Decoupling catalyst aggregation, ripening, and coalescence processes inside operating fuel cells

Abstract

Simultaneous in situ X-ray diffraction (XRD) and small angle X-ray scattering (SAXS) of hydrogen fuel cell electrocatalyst layers allows nanoparticle degradation mechanisms of aggregation, coalescence and ripening to be independently decoupled during cell operation. The ratio of particle size to crystallite size is proposed as a direct measurement of catalyst particle–particle interactions. This metric is applied to track the aggregation of a practical industrial fuel cell catalyst in situ, during accelerated degradation. The dominant catalyst degradation mode changes over the course of the device’s life cycle, passing through distinct phases of aggregation, coalescence and ripening. Understanding the relative contribution of each degradation mode is necessary for engineering next-generation catalysts with commercially acceptable durability.