ELECTRON MICROSCOPY AND SMALL-ANGLE X-RAY SCATTERING ANALYSIS OF THE CATALYST LAYER DEGRA

The catalyst layer is one of the most critical components of a PEM fuel cell. The catalyst, in the form of platinum nanoparticles, tends to aggregate and sinter during operation, with the consequence to reduce its active area thus the efficiency of the entire fuel cell. This paper aims to highlight the efficiency of scanning electron microscopy (SEM) and synchrotron small-angle X-ray scattering (SAXS) to characterize the catalyst layer degradation of a commercial MEA for high temperature PEM fuel cells. SEM is an effective tool for the surface analysis of the samples, since it is able to obtain a magnification from 10x up to 105x. SAXS is a suitable technique to investigate the structural features of colloidal scale (between 10 and 103 Å). The paper presents in detail the analysis of three MEAs: one is a virgin sample, one was operated discontinuously in a single fuel cell, one operated in a 25 cells stack. The experiments show the degradation of the catalyst layer after operation. In particular, the agglomeration of the Pt particles leads to a growth in size from 5 nm up to 8 nm.