Ru-doped lanthanum strontium titanates for the anode of solid oxide fuel cells

Lanthanum strontium titanate perovskite (LST) was doped with Ru (La0.4Sr0.6Ti1−xRuxO3−δ (LSTR), x = 0.02, 0.05), and its properties were characterized by various methods for possible use as the anode material in solid oxide fuel cells (SOFCs). The thermal expansion coefficients of Ru-doped samples (10.2-10.3 × 10−6 K−1) are about the same as LST (10.4 × 10−6 K−1), which is similar to that of YSZ. It has been found that under a reducing atmosphere, doped Ru is precipitated from the structure. This decreases the total electrical conductivity and increases the ionic conductivity because of the increased number of B-site deficiencies created by the Ru precipitation. Impedance spectra measured with the buttons cells of the LSTRs-YSZ/YSZ/LSM-YSZ/LSM configuration reveal that the polarization resistance with the LST-YSZ anode increases with time (from 4.95 Ω cm2 to 5.78 Ω cm2 in 24 h of H2 fuel atmosphere), whereas the resistance with Ru-doped LST-YSZ anodes decreases with time (from 4.87 Ω cm2 and 4.17 Ω cm2 to 4.06 Ω cm2 and 2.74 Ω cm2 for the LSTR0.02-YSZ and LSTR0.05-YSZ anodes, respectively). Accordingly, the final maximum power density at 850 °C also increases from 52 mW/cm2 for LST-YSZ to 74 mW/cm2 and 115 mW/cm2 for the LSTR0.02-YSZ and LSTR0.05-YSZ anodes, respectively.