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

Constructing desired Cu─Cu sites to strengthen C─C coupling behavior is significant for improving CO₂ electroreduction reaction (CO₂RR) performance. However, unstable Cu sites will induce complicated reaction intermediates and an alterable reaction pathway in CO₂RR process. Herein, two types of iodine-bridged atomic clusters with different site vibratility are designed via constructing Cu₆ polymorphic isomers to reveal the relationship between Cu site vibratility and CO₂RR performance. The trigonal Cu₆ cluster (T-Cu₆I₆) 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 Cu₆ cluster (C-Cu₆I₆, 25% vibratility degree). Specifically, the Faradaic efficiency of C₂ products on T-Cu₆I₆ can be up to 78%, higher than that of C-Cu₆I₆ (41%). The in situ spectroscopic characterizations and theoretical calculations disclose that slight vibrative Cu sites in T-Cu₆I₆ are in favor of ^*CO protonation and C─C coupling during CO₂RR. This work presents an exploitation of site-vibrative-dependent electrocatalytic performance by accelerating the reaction kinetics.