Highly Selective and Scalable Electrolysis for Gaseous CO2 Reduction in the Zero-Gap Electrolyzer

Abstract

The electroreduction of carbon dioxide (CO2) to chemicals represents a promising pathway for the storage of renewable electricity and toward low-carbon-footprint chemicals production. Prior study on CO2RR have focused on the catalytic properties of various materials in liquid condition. However, the current density for CO2RR is restricted under 30 mA cm–2 due to the mass transfer limit and low solubility of CO2 in the aqueous solution. To increase the current density, the gas fed CO2 electrolysis system was investigated using a gas-diffusion layer (GDL) system. Masel et al. reported about new zero-gap CO2 electrolysis device that uses an anion exchange membrane (AEM, SustainionTM) with humidified CO2 flow in the cathode and shows a current density of 200 mA cm-2 with steady FECO of over 90% using Ag catalyst.Herein, we developed a convenient Ag-based and Cu-based electrode with high selectivity and high current density for electrochemical conversion of CO2 to CO and ethylene in a zero-gap electrolyzer, respectively. We tested the electrochemical properties of the prepared Ag-based electrode in the gaseous CO2-fed electrolyzer and H-type electrochemical cell with respect to CO2RR. Ag coral electrode achieves CO partial current density of 312 mA cm–2 with FECO > 95%. Cu-KOH electrode demonstrate 260 mA cm–2 current density with 60.5 % C2H4 faraday efficiency at 10 cm2 electrode area. Moreover, the prepared electrode was analyzed the change of electronic structure using in-situ/operando X-ray absorption spectroscopy (XAFS) at real gas fed zero-gap electrolyzer condition. Based on these results, we could give insights about the scalable electrolyzer system for electrochemical conversion of CO2 with high catalytic activity and selectivity.