III International Conference

PP-II-98vacuum. The colloid synthesis was performed in a dry nitrogen atmosphere using dry solventsand nonhydrated salts.The prepared catalysts were characterized by X-ray diffraction, transmission electronmicroscopy and IR and UV-Vis spectroscopy. All the catalysts were tested in an aqueoussolution of alcohols, with a membrane /electrode assembly. The oxidized alcohols weremethanol, ethanol, 2- propanol, cyclohexanol. In order to understand the relation between thecatalysts and the fuels the adsorbate was analyzed by voltametry for the membrane-electrodeassembles. Typical TEM images of colloids show remarkably uniform and high dispersion ofthe metal and the alloy particles.abFig. 1 TEM images of Pt (a) and PtSn (b) colloids obtained by first methodThe as-synthesized PtMe/C samples display considerable crystallinity before the heattreatment. Crystallization increases with the heating time. The Pt or PtMe colloidal formationprocess was monitored by UV-Vis spectroscopy. The obtained spectra show graduallydecreasing absorbtion from the ultraviolet region to 700 nm. This indicates the formation ofPtMe alloy nanoparticle. The electrocatalytic tests show that Pt/C is not very active catalystfor oxidation of alcohols. Addition of the second metal enhances the activity and improves theperformance of the cell. For the catalysts with colloids obtained by the first method the betterperformances in oxidation of methanol were obtained for PtRu/C. PtSn/C catalysts withcolloids obtained by the second method are better in oxidation of 2-propanol andcyclohexanol. A high variation of performance was evidenced for PtFe/C catalysts obtainedby different methods.References1. F. Joensen, J.R. Rostrup-Nielsen, J. Powder Sorces, 105 (2002) 195.2. H.P. Choo, K.Y. Liew, H.F. Liu, C.E. Seng, J. Mol. Catal. A., 165 (2001) 127.3. H. Bonnemann and K.S. Nagabhushana, J. New mat. Electrochem. Systems, 7 (2004) 93.342