Anion Exchange Membrane Transport and Accelerated Lifetime Testing of Membrane Electrode Assembly Cells for the Electrochemical Reduction of CO₂-to-C₂ Products

Electrocatalytic carbon dioxide (CO₂) reduction to C₂₊ products holds promise for low carbon intensity fuels, chemicals, and food; however, durability challenges, particularly those associated with carbonate salt precipitation, hinder their commercialization. This report considers water (H₂O) and ion transport properties of conventional anion exchange membranes (AEMs) in zero-gap membrane electrode assembly (MEA) configurations using Cu electrocatalysts. Transport characterizations include H₂O diffusion, permeability, potassium ion (K⁺) diffusion, and transference numbers using commercial piperidinium-based (Versogen), quaternary ammonium-based (Fumasep), and imidazolium-based (Dioxide Materials) AEMs. Accelerated lifetime testing of CO₂ reduction in MEA cells was conducted using galvanostatic stepping at 6 h intervals to define a precipitation-free operating window. A “critical current density” was identified based on cell potential and cathode pressure behaviors during the current density stepping experiments. When operating the MEA cell in a galvanostatic mode at the critical current density values, cathode drying and precipitation were typically observed in under 60 h of continuous electrolysis; however, operating the cell at a fraction (75%) of the critical current extended continuous operation in the range of 500 to 1000 h.