Effect of Ni nanoparticle distribution on hydrogen uptake in carbon nanotubes

Ni decoration on carbon nanotubes (CNTs) performed by electroless nickel (EN) deposition is investigated. The effect of Ni particle distribution on hydrogen uptake of CNTs is also studied. The chemical composition, crystal structure and microstructure of the CNTs with or without Ni loading are characterized using an inductively coupled plasma spectrometer (ICP), X-ray diffraction meter (XRD) and transmission electron microscope (TEM) coupled with an energy dispersive spectroscope (EDS). The hydrogen uptake in CNTs with or without Ni loading is measured using a high-pressure microbalance at room temperature under a hydrogen pressure of 6.89 MPa. The experimental results show that fine and well-dispersed metallic Ni nanoparticles can be obtained by EN. The density and particle distribution depend on deposition temperature and time. An enhanced hydrogen storage capacity of CNTs can be obtained by Ni decoration, which provided a spillover reaction. The hydrogen storage capacity of the as-received CNTs was 0.39 wt.%. As much as 1.27 wt.% of hydrogen can be stored when uniformly distributed nano-sized Ni particles are formed on the surface of the CNTs. However, the beneficial effect is lost when the active sites for either physical or chemical adsorption are blocked by excessive Ni loading.