Asymmetric atomic sites make different: Recent progress in electrocatalytic CO2 reduction

Electrochemical CO2 reduction reaction (CO2RR) provides an effective solution to the problems of greenhouse effect and energy shortage. As one of the catalysts for CO2RR, symmetric M-N4 atomic moieties still suffer from low product selectivity and high reaction overpotentials. The asymmetric coordination configurations are expected to modulate the adsorption/desorption behavior of key reaction intermediates, thereby suppressing the occurrence of side reactions and accelerating the reaction rate. This review discussed the recent progress of asymmetrically coordinated atomic site catalysts in electrocatalytic CO2RR. The asymmetric atomic sites, including low-coordination sites, heteroatom coordination sites and bi-metal sites were presented, which could be induced by the breakage of M-N bonds or/and the formation of M-X bonds. The regulation of electronic structure, the optimization of reaction paths and catalytic selectivity towards asymmetric configurations were discussed. At last, several research prospects were proposed, aiming to deepen and promote the development of asymmetric sites for electrochemical CO2RR.