Improved catalytic performance of CO₂ electrochemical reduction reaction towards ethanol on chlorine-modified Cu-based electrocatalyst

Effective electrochemical conversion of CO₂ to value-added liquid multi-carbon products driven by renewable energy is a promising approach to alleviate excessive CO₂ emission and achieve large-scale renewable energy storage. However, the selectivity and catalytic activity towards liquid multi-carbon products of CO₂ electroreduction reaction are still unsatisfactory due to the sluggish C–C coupling process and the formation of complex oxygen-containing intermediates. Hence, designing and fabricating highly effective electrocatalysts is crucial for practical applications in this field. Here, we developed Cl-modified Cu catalyst (Cu-Cl) for efficient electrochemical reduction of CO₂ to ethanol. The optimal Faradaic efficiency and partial current density of ethanol on the Cu-Cl sample reached 26.2% and 343.2 mA·cm⁻² at −0.74 V (vs. reversible hydrogen electrode (RHE)), which were 1.66 and 1.76 times higher than those of the catalyst without Cl decoration, outperforming those in most previously reported works. Density functional theory (DFT) calculations revealed that the Cl-modified Cu surface suppressed the parasitic hydrogen evolution reaction (HER) and reduced the energy barrier for the C–C coupling process, making the formation of key intermediates favorable for ethanol production. Thus, the decoration of Cl on the Cu surface facilitated ethanol formation.