A defective iron-based perovskite cathode for high-performance IT-SOFCs: Tailoring the oxygen vacancies using Nb/Ta co-doping

The sluggish kinetics of the electrochemical oxygen reduction reaction (ORR) in intermediate -temperature solid oxide fuel cells (IT-SOFCs) greatly limits the overall cell performance. In this study, an efficient and durable cathode material for IT-SOFCs is designed based on density functional theory (DFT) calculations by co-doping with Nb and Ta the B-site of the SrFeO3_d perovskite oxide. The DFT calculations suggest that Nb/Ta co-doping can regulate the energy band of the parent SrFeO3_d and help electron transfer. In symmetrical cells, such cathode with a SrFe0.8Nb0.1Ta0.1O3_d(SFNT) detailed formula achieves a low cathode polarization resistance of 0.147 X cm2 at 650 degrees C. Electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS) analysis confirm that the co-doping of Nb/Ta in SrFeO3_d B-site increases the balanced concentration of oxygen vacancies, enhancing the electrochemical performance when compared to 20 mol% Nb single-doped perovskite oxide. The cathode button cell with Ni-SDC|SDC|SFNT configuration achieves an outstanding peak power density of 1.3 W cm_2 at 650 degrees C. Moreover, the button cell shows durability for 110 h under 0.65 Vat 600 degrees C using wet H2 as fuel. (c) 2023 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

In intermediate-temperature solid oxide fuel cells, doping with Nb and Ta in the cathode material improves electron transfer and enhances the electrochemical performance. The co-doping of Nb/Ta in SrFeO3 increases the balanced concentration of oxygen vacancies, leading to a low cathode polarization resistance and outstanding peak power density. The button cell also shows durability under high temperature and wet H2 fuel.