An accurate “metal pre-buried” strategy for constructing Ni–N2C2 single-atom sites with high metal loadings toward electrocatalytic CO2 reduction

Abstract

Although single-atom catalysts (SACs) dispersed on N-doped carbon supports with the M–N₂C₂ configuration have high application potential in electrocatalysis, combining this configuration with high metal loadings remains a considerable challenge. In this study, a Ni-salen polymer with a confined metal position and precise coordination mode (Ni–N₂O₂) serves as a precursor, which not only suppresses the aggregation of metal atoms but also promotes the creation of Ni–N₂C₂ centers owing to the cleavage of Ni–O bonds and formation of Ni–C bonds during high-temperature pyrolysis. A Ni–N₂C₂ SAC with a metal loading of 9.15 wt% exhibits excellent catalytic performance for the CO₂ electroreduction to CO with a faradaic efficiency (FE_CO) of 98.7% at −0.82 V vs. the reversible hydrogen electrode (RHE). Theoretical calculation data have further demonstrated that the modified electronic structure of the Ni–N₂C₂-p model is responsible for its high intrinsic activity. This work proposes a new strategy for maintaining both the precise Ni–N₂C₂ structure and high metal loading.