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.