Permselective MOF-Based Gas Diffusion Electrode for Direct Conversion of CO₂ from Quasi Flue Gas

Abstract

Industrial activities lead to a substantial share of current anthropogenic CO2 emissions and are some of the most challenging to abate. Direct utilization of industrial flue gases to produce fuels or value-added chemicals is challenging due to the presence of impurities and low concentrations of CO2. Herein, we demonstrate a rational assembly of a permselective gas diffusion electrode (PGDE) for direct CO2 conversion from quasi flue gas (i.e., 10–15% CO2, 4% O2, and N2 balance at 100% relative humidity). The electrode design consists of a metal–organic framework (MOF) based mixed matrix membrane (MMM) that enables the selective permeation of CO2 to a silver electrocatalyst. The MOF is CALF-20, notable for the ability to physisorb CO2 in wet gas streams. Applying this approach, we convert N2-diluted CO2 streams to CO at a faradaic efficiency of 95% compared to 58% for the nonmodified counterpart electrode with MMM. The PGDE retained its electrochemical performance when introducing O2 by preventing ∼84% loss of current toward parasitic oxygen reduction reaction (ORR) and reported 30 mA cm–2 CO partial current density. Further, wetting the gas stream showed a negligible effect on the MOF and the electrochemical performance. Using our PDGE, we report nearly constant CO selectivity over 19 h in a membrane electrode assembly electrolyzer. This approach offers the potential for direct utilization of low-concentration CO2 while avoiding the economic and environmental costs of obtaining purified CO2 feedstocks.