(377x) Transport Kinetics and Selectivity for Carbon Dioxide and Water for Gas Phase Electrolysis

The effects of electrode and membrane chemistry and structure on the overall reaction kinetics for the electrochemical reduction of O₂, chemical reactions with CO₂, and the transport kinetics through a membrane electrode assembly (MEA) were characterized through physiochemical relationships. Gas phase electrolysis using an MEA provides an alternative to gas separation over adsorbents, selective membranes, or reactive systems. In the case of CO₂ separation, the MEAs eliminates the heat and humidity generated from exothermic adsorption beds and reduces the power demand associated with membrane systems. Electrochemical impedance spectroscopy (EIS) measurements were used to determine the balance between the control of the electrocatalyst formation chemistry, pore structure, membrane chemistry, and gas diffusion layer and electrode structure. The electrochemical system was scaled-up with a larger electrode area and demonstrated within a closed-circuit breathing loop to maintain near-zero CO₂ concentration in the effluent. A 5 mol% CO₂, high-humidity gas mixture was delivered to the MEA at a rate of 2.1–4.2 mL/cm²Â·min while the current density was varied between 4–40 mA/cm². The MEAs maintained linear performance over a range of active area within a multi-cell system.