Abstract
Electrochemical reduction of CO2 (ERCO2) in gas diffusion electrode (GDE)-based electrolyzers represents a potential strategy for global decarbonization, achieving simultaneously the valorization of this abundant carbon resource. While significant progress has been achieved in enhancing CO2 conversion in these systems, further advances are required to enable their practical implementation at the industrial scale. Physics-based simulations offer a powerful tool to guide the optimization of design and operating parameters as well as for the efficient scale-up of CO2 electrolyzers. In this work, we have developed a three-dimensional multiphysics model of the cathodic compartment of a GDE electrolyzer for ERCO2 to formate. For that purpose, the software COMSOL Multiphysics has been used. The model is experimentally validated, confirming its accuracy at reproducing current density and Faradaic efficiency at cathode potentials in the range -1.2 V and -1.7 V. Moreover, kinetic parameters are fitted to experimental data performing several parametric sweeps to minimize discrepancies between simulated and measured current densities. We obtain charge transfer coefficients (alpha_c_k) of 0.07 and 0.34, together with exchange current densities (i0, k) of 30 mA·cm-2 and 10-4 mA·cm-2 for ERCO2 and the competing hydrogen evolution reaction, respectively. Finally, the model is used to predict formate concentration under varying applied potential conditions. Collectively, our three-dimensional multiphysics model reliably predicts CO2 conversion to formate, thus representing a useful tool for guiding system optimization and scale-up. Moreover, the systematic methodology followed for developing the model can be readily extended to the design and analysis of other electrochemical cells beyond CO2-to-formate conversion.