Synthesis of hydrogen absorbing alloy in nanocarbons and evaluation of their properties for hydrogen absorption and separation

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The high pressure absorption of H2 by single-walled carbon nanohorns including Pd-Ni alloy nanoparticles prepared by a gas-injected arc-in-water method was measured by a magnetic suspension balance. It was found that the amount of H2 absorbed by Pd-Ni alloy particles in Pd-Ni/SWCNHs was significantly larger than that absorbed by ordinal Pd-Ni alloys and pure-carbon SWCNHs of the equivalent mass. It can be speculated that this large amount of H2 absorbed by Pd-Ni/SWCNHs is due to spill-over effect of H2 by which H2 is catalytically dissociated at the alloy surfaces, and the dissociative H would diffuse through the carbonaceous part of SWNHs to reach the Pd-Ni nanoparticles dispersing therein. Some portion of dissociative H would remain in carbonaceous parts. A mild oxidation treatment was conducted on Pd-Ni/SWCHs in O2 at 350 oC to generate micropore channels in the carbonaceous parts of Pd-Ni/SWCHs, resulting that the H2 absorption rate was drastically enhanced.