Preparation and characterization of Pt/C and PtRu/C electrocatalysts for direct ethanol fuel cells

Nano-sized Pt and PtRu colloids are prepared by a microwave-assisted polyol process, and transferred to a toluene solution of decanthiol. Vulcan XC-72 is then added to the toluene solution to adsorb the thiolated Pt and PtRu colloids. Transmission electron microscopy examinations show nearly spherical particles and narrow size distributions for both supported and unsupported metals. The carbon-supported Pt and PtRu nanoparticles are activated by thermal treatment to remove the thiol stabilizing shell. All Pt and PtRu catalysts (except Pt23Ru77) give the X-ray diffraction pattern of a face-centered cubic (fcc) crystal structure, whereas the Pt23Ru77 alloy is more typical of the hexagonal close packed (hcp) structure. The electro-oxidation of liquid ethanol on these catalysts is investigated at room temperature by cyclic voltammetry. The results demonstrate that the alloy catalyst is catalytically more active than pure platinum. Preliminary tests on a single cell of a direct ethanol fuel cell (DEFC) indicate that a Pt52Ru48/C anode catalyst gives the best electrocatalytic performance among all the carbon-supported Pt and PtRu catalysts.