Multi walled carbon nanotubes functionalized by hydroxyl and Schiff base and their hydrogen storage properties

Abstract

The hydroxyl and Schiff base functionalization, characterization, and H2 storage of multi walled carbon nanotubes (MWCNTs) have been investigated in the present work. The samples were analyzed using Brunauer-Emmett-Teller, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The adsorption of H2 gas was performed by volumetric method in different pressures at 77 K using the Hiden IMI PSI instrument. The surface area of MWCNT decreased with functionalization, but the surface areas of MWCNT-O-Schiff base-Me complexes generally increased. Scanning electron images showed that due to the increase in hydrophilic properties of modified samples, MWCNTs were separated from each other and morphology changed. According to the Fourier transform infrared analysis, functional groups were formed on the structures. While MWCNT was thermally stable, the functionalized samples degraded in three steps. Functionalized MWCNTs were higher hydrogen storage capacity than MWCNT. It was found that the hydrogen storage capacity of MWCNT, MWCNT-OH and MWCNT-O-Schiff base were 0.281, 0.321 and 0.37 wt% at 10 bar, respectively at cryogenic temperature. The hydrogen storage capacities of MWCNT-O-Schiff base-Me complexes varied in the range of 0.101-0.396 wt%. MWCNT-O-Schiff base-Cu had the highest hydrogen storage capacity.