Cu-doped ZnO/TiO2 photocatalyst: synthesis, characterization and effectiveness on band gap energy level
Volume Title: 1
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Abstract
Copper doped zinc oxide/titanium dioxide nanocrystals (Cu-ZnO/TiO2) were synthesised by entrapping copper ions in a crystalline matrix of ZnO/TiO2 through the sol-gel method. Copper with different concentrations between 1% and 5 % were loaded into a photocatalyst matrix with the TiO2/ZnO ratio of 70% to 30%. The matrix was calcinated at two different temperatures of 500°C and 700°C. Thermal property and absorption spectra of Cu Doped ZnO/TiO2 were characterized by thermogravimetric analysis (TGA) and a UV–Vis spectrophotometer. Besides, the band gap energy level of the synthesized catalyst was estimated through Kubelka-Munk’s model and Plank equation. The results revealed that Cu-ZnO/TiO2 had a more thermally stable lattice compared to TiO2/ZnO and therefore the phase transformation from anatase to rutile was retarded under higher calcination temperature in the Cu-ZnO/TiO2 lattice. Apart from calcination temperature, dopant content was found to affect optical band gap energy level. Accordingly, the narrowest band gap level was observed in the sample with the copper content of 3wt%, calcinated at 500°C. Among the samples, the doped photocatalysts that were calcinated at 500°C, showed low band gap energies which was were to the presence of CuO and Cu2O on the surface of the photocatalyst and/or from the residual copper due to incomplete pyrolysis. Cupric oxide, CuO has a band gap energy level of 1.4eV while cuprous oxide, Cu2O has a band gap energy level of 2.2eV.
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