Effects of carbon aggregates and ionomer distribution on the performance of PEM fuel cell catalyst layer: A pore-scale study

An in-depth understanding of the structure-performance relationship of the catalyst layer is crucial for its optimal design. In this work, the effects of carbon aggregation and ionomer distribution morphologies on the performance of the catalyst layer are investigated by pore-scale simulation. First, an optimized stochastic algorithm that can control the carbon aggregation degree and ionomer morphology is proposed to reconstruct realistic catalyst layer structures. The structural characteristics of the catalyst layer, such as pore size distribution, agglomerate size, and ionomer connectivity, are analyzed. A pore-scale model based on the lattice Boltzmann method is developed to simulate the reactive transport processes in the catalyst layer. The results indicate that the reasonable aggregation degree of carbon supports can balance the pore and cross-ionomer transport resistances of the oxygen to achieve optimal catalyst layer performance. The uniform ionomer coating in the catalyst layer can further improve the performance, and the optimal ionomer content is determined by balancing the electrochemical active surface area and the oxygen transport resistance. Based on the simulation results, a key principle for the optimal design of the catalyst layer is also proposed.