Raman Spectroscopy of an Aged Low Temperature Polymer Electrolyte Fuel Cell Membrane

Abstract

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).

3 In situ and operando determination of the water content distribution in proton conducting membranes for fuel cells: a critical review

“…113 and 114 and references therein). Concerning proton conducting polymers, the high spatial resolution of this method was previously exploited ex situ to map the distribution of functional molecular groups, 115,116 to study the extent of degradation of fuel cell tested materials [117][118][119][120][121] and to investigate Schroeder's paradox 122 as well as the effect of mechanical stress on the local water content. 123 But the most common use of ex situ Raman spectroscopy remains to check chemical composition and structure of new composite membranes.…”

Depth‐resolved micro‐Raman spectroscopy of tri‐layer PFSA membrane for PEM fuel cells: how to obtain reliable inner water contents

“…As far as transparent proton conducting polymers are concerned, the μ‐Raman ability of in‐depth analysis by optical sectioning (i.e. the nondestructive study of thin sample slices as a function of depth) has been exploited to map the distribution of functional molecular groups, to study the extent of degradation of fuel cell tested materials and to investigate the PFSA local water content as a function of ageing and mechanical stress . An emerging application is the in situ measurement of concentration profiles of water diffusing across the membrane thickness .…”

Challenges and opportunities for characterisation of high-temperature polymer electrolyte membrane fuel cells: a review

“…Raman spectroscopy is a exible, non-invasive analytical technique with micron spatial resolutions. 422 Raman spectroscopy in LT-PEMFC research has been used to investigate the chemical structure of catalyst and support materials, [423][424][425] analyse membrane degradation, 426 including the distinction between loss of sulphonic end groups and uorinated backbone, 427 and determine membrane water content. 428 One benet of Raman over infrared spectroscopy is that the spectra are not overwhelmed by the presence of liquid water.…”