Tailoring the chemical stability of Ba(Ce_{0.8 - x}Zr_x)Y_0.2O_{3 - δ} protonic conductors for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFCs)

A soft chemistry method was used to synthesize BaCe_{0.8 - x}Zr_xY_0.2O_{3 - δ} (BCZY, with 0.0 ≤ x ≤ 0.8) proton conductors to combine the high proton conductivity of barium cerate and good chemical stability of barium zirconate. To verify the chemical stability, all the synthesized oxides were exposed to 100% CO₂ at 900 °C for 3 h and the phase composition of the resulting specimens was investigated by X-ray diffraction (XRD) analysis. The chemical stability against CO₂ increased with increasing the Zr content, with good results for samples with x ≥ 0.5. The electrical conductivity of the samples was investigated as a function of the Zr content using Electrochemical Impedance Spectroscopy (EIS) measurements. Hydrogen-air fuel cell experiments were carried out at 700 °C using the BCZY proton conducting electrolytes and platinum electrodes. Promising performance was observed for BaCe_0.3Zr_0.5Y_0.2O_{3 - δ} because it maintains the good chemical stability of barium zirconate but with improved electrical conductivity and fuel cell performance.