CuO/TiO2 nanocomposite photocatalyst for efficient MO degradation

Abstract

Many studies have been performed to degrade the methyl orange (MO) dye by introducing titanium dioxide (TiO2) semiconductor material as photocatalyst because TiO2 having unique characterizations such as low toxicity and good chemical stability. However, its photocatalytic reaction is limited by low surface area as well as the rapid recombination of photogenerated electron-hole pairs and only has ability to absorb a small fraction (<5%) of indoor light. Therefore, in this study, copper oxide/titanium dioxide (CuO/TiO2) nanocomposite photocatalyst was proposed and synthesized using wet precipitation method. The synthesised photocatalyst was characterized by using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM), Energy dispersive x-ray (EDX), Thermogravimetric analysis (TGA), Nitrogen gas adsorption-desorption Brunauer, Emmett, teller (BET) and UV-Visible Spectroscopy. Spectra obtained from FTIR have proved that there are existence of O-H stretching, O-H bending and metal-oxygen bond that correlates to the functional groups of the samples. As affirmed by XRD analysis, crystalline anatase TiO2 phase was obtained for pure TiO2 samples. Anatase TiO2 phase is remained, and the additional peaks belong to copper oxide was observed for CuO/TiO2 nanocomposite photocatalyst sample suggesting that copper oxide was successfully loaded onto TiO2. The morphological study from SEM shows the presence of irregular particles of copper oxide and agglomerated TiO2 bulk particles. The CuO/TiO2 nanocomposite photocatalyst's presence of copper, titanium, and oxygen was confirmed by EDX analysis. TGA results show that pure CuO, TiO2 and CuO/TiO2 nanocomposite photocatalyst were thermally stable as only 6.7, 6.8 and 7.9 % weight loss were observed, due to the water removal. The specific surface area of CuO, TiO2 and CuO/TiO2 composite photocatalysts were found to be 20.50 m2 /g, 15.26 m2 /g and 37.12 m2 /g, respectively. They also exhibit type IV isotherms which is indicated the presence of mesopores in sample. This mesoporous structure provided high pore size within 2 to 50 nm in the sample. The photocatalytic activity study demonstrates that the 1.0 g CuO/TiO2 with the ratio of (0.5:1) could degraded 90.46 % of 10 ppm Methyl Orange (MO) dye at pH 6, which is better than pure TiO2, pure CuO and other CuO/TiO2 nanocomposites after 3 hours reaction. This is attributed to the presence of CuO at optimum amount which can increased the surface area, promoted electron-hole separation, and decelerated the charge carrier recombination. At 1 ppm MO, 100 % degradation was observed using similar photocatalyst and condition. However, the degradation rate of Methylene Blue (MB) and phenol was slightly reduced to almost 95.47 % and 80.65 % after 180 minutes reaction, due to their chemical structure and stability.