Heteroatom‐Engineered Triatomic Cu Cluster on G‐C ₃ N ₄ for Selective CO ₂ ‐to‐Ethylene Electrocatalysis

ABSTRACT Electrochemical reduction of CO 2 into multi‐carbon products offers a sustainable route to carbon recycling, yet achieving selective C─C coupling remains challenging. Here, we investigate the performance of heteroatom‐doped Cu 3 clusters supported on g‐C 3 N 4 for CO 2 ‐to‐C 2 H 4 conversion. Through DFT calculations and transition‐state analysis, we demonstrate that doping with P and Se stabilizes the Cu 3 clusters, enhances * CO adsorption, and lowers the energy barrier for the rate‐determining * CO + * CHO → * COCHO C─C coupling step to 0.84 and 0.92 eV, respectively. Thermodynamic analysis reveals a preference for ethylene formation over ethanol, with overpotentials as low as 0.33 and 0.10 V for P‐ and Se‐doped systems. Electronic structure analysis shows that first‐shell substitution with P or Se creates charge‐asymmetric sites, strengthens * CO and * CHO binding, and shifts antibonding Cu─CO states to higher energies, thereby promoting efficient C─C coupling. Electrochemically, the Se‐modified catalyst delivers a remarkable ethylene Faradaic efficiency of ∼54% at 250 mA cm −2 , and maintains stable performance for 30 h under flow‐cell conditions. This study establishes a synergistic theory‐experiment framework for optimizing CO 2 RR catalysts, emphasizing the critical role of precise cluster engineering and charge‐gradient doping in promoting efficient C─C coupling.