Enhanced multi-carbon selectivity via CO electroreduction approach

Abstract

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.