The reaction mechanism for the oxidation of ethanol on carbon supported Pt, PtSn and PtSn-based trimetallic catalysts has been investigated by in situ Fourier transform infrared (FTIR) spectroscopy. The results showed that the catalytic activity of Pt80Sn10Ni10/C and Pt80Sn10Pd10/C for electrooxidation of ethanol is directly favoured to acetic acid potential at around 0.25 and 0.3 V vs. RHE, respectively. These suggest that the addition of Ni or Pd to PtSn greatly enhances the formation of acetic acid at lower potential. However, Pt/C, Pt80Sn10Ni10/C and Pt80Sn10 Rh-10/C electrocatalysts showed a better performance than Pt90Sn10/C, Pt80Sn10Co10/C and PtsoSnioPdio/C electrocatalysts for the production of CO2 during ethanol oxidation. Therefore, the pathway forming CO2 is favoured by the presence of Ni and Rh in the PtSn. (C) 2013 Elsevier B.V. All rights reserved.