Investigation into the effect of molybdenum-site substitution on the performance of Sr2Fe1.5Mo0.5O6−δ for intermediate temperature solid oxide fuel cells

• Nb was doped to increase oxygen vacancy and electrical conductivity, furthermore enhance electro–catalytic activity.
• The Sr2Fe1.5Mo0.4Nb0.1O6−δ cathode exhibits area specific resistance of 0.068 Ω cm2 at 800 °C.
• High performance of SFMNb0.1 cathode is demonstrated by excellent maximum power density as high as 1102 mW cm−2 at 800 °C.

In this paper, niobium doping is evaluated as a means of enhancing the electrochemical performance of a Sr2Fe1.5Mo0.5O6−δ (SFM) perovskite structure cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs) applications. As the radius of Nb approximates that of Mo and exhibits +4/+5 mixed valences, its substitution is expected to improve material performance. A series of Sr2Fe1.5Mo0.5−xNbxO6−δ (x = 0.05, 0.10, 0.15, 0.20) cathode materials are prepared and the phase structure, chemical compatibility, microstructure, electrical conductivity, polarization resistance and power generation are systematically characterized. Among the series of samples, Sr2Fe1.5Mo0.4Nb0.10O6−δ (SFMNb0.10) exhibits the highest conductivity value of 30 S cm−1 at 550 °C, and the lowest area specific resistance of 0.068 Ω cm2 at 800 °C. Furthermore, an anode-supported single cell incorporating a SFMNb0.10 cathode presents a maximum power density of 1102 mW cm−2 at 800 °C. Furthermore no obvious performance degradation is observed over 15 h at 750 °C with wet H2 (3% H2O) as fuel and ambient air as the oxidant. These results demonstrate that SFMNb shows great promise as a novel cathode material for IT-SOFCs.