Surface modulated B-site doping of PrBa0.5Sr0.5Co2-xFexO5+δ as highly efficient cathode for intermediate-temperature solid oxide fuel cells

Layered perovskite oxides (PrBaCo2O5+delta) have gained widespread interest as promising electrodes in intermediate-temperature solid oxide fuel cells (IT-SOFCs) because of their excellent oxygen diffusion and transport performance. However, it remains a great challenge to simultaneously realize thermal match and sufficient operational stability in existing IT-SOFCs. Herein, the layered perovskite PrBa0.5Sr0.5Co2-xFexO5+delta (PBSCFx) with strong oxygen reduction reaction (ORR) activity in half-cell and high power density in single cell was designed by partial substitution of Co with Fe. A systematic and comprehensive elaboration on the composition-structure-property relationships of PBSCFx was proposed. Furthermore, the complex electro-chemical behavior of the single cell was investigated using equivalent circuit method (ECM) and distribution of relaxation time (DRT). Impressively, the polarization impedance of PBSCF05 (x = 0.5) is only 0.037 omega & sdot;cm2 (T = 750 degrees C). The single cell with PBSCF05-GDC as the cathode can reach the maximum power density of 0.996 W/ cm2 (T = 800 degrees C), and exhibits good stability in 216 h of long-term operation (T = 750 degrees C). The superior electrochemical performance of PBSCF05 is mainly attributed to the reduction of high frequency and interme-diate frequency polarization resistance, which corresponds to the enhanced transfer process of oxygen ions, oxygen surface exchange and charge transfer process. This work highlights a simple B-site doping strategy to achieve the thermal match in IT-SOFCs, and furthermore, it expands the opportunities for effective utilization of ECM and DRT technology in the high-performance of IT-SOFCs.