Synergistic enhancement of the electrocatalytic reduction of CO2 to hydrocarbons at a large-sized Cu@Ag electrode†

The electrochemical CO₂ reduction reaction (CO₂RR) underlies a strategic approach to energy and environmental challenges. Large-sized materials offer industrial scalability due to their simplicity and cost-effectiveness. However, traditional large-sized Cu catalysts preferentially catalyze the hydrogen evolution reaction (HER) over the CO₂RR. Hence, the development of large-sized catalysts with enhanced reducibility is imperative for an efficient CO₂RR. In this study, a large-sized Cu@Ag catalyst was designed using electrodeposition, which enhanced the CO₂RR and suppressed the HER. The faradaic efficiency (FE) for hydrocarbons of the Cu@Ag catalyst was 59.8%, surpassing that of bare Cu nanoparticles by 21.4%. FE_H2 was notably reduced to 31.6%, compared to 63.0% for Ag foil and 55.2% for bare Cu nanoparticles. Theoretical calculations indicated a reconfiguration of Cu 3d orbitals in the Cu@Ag catalyst. The d_x²−y² orbital, being the highest occupied, modulated the affinity of CO₂ molecules and favored hydrocarbon formation. Additionally, the charge density at the Cu@Ag boundaries increased, facilitating C–C coupling. In particular, the C₂H₄/CH₄ ratio was enhanced by approximately 30-fold compared to using bare Cu nanoparticles. This study demonstrated that the synergistic mechanism of the Cu@Ag catalyst is key to enhancing the CO₂RR and inhibiting the competing HER, thus elucidating the molecular mechanisms for the conversion of CO₂ into valuable chemicals using large-sized Cu-based catalysts.