Sol–gel pore-confined strategy to synthesize atomically dispersed metal sites for enhanced CO2 electroreduction

Excavating highly efficient and cost-effective non-noble metal single-atom catalysts for electrocatalytic CO₂ reduction reaction (CO₂RR) is of paramount significance. However, the general and universal strategy for designing atomically dispersed metals as accessible active sites is still in its infancy. Herein, we reported a general sol–gel pore-confined strategy for preparing a series of isolated transition metal single atoms (Fe/Co/Ni/Cu) anchored on nitrogen-doped carbon matrix. Benefiting from synergistic effect of M-N₄ coordination and neighboring N doping, the Fe-N₄-C catalyst exhibited superior capability with a Faradaic efficiency of 96.9%, achieving highly stable electrocatalytic activity for more than 20 h. Density functional theory (DFT) calculations further revealed the changes in the d_xz orbital of Fe, with a decrease in the out-of-plane component. Thus, a lower free energy barrier (ΔG) in thermodynamic pathway and the accelerated proton transfer to *COOH in kinetic pathway both enhanced electrocatalytic process.