Chemical degradation, PFSA membranes mechanism

In spite of the documented, relatively high chemical stability of poly(PFSA) membranes in the fuel-cell environment, recent extensive work looking into the origins of performance loss observed in PEFCs has revealed important mechanisms of degradation that apply to perfluorinated membranes (while being further amplified in nonperfluorinated membranes). An important mechanism of membrane... 

The chemical degradation of PFSA membranes is mainly caused by the gas crossover, forming hydrogen peroxide, which reacts with impurities (e.g., iron contaminations) producing hydroxyl and hydroperoxy radicals that could attack (decompose) the membrane (refer to Chapter 4 for detailed degradation mechanisms). 

Before discussing membrane chemical degradation in detail, the factors governing the degradation mechanism must be identified. Among three major types of membrane materials, hydrocarbon, partially fluorinated, and perfluorinated ionomers, perfluorinated sulfonic acid (PFSA) is the most widely used membrane material owing to its high chemical stability (Schiraldi 2006). 

Detailed discussions on the membrane chemical degradation mechanisms will first be divided into three main categories hydrocarbon membranes, g-PSSA membranes, and PFSA membranes. General degradation pathways and correlations between different types of membranes will be discussed at the end of this section. 

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