Reaction of the stage-1 graphite tetrachloroaluminate intercalation compound prepared from highly oriented pyrolytic graphite with anhydrous HF yields expanded graphite. According to scanning electron microscopy, exfoliation of graphite layers occurs more intensely as the reaction temperature increases. X-ray diffraction shows the expanded graphite has low crystallinity and the layer structure of graphite is highly disordered. X-ray photoelectron spectroscopy confirms formation of AlF 3 and absence of Cl and covalent C−F bonds. Infrared spectroscopy reveals the gaseous species released during the expansion are HCl and CF 4. These observations suggest the following reaction is the source of the expansion: C x AlCl 4(s) + 4HF (l) → (x-0.25)C (s) + AlF 3(s) + 4HCl (g) + 0.25CF 4(g) .
In this study titanate-based perovskite anodes containing Ni such as Ni-La x Sr 1-x TiO 3 (LST) have been investigated for direct internal reforming solid oxide fuel cells, which directly utilize hydrocarbons as fuels in the anode. Catalytic activity tests of Nititanate cermets were carried out in methane steam reforming, and Ni-LST exhibited comparable activity to Ni-YSZ (yttria-stabilized zirconia). Moderate power generation performance was observed over Ni-LST prepared by the impregnation method when the Ni content was decreased to 10 wt%, whereas almost no current was attained over Ni-YSZ for the decrease in the Ni content. The 10 wt%Ni-LST anode prepared by the impregnation method exhibited stable power generation characteristics in severe direct internal reforming operation at steam-to-carbon ratio of 0.1 at 1000ºC under a constant current load of 200 mA cm −2 .
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