Reversible hydrogen storage in functionalized single-walled carbon nanotubes

Abstract

In this work, functionalized carbon nanotubes (CNTs) based hydrogen storage medium has been designed by the facile drop-casting method. Initially, the commercial single-walled carbon nanotubes (SWCNTs) were purified by standard methods and functionalized with borane (BH3). The morphology of SWCNTs was imaged by transmission electron microscopy (TEM). The energy dispersive spectroscopy (ED) shows that the purified SWCNTs are free from elemental impurities. The functional groups in the functionalized SWCNTs were analyzed by fourier transform infra-red spectroscopy (FTIR). Then, the functionalized SWCNTs were hydrogenated in a Seivert like hydrogenation setup for different time duration. Elemental analysis (CHN) combined with thermo gravimetric/thermal desorption spectroscopy (TG/TDS) measurements were used to quantify the amount of hydrogen stored in the functionalized SWCNTs. A maximum hydrogen storage capacity of 4.77wt% is achieved at 50°C and the entire (100%) stored hydrogen is released in the temperature range of 90–125°C. The amount of hydrogen stored in functionalized SWCNTs increases with increasing hydrogenation duration. The entire hydrogenation and dehydrogenation process was probed by Raman and CHN-elemental analyses. The whole hydrogenation and dehydrogenation experiments were stabilized and they were repeatable. The achieved hydrogen storage capacity in this investigation is close to the US DOE target.