High-rate electroreduction of carbon monoxide to multi-carbon products

Carbon monoxide electrolysis has previously been reported to yield enhanced multi-carbon (C2+) Faradaic efficiencies of up to ~55%, but only at low reaction rates. This is due to the low solubility of CO in aqueous electrolytes and operation in batch-type reactors. Here, we present a high-performance CO flow electrolyser with a well controlled electrode–electrolyte interface that can reach total current densities of up to 1 A cm–2, together with improved C2+ selectivities. Computational transport modelling and isotopic C18O reduction experiments suggest that the enhanced activity is due to a higher surface pH under CO reduction conditions, which facilitates the production of acetate. At optimal operating conditions, we achieve a C2+ Faradaic efficiency of ~91% with a C2+ partial current density over 630 mA cm–2. Further investigations show that maintaining an efficient triple-phase boundary at the electrode–electrolyte interface is the most critical challenge in achieving a stable CO/CO2 electrolysis process at high rates. The low solubility of CO in aqueous electrolytes limits the implementation of CO electrolysers, since low current densities are typically achieved despite the fact that they deliver rather high Faradaic efficiencies to multi-carbon products. Now, Jiao and co-workers report a CO flow electrolyser with a well-controlled electrode–electrolyte interface that can achieve multi-carbon Faradaic efficiencies of 91% with a partial current density of 630 mA cm–2.