Abstract
SrMo1−xMxO3−δ (M = Fe and Cr, x = 0.1 and 0.2) oxides have been recently described as excellent anode materials for solid oxide fuel cells at intermediate temperatures (IT-SOFC) with LSGM as the electrolyte. In this work, we have improved their properties by doping with aliovalent Mg ions at the B-site of the parent SrMoO3 perovskite. SrMo1−xMgxO3−δ (x = 0.1, 0.2) oxides have been prepared, characterized and tested as anode materials in single solid-oxide fuel cells, yielding output powers near 900 mW/cm−2 at 850 °C using pure H2 as fuel. We have studied its crystal structure with an “in situ” neutron power diffraction (NPD) experiment at temperatures as high as 800 °C, emulating the working conditions of an SOFC. Adequately high oxygen deficiencies, observed by NPD, together with elevated disk-shaped anisotropic displacement factors suggest a high ionic conductivity at the working temperatures. Furthermore, thermal expansion measurements, chemical compatibility with the LSGM electrolyte, electronic conductivity and reversibility upon cycling in oxidizing-reducing atmospheres have been carried out to find out the correlation between the excellent performance as an anode and the structural features.
Highlights
Solid oxide fuel cells at intermediate temperatures (IT-SOFC) are electrochemical devices able to convert the energy involved in the combustion of a fuel directly into electrical energy
We demonstrated that Fe and Cr doping promotes the ionic conductivity of these oxides, combining excellent mixed ionic and electronic conduction (MIEC)
The cells were tested in a vertical tubular furnace at 800 and 850 ̋ C; the anode side was fed with pure H2, with a flow of 20 mLmin 1, whereas the cathode worked in air
Summary
Solid oxide fuel cells at intermediate temperatures (IT-SOFC) are electrochemical devices able to convert the energy involved in the combustion of a fuel directly into electrical energy. SOFCs often use anodes based on Ni-YSZ (yttria-stabilized zirconia) and Ni-LDC (lanthanum-dope ceria) cermets These composite anodes have an excellent catalytic activity for the fuel-oxidation reaction and high electronic and ionic conductivity, but these materials promote carbon formation during the direct oxidation of hydrocarbon fuels and suffer from sintering problems during the cell operation [1,2,3]. Mo4+ at the octahedral B positions has an extremely high electrical conductivity at room temperature (104 Scm1 [5]); molybdenum is a very suitable element to catalyze the fuel-oxidation reaction. This oxygen-stoichiometric oxide cannot exhibit the required. Thermal expansion, chemical compatibility, electrical conductivity and the reversibility of the oxidation-reduction process were investigated
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