Selective and High Current CO2 Electro-Reduction to Multicarbon Products in Near-Neutral KCl Electrolytes

Reducing CO2 to value-added multicarbon (C2+) fuels and chemicals using renewable energy is a viable way to circumvent CO2 buildup in the atmosphere and facilitate closing the carbon cycle. To date it remains a challenge to achieve high product selectivity and long-term stability of electrocatalytic carbon dioxide reduction reaction (CO2RR) especially at practically relevant high current levels >100 mA cm(-2). Here, we report a simple electrodeposited Cu electrocatalyst on a hydrophobic porous gas-diffusion layer (GDL) electrode affording stable and selective CO2RR to C2+ products in nearneutral KCI electrolytes. By directing the CO, stream to fully submerged hydrophobic GDLs in a H-cell, high C2+ partial current densities near 100 mA cm(-2) were achieved. In a flow-cell setup, the Cu/GDL cathode in 2 M KCl afforded stable CO2RR superior to that in widely used KOH electrolytes. We found that Cu etching/corrosion associated with trace oxygen played a role in the catalyst instability in alkaline media under cathodic CO2 RR conditions, a problem largely suppressed in near-neutral electrolyte. A two-electrode CO2 electrolyzer was constructed with a Cu/GDL cathode in KCI catholyte and an anode comprised of nickel-iron hydroxide on nickel foam (NiFe/NF) in a KOH anolyte separated by Nafion membrane. By periodically adding HCl to the KCl catholyte to compensate the increasing pH and remove accumulated (bi)carbonates, we observed little decay over similar to 30 h in flow-cell CO2RR activity and selectivity at 150 mA cm(-2) with a high Faradaic efficiency (FE) of similar to 75% and energy efficiency of 40% for C2+ products.

Automated summary

A stable and selective electrocatalytic carbon dioxide reduction reaction (CO2RR) to C2+ products was achieved using a Cu electrocatalyst on a hydrophobic gas-diffusion layer (GDL) electrode in near-neutral KCl electrolytes. The instability of the catalyst in alkaline media under cathodic CO2RR conditions was largely suppressed by using a near-neutral electrolyte, showcasing the potential for long-term stability in CO2RR applications.