Development of Medium-Temperature Solid Oxide Fuel Cells and CO2 and H2O Co-Electrolysis Cells in Estonia

Abstract

Estonian solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) programs started in 2001 and 2012, respectively. Solid oxide fuel and co-electrolysis cell single cells based on Ni-Ce0.9Gd0.1O2- d or Ni-Zr0.92Y0.08O2- d supporting anodes/cathodes, bi-layered Zr0.92Y0.08O2- d | Ce0.9Gd0.1O2- d or Zr0.94Sc0.06O2- d | Ce0.9Gd0.1O2- d electrolytes and micro-meso-porous La0.6Sr0.4CoO3- d, Gd0.6Sr0.4CoO3- d or Pr0.6Sr0.4CoO3- d cathodes/anodes, respectively, prepared from nano-microporous powders at different sintering temperatures and pore former additions in the raw cathode and anode pastes have been studied. Ni-free anodes/cathodes have been also synthesized and tested at temperatures from 550 to 800 °C. Different physical (FIB-TOF-SIMS, XRD, high-temperature XRD under electrochemical working conditions, FIB-SEM-EDX, AFM, gas chromatography-mass spectrometry, BET) and electrochemical (cyclic voltammetry, chronoamperometry and electrochemical impedance) methods have been applied. Influence of the anode and cathode porosity, depending on the electrode preparation methods, and also of the bi-layered electrolyte properties (chemical composition, thickness, etc.) on the power density of the SOFC and SOEC single cells has been shown and discussed. The synchrotron radiation based X-ray absorption spectroscopy under electrochemical polarization and different fuel feeding and temperature cyclation conditions has been applied for chemical analysis of surface composition of the SOFC anodes.