Hydrogen storage in carbon nanotubes revisited

The reported hydrogen uptake of carbon nanotubes (CNTs) has been the subject of much controversy. We have measured the hydrogen uptake capacity of different types of CNTs using a volumetric measurement setup specifically-designed for CNTs. It was found that under a pressure of ∼12 MPa and at room temperature, the hydrogen storage capacity of the CNTs is less than 1.7 wt.%, which is far below the benchmark set for on-board hydrogen storage systems by the US Department of Energy. These results suggest that it is no longer worth investigating hydrogen uptake in pure CNTs for on-board applications. However, our recent research indicates that CNTs can be an effective additive to some other hydrogen storage materials to improve their kinetics.