By means of model analysis, we show that, in the presence of syngas, the electro-oxidation of H-2 and that of CO occur in parallel and contemporarily on Samaria-doped Ceria (Sm0.2Ce0.8O1.9, SDC) Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFCs). The activation of a co-oxidative route is a most distinguishing feature of Ce-based cells, compared to traditional SOFCs. SDC electrolyte supported IT-SOFCs with Cu-Pd-CZ80 composite anodes and LSCF cathodes were tested under a wide range of operating conditions. Polarization and EIS measurements were collected at 600 degrees C and 650 degrees C with syngas mixtures (23-0.4H(2)/CO ratio), H-2/N-2 mixtures (from 97 to 30% H-2 v/v) and CO/CO2 mixtures (from 97 to 50% CO v/v). A 1D, dynamic and heterogeneous model of the cell was applied to analyze the polarization and the EIS curves. The kinetics of the reactions of H-2 electro-oxidation, CO electro-oxidation and O-2 reduction were individually investigated and global power law rates were derived. The syngas experiments were simulated on a fully predictive basis and no parameter adjustment, confirming that the polarization behavior could be best reproduced exclusively by assuming the presence of the co-oxidative route. The IT-SOFCs were also exposed to biogas mixtures, revealing that the dry-reforming reaction was active. (C) 2015 Elsevier B.V. All rights reserved.