Numerical framework to study structural wetting properties of proton exchange membrane fuel cell catalyst layers with manufacturing parameters

Understanding the relationship between flooding behavior of Proton Exchange Membrane Fuel Cell Catalyst Layers (CLs) and their manufacturing parameters is of crucial importance to achieve global cell performance goals. We report here a novel computational workflow able to predict how manufacturing parameters impact the CL microstructure and its associated transport properties. The workflow comprises one discrete element method model for 3D CL microstructure generation that uses four manufacturing parameters inputs. The microstructures are then characterized with a novel two phase-field lattice Boltzmann model. A two-contact angle description was chosen to unravel the wetting behavior difference between the ionomer and carbon with platinum. The physics were verified using standard tests. The modeling workflow was tested on five microstructures generated with different water to isopropanol volumetric ratio in the solvent composition used to prepare the CL inks. Liquid water coverage ratio on the solid phases, relative permeabilities, and capillary pressures were calculated for each case and compared. The coverage ratio is noticeably influenced by the solvent composition, while the two-phase invasion is mostly impacted by the contact angle of the materials. Additionally, regular correlations used in macroscopic models were compared with the obtained results. We believe that our approach allows gaining unprecedented insights on the transport processes happening in CLs and can be also implemented in a macro-scale model for performance estimation.