The particle size effect for ethanol oxidation on carbon supported platinum catalysts in the Pt particle size range from 2.2 to 3.6 nm was investigated both in half-cell and in a single direct ethanol fuel cells (DECF). The specific activity for ethanol oxidation presented a maximum at a Pt particle size of 2.5 nm, ascribed to the best compromise between structural effects and/or oxophilicity effects of the Pt surface. In DEFCs, the particle size effect at the anode side was less significant than that observed in half-cell measurements, likely due to concomitant effects of ethanol oxidation products on the oxygen reduction at the cathode side. (C) 2011 Elsevier B.V. All rights reserved.