(157e) Simulations and Analysis of Fuel Cell Catalyst Degradation for the Development of Standardized Test Protocols

Fuel cells show promise as green energy and zero emission power source for several applications including transportation and stationary power production. Yet, the cost associated with energy production using fuel cells is higher than that of the conventional fossil fuels based technologies, which limits their commercial success. Platinum is the most widely used catalyst in fuel cell systems and it suffers from rapid degradation and depletion from the membrane electrode assembly. The degradation of catalysts can occur by several mechanisms namely dissolution, agglomeration, particle breakdown etc. Developing fuel cell catalysts with improved resistance to these degradation methods is a major challenge. However, tools to characterize the long term stability and durability of these new catalysts are not fully developed. In order to characterize the long term durability of catalyst materials and particles, there is a need to develop reliable and fast characterization techniques, using which new catalyst can be evaluated expeditiously.  This will accelerate the development of new catalysts with much better long term reliability. Theories in literature consider several mechanisms of catalyst degradation and quantify them at certain operating voltages. Traditionally  degradation is characterized through cyclic voltammetry (CV) over several thousand sweep cycles of voltage.

In this work, we simulate the degradation of platinum catalysts in the presence of various voltage cycle patterns utilizing the kinetics of the platinum degradation reaction. The parameters of the CV model are obtained by comparing the model with experiments. The degradation mechanisms that we consider are dissolution and oxide formation in platinum. This model is also extended to include the effect of agglomeration to study the particle size distribution using Oswald ripening dynamics. The use of the proposed approach in developing test protocols for rapid screening of new catalysts will be highlighted.