Development of Protonic Ceramic Fuel Cells Using Yb-Doped BaZrO3 Electrolytes

Abstract

Acceptor-doped barium zirconate was used as the electrolyte material because it has CO2 stability. Previous studies have shown that yttrium-doped barium zirconate (BZY) has the highest proton conductivity. However, cells using BZY crack in the conventional ceramic tape-casting and firing process used to fabricate laminated ceramic electronic devices. This is because the NiO used for the anode reacts with BZY to form BaY2NiO5.The reactivity between the acceptor-doped barium zirconate and NiO was examined at the 1500 °C firing temperature. Ytterbium-doped barium zirconate (BZYb) did not form the complex oxide with NiO. Using BZYb revealed no problems such as cell cracking. In the cell using BZYb, the maximum power density at 700 °C and 600 °C were 0.70 Wcm-2 and 0.49 Wcm-2, respectively. Electrochemical impedance spectroscopy of the cell showed that the ohmic resistance was 0.28 Wcm2, approximately three times larger than the resistance value calculated using the bulk conductivity of BZYb and electrolyte thickness. It seems to be due to the solid solution of Ni in the electrolyte. To improve performance, techniques to prevent Ni solid solution diffusion are necessary.