Accelerating C─C Coupling Kinetics in Electrocatalytic CO 2 Reduction by Precisely Atomic Cu 6 Cluster with Controllable Site Vibratility

Abstract Constructing desired Cu─Cu sites to strengthen C─C coupling behavior is significant for improving CO 2 electroreduction reaction (CO 2 RR) performance. However, unstable Cu sites will induce complicated reaction intermediates and an alterable reaction pathway in CO 2 RR process. Herein, two types of iodine‐bridged atomic clusters with different site vibratility are designed via constructing Cu 6 polymorphic isomers to reveal the relationship between Cu site vibratility and CO 2 RR performance. The trigonal Cu 6 cluster (T‐Cu 6 I 6 ) with 1.5% vibratility degree shows a more stable site structure, which can match well with the intermediates and accelerate C─C coupling kinetics in comparison with the cubic Cu 6 cluster (C‐Cu 6 I 6 , 25% vibratility degree). Specifically, the Faradaic efficiency of C 2 products on T‐Cu 6 I 6 can be up to 78%, higher than that of C‐Cu 6 I 6 (41%). The in situ spectroscopic characterizations and theoretical calculations disclose that slight vibrative Cu sites in T‐Cu 6 I 6 are in favor of * CO protonation and C─C coupling during CO 2 RR. This work presents an exploitation of site‐vibrative‐dependent electrocatalytic performance by accelerating the reaction kinetics.