CO2 electroreduction to multicarbon products from carbonate capture liquid

Alkali hydroxide systems capture CO2 as carbonate; however, generating a pure CO2 stream requires significant energy input, typically from thermal cycling to 900°C. What is more, the subsequent valorization of gas-phase CO2 into products presents additional energy requirements and system complexities, including managing the formation of (bi)carbonate in an electrolyte and separating unreacted CO2 downstream. Here, we report the direct electrochemical conversion of CO2, captured in the form of carbonate, into multicarbon (C2+) products. Using an interposer and a Cu/CoPc-CNTs electrocatalyst, we achieve 47% C2+ Faradaic efficiency at 300 mA cm−2 and a full cell voltage of 4.1 V. We report 56 wt % of C2H4 and no detectable C1 gas in the product gas stream: CO, CH4, and CO2 combined total below 0.9 wt % (0.1 vol %). This approach obviates the need for energy to regenerate lost CO2, an issue seen in prior CO2-to-C2+ reports.