Cation-ordered perovskite-type anode and cathode materials for solid oxide fuel cells

In this work selected cation-ordered perovskite-type anode and cathode materials were investigated in terms of their possible application in intermediate temperature solid oxide fuel cells (IT-SOFC). Their phase composition, oxygen content, chemical diffusion coefficient of oxygen D and surface exchange coefficient K, chemical stability in relation to ceria electrolyte, and stability of the anode material in reducing atmosphere were studied. It was found that Sr_0.5Ba_1.5CoMoO _{6 - δ} anode material exhibits Fm-3m symmetry with B-site rock salt-type cation ordering, while YBaCo₂O_{5 + δ} cathode material possesses P4/mmm space group with A-site layered-type cation ordering. In the case of SmBa_0.5Sr_0.5Co _1.5Fe_0.5O_{5 + δ} compound, partial (> 70 wt.%) A-site layer-type ordering was observed. Electrical conductivity σ of Sr_0.5Ba_1.5CoMoO_{6 - δ} anode material is much lower (< 0.1 S·cm^{- 1}), as compared to the studied cathode materials, for which σ > 100 S·cm^{- 1} in 600-800 °C temperature range was measured. However, in reducing conditions, conductivity of Sr_0.5Ba_1.5CoMoO_{6 - δ} is significantly enhanced (~ 0.5 S·cm^{- 1}). Chemical stability studies at 1000°C revealed that YBaCo₂O_{5 + δ} reacts with Ce_0.8Gd_0.2O_1.9, while SmBa _0.5Sr_0.5Co_1.5Fe_0.5O _{5 + δ} remains stable. In the case of Sr_0.5Ba _1.5CoMoO_{6 - δ} compound, long time annealing in reducing atmosphere of 5 vol.% H₂ in Ar at 800°C caused decomposition of the material. Despite poor stability of the anode material in reducing conditions, relatively good performance of constructed H₂ | Sr_0.5Ba_1.5CoMoO_{6 - δ} | Ce _0.8Gd_0.2O_1.9 | SmBa_0.5Sr _0.5Co_1.5Fe_0.5O_{5 + δ} IT-SOFCs was recorded.