Electroreduction of diluted CO2 to multicarbon products with high carbon utilization at 800 mA cm–2 in strongly acidic media

Acidic CO2 electroreduction using diluted CO2 (as in flue gas) as the feedstock can simultaneously circumvent the CO2 purification step and lower the carbon loss in conventional alkaline or neutral electrolyte, and thus is highly desired but has rarely been achieved thus far. Herein, we report a simple and general strategy using an imidazolium-based anion-exchange ionomer as the coating layer, which could enrich the diluted CO2 to generate a high local CO2 concentration, and simultaneously block the proton transport to the cathode surface to suppress the competing hydrogen evolution reaction. As a result, the ionomer-modified Cu catalyst can achieve an efficient electroreduction of diluted CO2 (15 vol% CO2) to multicarbon (C2+) products in strong acid (pH 0.8), with a high C2+ Faradaic efficiency of 70.5% and a high single-pass carbon efficiency of 73.6% at a current density of 800 mA cm–2, competitive with that obtained with pure CO2. These findings provide opportunity for the direct electrochemical conversion of flue gas into valuable products with high efficiency.