▎ 摘　　要

Single atom catalysts (SACs) with atomically dispersed catalytic sites have shown great promise for energy related chemical reactions. In this work, a facile and general approach to synthesize a large variety of transition metal (Fe, Ni, Co, Cu, etc.) SACs with a large surface area and a hierarchical structure using layered montmorillonite (MMT) as the structural template was developed. Specifically, the as-synthesized nickel SAC (Ni-SAC) exhibits outstanding performance toward electrochemical CO2 reduction, achieving CO2-to-CO conversion with more than 90% faradaic efficiency in the potential range from -0.6 to -1.1 V vs. RHE, and the iron SAC (Fe-SAC) displays excellent ORR activity, with the half-wave potential surpassing that of the state-of-the-art Pt/C catalyst.