Fabrication and characterization of a tubular ceramic fuel cell based on BaZr0.1Ce0.7Y0.1Yb0.1O3-δ proton conducting electrolyte

Abstract A proton conducting anode supported tubular fuel cell is fabricated in this research using the highly proton conductive BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb) electrolyte. The cell is in a Ni-BZCYYb/BZCYYb/LSCF-BZCYYb configuration consisting of a support, electrolyte and cathode with thicknesses of 680 μm, 25 μm and 90 μm, respectively. The cell delivers maximum power densities of 331, 362 and 416 mW/cm 2 at 600, 650 and 700 °C, respectively. AC impedance spectroscopy results show values of 0.94 Ω.cm 2 , 0.73 Ω.cm 2 , and 0.60 Ω.cm 2 for total resistance at the corresponding temperatures while the major resistance contributor is the ohmic resistance. The Ni-BZCYYb anode microstructure shows detachment of Ni and the BZCYYb in most regions as well as pores inside the Ni grains. Despite the low anode porosity (25%), the cell gives a very low concentration polarization value (0.05 Ω.cm 2 ) indicating that the fuel gas could readily diffuse into the microstructure. This might be attributed to water forming on the cathode side, which masks the necessity of having a high porosity anode. The cell fails when tested under CO:H 2 of 1:1 at 700 °C due to significant carbon (graphite) formation indicating that proton conductors based on barium cerates are not appropriate choices for application under hydrocarbon fuels.