Nigel Mark Sammes

In situ preparation of a La1.2Sr0.8Mn0.4Fe0.6O4 Ruddlesden–Popper phase with exsolved Fe nanoparticles as an anode for SOFCs

A highly stable electrode material of Ruddlesden–Popper structure, La1.2Sr0.8Mn0.4Fe0.6O4 (RPLSMF), is prepared from La0.6Sr0.4Mn0.2Fe0.8O3 (LSMF) perovskite by in situ annealing in flowing H2 at the operation temperature of solid oxide fuel cells. The crystallinity, morphology, and oxidation states of each element and electrochemical properties of RPLSMF are characterized. Doping Mn into the B-site of RPLSMF improves the phase stability of the structure in H2 to prevent formation of La2O3. The XPS results also suggest that improved phase stability promotes formation of Fe2+/3+ pairs that facilitate fuel oxidation by redox coupling. Additionally, during phase transition to RPLSMF, metallic Fe nanoparticles form, which enlarge H2 chemisorption and oxidation sites. Consequently, RPLSMF exhibits outstanding and stable electrochemical activity with a maximum power density of 0.72 W cm−2 at 1073 K when used as an anode material in LSGM electrolyte-supported cells. As the phase transition between the RPLSMF and LSMF is reversible under a redox environment, RPLSMF/GDC is applied as an electrode in the symmetrical cell of RPLSMF-GDC/LSGM/LSMF-GDC. It exhibits a substantial power density of 0.64 W cm−2 with a total polarization resistance of 0.51 Ω cm2.

Preliminary Studies about Synthesis and Electrical Properties of Ruthenium Doped Lanthanum Strontium Titanate as a Potential Anode of Solid Oxide Fuel Cells

The lanthanum strontium titanate (LST) is one of the most representative alternative anode materials. Although it shows low catalytic properties, the disadvantage could be improved by doping of ruthenium which is widely used as catalyst under steam reforming reaction or oxidation reaction. The ruthenium doped lanthanum strontium titanates (LSTRs) powders were synthesized by complex EDTA-citrate method showing well crystallinity. Additionally, the prepared samples were evaluated through various experimental tests. For example, the stability in the reducing atmosphere and chemical compatibility with YSZ electrolyte such as reactivity test in high temperature were confirmed by XRD (Xray diffraction). And electrical conductivity in wet H 2 atmosphere at 900 ˚C is about 350.6 S/cm, 342.4 S/cm and 179.1 S/cm with sintered bar of LST, LSTR0.02 and LSTR0.05, respectively.