Membrane ionomers

A membrane ionomer, in particular a polyelectrolyte with an inert backbone such as Nation . They require a plasticizer (typically water) to achieve good conductivity levels and are associated primarily, in their protonconducting form, with solid polymer-electrolyte fuel cells. 

Limoges et al. looked at the HOR catalytic activities of a series of heteropolyacids (HPAs) containing Mo and V. The CD is too low (a few mA/cm ) for them to be used as stand-alone anode catalysts, although it should be pointed out that the HPA loading of the anode used in this study was one to two orders of magnitude lower on a molar basis than that of a typical Pt anode. However, HPAs have been shown to be promising proton-conductive membrane/ionomer tillers and effective catalysts for H2O2 decomposition. On this basis, they may eventually become a part of fuel cell electrodes. 

The membrane and ionomer humidification requirements are of paramount importance for PEMFC operation since the proton conductivity is a fundamental necessity in the membrane as well as in the electrode for the fuel cell to function. The operating conditions of current PEMFCs are dictated by the properties of the membranes/ionomers. Now, the most important membrane type (e.g., Nafion membranes from DuPont) is based on PFSA ionomers that are used in the membrane... 

Nation 115 membrane-ionomer Aquivion membrane-ionomer... 

Table 8.4 Comparison ionomer membrane/ionomer blend membrane...

Under normal PEMFC operation conditions (<95 C), thermal degradation of membrane ionomer is generally of little concern. Sulfonate groups in PFS A ionomer decompose at approximately 280-300°C (St Pierre et al. 2000). Thermal decomposition of membranes by local combustion can become a potential pathway leading to membrane failures, especially when a pinhole is formed (Aoki et al. 2006a). By exchange of the proton for potassium ion, the thermal stability of Nafion is enhanced (Wilkie et al. 1991). So a heavily contaminated MEA can potentially slow down catastrophic failures. On the other hand, the required contamination level can be so high that the conductivity suffers to an unacceptable level. 

Eigure 4a shows the AB-ERR chart for a lOppm CO reformate. A possible sweet spot, a minimum ERR at 1.5% AB, is picked as the optimum AB level. The lowest ERR indicates a minimum in H O production at 1.5%, hence the lowest membrane/ionomer degradation rate. The amount of H O formation increases with an increase in the amount of O and/or the percentage yield of H Oj from the ORR. Eor example, the H O formation is augmented by an increase in 0 when... 

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