Carbon-supported Pt-Ru (1:1) catalysts were synthesized from aqueous solutions of Pt(IV) and Ru(IV) salts by two different reductive methods and characterized in comparison to a commercial Pt-Ru/C catalyst purchased from E-TEK, Inc. The three catalysts differ in particle size, dispersion, and degree of alloying, as determined by X-ray diffraction and transmission electron microscopy. Cyclic voltammetry in different methanol concentrations and CO-stripping experiments were conducted to check their electrocatalytic activity. The results obtained are in good agreement with single-cell measurements using H-2/CO mixtures with concentrations of 75 and 150 ppm CO. The synthesized catalysts show improved activities for low CO concentrations at 75degreesC cell temperature. In addition, for the synthesized catalysts only low CO coverages were found at the electrode surface by special in situ infrared reflectance techniques in contrast to the commercial one.