Steering the selectivity of electrochemical CO₂ reduction in acidic media

Abstract

Improving carbon utilization efficiency is the key to developing next-generation electrolysers for CO2 reduction reaction (CO2RR). The current CO2RR electrolyser relies on the use of neutral/alkaline media to suppress the competitive hydrogen production and improve the activity of CO2RR. However, the produced carbonate/bicarbonate leads to severe carbon loss. Performing CO2RR in acidic media can suppress the carbonate formation while hydrogen production is the major issue. Herein, we found that the activity of acidic CO2RR can be well tuned through electrolyte optimization on Cu and Ag catalyst. DFT calculation suggests that this results from the change of local electronic structure on Cu by surface adsorbed alkali metal ions. Electrolytes with high content of K+ promote the overall CO2RR activity, especially multi-carbon production in acidic media. CH4 is the dominant product in Na+ only electrolyte on Cu, with a Faradaic efficiency of 48 % at 220 mA cm−2 in pH=2 solution.