Optimum Nafion content in PEM fuel cell electrodes

Nafion ionomer is impregnated or incorporated in the PEM fuel cell electrodes to achieve high power density. Though many studies have been reported on the effect of Nafion content on electrode performance, best results have been reported at different Nafion loadings by different researchers. Nafion ionomer helps to increase the three-dimensional zone of catalytic activity and platinum utilization in the electrode. It also helps to retain moisture and prevent membrane dehydration especially at high current densities. An optimum Nafion content in the electrode is necessary to achieve high performance. As the platinum loading increases, the electrode thickness and Nafion thickness grows and hence the optimum Nafion content may depend on the platinum loading. In this paper, we have examined the correlation of platinum loading and optimum Nafion content in the electrode. We have found that optimum Nafion requirement depends on the platinum loading and it increases with decrease in Pt loading. For electrodes with 0.5, 0.25 and 0.1 mg/cm 2 Pt loading, best performance was obtained at about 20, 40 and 50% Nafion ionomer loading, respectively.