Application of symmetric solid oxide fuel cell in fuel containing sulfur: I. Effect of electrodes

• Symmetric SOFC with electrode Sr2XMoO6 was applied in fuel containing sulfur for the first time.
• Evaluations on catalytic activities and degree of sulfur poisoning of symmetric electrode.
• Sr2CoMoO6 is a good candidate for symmetric electrodes.
• Sulfur tolerance can be realized at lower temperature for Sr2XMoO6.
• Sr2CoMoO6 can be regenerated ex-situ in hot air.

Symmetric solid oxide fuel cells (SFCs) with double perovskite materials serving as symmetric electrodes are applied for the first time in fuel containing sulfur, aiming to explore solution to sulfur poison. Temperature-programmed techniques, including H2-TPR, O2-TPD, were used to evaluate catalytic activities of electrodes in different atmosphere, while stabilities of electrode materials in sulfur containing fuel gas were characterized in terms of phase structures, conductivity, and microstructures by SEM, four-probe method and XRD as a function of temperature and operating time. It is evidenced that Sr2CoMoO6 (denoted as SCMO) possesses better hydrogen reducibility, oxygen desorption and stability in sulfur containing fuel gas. In configuration of Sr2XMoO6 (X = Co, Ni)|Ce0.85Sm0.15O2−δ (SDC)|Sr2XMoO6, the maximum power density Pmax reaches 95 mW cm−2 for SCMO and 68 mW cm−2 for SNMO with H2-0.1% H2S at 750 °C. Lower polarization resistance of SCMO (about 2.7 Ω cm2 at 750 °C) is achieved. It is interestingly noted that SFC performance composed of ex-situ regenerated symmetric electrodes SCMO falls only by 21%, as compared to that of fresh electrodes. The combinations of thermal analysis (TG-DTA) and surface analysis (XPS) convince that an ex-situ regeneration of symmetric electrode can be realized.

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