Continuous CO2 electrolysis using a CO2 exsolution-induced flow cell

CO2 electrolysis promises a route to carbon-based chemicals and fuels using renewable energy and resources. However, industrial application is limited by the transfer of CO2, electrons, protons and products (CEPP) at high current densities. Here we present an electrolyser that uses the forced convection of an aqueous CO2-saturated catholyte throughout a porous electrode and exploits the in situ formation of CO2(g)-liquid-catalyst interfaces to improve the CEPP transfer and reach high current densities. The CO2 supply is expedited by an increased exsolution of gaseous CO2 from dissolved CO2 and bicarbonate due to the effect of local pressure decreases; simultaneous CEPP transfer is promoted with a tenfold decrease in the diffusion layer thickness. This system also enables catalyst synthesis by in situ electrodeposition and ligand modification. We achieved a maximum current density of 3.37 A cm(-2) with a Ag-based catalyst, and assemble a scaled-up 4 x 100 cm(2) electrolyser stack that produces CO at a rate of 90.6 l h(-1). The performance of CO2 electrolysers is often limited by poor transfer of reactants and products. Here the authors design a CO2 electrolyser in which forced convection of the catholyte throughout a porous electrode addresses this issue and allows high current densities to be reached.