Nafion degradation mechanism

Fig. 1. Degradation mechanism of Orange n on Nafion/Fe membranes under light.

Many efforts have been made to find the proper alternative to Nafion at elevated temperature operation for PEMFCs, as Nafion degrades at temperatures higher than 110-130 °C. It was found that the organie-inorganic composite membrane can improve its own mechanical strength and thermal stability at... 

Increased temperatures have a strong correlation to some of the key degradation mechanisms. Membrane degradation due to chemical mechanisms as indicated by fluoride release rate has been shown to follow an Arrhenius relationship with temperature, with an increase of 1.8 times for a 10 °C rise. Figure 6.4 shows the relationship between temperature and the fluoride release rate as measured in the cathode and anode effluent at open-circuit voltage operation for an MEA containing DuPont Nafion 112 membrane. This trend is consistent with data reported in the Uterature, e.g. Madden et al. (2009). Sethuraman et al. (2008) showed the effect of temperature on lifetime at open-circuit voltage and found a lifetime of -500 h at 80 °C was dramatically decreased to -60 h at 100 °C and only -30 h at 120 °C (Sethuraman et al., 2008). 

Many polymers synthesized by free-radical polymerization can sustain depolymerization via a chain unzipping mechanism. Thermal degradation of Nafion indicates that chain unzipping is the main mechanism for Nafion degradation (Wilkie et al. 1991). 

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