(424a) Hydrogen Storage in Carbon Nanotube and Palladium Composite Materials

The hydrogen storage capacity of a commercially available, HiPco (high pressure CO conversion) single-wall carbon nanotube (SWNT) was measured over a hydrogen pressure range of 0-35 Bar at room temperature. The storage capacity was volumetrically measured from pressure-concentration-temperature (PCT) isotherms using a small-sample Sieverts type apparatus that has a small volume pressure reservoir and a sample chamber of less than 1 ml. The SWNT sample showed 0.17 wt% of hydrogen uptake capacity at 30 Bar of hydrogen pressure. SWNT and palladium composite materials were synthesized by depositing Pd catalyst on the nanotube surface. The Pd nanoparticles were electrochemically (EC) and sputter-deposited (Sp) on the SWNT. The storage capacity of the EC-doped Pd SWNT at 30 Bar was measured at 0.48-0.52 wt% after correcting for the hydrogen stored in the Pd nanoparticles. Sp-doped sample showed a larger uptake enhancement of a factor between 4.1 and 4.8 (0.69-0.82 wt%) over the un-doped SWNT sample. The results of Xray photoemission spectroscopy and e-beam heating experiment during in-situ transmission electron microscopy observations are presented with presumable reasoning for the larger effect observed in the Sp-doped SWNT. The hydrogen uptake measurements for SWNT and Pt composite materials are also presented with their microstructure characterizations.