Nb-doped Sr2Fe1.5Mo0.5O6-δ electrode with enhanced stability and electrochemical performance for symmetrical solid oxide fuel cells

In this study, Nb doped double perovskite oxide (Sr2Fe1.4Nb0.1Mo0.5O6-δ) is prepared and tested as symmetrical electrodes for intermediate temperature solid oxide fuel cells. X-ray diffraction demonstrates that Sr2Fe1.4Nb0.1Mo0.5O6-δ maintains more stable cubic perovskite phase structure than its raw material (Sr2Fe1.5Mo0.5O6-δ) under reducing atmosphere. X-ray photoelectron spectrometry shows that Nb doping significantly enhances bond strength of FeOFe(Nb) so that Fe ion maintains more stable oxidation states after reducing. At 600 °C, Nb doping also increases the conductivity from 17.62 to 27.61 cm−1 in air and from 11.11 S cm−1 to 15.86 S cm−1 in wet hydrogen (∼3% H2O). Furthermore, Sr2Fe1.4Nb0.1Mo0.5O6-δ exhibits enhanced electrochemical performances in terms of lower polarization resistance under both oxidizing and reducing atmospheres. Peak power densities of 364.93 and 531.49 mW cm−2 at 750 and 800 °C are obtained based on a single symmetrical cell with Sr2Fe1.4Nb0.1Mo0.5O6-δ electrode, which also shows excellent redox stabilities. All of these results confirm that Sr2Fe1.4Nb0.1Mo0.5O6-δ electrode has promising prospects for the symmetrical intermediate temperature solid oxide fuel cells.