The cost and durability of the membrane electrode assembly (MEA) are today limiting factors for large‐scale commercialisation of the polymer electrolyte membrane fuel cell (PEMFC). The MEA durability in a real working fuel cell (FC) is closely linked to specific operating conditions such as temperature, gas humidity, load dynamics, etc. This often results in both chemical and mechanical degradation of the ion‐conducting membrane and subsequent operation failure of the FC. In this study, Raman spectroscopy is used to identify and distinguish between two different degradation processes for a 1,500 h in situ aged FC membrane. The primary process is due to the loss of proton conducting sulphonic acid end groups over the entire membrane. The secondary process is a degradation of the fluorinated backbone concentrated to the cathode interface; making possible the collapse of carbon into the resulting voids of the membrane. Using spatially resolved Raman spectroscopy we can unambiguously observe both the localisation and the state of the carbon inside the membrane; being similar/identical to the microporous layer (MPL).
Increased life-time of the proton conducting membrane of polymer electrolyte membrane fuel cells is the key to improve the endurance of fuel cell stacks. Here we present a Raman spectroscopy investigation of a fully fluorinated sulfonated membrane from a 1500h FC steady-state experiment compared with Nafion® membranes aged in hydrogen peroxide and Fenton's solution. The latter approach as an attempt to develop a screening method based on accelerated ageing. In all membranes degradation is evident. The Raman results of the fuel cell tested membrane demonstrate a loss of functional sulfonic acid groups throughout the membrane. The accelerated ageing, on the other hand, results in degradation readily observed: e.g. loss of polymer material, opaque areas, and brittleness. Notably, the relative concentration of functional sulfonic groups stays constant, indicating that the accelerated ageing methods primarily attack the backbone of the membrane.
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