Investigation of ternary catalysts for methanol electrooxidation

The electrochemical oxidation of methanol was investigated on Pt-Ru-X ternary metallic catalysts (with X=Au, Co, Cu, Fe, Mo, Ni, Sn or W). The catalysts were prepared by electrochemical deposition and dispersed in a conductive three-dimensional matrix, an electronic conducting polymer, polyaniline (PAni). A comparative study of the behaviour of several ternary catalysts towards the electro-oxidation of methanol shows that PAni/Pt-Ru-Mo is the most efficient anode at potentials up to 500mV vs RHE. This latter ternary electrocatalyst leads to current densities up to 10 times higher than those measured with PAni/Pt-Ru in this potential range. Moreover, the catalyst appears to be stable for potentials lower than 550mV vs RHE. According to EDX analysis, the good behaviour of the Pt-Ru-Mo ternary catalyst seems to result from the presence of a small amount of the third metal, at an atomic ratio close to 5%. This set of encouraging results has also been confirmed by preliminary measurements in a single cell direct methanol fuel cell (DMFC) containing a home made PAni/Pt-Ru-Mo anode. The ternary catalyst leads to higher power densities than the PAni/Pt-Ru binary catalyst under the same experimental conditions.