Multiscale model to resolve the chemical environment in a pressurized CO2-captured solution electrolyzer

Abstract

The community of electrochemical CO2 reduction is almost exclusively focused on gaseous CO2-fed electrolyzers. Here, we proposed a pressurized CO2-Captured solution electrolyzer to produce solar Fuel of CO (abbreviated “CCF”) without the need to regenerate gaseous CO2. Specifically, we developed an experimentally validated multiscale model to quantitatively investigate the effect of pressure-induced chemical environment and to resolve the complex relationship between this effect and the activity and selectivity of CO production. Our results show that the pressure-induced variation of the cathode pH has a negative effect on the hydrogen evolution reaction, whereas the species coverage variation positively affects CO2 reduction. These effects are more pronounced at pressures below 15 bar (1 bar = 101 kPa). Consequently, a mild increase in the pressure of the CO2-captured solution from 1 to 10 bar leads to a dramatic enhancement in selectivity. Using a commercial Ag nanoparticle catalyst, our pressurized CCF prototype achieved CO selectivity higher than 95% at a low cathode potential of −0.6 V versus reversible hydrogen electrode (RHE), comparable to that under the gaseous CO2-fed condition. This enables the demonstration of a solar-to-CO efficiency of 16.8%, superior to any known devices with an aqueous feed.