Computational insights into CO₂ electrochemical cells : Multiscale modeling and Performance enhancement

Electrochemical conversion of carbon dioxide (CO₂) can produce value-added chemicals and fuels such as carbon monoxide, methane, ethylene, formate/formic acid, and other multi-carbon products. This electron-to-molecule conversion technology represents a reliable pathway for achieving carbon-based fuels and commodities. This work focuses modeling approaches to improve the CO₂ reduction reaction and reduce cell operation costs.

An advanced electrochemical models were incorporated at various length scales, ranging from macroscale (cell level) to microscale (electrode level), to investigate cell performance and optimize electrode morphology for enhanced CO₂ reduction. A generalized modified Poisson-Nernst-Planck equation was employed to analyze ion transport with inclusion of the steric effect. The mathematical model was crafted to distinguish the current contribution from the ionomer additive phase (AEM) coated over cathode (Bismuth oxide) and from the liquid electrolyte phase. The modeling efforts correlated optimal electrolyte flow conditions with ionomer coverage over the catalyst to estimate optimal operating conditions. On comparing experimental and simulation results such as polarization curves, Faradaic efficiencies, the model demonstrates versality and applicability of various cell architectures. From the overall observations, it can be concluded that MEA cell type with electrolyte fed to anode side has lesser (bi)carbonate formation resulting in better single pass efficiency.

In addition to the macroscopic scale model, an advanced three-dimensional microstructural model was developed to investigate the influence of electrode morphology on electronic and ionic pathways. Based on morphological parameters such as volume fractions, particle size distributions, and ionomer coverage, synthetic microstructures were generated for the model. These microstructure was implemented in the COMSOL multiphysics equipped with custom MATLAB code. The microscale model focuses on reaction kinetics at several interfaces, including catalyst/ionomer, catalyst/liquid electrolyte, gas/liquid phases. These results and analyses help identify optimal morphological parameters like ionomer coverage, ionomer location, and electrolyte flooding condition in pore regions.