Electrodes Designed for Converting Bicarbonate into CO

Abstract

The deployment of electrolyzers that convert CO2 into chemicals and fuels requires appropriate integration with upstream carbon capture processes. To this end, the electrolytic conversion of aqueous (bi)carbonate offers the opportunity to avoid the energy-intensive steps currently used to extract pressurized CO2 from carbon capture solutions. We demonstrate here that an optimized silver gas diffusion electrode (GDE) architecture enables conversion of model carbon capture solutions (i.e., 3 M KHCO3) into CO at partial current densities (JCO) greater than 100 mA cm–2 with CO2 utilization rates of ∼70%. These results exceed the performance of any previously reported liquid-fed CO2 electrolyzers and rival gas-fed devices. We were able to hit these metrics through the systematic design of gas diffusion layer (GDL) components (e.g., polytetrafluoroethylene) and catalyst layer constituents (i.e., Nafion, silver) on CO production. A key finding of this work is that hydrophobic GDE components (which are common to gas-fed CO2RR electrolyzers) decrease in situ CO2 generation and thus the formation of the final CO product. These findings show a clear path toward industrially relevant reactors that couple electrolytic CO2 conversion with carbon capture.