Nb-doped double perovskite Sr2CoFeO6−δ as an efficient and prospective electrode for quasi-symmetrical solid oxide fuel cells

Abstract

The utilization of identical anode and cathode materials in symmetrical solid oxide fuel cells (SSOFCs) can efficiently reduce their fabrication costs and prolong their operational life. Herein, Nb-doped double perovskite Sr2CoFeO6-δ of a traditional cathode was employed as the electrode material for SSOFCs. Notably, the electrochemical performance and reversibility were improved due to Nb doping. The Nb-doped sample Sr2CoFe0.7Nb0.3O6−δ.5 (SCFN3) was synthesized in air, which decomposed into Co–Fe alloy, SrCoO2.25, and Sr3FeNbO6−δ in H2. Following calcination in air, the sample reverted to the original perovskite structure. The SCFN3 sample exhibited good chemical compatibility with SOFC electrolytes such as La0.8Sr0.2Ga0.8Mg0.2O3−δ (LSGM), Sm0.2Ce0.8O2−δ, and BaZr0.1Ce0.7Y0.1Yb0.1O3−δ. A single cell consisting of 300-μm LSGM electrolyte exhibited maximum power densities of 951, 510, 563, and 397 mW/cm2 at 850℃ when using H2, C3H8, liquid C2H5OH, and solid C as fuels, respectively. These findings adequately demonstrate the fuel-flexible characteristics of SOFCs.