The electrooxidation of ethanol and carbon monoxide on Pt nanoparticles (NPs) supported on carbon nanofibers (CNFs) and carbon blacks (oxidized and non-oxidized) is studied. Quite similar characteristics are found for Pt NPs, including particle size and crystal phases, regardless of the nature of carbon support. Cyclic voltammetries and current-transient curves show higher ethanol oxidation current density for Pt/CNF than for Pt/Vulcan. In situ spectroelectrochemical techniques including Fourier transform infrared spectroscopy (FTIR) and differential electrochemical mass spectrometry (DEMS), are employed in order to identify adsorbed reaction intermediates and products. Pt/CNF results in a lower CO poisoning of the NP surface compared to Pt/Vulcan, allowing higher amount of free Pt active sites for the oxidation of ethanol which leads to the formation of acetic acid during the reaction. (C) 2017 Elsevier Inc. All rights reserved.