CHARACTERIZATION OF SOLID OXIDE FUEL-CELLS BASED ON SOLID ELECTROLYTES OR MIXED IONIC ELECTRONIC CONDUCTORS

The relation between cell voltage (V-Cell), applied chemical potential difference (Delta mu(O-2)) and cell current (I-t) for solid oxide fue l cells (SOFC) based on mixed ionic electronic conductors is derived b y considering also the effect of electrode impedance. Four-probe measu rements, combined with current interruption analysis, are considered t o yield the relation between ionic current (I-i) and overpotential (et a) The theoretical relations are used to analyze experiments on fuel c ells with Ce0.8Sm0.2O1.9 and C0.8Gd0.2O1.9 electrolytes with La0.8Sr0. 16CoO3 or Pt as the cathode and Ni/Ce0.9Ca0.1O1.9-x or Pt as the anode . The electrode overpotentials of these cells, determined by current i nterruption measurements, are discussed assuming different models incl uding impeded mass transport in the gas phase for molecular and monoat omic oxygen and Butler-Volmer type charge transfer overpotential.