Application of TGA techniques to analyze the compositional and structural degradation of PEMFC MEAs

Abstract

Thermogravimetric analysis (TGA) has been proposed as a new post-analysis tool of membrane electrode assembly (MEA) for polymer electrolyte membrane fuel (PEMFC). Analysis of catalyst layer (CL) samples with various Nafion ionomer contents quantitatively confirmed that the Nafion ionomer decomposed first at around 320 degrees C and the support carbon at around 410 degrees C. For the degradation analysis of MEAs, the amount variation of components, including platinum (Pt) and attached gas diffusion layer (GDL), and the degree of Pt agglomeration could be evaluated from weight changes and DTG peak shifts (the platinum activation effect), respectively. For an MEA degraded by start-up/shut-down cycling, Pt agglomeration and significant GDL attachment, as well as invariant Pt amount and slight weight decrease of Nafion and supporting carbon, could be analyzed by a single TGA measurement. Similar degradation analysis was also possible for stack-operated MEAs. This TGA analysis technique is expected to be effectively utilized as a preliminary diagnosis tool in a routine characterization of degraded PEMFC MEAs.