Electrode properties of Cu-doped Bi0.5Sr0.5FeO3−δ cobalt-free perovskite as cathode for intermediate-temperature solid oxide fuel cells

Abstract

A cobalt-free perovskite oxide Bi0.5Sr0.5Fe0.8Cu0.2O3−δ (BSFC) has been investigated as novel cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The BSFC cathode exhibits good thermal stability and chemical compatibility with Ce0.9Gd0.1O1.95 (CGO) electrolyte below 950 °C. The average thermal expansion coefficient (TEC) of BSFC is 13.1 × 10−6 K−1 within a temperature range of 50–800 °C in air, which is close to that of CGO electrolyte. Meanwhile, the polarization resistant values (RP) of BSFC cathode on CGO electrolyte are 0.13, 0.32 and 0.76 Ω cm2 at 700, 650 and 600 °C, respectively; the lowest cathode overpotential is 37 mV at a current density of 125 mA cm−2 at 700 °C in air. The CGO electrolyte-supported single cell with BSFC cathode exhibits maximum power density of 290 mW cm−2 at 700 °C using dry H2 as the fuel. The rate-limiting step for oxygen reduction reaction (ORR) on BSFC cathode is oxygen surface adsorption-dissociation process. The attractive electrochemical performance demonstrates that BSFC oxide is a promising cathode material for IT-SOFCs.