Methodology for Evaluation of Contributions of Ostwald Ripening and Particle Agglomeration to Growth of Catalyst Particles in PEM Fuel Cells

Abstract

AbstractThe degradation of the catalyst layer represents one of the main limiting factors in a wider adoption of fuel cells. The identification of the contributions of different mechanisms of catalyst degradation, namely the Ostwald ripening and particle agglomeration, is an important step in the development of mitigation strategies for increasing fuel cell reliability and prolonging its life time.In this paper, the degradation phenomena in high temperature polymer electrolyte membrane fuel cell (HT‐PEMFC) are analyzed using a physically‐based model of fuel cell operation and catalyst degradation, describing carbon corrosion, platinum dissolution and consequent growth of catalyst particles. The model results indicate significantly different time dependence of catalyst particle growth resulting from different mechanisms: linear growth in the case of particle agglomeration and root‐like time dependence for the Ostwald ripening.Based on these results, a new analytic method is proposed, performed by the fitting of a test root‐function to the time profile of the particle size growth and using best‐fit parameters to identify the prevailing growth mechanism. Using this method on a particle growth time trace deduced from in situ cyclic voltammetry measurement during HT‐PEMFC degradation, we are able to identify the agglomeration as the main mechanism of catalyst particle grow.