INTERFACIAL POLARIZATION CHARACTERISTICS OF PT-VERTICAL-BAR-BACE0.8GD0.2O3-VERTICAL-BAR-PT CELLS AT INTERMEDIATE TEMPERATURES

Impedance spectroscopy of Pt\BaCe0.8Gd0.2O3\Pt cells indicates that bo th mass and charge-transfer influence the electrode kinetics of the in terfacial reactions. Charge-transfer appears to dominate the electrode kinetics when the partial pressure of oxygen is sufficiently high, wh ereas mass transfer seems to be rate limiting at low oxygen partial pr essures. Under the influence of an applied de bias, concentration pola rization at the cathode is more severe than that at the anode. In a H- 2-containing atmosphere, the electrode kinetics seem to, be limited pr imarily by charge-transfer. Further, water vapor has a significant eff ect on the electrode kinetics. In an O-2-containing atmosphere, the in troduction of 3 volume percent (v/o) H2O dramatically increases the in terfacial resistances. In contrast, in a H-2-containing atmosphere the presence of 3 v/o H2O significantly reduces the interfacial resistanc es. Overall, the interfacial resistances are the factors limiting the performance of intermediate-temperature solid oxide fuel cells based o n BaCe0.8Gd0.2O3 electrolytes. Minimizing polarization resistance aris ing from both charge and mass transfer is the key to achieving high-pe rformance solid oxide fuel cells.