Papers by Keyword: Photocatalytic Activity

Abstract: The present study compares the photocatalytic degradation of methylene blue in the presence of natural zeolite supported Ni-doped ZnO and bare Ni-doped ZnO nanoparticles. The photocatalyst was prepared by co-precipitation method and the photocatalytic activity of the photocatalyst was investigated under UV light irradiation. The results showed that the photocatalytic efficiency of zeolite supported Ni-doped ZnO nanoparticles is better than that of bare Ni-doped ZnO nanoparticles. The influence of experimental parameters on the photodegradation of methylene blue was studied and it was observed that photocatalytic activity varied with pH, initial methylene blue concentration and the amount of photocatalyst. The scavenger technique shows that electron plays an important role in the bare Ni-doped ZnO, while in zeolite supported Ni-doped ZnO, ^●OH is the prominent active species.

Abstract: Transition metal ions (Co and Cr) doped ZnO nanoparticles supported on natural zeolite were synthesized using co-precipitation method. The synthesized samples were characterized by means of X-ray diffraction, energy dispersive X-ray, Fourier-transform infrared absorption, and UV-visible diffuse reflectance spectroscopy. The samples were further used as photocatalyst for degradation of methyl orange and methylene blue in aqueous solutions under UV light irradiation. The results showed that zeolite supported Cr-doped ZnO nanoparticles is more efficient compared with zeolite supported Co-doped ZnO nanoparticles. It is also revealed that zeolite supported samples possessed higher photocatalytic efficiency compared to bare samples.

Abstract: Platinum doped Tungsten Oxide (WO₃/Pt) has been successfully coated on the glass substrate using spray deposition method. Doping of Pt on WO₃ was carried out by phodeposition method. The amount of Pt was varied by weight fraction of 0%, 1%, 2%, 4%. These films were characterized using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). It is found that the crystal structure of WO₃ was not change with the Pt addition. However, the dominant plane orientation and the size of crystal were influenced by Pt addition. The crystal size increases with increasing the amount of Pt. After Pt addition, the film morphology showed the presence of pillar structure. The photocatalytic activity test resulted that WO₃/Pt photocatalyst has the ability for degradation of methylene blue (MB) under sunlight irradion. Significantly, the maximum efficiency of photodegradation was observed at 4% Pt doping amount in the WO₃ sample.

Abstract: We report on the synthesis of nanostructured TiO₂ for various structural phases and observed the rate of degradation of methyl orange (MO) upon UV irradiation. Mixed phase nanocrystalline TiO₂ at temperature of 800°C shows higher rate of degradation of MO with the rate of 0.0203/min compared to other phases. This rate corresponds to the percentage of MO degradation of 58.85%, 71.69%, 86.25% and 91.82% for duration of 30, 60, 90 and 120 min of UV irradiations, respectively. The TiO₂ powder was prepared using titanium (IV) butoxide as the precursor via sol gel process. The samples were characterized using X-ray diffractometer (XRD) and field emission scanning electron microscopy (FESEM). The rate of degradation of MO after UV exposure was measured using UV-Vis spectrophotometer. The first order reaction rate constants (k_app) of anatase; mixed-phase; and rutile phases were 0.0130, 0.0203 and 0.0029, respectively, which shows that mixed-phase TiO₂ has higher k_app value indicating higher rate of degradation. The PVA/TiO₂ nanofibers were produced via electrospinning technique and similar tests on the nanofibers were conducted.Energy dispersive X-ray spectroscopy (EDX) indicates significant presence of TiO₂ is in nanofibers and the average diameter of the nanofibers was 600 nm.

Abstract: Carbon (C) and Nitrogen (N) modified TiO₂ photocatalysts were prepared by using two different precursors namely peat and urea using commercial TiO₂-P25. The results from HR-TEM and XPS analyses shows different interactions between C-TiO₂ and N-TiO₂ photocatalysts where C is only coated on top of TiO₂ while N is chemically bonded in TiO₂ particle. Higher photocatalytic activity for both C and N modified TiO₂ were observed under degradation of reactive red 4 dye (RR4) with the degradation rate were c.a 2.5 and 2.7 times faster compared with pristine TiO₂. The photoluminescence (PL) analysis data showed the lowest PL intensity over C coated TiO₂ followed by pristine TiO₂ while N doped TiO₂ exhibited the highest PL intensity. The lowest PL intensity of C coated TiO₂ was due to the presence of C as electron acceptor while the highest PL intensity for N doped TiO₂ was due to the oxygen vacancies and TiO₂ defect structure.

Abstract: TiO₂ nanotubes arrays were prepared by anodization of Ti in EG containing H₃PO₄ and NH₄F electrolyte. The samples were characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray spectroscopy (EDX) and photoluminescence spectra (PL). The as-anodized TiO₂ nanotubes were annealed in inert (argon), reducing (nitrogen), or oxidizing (oxygen) atmosphere at 400 °C for 4 hr. XRD analysis revealed that the TiO₂ nanotubes were anatase after annealing. In this study, the TiO₂ nanotubes annealed in argon exhibited the highest degradation rate of methyl orange (MO) solution under ultraviolet irradiation among the samples. The degradation rate was approximately 98% after 5h, which may be ascribed to the large amount of oxygen vacancies and defects (phosphorus) within the Ar - TiO₂ sample that simultaneously increased the degradation rate of MO.

Abstract: Titanium (Ti) coatings on alumina (Al₂O₃) balls fabricated by mechanical coating technique (MCT) were oxidized at relatively low temperatures. Crystal structure and microstructure of the coatings were investigated. Photocatalytic activity of the coatings was evaluated and discussed. The results showed that TiO₂ films on Ti or Ti/TiO₂ coatings were fabricated by the MCT and subsequent heat oxidation. The TiO₂ is anatase phase if the heat oxidation temperature is under 773 K. The TiO₂ is the mixed phases of anatase and rutile if the heat oxidation temperature is in the range of 673–973 K. Besides, rutile TiO₂ is formed if the heat oxidation temperature is beyond 1073 K. Photocatalytic activity of anatase TiO₂ is higher than rutile TiO₂.

Abstract: Photocatalytic TiO₂–Copper oxides composite coatings were prepared by the mechanical coating technique (MCT) and subsequent heat oxidation. The results showed that Cu particles were mainly adhered to the surfaces of the Ti–Cu composite coatings. After heat oxidation,the Ti coatings were partly oxidized to rutile TiO₂ and a Ti–TiO₂–Cu₂O–CuO composite microstructure was formed. These composite coatings had relative high photocatalytic activity because of the formation of the TiO₂–Ti composite microstructure and TiO₂–Cu₂O–CuO p–n heterojunctions.

Abstract: The small-stones-like BaSb₂O₆ had been successfully prepared through two-step reaction by using inexpensive Sb₂O₃ reactant. The effects of reaction conditions (temperature, time) on photocatalytic efficiency were researched. The photocatalytic activity of BaSb₂O₆ was evaluated by photodegradation of methylene blue (MB). The results showed that the decolorization rate of methylene blue was over 90% under ultraviolet lamp (500 W) beam for 40min. Its structures and morphologies had been investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM). The results showed that XRD pattern of BaSb₂O₆ was consistent with standard card and morphology of BaSb₂O₆ was smooth close-packed state "small stones", fine particles & no agglomeration.

Abstract: The present work was dedicated to the tailored synthesis of TiO₂ nanopowders doped with nitrogen (called TiO_2−xN_x ) for the photocatalytic degradation of methyl orange. In particular, the systems were synthesized by a sol-gel combustion route starting from nitric acid and tetrabutyl titanate (Ti (OC₄H₉)₄) as raw materials. The powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), suggesting that anatase phase is obtained at pH value of 4-6 and the heat-treated temperatures as low as 425°C. The photocatalytic activities of the N-doped TiO₂ nanopowders were monitored from the results of the degradation rate of methyl orange (MO) under solar light irradiation. The dependence of dye degradation rate on photocatalyst amount and initial pH was investigated. Under solar light irradiation, the TiO₂ doped with 30% N exhibited the highest photocatalytic reactivity, which could be attributed to the structure of the combustion-synthesized catalyst and the change of the bandgap induced by nitrogen inclusion.