Chemical degradation mitigation

Figure 8.24 shows the model capabilities to address competitive degradation phenomena membrane chemical degradation makes the proton conductivity decrease and thus potential cathode decreases which in turn decreases the kinetics of the cathode Pt degradation. In other words, membrane degradation can mitigate Pt degradation in the cathode, under specific operation conditions. 

Corns F D, Liu H and Owejan J E (2008), Mitigation of perfluorosulfonic acid membrane chemical degradation using cerium and manganese ions , ECS Trans, 16 1735-1747. 

Chemical degradation of PFSA membranes seems to be accelerated by elevated temperature, OCV conditions, low relative humidity, and elevated gas pressures. The main mitigation is the addition of radical scavengers and removal of non-perfluorinated groups. Note, that the amount of metal scavenger ions added to the membrane is limited and does not affect much the conductivity. 

To summarize this section, or gas crossover and reaction of the crossed-over gas on a catalytic surface are the most fundamental governing mechanisms for membrane chemical degradation. This lays a foundation before experimental parameters, other impacting factors, detailed degradation mechanisms, and potential mitigation methods can be discussed in later sections. 

M. Quintus et al., Chemical membrane degradation in automotive fuel cell -Mechanisms and mitigation, 2nd Annual International Symposium on Fuel Cell Durability Performance, Miami Beach, FL,7-8 Dec 2006... 

FIGURE 4.2 (See color insert following page 46.) Ricin sorption isotherms for several different clay minerals. (Zartman, R E., Green. C.J., San Francisco, M.J., Zak, J.C., Jaynes, W.E. and Boroda, E., 2002, Mitigation of ricin contamination in soils Sorption and degradation, Joint Services Scientific Conference on Chemical and Biological Defense Research, Hunt Valley, MD, November.)... 

Are hazards of legacy chemicals (e.g., abandoned, residual chemicals in tanks and pipes with inadequate controls) properly identified and addressed Have their potentially degraded storage conditions been considered Have these chemicals been sampled and characterized Are there adequate controls to prevent and mitigate adverse consequences Are the containers of these chemicals periodically inspected and maintained Are the hazards of these chemicals appropriately and sufficiently addressed in the facility s safety basis ... 

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