Lattice-Boltzmann Modelling of Flooding in Gas Diffusion Electrodes for Stable Electrochemical Carbon Dioxide Reduction (CO2R)

Abstract: Carbon dioxide (CO2) electrolysis, powered by renewable energy, is a promising route for utilizing captured CO2 to produce valuable chemical feedstocks such as carbon monoxide and ethylene. One of the key challenges in CO2 electrolysis, also known as CO2 reduction (CO2R), is managing the mass transfer of reactants and products to and from the cathode catalyst in the electrolyser. State-of-the-art CO2R electrolysers employ carbon paper-based gas diffusion electrodes (GDEs) to enhance mass transfer. GDEs are high-surface-area porous structures that support the electrocatalyst and facilitate interaction between gaseous CO2 and aqueous electrolyte reactants. However, electrolyte flooding of the GDE due to pressure imbalances and wettability changes affects the long-term stability of the electrolyser., To develop resilient and efficient electrolysers, it is important to understand the complex multiphase transport within these devices. Experimental analysis of flooding behavior is challenging, as conventional x-ray imaging often lacks contrast between the constituent material and liquid phases. Fortunately, combining experimental measurements with pore-scale numerical modeling can provide insights into the mechanisms leading to flooding during CO2R and inform GDE design. This study first presents and validates a method to stochastically generate a wet-proofed carbon paper sample, comparing it with physical characteristics experimentally reported. Following this, a preliminary validation of the phase-field lattice Boltzmann method (PFLBM) to capture flooding behavior in a mixed-wet GDE under capillary and inertial flow is conducted and contrasted with state-of-the-art results in literature. Future work will apply the stochastic methods and PFLBM introduced here to analyze the impact of GDE surface defects on flooding. Keywords: Multiphase flows, Computational fluid dynamics, Flow in porous media, Electrochemical systems