A Mathematical Model for the Membrane Electrode Assembly of a Bicarbonate Electrolyzer

Bicarbonate electrolyzers are devices designed to convert CO2 released in situ from bicarbonate ions into chemicals and fuels without an external source of CO2 gas. A one-dimensional steady-state isothermal model is developed for the membrane electrode assembly of a bicarbonate CO2 electrolyzer with a bipolar membrane design. The model incorporates species transport in both the anode and cathode electrodes due to convection, diffusion, and migration, and accounts for the catalyzed water splitting reaction at the interface of the anion exchange layer and the cation exchange layer of the bipolar membrane. A direct comparison of model simulations with available experimental data shows that the model can accurately simulate measured Faradaic efficiency and CO yield for all operating current densities. The model can also accurately simulate most of the polarization curve, with the only limitation being in the range dominated by mass transport. Compared to the other parameters studied in this paper, numerical results show that the performance of the bicarbonate CO2 electrolyzer is more sensitive to both aqueous electrolyte saturation in the cathode catalyst layer and the catalyzed water splitting efficiency of the bipolar membrane.