Accelerated Degradation of Perfluorinated Sulfonic Acid Membranes

Abstract

The degradation of PFSA membranes in fuel cells is a critical factor for fuel cell life time. Ex situ methods for determining the degradation processes have been used extensively, mainly radically initiated from gas or liquid phase. Gas phase degradation has proven to cause cleavage of the main polymer chain causing the degradation speed to increase. In this study decomposition products washed out in the water form both gas and liquid phase degradation experiments have been analyzed. Decomposition products were pre-concentrated using solid phase extraction (SPE) and analyzed with HPLC-MS. The distribution of decomposition products is significantly different for gas phase and liquid phase degradation. The same analysis procedure is applied on water condensed during fuel cell operation. The HPLC-MS chromatogram showed that the condition inside a fuel cell operating at optimal conditions, most probably is less harsh than those in both liquid and gas phase ex situ degradation experiments.

Time-resolved monitoring of composite Nafion™ XL membrane degradation induced by Fenton's reaction

“…In the literature, analyses of water effluents during fuel cell operation as well as Fenton solutions after ex-situ degradation permitted to clearly identify the product A [11,[69][70][71] and the trifluoroacetic acid (TFA) [71,72] as degradation products of PFSA membranes. More particularly, product A has a chemical structure deriving from that of the PFSA side-chain.…”

“…One must note that fluoride ions, which are present as hydrofluoric acid in acidic media, as well as other small molecules like TFA (its boiling temperature being 72°C) could evaporate upon degradation process taking place at 80°C. Finally, non-fluorinated molecules such as sulfate + or hydrogen sulfate + ions can also be released by the membranes in solution during the degradation process [11,29,32,71,72].…”

Local ageing effects of polymer electrolyte fuel cell membrane electrode assemblies due to accelerated durability testing

“…The daily profile of the reference test consists of 48 FC‐DLCs, according to Figure 3 (red line), eight short breaks of 20 min and a 4‐h break for regeneration. Standstill periods during which the stack is cooled down can regenerate the reversible voltage losses [14]. A maximum stack load of 1.5 A/cm 2 was applied.…”

“…In order to additionally stress the membrane mechanically, the ADT includes changing operating conditions, divided into the two states 'hot/dry' and 'cold/wet'. Those operating conditions were chosen according to recommended low and high values for fuel cell operation in automotive applications [14]. In addition, the electrodes can be affected by harsher operating conditions.…”

Rapid Radical Degradation Test of Polyaromatic Fuel Cell Membranes by Electron Paramagnetic Resonance

“…This is puzzling, since there can be no doubt that Nafion degrades, and a radical mechanism very close to that inferred here for polyaromatic membranes is normally assumed. The ether bridges in Nafion were found to be preferentially broken, fragmentation of the main chain was found several times for example by chromatographic product analysis or loss of molecular weight . Even evidence for the cross-linking to O−S−O was found by infrared spectroscopy for perfluorinated samples .…”