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 CO2 electrolysis performance. An alternative way is to use mixed CO/CO2 feeds from incomplete industrial combustion of fossil fuels, but its effect on catalyst microenvironments has been poorly understood. Here we investigate CO/CO2 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.

Automated summary

Tuning catalyst microenvironments by electrolytes and organic modifications improves the performance of CO2 electrolysis. The influence of mixed CO/CO2 feeds from incomplete industrial combustion on catalyst microenvironments has been investigated. CO/CO2 co-electrolysis over CuO nanosheets was studied in an alkaline membrane electrode assembly electrolyser. The optimized conditions achieved high Faradaic efficiency, partial current density, selectivity, and yield, outperforming thermocatalytic CO hydrogenation. The scale-up demonstration using an electrolyser stack showed high rates of ethylene and acetate formation.