The adsorption of ethanol and acetaldehyde on carbon Vulcan supported Pt fuel cell catalyst and the electrochemical desorption of the adsorption products were studied, using electrochemical measurements and differential electrochemical mass spectrosmetry (DEMS), under continuous flow conditions. Faradaic current adsorption transients at different constant adsorption potentials, which also include CO adsorption for comparison, show pronounced effects of the adsorption potential and the nature of the reactant molecule. Acetaldehyde adsorption is much faster than ethanol adsorption at all potentials. Pronounced Had induced blocking effects for ethanol adsorption are observed at very cathodic adsorption potentials, < 0.16 V, while for acetaldehyde adsorption this effect is much less significant. Comparison of the adsorption charge for CO adsorption with the H‐upd charge allows differentiation between H‐displacement and double‐layer charging effects. Continuous bulk oxidation is observed for both reactants at potentials > 0.31 V; for acetaldehyde adsorption, increasing bulk reduction is found at low potentials. Based on the electron yield per CO2 molecule formed and on the similarity with the CO stripping characteristics the dominant stable adsorbate is CO, coadsorbed with smaller amounts of (partly oxidized) hydrocarbon decomposition fragments, which are also oxidized at higher potentials (> 0.85 V) and which can be reductively desorbed as methane or, to a very small extent, as ethane. The presence of small amounts of adsorbed C2 species and the oxidative dissociation of these species in the main CO oxidation potential range is clearly demonstrated by increased methane desorption after a potential shift to 0.85 V. The data demonstrate that the Pt/Vulcan catalyst is very reactive for C‐C bond breaking upon adsorption of these reactants.