Enhanced multi-carbon selectivity via CO electroreduction approach

Electrochemical CO₂ reduction reaction (eCO₂RR) attracted much attention as potential pathways for carbon utilization and sustainable chemical production. Many efforts have been devoted into improving eCO₂RR selectivity to multi-carbon (C₂₊) products as well as energetic efficiency, which often involve the use of a highly alkaline electrolyte. The employment of alkaline electrolyte in eCO₂RR inevitably causes the formation of carbonates and loss of CO₂ feedstock. Electrochemical CO reduction reaction (eCORR) has been proposed as a potential strategy to mitigate the carbonate formation issues. In this study, we conducted a detailed comparison of the electrocatalytic behaviors of Cu catalysts in both eCO₂RR and eCORR using a microfluidic flow cell under alkaline electrolyte conditions. Single-pass conversion of both reactions was studied under feedstock-deficient conditions through varying the feeding rates of CO₂ or CO and their partial pressures. In eCO₂RR, the Cu catalysts showed a relatively low carbon efficiency (i.e., the amount of carbon ended in the desired products divided by the total amount of CO₂ consumed) of less than 23% due to the formation of carbonate, whereas the catalysts exhibited a significantly higher carbon efficiency (up to 84%) in eCORR. Among all three Cu catalysts, the oxide-derived Cu plates showed the highest C₂₊ Faradaic efficiency of 83% at −0.59 V versus RHE in eCORR, corresponding to a C₂₊ partial current densities of 166 mA cm⁻².