Recent progress of 3d transition metal as single-atom catalysts for electrochemical CO2 reduction to CO

Electrochemical carbon dioxide reduction (ECR) presents a promising technology to attain carbon neutrality. Recent studies have indicated that transition metal atoms as single-atom catalysts (SACs) show many advantages in ECR due to their tunable electronic structure, high atom utilization rate, and uniform active site. Among the various reduction products, CO is an important chemical feedstock that can be used in some essential processes such as Fischer-Tropsch, which produces a series of chemicals and fuels. However, few relevant reviews focus on 3d transition atoms as SACs for ECR to CO. In this review, we first emphasize the advantages of SACs and the CO product. Then, we summarize the recent development of SACs (Mn, Fe, Co, Ni, Cu, and Zn) in ECR to CO, focusing on the configurations of the active center. Finally, we briefly propose suggestions for future advancement of transition metal SACs for ECR to CO.