Evaluation of Degradation Mechanisms of Polymer Electrolyte Fuel Cell Using DEM Simulation

Polymer electrolyte fuel cells (PEFCs), which have various advantages such as high power output, high conversion efficiency, and low operating temperature, are expected to be applied to heavy-duty vehicles with a high environmental impact, and further performance and durability improvements are required for practical use. Currently, the degradation of power generation performance due to long-term operation is an issue in the practical application of PEFCs and it is considered that one of the causes of this degradation is the corrosion of the carbon support. However, the dynamic process of catalyst layer structure change due to CB particle corrosion has not yet been clarified, and the relationship between power generation performance change and catalyst layer microstructure has not been linked. It is also considered difficult to do so experimentally with the current state of the art. In this study, we focused on analyzing the dynamic structural change behavior of the catalyst layer due to corrosion of the carbon support by using numerical model simulation. By using the catalyst layer created by the numerical model, we simulated the power generation reaction and to identify the factors that cause the degradation of power generation performance. Discrete element method (DEM) was used to calculate the structure of catalyst layer by using carbon support, which is a branch-like aggregate of carbon black (CB) particles. The aggregate arrangement was determined based on the translational and rotational equations of motion for individual aggregates, elasticity between particles, and viscous damping 1) . Based on previous studies 2) 3) , the carbon corrosion reaction caused by the reaction between the products of the carbon surface reaction and the platinum oxidation reaction is considered, reflecting localized carbon corrosion within the catalyst layer. Also, we hypothesized that the porosity increases due to the shrinkage of CB particles in the early stage of corrosion, followed by a decrease in porosity and thickness due to the separation of the sintered parts of the CB particles that compose the aggregates. Furthermore, in this model, the fastening pressure is related to the timing of the structural collapse of the catalyst layer. Therefore, in this study, we performed calculations considering the neck breakdown of the aggregate due to the fastening pressure. The particles were assumed to be non-porous carbon (Vulcan), and calculations were performed under the s