Determination of ionic resistance and optimal composition in the anodic catalyst layers of DMFC using AC impedance

In the present study, a method based on transmission-line mode for a porous electrode was used to measure the ionic resistance of the anode catalyst layer under in situ fuel cell operation condition. The influence of Nafion content and catalyst loading in the anode catalyst layer on the methanol electro-oxidation and direct methanol fuel cell (DMFC) performance based on unsupported Pt-Ru black was investigated by using the AC impedance method. The optimal Nafion content was found to be 15 wt% at 75∘C. The optimal Pt-Ru loading is related to the operating temperature, for example, about 2.0 mg/cm2 for 75-90∘C, 3.0 mg/cm2 for 50∘C. Over these values, the cell performance decreased due to the increases in ohmic and mass transfer resistances. It was found that the peak power density obtained was 217 mW/cm2 with optimal catalyst and Nafion loading at 75∘C using oxygen.