Abstract
In this study, the hydrogen storage capacity of purified multiwalled carbon nanotubes (MWCNTs) was enhanced from 13- to 15-fold at a temperature of 298 K and pressure of 2.0 MPa, upon incorporation of 1.57–1.88 wt% of ultrafine Ti nanoparticles. The effect of a hydrogen spillover Ti catalyst on MWCNTs prepared using the sputtering method was investigated. A comparison between the hydrogen uptake by MWCNTs sputtered with Ti for 3000 s and that for 6000 s was also performed using the Sievert's volumetric apparatus. The significant enhancement in hydrogen uptake was attributed to the interfacial diffusion of hydrogen from Ti to the MWCNTs. The re-adsorption of hydrogen on the pristine MWCNTs and Ti-decorated MWCNTs dehydrogenated at 200 °C indicated that the samples did not compromise their reversible hydrogen uptake during the hydrogenation–dehydrogenation cycles. It was also found that longer exposure of Ti to the MWCNTs during sputtering improved the hydrogen storage capacity. This improvement could be attributed to the presence of a higher amount of Ti deposited on the MWCNTs, as indicated by thermogravimetric analysis study.
Representation of hydrogen uptake and spillover mechanism of ultrafine Ti nanoparticle decorated MWCNTs. [Display omitted]
•Preparation of Ti/MWCNTs composites by time dependent sputtering method.•SEM and TEM analysis demonstrates nanostructured characterization of samples.•Hydrogen storage improvement of composite is 13- and 15- fold compared to pristine.•Enhancement is associated with interfacial diffusion of hydrogen from Ti to MWCNTs.•Reversibility of hydrogen uptake intact upon hydrogenation–dehydrogenation cycles.