Effect of Cu and MWCNT's doping in ZrO₂ for visible light photodegradation of methylene blue

Compounds Cu/ZrO 2 and Cu/MWCNTs/ZrO 2 were obtained from doping zirconium oxide with copper and multiwall carbon nanotubes (MWCNTs) using the sol–gel. For the synthesis, zirconium tetrabutoxide was used as a precursor and the obtained powders were thermally treated at 600 ∘ C. The powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Visible and FTIR Spectroscopy. The photocatalytic tests were carried out with methylene blue as a contaminant. The compounds showed tetragonal phase Cu doped and Cu/MWCNTs doped, respectively. The absorbance difference between the ZrO 2 compound and the doped ones showed absorption bands at 2.47 eV attributed to the d–d transition of the Cu 2 +ions and at 5.6 eV, attributed to the direct band-to-band transition of the ZrO 2 band gap. The compound that presented the best photocatalytic activity is Cu/MWCNTs/ZrO 2 .