Electrochemical Performance of Cobalt-Free Nb and Ta Co-Doped Perovskite Cathodes for Intermediate-Temperature Solid Oxide Fuel Cells

Tuning the Phase Transition of SrFeO3-δ by Mn toward Enhanced Catalytic Activity and CO2 Resistance for the Oxygen Reduction Reaction

Developing high-performance cathodes with sufficient stability against CO₂ rooting in ambient atmosphere is crucial to realizing the practical application of solid-oxide fuel cells. Herein, the Mn dopant is investigated to regulate the phase structure and cathode performance of SrFeO_3-δ perovskites through partially replacing the B-site Fe. Compared with parent SrFeO_3-δ, Mn-doped materials, SrFe_1-xMn_xO_3-δ (x = 0.05 and 0.1), show stabilized cubic perovskites at room temperature. Meanwhile, doping Mn accelerates the oxygen reduction reaction process, showing a reduced polarization resistance of 0.155 Ω·cm² at 700 °C for SrFe_0.95Mn_0.05O_3-δ, which is less than 30% of SrFeO_3-δ. In addition, the Mn dopant improves the chemical oxygen surface exchange and bulk diffusion coefficients. Furthermore, Mn enhances the tolerance toward CO₂ corrosion in various CO₂ atmospheres. Density functional theory calculations also reveal that Mn can strengthen the structural stability and increase the activity for the oxygen reduction reaction.

Evaluation of BaCo0.4Fe0.4Zr0.2-x Ni x O3-δ perovskite cathode using nickel as a sintering aid for IT-SOFC

In this research work, BaCo₀.₄Fe₀.₄Zr_0.2-x Ni _x O_3-δ (x = 0, 0.01, 0.02, 0.03, 0.04) perovskite cathode material for IT-SOFC is synthesized successfully using a combustion method and sintered at low temperature. The effects of nickel as a sintering aid on the properties of BaCo₀.₄Fe₀.₄Zr₀.₂O_3-δ are investigated through different characterization methods. The addition of nickel increased the densification and grain growth at a lower sintering temperature 1200 °C. XRD analysis confirms a single phase of BaCo₀.₄Fe₀.₄Zr₀.₂O_3-δ , and an increase in crystalline size is observed. SEM micrographs show formation of dense microstructure with increased nickel concentration. TGA analysis revealed that BaCo₀.₄Fe₀.₄Zr_0.2-x Ni _x cathode materials are thermally stable within the SOFC temperature range, and negligible weight loss of 2.3% is observed. The bonds of hydroxyl groups and metal oxides are confirmed for all samples through FTIR analysis. The highest electrical properties are observed for BaCo₀.₄Fe₀.₄Zr_0.2-x Ni _x (x = 0.04) due to increased densification and electronic defects compared to other compositions. The maximum power density of 0.47 W cm^-2 is obtained for a cell having cathode material BaCo₀.₄Fe₀.₄Zr_0.2-x Ni _x (x = 0.02) owing to its permeable and well-connected structure compared to others.