Double Perovskite Sr₂CoFeO₅₊_δ: Preparation and Performance as Cathode Material for Intermediate-temperature Solid Oxide Fuel Cells

Abstract

As the operating temperature decreases, intermediate-temperature solid oxide fuel cells (IT-SOFCs) require cathode materials with high catalytic activity.In this study, double perovskite Sr2CoFeO5+δ (SCF) was synthesized by Sol-Gel method, and the effect of different ratios of SCF cathode compounded with 20% (molar fraction) Sm2O3 doped CeO2 (SDC) on the electrode performance was elucidated.The SOFC single-cell performance was improved by the optimized chemical expansion and area-specific resistance (ASR) from composite electrodes.Results show that, the good chemical compatibility with common electrolytes can be observed from the SCF cathode after annealing at 950 ℃ for 10 h, and the average thermal expansion coefficient (TEC) of pure SCF can be significantly reduced for the composite sample of SCF and SDC at a mass ratio of 1:1, from 2.44×10 -5 to 1.54×10 -5 K -1 .ASR of SCF-xSDC (SDC content: 20%, 30%, 40%, 50%(in mass)) composite cathodes were as low as 0.036, 0.034, 0.028 and 0.092 Ω•cm 2 at 800 ℃, respectively.The SCF-40SDC composite cathode exhibited the lowest ASR value in the whole temperature range.Based on the 0.3 mm-thick La0.9Sr0.1Ga0.8Mg0.2O3-δ(LSGM) electrolyte, the maximum power density of SOFC using SCF-40SDC (757 mW• cm -2 ) as a cathode is higher than that of SCF (684 mW• cm -2 ).These results demonstrate that the SCF-40SDC composite cathode is a promising candidate for application in IT-SOFCs.