Hydrogen Storage in Decorated Multiwalled Carbon Nanotubes by Ca, Co, Fe, Ni, and Pd Nanoparticles under Ambient Conditions

We report a study on hydrogen storage in Ca, Co, Fe, Ni, and Pd decorated multiwalled carbon nanotubes (MWCNTs) by using two techniques: volumetric and electrochemical. The results showed that hydrogen molecules are adsorbed on the defect sites and transported to the spaces between adjacent carbon via diffusion through both defect sites and opened tips into the layers. Hydrogen storage capacity can be improved in the decorated MWCNT by Co, Fe, Ni, and Ca metals in two approaches: (i) H-2 adsorption via Kubas interaction and (ii) dissociation of H-2 molecules on the metal particles. The results reveal that Pd are more effective catalyst for hydrogen storage process. It was found that dissociation of H-2 occurs on the Pd particle, and hydrogen atoms are entered into the spaces between adjacent carbon layers. They create loosely bonds of CHx species and Pd-C-H-x complex which can be decomposed easily at lower temperatures as compared to C-H chemical bonds.