The electrocatalytic activity of Pt/C and Pt-Rh/C electrocatalysts for the ethanol oxidation reaction (EOR) was investigated by potentiostatic and potentiodynamic techniques by differential electrochemistry mass spectrometry (DEMS) in a flow cell system. The 10 wt% electrocatalysts were synthesized by a modified polyol method and physically characterized by different techniques including X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The chronoamperometry study shows that, although the ethanol oxidation starts at lower potential on Pt-Rh/C, the kinetics of the reaction is faster on Pt/C. Differential Electrochemical Mass Spectrometry (DBMS) allowed the detection of volatile intermediates/products of the EOR. At low potential, the ionic current corresponding to the signal m/z = 15 increases, conversely to the signal m/z = 44; this points out the production of adsorbed CRx species and thus possibly of adsorbed CO either during the negative scan or the previous positive scan of the cyclic voltammetry. The CO2 current efficiency (CCE) was also determined on both electrocatalysts after calibration of the m/z = 22 signal: the CCE value can reach up to 25% on Pt-Rh/C at room temperature, compared to ca. 5% on Pt/C. (C) 2014 The Electrochemical Society. All rights reserved.