Spontaneous Metal-Chelation Strategy for Highly Dense Ni Single-Atom Catalysts with Asymmetric Coordination in CO2 Electroreduction

Developing metal-nitrogen-doped carbon single-atom catalysts (M-NC SACs) with high loadings for the electrochemical CO2 reduction reaction (eCO2RR) remains challenging owing to the risk of metal aggregation. Herein, the study presents a facile strategy for synthesizing M-NC SACs using metal-chelating ligands, eliminating the need for additional processing steps. Specifically, using ethylenediaminetetraacetic acid as a strong metal-chelating ligand, the formation of Ni nanoparticles is effectively prevented and a high loading of approximate to 2.7 wt.% is achieved, leading to the development of high-loading Ni SACs. The resulting catalysts exhibit a high CO faradaic efficiency (FECO) of 96.6% and CO partial current density of -120.2 mA cm-2 and retain a FECO over 90% in a broad potential range of -0.4 to -0.9 V versus the reversible hydrogen electrode. Furthermore, theoretical calculations indicate that the asymmetric Ni-N3C1 local coordination structure within the catalyst reveals an optimal balance between *COOH formation and *CO desorption, which enhances the activity for eCO2RR to CO. This study offers an efficient strategy to suppress metal nanoparticle formation while simultaneously improving the metal loading in M-NC SACs.