Effect of tungsten doping on strontium ferrite electrode for symmetrical solid oxide electrochemical cell

Tungsten-doped strontium ferrite (SrFe1-xWxO3-delta, SFW) is prepared and characterized as the electrode materials for symmetrical solid oxide electrochemical cell. X-ray diffraction refinement reveals the symmetrical structure transform from cubic (opm (3) over barm) for x = 0.1 to tetragonal (I4/m) when x = 0.2. According to the analysis including electrical conductivity, Hydrogen temperature-programmed reduction (H-2-TPR), thermal expansion and X-ray photoelectron spectra (XPS), it suggests that the decrease in conductivity, content of Fe2+ and oxygen vacancy concentration with the increase of W content is attributed to the stronger lattice framework. The oxygen vacancy can be dramatically activated around 600 degrees C. Using SrFe0.8W0.2O3-delta as the electrodes, symmetrical single cells supported on doped ceria electrolytes can achieve acceptable power density (0.19 W cm(-2) at 750 degrees C) and considerable stability. Meanwhile symmetrical cells with La0.9Sr0.1Ga0.8Mg0.2O3-delta (LSGM) electrolyte substrates can achieve 0.75 A cm(-2) at 800 degrees C under the voltage of OCV (open circuit voltage) +0.5 V when it is operated in electrolysis mode. SrFe0.8W0.2O3-delta can gain a considerable stability and electrochemical activity under both oxide and reductive atmospheres. Oxygen vacancy formation energy (E-vac) and electron density distribution are computed to verify the enhancement on crystal structure stability by doping W. The E-vac critically depends on the distance from the W atom. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.