Effect of thermal fluorination on the hydrogen storage capacity of multi-walled carbon nanotubes

Thermal fluorination of multi-walled carbon nanotubes (MWCNTs) was performed to improve their hydrogen storage capacity, based on three considerations. First, the surface of the MWCNTs was altered by thermal fluorination to create a pathway for the storage of hydrogen molecules inside the MWCNTs. These surface treatments increased the number of MWCNT defects through attack by fluorine radicals. The defects were identified using Raman peaks and TEM images. Second, thermal fluorination changed the pore structure by enlarging the specific surface area and the pore volume, which increased the number of hydrogen adsorption sites. Last, the induced fluorine groups enhanced the hydrogen storage capacity through attraction effects on the electron in the hydrogen molecules due to the high electronegativity of fluorine. In conclusion, thermal fluorination increased the hydrogen storage capacity of MWCNTs four-fold to 1.69 wt%.