Coverage-driven selectivity switch from ethylene to acetate in high-rate CO2/CO electrolysis

Tuning catalyst microenvironments by electrolytes and organic modifications is effective in improving CO 2 electrolysis performance. An alternative way is to use mixed CO/CO 2 feeds from incomplete industrial combustion of fossil fuels, but its effect on catalyst microenvironments has been poorly understood. Here we investigate CO/CO 2 co-electrolysis over CuO nanosheets in an alkaline membrane electrode assembly electrolyser. With increasing CO pressure in the feed, the major product gradually switches from ethylene to acetate, attributed to the increased CO coverage and local pH. Under optimized conditions, the Faradaic efficiency and partial current density of multicarbon products reach 90.0% and 3.1 A cm −2 , corresponding to a carbon selectivity of 100.0% and yield of 75.0%, outperforming thermocatalytic CO hydrogenation. The scale-up demonstration using an electrolyser stack achieves the highest ethylene formation rate of 457.5 ml min –1 at 150 A and acetate formation rate of 2.97 g min –1 at 250 A. Catalyst microenvironment induced by mixed CO/CO 2 feeds in an alkaline membrane assembly electrolyser determines the catalytic activity and product selectivity in CO 2 /CO electrolysis.