Enhancing C₂ Selectivity in Electrocatalytic CO₂ Reduction Via Synergy of Plasmonic Hot Electrons and Photothermal Effect

Surface plasmon‐enhanced electrocatalytic CO 2 reduction offers an attractive dimension beyond conventional electrocatalytic methods by optimizing photon utilization to simplify electrocatalytic reactor designs and enhance reaction activity/selectivity. However, the synergistic regulation mechanism of the complex multiple plasmonic effects on the CO 2 reduction reaction, particularly under electrochemical bias, remains to be thoroughly investigated. This study, based on copper plasmonic electrodes, reveals the key role of localized surface plasmon resonance (LSPR) in enhancing CO 2 conversion and facilitating the transition of the key intermediate *CO from bridge to atop adsorption configuration. Through a combination of experiments and density functional theory calculations, we show that the synergy of plasmonic hot electrons and photothermal effect effectively reduces the C─C coupling energy barrier. Systematic measurements clarify the correlation between the plasmonic excitation of the electrode and the enhanced selectivity of C 2 products. Under optimized conditions, synergetic plasmonic effects significantly promote the CO 2 conversion and enhance the Faradaic efficiency (FE) of C 2 products, with a maximum increase from 57% to 87%. This work not only provides a new perspective for understanding the complex synergistic mechanisms of plasmonic effects, but also opens a new avenue for achieving selective electrocatalytic CO 2 conversion.