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.