Papers by Keyword: Photocatalyst

Abstract: TiO₂ modified Fe₃O₄ nanocomposite as photocatalyst in CO₂ indirect reduction was synthesized by an ultrasonic-assisted sol-gel method and its photocatalytic activity was studied as well. The modification of the TiO₂ composite was attempted to modify titanium dioxide to have better performance as a photocatalyst. Magnetite synthesis was carried out by the sono-coprecipitation method with the addition of the capping agent. The magnetite was coated with TiO₂ via the sol-gel method under ultrasonic irradiation. The products were characterized by X-ray diffraction (XRD), Fourier transforms infrared spectrophotometry (FT-IR), transmission electron microscopy (TEM), and turbidimetry. The final product was also analyzed by diffuse reflectance UV-Visible (DR-UV) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX). The product of indirect reduction was analyzed by gas chromatography-mass spectrometry (GC-MS). Photocatalytic reaction with Fe₃O₄/TiO₂ nanocomposite produced a higher concentration of methanol than using TiO₂. Methanol concentration produced from the photocatalytic reaction using TiO₂ and Fe₃O₄/TiO₂ was 6.63% and 16.82%.

Abstract: To handle persistent toxic organic contaminants in water, advanced oxidation process (AOP) by titanium dioxide (TiO₂) and its composites has been extensively utilized. A smart combination of composite materials was synthesized to improve photocatalytic activity of TiO₂ via engineering effective charge transfer. In this study, synthesis of Ag/Graphite Oxide (GO)/TiO₂ was investigated. Degussa P25 TiO₂ (Rutile:Anatase of 85:15, 99.9%, 20nm) nanopowder was purchased. Graphite oxide was prepared using modified Hummer’s method. Photoreduction and ultrasonication were conducted to prepare Ag nanoparticles (AgNPs). XRD was used to confirm formation of Ag- GO- TiO₂, i.e., peaks of GO, AgNPs and phases of anatase and rutile of TiO₂ P25. Backscattered SEM was used to identify the AgNPs in different compositions of the AgNPs/GO/TiO₂ composites. TEM was used for high resolution images to observe sizes and shapes of nanomaterials involved. X-ray absorption near edge structure (XANES) spectra of the Ag L₃-edge were used to confirm zero-valence AgNPs. The best performed photocatalyst from this study was 5Ag0.5GOTiO₂ with 78.86 % degradation of RhB after 2 hours. The AgNPs were found to be spherical with sizes of around 2-10 nanometers and evenly distributed within the GO/TiO₂ matrix.

Abstract: Humic acid (HA) is a major component of natural organic substances and affects water quality, such as color, taste and odor. Therefore, removal of HA from surface water or wastewater is very important. In this paper, the photodegradation kinetics of these compounds using TiO₂/ZnO/Co composite photocatalyst under visible light irradiation was investigated. The progress of photocatalytic degradation of the HA has been observed by measuring the absorbance in UV-Visible spectrophotometer. The results reveal that the TiO₂/ZnO/Co composite photocatalyst exhibits much better photocatalytic activity than those of pure TiO₂ and TiO₂/ZnO on photodegradation of HA under visible light irradiation, with degradation rate constants were found 0.0163, 0.0079 and 0.0032 (min^-1), respectively.

Abstract: Metal oxide semiconducting compounds have potential application as photocatalyst materials to decompose many types of dyes and pollutants in the water. Zn₂SnO₄ and SnO₂ are semiconducting materials that have photocatalytic properties and the properties of those two semiconducting materials in the composite form have been studied. Metal oxide compounds of Zn₂SnO₄ and SnO₂ have been prepared through sonochemical methods using ZnCl₂ and SnCl₄.5H₂O as precursors. After sonication and heat treatment at 1000 °C, we could obtain Zn₂SnO₄ and SnO₂ compound in the sample as confirmed by x-ray diffraction measurement. The volume fraction of Zn₂SnO₄ and SnO₂ phases in the sample were found to be at 60 % and 40 %, respectively. The absorption spectra revealed that the band gap of the composite materials is 3.7 eV. This material could degrade all of the methylene blue with concentration of 6.0 x 10^-6 M in 120 minutes. The band structure calculation revealed that the comparable band gap values are found for Zn₂SnO₄ and SnO₂ compounds. However, the absorption edges for those compounds are slightly different, with absorption edge at 3.2 eV for SnO₂ and 3.6 eV for Zn₂SnO₄, respectively.

Abstract: Polydimethylacrylamide (PDMA) microgels and niobate nanosheet/PDMA composite microgels were fabricated by using a microfluidic device. Morphologies and sizes of the composite microgels were tuned by adjusting synthetic conditions such as viscosity of oil phases, hydrophilicity and concentration of surfactants, and flow rates of oil phase and water phase. Furthermore, it was found that the dispersion of nanosheets was better when the composite microgels were synthesized by photopolymerization compared to redox polymerization.

Abstract: Sm₂O₃/ZnO nanoparticles were prepared via microwave-assisted hydrothermal and sol-gel combustion synthesis. Characteristics of obtained samples were compared in dependence of Sm₂O₃ content and calcination temperature. Prepared nanostructures were characterized with scanning electron microscopy and X-ray diffraction. Nanoparticles prepared via microwave-assisted hydrothermal and sol-gel method have flower-like and spherical shape respectively. The photocatalytic activity of samples under solar light simulated illumination was found to be affected by content of Sm₂O₃, calcination temperature and preparation method. The first-order rate constant of MB solution degradation of samples prepared via microwave-assisted hydrothermal method approximately three times exceeds that of sol-gel samples.

Abstract: The S-doped g-C₃N₄ materials were prepared by heating mixtures of urea and thiourea with various weight ratios at 550 °C, and denoted as x:y SCN, where x:y is weight ratios of urea to thiourea. The obtained samples were characterized by X-ray diffraction, diffuse reflectance ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric differential thermal analysis, scanning electron microscopy and infrared spectra. The results showed that all the x:y SCN materials exhibit the presence of doping S in the structure of g-C₃N₄ and higher capability in the photodegradation of Rhodamin B in aqueous solution under visible light condition than pure g-C₃N₄. Among the SCN samples, 75:25 SCN performed the highest photocatalytic activity, which is believed the presence of the largest amount of doping S in the matrix of g-C₃N₄, leading to reduction of their bandgap. The reduction of bandgap for S-doped g-C₃N₄ materials compared to pure g-C₃N₄ was proved by theoretical calculation.

Abstract: In this paper, α–Fe₂O₃ photocatalyst with enhanced solar–driven photocatalytic activity was obtained from natural local groundwater sediment using a chemical solution method with subsequent calcination. The phase structures and crystallite size characterized by X–ray diffraction. The morphology and the particle size were investigated by scanning electron microscopy. The α–Fe₂O₃ was used as a catalyst to photodegrade MB under visible light illumination. The photocatalytic reaction rate constant of the α–Fe₂O₃ photocatalyst in the photocatalytic degradation of MB dye solution under LED light illumination with the presence of H₂O₂ was calculated to be 1.70×10^–2 min^–1. Moreover, the effect of H₂O₂ concentration on photocatalytic efficiency and the photocatalytic mechanism also were discussed.

Abstract: Nanostructured manganese-containing oxide coatings on titanium were formed by method of plasma electrolytic oxidation in tetraborate aqueous electrolyte containing manganese acetate with and without the acetonitrile addition. These oxide layers with high content of manganese and coated by ordered "leaf-like" mesh nanostructures are formed in the electrolyte without acetonitrile addition. The oxide layers are displayed high acitivity towards oxidation CO and photoactivity in the degradation reaction of methylene blue. The addition of acetonitrile into electrolyte results in the change in the morphology of the coating surface, a significant reduction in the manganese content and, as a consequence, practical loss of activity in the oxidation of CO in CO₂ and a reduction in the photocatalytic activity in the decomposition of methylene blue.

Abstract: We synthesized TiO₂ nanoparticles dispersed hydroxyapatite (TiO₂-modifed HAp) by solvothermal treatment of α-tricalcium phosphate (α-TCP) using water-isopropanol solution including tetraisopropyl orthotitanate (TTIP). Rod-shaped HAp with TiO₂ nanoparticles were formed by solvothermal treatment. HAp formation decreased with increasing the isopropanol fraction in the solution with TTIP. With increasing the treatment period, the rate of HAp formation in sample increased. The aspect ratio of HAp decreased with increasing the isopropanol fraction in the solution. Synthesized TiO₂-modifed HAp samples shows the photocatalytic decoloration of methylene blue under UV irradiation.