Analysis of the electrochemical characteristics of a direct methanol fuel cell based on a Pt-Ru/C anode catalyst

A vapor-feed direct methanol fuel cell based on a Nafion 117(R) solid polymer electrolyte was investigated. Pt-Ru/C and Pt/C catalysts were employed for methanol oxidation and oxygen reduction, respectively. The structure, surface, and morphology of the catalysts were investigated by x-ray powder diffraction, x-ray photoelectron spectroscopy, and transmission electron microscopy. Crystalline face-centered cubic phases were found In the Pt and Pt-Ru catalysts. The alloy composition in the Pt-Ru/C catalyst was different from the nominal composition, probably due to the formation of surface RuOx species, as indicated by x-ray photoelectron spectroscopy. Transmission electron microscopy observation showed an increase of the average particle size and particle agglomeration in the Pt-Ru/C catalyst compared to the Pt/C catalyst. The membrane/electrode assembly was prepared by using a ''paste process'' method. Scanning electron microscopy and energy dispersive x-ray analyses showed good adhesion of catalyst layers to the membrane and a homogeneous distribution of the ionomer inside the catalyst. AC-impedance and galvanostatic steady-state polarization techniques were used to investigate the electrochemical performance of the direct methanol fuel ce;l.