Adsorption of bulk ethanol and bulk acetaldehyde at different potentials (E-ad = 0.05, 0.15, 0.3 and 0.5 V vs. RHE) followed by a potentiodynamic stripping of their adsorbates is performed on carbon-supported Pt/C electrocatalyst using on-line differential electrochemical mass spectrometry (DEMS) in a flow cell system. The 20 wt.% Pt/C electrocatalyst was synthesized by a modified polyol method and was physically characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The different ethanol and acetaldehyde adsorbates were identified and quantified for each adsorption potential: the distribution of adsorbates covering the electrocatalyst surface highly depends on the adsorption potential. No conclusion could be drawn concerning the occurrence of the oxidation of adsorbed CHx into COad between E = 0.5 and 0.8 V vs. RHE. On the contrary, this reaction seemed to occur mostly at high potentials (E > 0.9 V vs. RHE). Oxidation of C-2-species in CHx,ad could also be evidenced in parallel in this potential region for the oxidation of acetaldehyde adsorbates. (C) 2014 Elsevier Ltd. All rights reserved.