Are carbon nanostructures an efficient hydrogen storage medium?

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