State-space modeling of the anodic SOFC system Ni, H2-H2O|YSZ

A simplified anodic solid oxide fuel cell (SOFC) system, Ni, H-2-H2O\YSZ, is investigated using the so-called state-space modeling (SSM) approach that combines experiments, modeling, and simulations. The approach is first described in general. Then, an electrochemical model is established for the Ni, H-2-H2O\YSZ system. The kinetic constants necessary for the simulations are estimated on the basis of literature data. The model is validated by fitting the simulated to the experimental impedance spectra, which were measured under well-defined operating conditions, simulated directly from the assumed electrochemical model and the estimated kinetic constants. Simulations were also carried out varying the triple phase boundary (TPB) length, the partial pressure of hydrogen and of water, and the overpotential. A comparison of the simulated with the experimental data proves the feasibility of the approach for investigating the electrochemistry of SOFC anodes. However, it comes out that the assumed model requires modifications. An alternative model is proposed for further investigations. (C) 2002 Elsevier Science B.V. All rights reserved.