Upscaling and continuous operation of electrochemical CO2 to CO conversion in aqueous solutions on silver gas diffusion electrodes

Abstract

For the upscaling of the electrochemical conversion of CO2 to CO using Ag catalyst in water, gas diffusion electrodes (GDE) are needed for a sufficient supply of CO2 to obtain currents in the 100 mA cm−2 range. The effects of an upscale of one order of magnitude starting with 10 cm2 GDE size are presented. The penetration of electrolyte through the GDE needs to be regulated to balance the positive effects (avoid salt deposition) and the detrimental impacts (access blocking of CO2 to the GDE). Using a control of the partial pressure at the GDE to monitor the electrolyte penetration and enhancing CO2 feed by recirculation and turbulence promoters at the larger GDE. The first step of scale-up could be achieved without loss in performance. With three-compartment cells and 0.4 M K2SO4 electrolytes, the process is run at a current density of 150 mA cm−2 over a couple of hundred hours with a Faradaic efficiency for CO (FECO) of approximately 60% on 100 cm2 electrode area. It is discussed how to improve the performance by a management of the perspiration rate through the GDE to lay the scientific foundations for an industrial use of this technology.