The electrochemical decoration of multi-walled carbon nanotubes with nickel oxide coating

In this paper, nickel coatings have been deposited on the multi-walled carbon nanotubes (MWCNT). In the first stage, MWCNT powder was ultra-wave mixed in the acid bath (H₂SO₄ and HNO₃). The acid treating activates inert carbon surface introducing functional –OH and –COOH groups on the MWCNT surface. The mixture was diluted with distilled water and filtered for several times. The filtered sediment was dried in a plasma cleaner. The powder of such cleaned functionalized MWCNTs (fMWCNTs) was ultrasonicated with deionized water to produce stable colloid. Nickel atoms were injected into the colloid from a positive nickel electrode (with a negative graphite one). The Ni containing tubular nanostructures decorated the fMWCNTs at the specified regulated conditions (temperature, colloid concentration, electric current density). The electrochemically treated colloid was filtered and dried to a powder state (Ni-containing-fMWCNT powder). Hollow NiO nanotubes were produced by the annealing of the powder at 600°C (tubular nanostructured NiO powder). Both powders were examined by the Raman spectroscopy (RS), high-temperature X-ray diffraction (HTXRD), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA). The estimated high specific surface area of the nanostructured NiO powder is up to 97 m²/g at least and may be varied by time and the electric current of the electrochemical process. (paper)