SWNTs Bundle Dispersion Study and Analysis of its Potential as a Hydrogen Tank
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1042-S06-10
SWNTs Bundle Dispersion Study and Analysis of its Potential as a Hydrogen Tank Kyoichi Tange1,2, Katsuhiko Hirose3, katsutoshi Noda3, Rana Mohtadi4, and Yoshitsugu Kojima5 1 Toyota Motor Corpotration, Susono, 410-1193, Japan 2 Hiroshima University, Higashi-Horoshima, 739-8530, Japan 3 Toyota Motor Corporation, Susono, 410-1193, Japan 4 Toyota Motor Engineering and Manufacturing North America, Ann Arbor, MI, 48105 5 Hiroshima University, Higashi-hiroshima, 739-8530, Japan ABSTRACT Hybrid hydrogen tank utilizing high pressure storage combined with high purity and high surface area physi-sorption single wall carbon nanotubes (SWNTs) is considered to be one of the most promising hydrogen tank systems. For the purified SWNTs as-received from CNI with the HiPco method, the tube diameter was enlarged from 1nm-average to around 2nm by applying high temperature under vacuum condition. The specific surface area of the cap open SWNTs, determined by nitrogen adsorption at 77 K, was 1800 2000m2/g. This value is including the effect of bundle dispersion. In addition, we confirmed the high bulk density of 0.75g/cm3 after treating these large diameter SWNTs by the molding process. In conclusion, this work identified the potential capability to make compact (140~150L) and light (130~140kg) hybrid tank under high pressure (30-35MPa) hydrogen able to release 5kg of fuel at room temperature. This will be possible by both suppressing the formation of graphite completely during the diameter enlargement process and optimizing the diameter distribution and the distance between tubes.
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INTRODUCTION Hydrogen storage presents a main obstacle for large scale commercialization of fuel cell vehicles. DOE established the hydrogen storage tank target to be 6wt%, 45g/L by 2010 in order to attain similar driving range as for gasoline vehicles with same tank size and weight. Hydrogen could be stored in the bundles of SWNTs up to 5 to 10 mass %, where H2 molecules are physi-sorbed at the exterior of CNTs or at the interior spaces between nanotubes.1-2 Many epoch making data were reported around the year 2000 about physi-sorption using carbon related materials. But this boom seemed to disappear due to the data credibility. However, its true potential is not yet well understood. Sugimoto et al.3 reported the simulation results of achieving high H2 uptake amount of around 2.5 mass % at 273 K using 2nm (roughly) tube
diameter, bundle dispersed SWNTs in a hybrid tank filled with high pressure hydrogen (30-40MPa). The objective of this study is to point out the potential capability of achieving the required performance of the tank by incorporating SWNTs.
EXPERIMENT The author was successful in developing the equipment that measures the gas uptake rate up to 35MPa at room temperature. Using our technique, the error in the gas uptake measured was less than 10 Nml for a total gas volume, including compressed gas, of 1,000 to 10,000 Nml. This means that for 1 gram sample, an error of only less than 0.1mass% was introduced. High purity S
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