Decreasing resistances of membrane-electrode assemblies containing hydrocarbon-based ionomers for improving their anodic performances

Abstract To improve methanol-oxidation performances of membrane-electrode assemblies composed of a hydrocarbon-based ionomers, the resistances involved in the reaction were decreased. Electrochemical impedance spectroscopy revealed that the proton-conductive resistance ( R i ) in the anode was decreased from 0.54 to 0.40 Ω cm 2 by increasing a loading ratio of platinum–ruthenium to carbon support of anode catalyst from 54 to 73 wt.%. In addition, R i was decreased to be 0.25 Ω cm 2 by increasing ion-exchange capacity (IEC) of the ionomer from 1.4 to 2.9 mequiv. g −1 . Consequently, the polarization resistance of the anode was significantly decreased, in turn, increasing current density of methanol oxidation at the potential of 0.45 V from 0.110 to 0.244 A cm −2 .