Development of Pt and Pt – Fe Catalysts Supported on Multiwalled Carbon Nanotubes for Oxygen Reduction in Direct Methanol Fuel Cells

Ptand Pt–Fecatalysts supported on multiwalled carbon nanotubes (MWCNTs) were prepared by impregnation and reduction at intermediate temperature (400°C). The MWCNTs with diameters ranging from 20 to 100nmwere synthesized by a spray pyrolysis technique. Pt∕MWCNTsand Pt–Fe/MWCNT catalysts were characterized by X-ray diffraction, X-ray fluorescence, scanning electron microscope—energy dispersive X-ray analysis, and transmission electron microscopy techniques. The electrocatalytic behavior for the oxygen reduction reaction was investigated in rotating disk electrode configuration in an acidic medium, also in the presence of various methanol concentrations (0.01, 0.1, and 1M). An anodic shift of the peak potential for methanol oxidation of ∼150mVwas observed in the presence of 1Mmethanol concentration for the Pt–Fecatalyst compared to the Ptcatalyst. Both materials were used as cathodes in a direct methanol fuel cell at 30 and 60°C. A better performance was obtained for the cell based on Pt–Fe/MCWNTs as cathode catalyst. Although slight iron dissolution was observed after two weeks of discontinuous operation, the performance of the Pt–Fecatalyst was larger than the Ptcatalyst.