Study of Sr 2 Mg(Mo 0.8 Nb 0.2 )O 6−δ as anode material for solid oxide fuel cells using hydrocarbons as fuel

Sr2Mg(Mo0.8Nb0.2)O6−δ (SMMNb) was investigated as potential anode material of solid oxide fuel cells (SOFCs) for direct oxidation of methane. The compound was prepared by solid state reaction, followed by annealing under reducing atmosphere of 10% H2/N2 at 900 °C. The structural and morphological properties of fresh and reduced material were characterized by XRD, XPS and SEM. Additionally, catalytic properties towards oxidation of methane, electrical properties in reducing atmosphere as well as thermal and chemical compatibility with common SOFC electrolytes were investigated. These results reveal a double perovskite single phase in the fresh and reduced compound and, after reduction, a change in the niobium valence was observed. SMMNb shows a good activity for methane partial oxidation as well as combined reforming reaction. The material presents a semiconductor behaviour with n-type electronic conduction and an excellent thermal compatibility with SOFC electrolytes such as SDC, GDC and LSGM, based on similarity of values of TEC. However, this material reacts with zirconia-based electrolytes (YSZ and ScSZ). Although, a low electrochemical activity for H2 and CH4 oxidation was found, SMMNb demonstrates high tolerance to carbon deposition when the anode is exposed to methane.