Membrane-Based Zero Gap CO2 Electrolyzer with Au Cathode Prepared By Electrodeposition

Abstract

Electrochemical CO2 conversion has been recognized as a promising technology that can overcome the global warming. Also, the production of useful fuels (e.g. CO, HCOOH, CH4, CH3OH and C2H4) is capable via electrochemical reduction of CO2. It was demonstrated that at least 200 mA cm–2 of partial current density should be required for commercial operation. However, in conventional aqueous system, the CO2 electroreduction was limited to 35 mA cm–2 of current density due to low CO2 solubility into the electrolyte. Furthermore, the diffusion length of CO2 from bulk to catalyst is much longer in H-type cell system causing prevent easy supply of CO2. To overcome these problems, a single cell based on a membrane electrode assembly (MEA) with zero gap between the electrodes was introduced to facilitate CO2 mass transfer to the catalyst surface.In this study, we investigate the MEA-based CO2 electrolyzer with anion exchange membrane. The electrodeposited Au on gas diffusion electrode (GDL), which exhibits the high CO production selectivity in CO2 electroreduction, was directly used as a cathode of CO2 electrolyzer. The humidified CO2 gas is supplied into cathode to promote the CO2 mass transfer to the catalysts-membrane interfaces. Furthermore, the content of polytetrafluoroethylene on GDL was controlled in order to prevent the product crossover between compartments that is feasible to exhibit stable performance. Compared to conventional H-type cell system, the 2-order magnitude improvement of partial current density was shown in MEA-based zero gap CO2 electrolyzer owing to low ohmic resistance and facile CO2 mass transfer.