Ba0.5Sr0.5Co0.8-xFe0.2NbxO3-δ (x≤0.1) as cathode materials for intermediate temperature solid oxide fuel cells with an electron-blocking interlayer

Abstract For better performance and enhanced stability, the traditional MIEC cathode material BSCF was optimized by niobium-doping for intermediate temperature solid oxide fuel cells (IT-SOFCs) with an electron-blocking layer. The cathode materials Ba0.5Sr0.5Co0.8-xFe0.2NbxO3-δ (x ≤ 0.1) (BSCFNbx) were synthesized and the effects of niobium-doping level was investigated systematically. Our experimental results revealed that as the niobium-doping level increases, the resistibility of BSCFNbx to CO2 and H2O is enhanced greatly, the thermal expansion coefficient of BSCFNbx (x ≤ 0.1) decreases from 21.74 × 10−6 K−1 to 18.74 × 10−6 K−1, indicating that niobium-doping is conducive to chemical stability and combination between cathode and electrolyte. By mean of XPS characterization, the ratio of adsorption oxygen to lattice oxygen in BSCFNb0.05 reached the highest value among this series, which means the highest oxygen transport rate. In NiO-BaZr0.1Ce0.7Y0.2O3-δ| Ce0.8Sm0.2O2-δ (NiO-BZCY|SDC) - based single-cell applications, the highest electrochemical performance of 882 mW cm−2 and the lowest polarization resistance of 0.14 Ω cm2 at 700 °C occurred when the x is 0.05 in BSCFNbx. The electron-blocking layer generated in sintering process of the NiO-BZCY|SDC half-cell promotes the open circuit voltage (OCV) over 1.0 V, ensuring high performance of single-cells in our investigation. This work indicates that niobium-doping is an effective strategy to promote simultaneously performance and stability of cathode material for IT-SOFCs, and BSCFNb0.05 is a good potential material for IT-SOFCs.