A distributed charge transfer model for IT-SOFCs with MIEC electrolyte and composite electrodes is developed. A physically-based description of the electronic leakage current in the electrolyte is included, together with mass and charge conservation equations. The model is applied to simulate experimental polarization curves and impedance spectra collected on IT-SOFCs consisting of SDC electrolytes, Cu-Pd-CZ80 infiltrated anodes and LSCF/GDC composite cathodes. Hydrogen electro-oxidation experiments are examined (H-2/N-2 humidified mixtures, 700 degrees C, 30-100% H-2 molar fraction). A significant increase of the ohmic resistance measured in the impedance spectra is revealed at decreasing the H-2 partial pressure or increasing the voltage (from 0.71 Omega cm(2) at 100% H-2 to 0.81 Omega cm(2) at 30% H-2). Good agreement between the calculated and experimental polarization and EIS curves is achieved by fitting the exchange current density and the capacitance of each electrode. Model and theoretical analyses allow to rationalize the observed shift of the ohmic resistance, highlighting the key-role played by the electronic leakage current. Overall, the model is able to capture significant kinetic features of IT-SOFCs, and allows to gain insight into relevant parameters for the optimal design of the cell (electrochemically active thickness, current and potential distribution, mass diffusion gradients). (C) The Author(s) 2017. Published by ECS. All rights reserved.