A Membrane Electrolyte Assembly Cell to Remove O ₂ from Dilute CO ₂ Feeds

Conversion of CO2 to useful chemical intermediates may hold promise as a more sustainable approach to chemical manufacturing. However, CO2-containing streams captured from point sources contain other gaseous components such as N2 and O2, of which the latter may interfere with subsequent CO2 conversion steps. Higher [O2] in the CO2 feeds reduces the selectivity for CO formation in electrochemical CO2-to-CO conversion. This work reports a strategy for removing O2 from a CO2-rich stream to enable efficient subsequent CO2 conversion. We developed a scalable polymer electrolyte membrane-based electrolysis cell capable of significantly reducing [O2] in a gaseous feed. Specifically, the cell performs the oxygen reduction reaction on the cathode to remove the O2 from a gaseous feed, while emitting O2 on the anode via the oxygen evolution reaction, yielding an O2-depleted, CO2-rich stream. Key performance-determining parameters are the cell voltage, [O2] in the feed, and feed flow rate. The O2 extraction cell on both smaller (5 cm2) and larger (100 cm2) scales reduces the [O2] from 10 to 0.4 mol %, running for over 10 h at a rate of up to 0.08 g O2 cm–2 h–1. These findings demonstrate the suitability of this approach for the rapid removal of oxygen from gaseous streams.