Strontium-Doped BaZr_0.8Ni_0.2O_3-δ Cobalt-Free Cathode Materials for Solid Oxide Fuel Cell

Efficient cathode materials are essential to the overall cell performance of solid oxide fuel cell (SOFC). The high linear thermal expansion coefficient (TEC) of traditional cobalt-containing cathode materials, cobalt poisoning, and the expensive nature of cobalt mean that cobalt-free cathode materials must be examined. Sr-doped cobalt-free BaZr_0.8Ni_0.2O_3-δ cathode materials were synthesised using the conventional solid-state reaction method, and investigated as potential cathode materials for SOFC application. The synthesised Ba_1-xSr_xZr_0.8Ni_0.2O_3-δ (BSZN0, BSZN25, BSZN5; x = 0, 0.25 and 0.5) samples were characterized via X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, dilatometer, and electrochemical impedance spectroscopy. The XRD analysis of the synthesised samples revealed a well-defined peak position at 2theta, and indexed as pm-3 m cubic space group. At 800 °C, the electrical conductivity in air for BSZN0, BSZN25, and BSZN5 were 72.24 S/cm, 80.46 S/cm and 85.55 S/cm, respectively. The average linear thermal expansion coefficient obtained for BSZN0, BSZN25, and BSZN5 at 25 to 1000 °C were 10.4 × 10^–6 K⁻¹, 10. 9 × 10^–6 K⁻¹, and 11.2 × 10^–6 K⁻¹, respectively. The improved linear thermal elongation of BSZN0, BSZN25, and BSZN5 will ensure compatibility with commonly used electrolytes in SOFCs.