A detailed experimental comparison on the hydrogen storage ability of different forms of graphitic carbon nitride (bulk, nanotubes and sheets) with multiwalled carbon nanotubes

The reversible hydrogen storage of graphitic carbon nitride (g-C₃N₄) nanotubes at room temperature was first studied through experimental methods in this work and was compared to multiwalled carbon nanotubes (MWCNT), bulk g-C₃N_4, and g-C₃N₄ nanosheets. Compared with MWCNT which had a similar specific surface area around 60 m²/g, g-C₃N₄ nanotubes had a higher room temperature hydrogen storage capacity up from 0.46 wt% for MWCNT to 0.78 wt%. This value for the g-C₃N₄ nanotubes was also higher than the hydrogen storage capacity of bulk g-C₃N₄ (0.51 wt%) and g-C₃N₄ nanosheets (0.73 wt%), even though g-C₃N₄ nanosheets had the highest specific surface area of 161 m²/g. Temperature programming desorption (TPD) was applied to study the desorption behaviours and it was found that chemisorption contributed to the relative high storage capacity of g-C₃N₄ nanotubes.