Hydrogen storage in microwave-treated multi-walled carbon nanotubes

Multiwalled carbon nanotubes (MWCNTs) treated by microwave and heat treatment were used for hydrogen storage. Their storage capacity was measured using a quadruple quartz crystal microbalance in a moisture-free chamber at room temperature and at relatively low pressure (0.5 MPa). Deuterium was also used to monitor the presence of moisture. The hydrogen storage capacity of the microwave-treated MWCNTs was increased to nearly 0.35 wt% over 0.1 wt% for the pristine sample and increased further to 0.4 wt%, with improved stability after subsequent heat-treatment. The increase in the storage capacity by the microwave treatment was mostly attributed to the introduction of micropore surfaces, while the stability improvement after the subsequent heat treatment was related to the removal of functional groups. We also propose a measurement method that eliminates the moisture effect by measuring the storage capacity with hydrogen and deuterium gas.