Direct methanol fuel cells (DMFCs) are attractive because of the high energy density of methanol, the overall simplicity of the fuel cell system and the easy refueling.[1] The state-of-art DMFC systems are based on the use of platinum-ruthenium catalyst at the anode, platinum catalyst at the cathode, and a polymer electrolyte membrane separating the two electrodes.[2] Although fuel cell power source products are now available in the range of 50 Watt to 2 kW, the commercialization has not occurred in the anticipated large-scale mainly because of the high precious metal catalyst loadings and durability of ruthenium-based catalysts. Our present study is focused on the study of anode catalysts, specifically to improve durability and reduce its cost. To this end, we have examined binary catalysts consisting of platinum and a second metal M (M=niobium, tantalum and titanium) prepared by co-sputter-deposition.

Platinum and the metal M were co-sputtered from separate cathode targets simultaneously using a high-voltage direct current on a Toray paper substrate. The atomic composition of metal M to platinum was varied between 0.1-2 by fixing the sputtering power to the platinum target and varying the sputtering power to the target containing metal M. The structure, morphology and composition of the catalyst were investigated by SEM, EDX and XPS. The results of quasi-steady state voltammetry suggested that the well-known bi-functional mechanism for methanol oxidation was operative on Pt-Nb and Pt-Ta catalysts. With the same amount of platinum, the methanol oxidation current of Pt-Ta and Pt-Nb catalyst was significantly improved compared to a sputtered platinum catalyst (Figure 1). The methanol oxidation current of Pt-Ta and Pt-Nb catalyst was 11.1 times and 8.3 times of platinum catalyst at -0.1 V vs. mercury/mercury sulfate reference electrode. We will present our understanding of the interaction between Pt and M (M=Nb, Ta) in enhancing the electro-oxidation of methanol and report on our efforts towards optimization of the catalyst composition to lower the noble metal content and enable practical use of these new catalyst materials in fuel cells