Porous metal electrodes enable efficient electrolysis of carbon capture solutions

Abstract

Bicarbonate electrolysers convert aqueous carbon capture solutions enriched with bicarbonate into carbon products (e.g., CO), and generate hydroxide for further reaction with waste CO₂. These electrolysers link upstream carbon capture to electrochemical CO₂ utilization without high temperature or pressurization steps. We report here a bicarbonate electrolyser with a free-standing porous silver electrode rather than a composite carbon electrode widely used in electrolysers fed with gaseous CO₂. This free-standing metal electrode is easier to fabricate than a composite carbon electrode, and the higher hydrophilicity helps to mediate efficient electrolysis of 3.0 M bicarbonate solutions into CO: faradaic efficiencies for CO production of 59% at 100 mA cm⁻² at ambient pressure, and 95% at 100 mA cm⁻² and 4 atmospheres of pressure. These performance metrics are comparable to those observed for gas-fed CO₂ electrolysers. The free-standing porous metal electrode is more closely aligned with electrodes used in commercial electrolysers, and is also more durable than composite carbon electrodes. The porous metal electrode is also more resistant to impurities common to carbon capture solutions. Bicarbonate electrolysers with free-standing porous metal electrodes can benefit carbon capture schemes where OH⁻ solutions react with CO₂ to form bicarbonate-rich solutions.