Customization from Single to Dual Atomic Sites for Efficient Electrocatalytic CO Reduction to Value-added Chemicals.

In recent years, single-atom catalysts (SACs) have received increasing attention in the field of electrochemical CO RR with their efficient atom utilization efficiency and excellent catalytic performance. However, their low metal loading and the presence of linear relationships for single active sites with simple structures possibly restrict their activity and practical applications. Active site tailoring at the atomic level is a visionary approach to break the existing limitations of SACs. This paper first briefly introduces the synthesis strategies of SACs and DACs. Then, combining previous experimental and theoretical studies, this paper introduces four optimization strategies, namely spin-state tuning engineering, axial functionalization engineering, ligand engineering, and substrate tuning engineering, for improving the catalytic performance of SACs in the electrochemical CO RR process by combining previous experimental and theoretical studies. Then it is introduced that DACs exhibit significant advantages over SACs in increasing metal atom loading, promoting the adsorption and activation of CO molecules, modulating intermediate adsorption, and promoting C-C coupling. At the end of this paper, we briefly and succinctly summarize the main challenges and application prospects of SACs and DACs in the field of electrochemical CO RR at present.