The electrochemical crystallization of the copper (II) oxide on multi-walled carbon nanotubes

Copper (II) oxide (CuO) crystal structures have been grown on multi-walled carbon nanotubes (MWCNT). For this purpose, functional –COOH and –OH groups were introduced on the surface of MWCNTs by ultra-wave mixing in the H₂SO₄ and HNO₃ bath. The functionalized MWCNTs (fMWCNTs) were washed with distilled water and dried in plasma cleaner. Subsequently, the fMWCNTs were ultra-wave mixed with distilled water. CuO crystal structures were formed on the surface of the fMWCNTs during electrochemical dissolving of copper atoms from a copper electrode. The CuO crystal structures coated the fMWCNTs. These structures formed CuO nanotubes on the fMWCNTs at the specified conditions (colloid concentration, temperature, electric current density). The following annealing process at 500°C produced hollow CuO nanotubes preserving the precursor form. We used high-temperature X-ray diffraction (HTXRD), and Raman spectroscopy (RS) to study the chemical structures. Thermal gravimetric analysis (TGA) confirmed results of HTXRD and RS. Scanning electron microscopy (SEM) showed the tubular geometry of the CuO nanostructures. It was shown that powder of the structures features high specific surface area up to 300 m²/g at least. The possible applications of the structures in nanotechnology and of the powder as a catalyst are discussed. (paper)