Hydrogen Adsorption onto Nickel Modified Carbon Nanotubes

The Hot Filament Chemical Vapour Deposition (HFCVD) method was employed to study hydrogen adsorption on multi-walled carbon nanotubes (MWCNTs) modified by nickel doping. Prior to the nickel doping, effective functionalisation of CNTs was achieved by treating them in HNO₃/H₂O₂ medium. Samples were characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDS), and Fourier Transform Infrared (FTIR) and Raman spectroscopy techniques. SEM analyses revealed the morphology of the samples and the presence of nickel was identified by EDS analyses. Raman analysis revealed the enhancement of defects on the CNTs after the nickel modification. The defects created along with the catalytic activity of nickel supplied more hydrogen access to the CNTs. This was inferred from highest intensity ratio of D and G band (ID/IG) for hydrogen treated samples. However, FTIR spectra did not exhibit any C—H related bands. This confirms that the adsorption of hydrogen onto CNTs is primarily by surface adsorption.