Heterogeneous photocatalytic removal of Rhodamine-B (RhB) dye by metallic Au nanopatrticles deposited TiO2 photocatalyst was studied. For this study, a chemical reduction method by hydrazine hydrate for gold deposition was employed in order to synthesize Au/TiO2 nanocomposite system. For the characterization of the synthesized nanomaterials, X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), the Fourier transformation infrared spectroscopy (FTIR) and photoluminescence spectroscopy (PLS) techniques were performed. The obtained results show that the deposition of gold onto TiO2 surface could effectively inhibit the recombination of the photoinduced electron and holes, improving the absorption capability for the visible light source and leading to the increased surface OH group density. The degradation experiment reveals that the efficiency of color removal from RhB aqueous solution containing Au/TiO2 powders for the photocatalytic bleaching of RhB dye is more efficient than that of bare TiO2 sample upon UV-vis light activation. In addition, degradation kinetics of RhB dye in aqueous suspensions can be well simulated by the Langmuir-Hinshelwood model and obeys the pseudo-first order law, with a decolorization rate of 0.0252 min-1 to the photocatalytic removal of RhB dye.
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Iron-carbon-codoped mesoporous titania nanocrystallines were synthesized by a modified sol-gel method based on the self-assembly technique using polyethylene glycol sorbitan monostearate (Tween 60) as template. The samples were characterized by X-ray diffraction, N_{2} adsorption, UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, photoluminescence, electrochemical impedance spectroscopy, and transient photocurrent responses analysis. The photocatalytic activity of Fe-C-codoped TiO_{2} nanoparticles were evaluated by the degradation of methyl orange (MO), p-nitrophenol (PNP) and biphenol A (BPA) under visible light irradiation. It was found that the as-prepared Fe-C-codoped TiO_{2} sample showed excellent photocatalytic activity compared to undoped TiO_{2}. The highest activity was obtained for Fe-C-codoped TiO_{2} sample calcined at 520°. The enhanced photocatalytic performances were attributed to the synergetic effects of good crystallizing action, appropriate phase composition and slow recombination rate of photogenerated charge carriers. Based on the experimental results, a reasonable photocatalytic mechanism of as-prepared Fe-C-codoped TiO_{2} photocatalysts was also proposed and discussed.
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