Hydrogen storage enhancement of HiPCO SWNTs by palladium catalyst doping

Abstract

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 measured using a small-sample Sieverts apparatus that has a small volume pressure reservoir and a sample chamber of less than 1 ml. The sample showed 0.17 wt% of hydrogen uptake capacity at 30 Bar of hydrogen pressure. Palladium 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 over the un-doped sample. The results of in-situ XPS and TEM observations are also presented with presumable reasoning for the larger effect in Sp-doped SWNT.