Hydrogen storage in purified multi-walled carbon nanotubes: gas hydrogenation cycles effect on the adsorption kinetics and their performance

Multi-walled carbon nanotubes (MWCNTs) are an alternative for storage with low cost, eco-friendly, and good performance for both process adsorption and desorption. Herein, a purification procedure of MWCNTs was successfully described and studied by using XRD, TEM, Raman spectroscopy and by means of N(2) adsorption-desorption isotherms using the BET method. The H(2) storage properties at room temperature of the purified carbon nanotubes exposed to gas under pressures between 0.39 and 13.33 kPa was investigated by using the quartz crystal microbalance technique. It was found that the H(2) adsorption capacity is strongly dependent on the morphological and structural characteristics of the carbon nanotubes and their specific surface area. The best sample with specific surface area of 729.4 ± 3 m(2) g(−1) shows a maximum adsorption capacity of 3.46 wt% at 12.79 kPa of H(2) exposure pressure. The adsorption kinetics (t(95%)) from the different purified MWCNTs was also investigated as a function of the H(2) exposure pressure as well as the performance of these MWCNTs on the reversibility of the H(2) loading/unloading process when underwent to successive cycles of gas exposure.