L Journal of Alloys and Compounds 356–357 (2003) 433–437 www.elsevier.com / locate / jallcom Are carbon nanostructures an efficient hydrogen storage medium? a, a a a b * Michael Hirscher , Marion Becher , Miroslav Haluska , Frank von Zeppelin , Xiahong Chen , b b Urszula Dettlaff-Weglikowska , Siegmar Roth a ¨ Institut fur Physik, Max-Planck-Institut f ur Metallforschung, Heisenbergstr. 1, Stuttgart D-70569, Germany b ¨ ¨ Max-Planck-Institut f ur Festkorperforschung, Stuttgart, Germany Received 3 September 2002; accepted 31 December 2002 Abstract Literature data on the storage capacities of hydrogen in carbon nanostructures show a scatter over several orders of magnitude which cannot be solely explained by the limited quantity or purity of these novel nanoscale materials. With this in mind, this article revisits important experiments. Thermal desorption spectroscopy as a quantitative tool to measure the hydrogen storage capacity needs an appropriate calibration using a suitable hydride. Single-walled carbon nanotubes that have been treated by ultra-sonication show hydrogen uptake at room temperature. However, this storage can be assigned to metal particles incorporated during the sonication treatment. Reactive high-energy ball milling of graphite leads to a high hydrogen loading, however the temperatures for hydrogen release are far too high for application. In view of today’s knowledge, which is mainly based on experiments with small quantities and poorly characterised samples, carbon nanostructures at around room temperature cannot store the amount of hydrogen required for automotive applications.  2003 Elsevier B.V. All rights reserved. Keywords: Hydrogen storage; Carbon nanotubes; Nanostructured graphite 1. Introduction These data, however, exhibit a large scatter, as exemplified for single-walled carbon nanotubes (SWNTs) in Fig. 1. For Hydrogen storage in carbon materials is a very attractive graphitic nanofibers the results are even more scattered and topic since high gravimetric storage capacities may be storage capacities from 67 down to 0.1 wt% have been possible owing to the low specific weight of carbon. For reported. However, the extremely high storage capacities automotive applications, a hydrogen storage capacity of have never been independently reproduced in another greater than 6.5 wt% is required as set by the US Department of Energy [1]. Besides the capacity, industrial applications require ambient temperatures for hydrogen release and moderate pressures for storage. Today, different nanostructured carbon materials are available, e.g. carbon nanofibers, carbon nanohorns, multi- walled carbon nanotubes, and single-walled carbon nanotubes. All these new carbon structures exhibit a nanoscale extension in two dimensions. These new geometries, which have been discussed in several reviews [2], may give rise to new interactions of carbon with hydrogen. Very promising publications reporting high hydrogen storage capacities in carbon nanotubes resulted in enorm- ous research activity, yielding much experimental data. Fig. 1. Experimental data for hydrogen storage capacities (logarithmic *Corresponding author. scale) in SWNTs versus publication year for different methods, pressures E-mail address: hirscher@mf.mpg.de (M. Hirscher). and temperature regimes. 0925-8388 / 03 / $ – see front matter  2003 Elsevier B.V. All rights reserved. doi:10.1016 / S0925-8388(03)00142-7