronic structure regulation and limits their intrinsic activity. Herein, we develop an asymmetric Ni-N-Cl coordination structure synthesized via high-temperature NH 4 Cl vaporization assisted strategy. This Cl-mediated asymmetric coordination induces a distinct charge redistribution, generates an electron enriched Ni center and an upward shift of the d-band center closer to the Fermi level. These intrinsic modulations significantly facilitate CO 2 activation and proton transfer to the *COOH, thereby lowering the reaction energy barrier. Consequently, the Ni-N-Cl catalyst achieves a CO Faradaic efficiency of 99.67% at -0.7   V vs. RHE in H cell and 17   h long term stability at -100 mA cm -2 in flow cell. Furthermore, this catalyst delivers a peak power density of 1.62   mW   cm -2 and a durability of 53   h. This study provides a general methodology for the rational design of asymmetric single atom catalysts through orbital engineering for high-efficiency energy storage technologies. Download: Download high-res image (199KB) Download: Download full-size image