One of the key objectives in fuel cell technology is to improve the alcohol oxidation efficiency of Pt-based catalysts. A series of carbon-supported PtRu nanowires with different concentrations of Pt and Ru were prepared for application in methanol oxidation in acid media. The physicochemical properties and electrocatalytic activity of these catalysts during methanol oxidation are function on their structure, morphology and composition. A Pt 60 Ru 40 /C catalyst shows the best behaviour towards methanol electro-oxidation allowing decrease the onset potential approximately 0.2 V respect to others PtRu/C synthesised nanowires. The structural modification of Pt by Ru and synergetic character of RuPt are main factors that could contribute to reduction of energy necessary for electro-oxidation process. The Pt and PtRu nanowires have different sizes and distribution on the substrate. The average crystallite sizes, found by XRD, are in the 4.6-5.9 nm range and the lattice parameter is between 0.3903-0.3908 nm. Small differences with the values of the Pt/C catalyst were found. The XPS results show a prevailing presence of metallic Pt and Ru 4+ species.
iridium nanowire-shape electrocatalysts containing 20% of metallic loading were synthesized by chemical reduction method using formic acid as a reducing agent and tested towards the oxidation of ethanol in acidic medium. The developed electrocatalysts were synthesized with the following compositions: Pt 0.9 Ir 0.
This work aimed on the development of platinum and platinum-ruthenium nanowires supported on carbon powder, via chemical reduction using formic acid as a reducing agent, and the study of electrooxidation of methanol in acidic medium on these catalysts. The metal load of the nanowires in relation to the substrate was varied from 20, 30 and 40% and their composition for the Pt-Ru/C nanowires was maintained at 60:40. The nanocatalysts were characterized by X-ray diffraction, X-ray fluorescence, transmission electron microscopy (TEM) and cyclic voltammetry, showing that the nanowires have the cubic face-centered structure of platinum. The chemical composition of the catalysts is close to nominal. The TEM images showed that Pt/C and Pt 0.6 Ru 0.4 /C nanowires were successfully synthesized by the chemical reduction method presenting nanowires with a diameter between 4 and 13 nm and a length between 15 and 20 nm. The Pt 0.6 Ru 0.4 /C 20% catalytic composite exhibit the lowest CO oxidation onset potential (0.34 V) which is 0.3 V more negative than the obtained for a commercial Pt/C catalyst. The current density of the CO-stripping peak at the Pt 0.6 Ru 0.4 /C 20% catalytic composite is also 3 times higher than for the commercial Pt/C. The incorporation of ruthenium in the Pt/C nanowires and their decrease in metallic loading increased their efficiency towards the electrooxidation of methanol. The nanowires Pt 0.6 Ru 0.4 /C are thus promising materials as anodes for use in direct methanol fuel cells.
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