Different electrochemical techniques like cyclic voltammetry and chronoamperometry and tests in a single direct ethanol fuel cell (DEFC) were used to evaluate the catalytic activity of various compositions of PtSn electrodes prepared by thermal decomposition for ethanol electrooxidation. This oxidation process was also investigated by in situ infrared reflectance spectroscopy to determine the presence of adsorbed intermediates. The experimental results showed that PtSn can oxidize ethanol mainly to acetaldehyde and acetic acid. Adsorbed CO was also found, which demonstrates that the rupture of the C-C bond in the ethanol molecule can also take place during the oxidation process. This intermediate species was oxidized to CO2 which was detected by IR spectroscopy and chromatography. With Pt90Sn10/C as anode catalyst, single DEFC tests carried out using MEAs with a geometric electrode area of 5 cm(2) allowed to produce a power density of ca. 72 mW cm(-2) at 110 degrees C. (C) 2007 Elsevier B.V. All rights reserved.