Bi₂Ru₂O₇ Pyrochlore Electrodes for Bi2O3 based Electrolyte for IT-SOFC Applications

Bismuth ruthenate pyrochlore (Bi2Ru2O7: BRO) was tested as a cathode in several bismuth oxide-based electrolyte cells. Erbium oxide stabilized bismuth oxide (ESB) (Bi2O3)0.8 (Er2O3)0.2, Bi2V0.9Me0.1O5.35 (BIMEVOX10, Me = Co, Cu, Zn), and Bi2Ru2O7 (BRO) were synthesized via solid state reaction. ESB and BIMEVOX powders were pressed and sintered into dense pellets while BRO was deposited and sintered as porous electrodes onto ESB and BIMEVOX dense pellet surfaces. Morphologies and phases of the materials were characterized by Field Emission Scanning Electron Microscope and x-ray diffraction, respectively. Electrochemical performances of BRO/ESB and BRO/BIMEVOX symmetric cells were tested using Electrochemical Impedance Spectroscopy (EIS) at 200-700 °C in air. High polarization for BIMEVOX cells was observed, while ESB cells showed a promising behaviour. Different electrochemical performances of BRO electrodes, with ESB or BIMEVOX, indicated that the phases formed at electrodes/electrolyte interface controlled the cell polarization process.