Effect of cobalt and magnesium doping on the performance of Ba_0.5Sr_0.5Fe_0.8O₃ cathode for solid oxide fuel cell applications

Abstract

The chemical composition of the cathode material influences the performance of the low temperature solid oxide fuel cells (SOFCs). In the present work, two different cathode materials (Ba0.5Sr0.5Co0.2Fe0.8O3 and Ba0.5Sr0.5Mg0.2Fe0.8O3) were prepared to assess the role of Mg in the place of Co on the performance of the SOFC. Symmetric cells were fabricated by using Gadolinium doped Cerium (GDC) electrolyte. From the X-ray diffraction analysis, the lattice parameter was measured as increased from 3.954 Å to 3.975 Å for the cathode with the presence of Mg compared with Co. On the other hand, Mg decreased the electric conductivity (35 ± 1.6 S cm−1) compared with Co doping (56 ± 2.4 S cm−1). Higher porosity (4.8%) was observed in the cathode material with Mg which resulted in more triple phase boundaries and promoted higher gas diffusion. Lower polarization resistance (RP) values (7.95 and 1.07 Ω-cm2) were recorded at 600 °C and 700 °C respectively for the fuel cells fabricated with cathode having Mg compared with Co.