Ag Membranes for Electrochemical CO2 to CO Conversion in an MEA Type Set-up

While there has been a large push towards electrochemically derived fuels such as hydrogen, chemicals such as carbon monoxide have much more favorable economics(1) and are thus highly promising. Both Au and Ag are well-established catalysts for electrochemically producing CO,(2) but studies on upscaling these reactions to industrial relevant currents (> 100 mA/cm2) is lacking. This talk will discuss our work on using Ag membranes for electrochemical CO2 to CO conversion in a membrane electrode assembly (MEA) device. The cathode is completely carbon free and can produce predominantly CO at currents up to 250 mA/cm2 (@ approximately 3 V), and thereafter significant H2 evolution starts to occur. Typical tests were 24 hours, but some longer-term data will be show, demonstrating the stability of the system. Variations in humidity from the gaseous cathode side had effects on both performance and durability. The anode electrolyte was a bicarbonate solution with either an accompanying K, Na, or Cs cation. Variations in the cations resulted in a notable performance change even though an anion exchange membrane was present. By inserting a reference electrode into our anode side we could separate our cathodic, anodic, and ionic losses, thus allowing us to better understand our system. The advantages, disadvantages, and engineering knowledge gained from this work will be summarized. 1) Progress and Perspectives of Electrochemical CO2 Reduction on Copper in Aqueous Electrolyte. Nitopi et al., submitted 2018, 2) Electrocatalytic process of CO selectivity in electrochemical reduction of CO2 at metal electrodes in aqueous media. Hori et al., Electrochimica Acta, 1994, 39, 11-12, 1833-1839