Promotion on electrochemical performance of Ba‐deficient Ba1 − xBi0.05Co0.8Nb0.15O3 − δ cathode for intermediate temperature solid oxide fuel cells

Reducing the operating temperature is the developing trend for solid oxide fuel cells. The key is to develop the cathode with high electrocatalytic activity for oxygen reduction reaction operated at reduced temperatures. Ba‐deficient Ba_1 ? xBi_0.05Co_0.8Nb_0.15O_3 ? δ (Ba_1 ? xBCN, 0 ≤ x ≤ 0.10) are synthesized by solid‐state reaction method and evaluated as novel cathodes for intermediate‐temperature solid oxide fuel cells. Ba_1 ? xBCN is preserved to primitive cubic perovskite phase and meets the compatibility requirement with gadolinium doped ceria oxide (GDC) electrolyte at 950°C. Though the Ba deficiency distorts the cell symmetry, it improves the charge transfer steps rapidly, ascribing to the improvement of oxygen vacancy concentration. The polarization resistance of Ba_0.95BCN is as low as 0.056 Ω cm² in air at 700°C. The peak power density of the single cell with this cathode is as high as 1.41 W cm^?2 at 750°C with wet H₂ as fuel and air as oxidant, indicating the great potential for enhanced performance of Co‐based cathodes with A‐site deficiency.