Hydrogen storage in Pd–Ni doped defective carbon nanotubes through the formation of CHx (x = 1, 2)

Hydrogen storage by chemisorption on multiwalled carbon nanotubes (MWCNTs) was studied. Pristine MWCNTs could only store 0.1 wt.% of hydrogen at 573 K and ambient pressure, however, oxidation treatment to produce defects and subsequent loading with a Pd–Ni catalyst significantly increased the hydrogen storage capacity up to 6.6 wt.%. The hydrogen desorption temperature was above 500 K and an in situ diffuse reflectance IR Fourier-transform spectroscopy study indicated that the hydrogen was stored in the form of CHx (x = 1, 2) species. The study indicated that the most appropriate hydrogen chemisorption temperature was 550 K. For comparison, oxidized unloaded MWCNTs, oxidized MWCNTs separately loaded with either Pd or Ni, unoxidized fresh MWCNTs loaded with Pd–Ni, and activated carbon loaded with Pd–Ni were studied. The results showed that the defects and Pd–Ni catalyst were two essential factors for the high chemisorption of hydrogen on carbon nanotubes.