Potential-regulated CO migration and CC bond formation on a co single-atom/Fe₃ cluster tandem catalyst for CO₂...

The electrocatalytic reduction of CO₂ toward C₂ products offers a promising route for sustainable chemical synthesis but the formation and stabilization of C₂ intermediates remain challenging. Herein, we theoretically design a tandem catalyst composed of a Co single atom and an Fe₃ cluster co-anchored on N-doped graphene (CoN₄-Fe₃N₆@G). Density functional theory (DFT) calculations reveal that the Fe₃ site and Co site each generate one *CO species, after which *CO adsorbed at the Co site migrates to the Fe₃ site, enabling a dual-*CO precursor for CC coupling. Potential-dependent free-energy analyses identify complementary potential windows: +0.3 V favors *CO retention and migration and dual-*CO precursor assembly and, once *CO···*CHO is present, CC bond formation relative to further proton-coupled electron transfer (PCET) hydrogenation; -0.9 V drives PCET conversion and further C₂ hydrogenation but also enhances C₁ hydrogenation and H adsorption. These findings motivate a pulsed-potential hypothesis that coordinates intermediate retention and assembly with cathodic conversion. This work provides mechanistic insights into atom-cluster tandem catalysts for promoting C₂-intermediate formation in CO₂ electroreduction.