Physical-Statistical Modeling and Analyses of Catalyst Degradation in PEM Fuel Cells

Abstract

Platinum durability in the catalyst layers of polymer electrolyte fuel cells is a major challenge that delays the full commercialization of fuel cell vehicles. This work presents a physical-statistical model of platinum degradation. The modeling framework of the Pt degradation model encompasses the main processes at the particle level, namely catalyst dissolution, redeposition, coagulation, and detachment, and it accounts for the effluence of Pt ions into the polymer electrolyte membrane. Data sets analyzed with the model encompassinformation on changes in electrochemically active surface area, particle radius distribution, Pt mass distribution, and thickness of the catalyst layer. A systematic algorithm is developed to process experimental inputs and generate output information on kinetic rate parameters. The model-based data treatment proceeds in two stages: (i) statistical exploration of the complete parameter space using Monte Carlo techniques and (ii) an optimization routine to deconvolute contributions to degradation by different mechanisms anddetermination of the pertinent set of parameters. Model outcomes contribute to fuel cell performance and lifetime evaluation, development of strategies for degradation mitigation, and calibration of efforts in design and fabrication of catalyst materials and catalyst layers.