The electrochemical characteristics of the samarium and strontium doped layered perovskite (SmBa1−x Sr x Co2O5+δ, x = 0.5) have been investigated for possible application as a cathode material for an intermediate temperature-operating solid oxide fuel cell (IT-SOFC). The cathodic polarization of single-phase and composite cathodes with 10 mol % gadolinia-doped ceria (Ce0.9Gd0.1O2−δ, CGO91) shows that a weight ratio between SmBa0.5Sr0.5Co2O5+δ (SBSCO) and CGO91 of 1:1 (50 wt % SBSCO and 50 wt % CGO91, SBSCO:50) gives the lowest area specific resistance (ASR) of 0.10 Ω cm2 at 600 °C and 0.013 Ω cm2 at 700 °C. The maximum and minimum electrical conductivity in SBSCO are 1280 S cm−1 at 50 °C and 280 S cm−1 at 900 °C, with the influence of oxygen partial pressure indicating p-type conduction. The maximum power density of SBSCO:50 in an anode supported SOFC was 1.31 W cm−2 at 800 °C and 0.75 W cm−2 at 700 °C.

A combination of in situ analyses, including measurement of both electrical resistance and volumetric expansion, and thermogravimetric analysis (TGA) was employed to elucidate the deactivation process of a nickel-yttria-stabilized zirconia (Ni-YSZ) cermet (60 wt % NiO-YSZ) upon exposure to methane at 750°C. In conjunction with the aforementioned in situ techniques, a number of ex situ analyses, including scanning electron microscopy (SEM), electron probe microanalysis (EPMA), X-ray diffraction (XRD), and Raman spectroscopy, revealed that carbon deposition initially occurred at the Ni centers, followed by carbon dissolution into the Ni-YSZ cermet after an induction period of 200 min, which then led to threedimensional expansion. The structural change of the Ni-based cermet induced increases in electrical resistance of the material. The increased electrical resistance likely originated from the breakage of the Ni−Ni conducting network as well as from the formation of microscopic cracks within the Ni-YSZ material, resulting from the observed process of carbon dissolution. Moreover, a combination of TGA involving measurements of electrical resistance was demonstrated to be useful for determining amounts of carbon deposits critical for carbon dissolution. These results strongly suggest that changes in electrical resistance can be utilized to monitor the extent of carbon dissolution into the Ni-YSZ catalysts in situ, which would be helpful for the development of an efficient curing system for solid oxide fuel cells (SOFCs).

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