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TiO 2 /g-C 3 N 4 photocatalysts with the various TiO 2 /g-C 3 N 4 weight ratios from 1:2 to 1:6 were fabricated by mechanical mixing in water suspension followed by calcination. Pure TiO 2 was prepared by thermal hydrolysis and pure g-C 3 N 4 was prepared from commercial melamine by thermal annealing at 620 °C. All the nanocomposites were characterized by X-ray powder diffraction, UV–vis diffuse reflectance spectroscopy, Raman spectroscopy, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, photoelectrochemical measurements and nitrogen physisorption. The prepared mixtures along with pure TiO 2 and g-C 3 N 4 were tested for the photocatalytic decomposition of nitrous oxide under UVC (λ = 254 nm), UVA (λ = 365 nm) and Vis (λ > 400 nm) irradiation. The TiO 2 /g-C 3 N 4 nanocomposites showed moderate improvement compared to pure g-C 3 N 4 but pure TiO 2 proved to be a better photocatalyst under UVC irradiation. However, under UVA irradiation conditions, the photocatalytic activity of TiO 2 /g-C 3 N 4 (1:2) nanocomposite exhibited an increase compared to pure TiO 2 . Nevertheless, further increase of g-C 3 N 4 amount leads/led to a decrease in reactivity. These results are suggesting the nanocomposite with the optimal weight ratio of TiO 2 and g-C 3 N 4 have shifted absorption edge energy towards longer wavelengths and decreased the recombination rate of charge carriers compared to pure g-C 3 N 4 . This is probably due to the generation of heterojunction on the TiO 2 /g-C 3 N 4 interface. [ABSTRACT FROM AUTHOR]

Abstract: Catalysts with various Ag loading (0.7–5.2wt%) in the powder form were prepared by the sol–gel process controlled in the reverse micellar environment. X-ray diffraction (XRD), nitrogen adsorption measurement, UV–vis and elemental analysis were employed for characterization of catalysts. Effect of various silver loadings on photocatalytic activity of TiO2 catalysts in N2O photocatalytic decomposition was studied. Photocatalytic decomposition of N2O was performed in annular batch reactor illuminated with 8W Hg lamp (254nm wavelength). Reaction kinetic corresponds to first-order reaction rate which is in agreement with plausible reaction mechanisms. The highest N2O conversion of 77% after 24h was reach over TiO2 modified by 3.4wt% Ag. The Ag metal clusters could provoke a decrease in the electron–hole recombination rate. [Copyright &y& Elsevier]

Abstract: The kaolinite/TiO2 composite was prepared using thermal hydrolysis of kaolinite/titanyl sulphate suspension and characterized by XRFS, XRPD, SEM and N2 physical adsorption. Its photocatalytic properties were evaluated by photocatalytic reduction of CO2 by water and compared with commercial TiO2 photocatalyst Degussa P25. Results showed that the yields of CO2 photocatalytic reduction products methane and methanol were higher over a kaolinite/TiO2 composite than over commercial TiO2 (Degussa P25) in spite of smaller proportion of TiO2 in the composite. Introducing of TiO2 nanoparticles into the kaolinite structure caused a decrease of anatase crystallite size. Kaolinite can also change acidobasic properties of catalyst surface, inhibit the recombination of electron–hole pairs and prevent the formation of TiO2 aggregates in suspension. These facts can contribute to the observed higher photocatalytic efficiency of kaolinite/TiO2 compared to the commercial TiO2 photocatalyst. [Copyright &y& Elsevier]

Abstract: Pure TiO2 and various silver-enriched TiO2 powders were prepared by the sol–gel process controlled in the reverse micellar environment. The catalysts were tested in CO2 photocatalytic reduction and characterized by X-ray diffraction (XRD), nitrogen adsorption measurement and UV–vis. Methane and methanol were the main reduction products. The yield of methane and methanol increases when modifying the TiO2 by silver incorporation is caused by two mechanisms: up to 5% of Ag in TiO2 the Ag impurity band inside the TiO2 bandgap decreases the absorption edge and increases so the electron–hole pair generation, above 5% of Ag in TiO2 Ag metallic clusters are formed in TiO2 crystals with Shottky barrier at the metal–semiconductor interface, which spatially separates electron and holes and increases their lifetime (decreases probability of their recombination). [Copyright &y& Elsevier]

Abstract: Pure TiO2 anatase particles with a crystallite diameters ranging from 4.5 to 29nm were prepared by precipitation and sol–gel method, characterized by X-ray diffraction (XRD), BET surface area measurement, UV–vis and scanning electron microscopy (SEM) and tested in CO2 photocatalytic reduction. Methane and methanol were the main reduction products. The optimum particle size corresponding to the highest yields of both products was 14nm. The observed optimum particle size is a result of competing effects of specific surface area, charge–carrier dynamics and light absorption efficiency. [Copyright &y& Elsevier]

Abstract: ZnS nanoparticles stabilized by cetyltrimethylammonium bromide (CTAB) were deposited on montmorillonite (MMT) forming a ZnS–CTA–MMT nanocomposite. The nanocomposite was characterized by scanning electron microscopy (SEM), Fourier transformed infrared (FTIR) and UV diffuse reflectance spectra (DRS) spectrometry, X-ray powder diffraction (XRD) and specific surface area measurements. Thereafter, it was used for photocatalytic reactions under UV irradiation (Hg lamp) in three different reaction media with different pH: NaOH solution, HCl solution and water. Prior to the photocatalytic reactions the dispersions were saturated by carbon dioxide to buffer the systems. The main reaction products in gas phase determined by gas chromatography were hydrogen and methane. The reactions were monitored by measuring oxidation–reduction potentials. The highest yields of hydrogen were obtained in the dispersion acidified by HCl but the concentrations of methane were similar in all tested media. Hydrogen was supposed to be formed by the reaction of two hydrogen radicals. Methane was formed by the reduction of carbon dioxide and by the partial decomposition of CTAB. [Copyright &y& Elsevier]

Abstract: Five pure and silver-enriched TiO2 catalysts with various Ag loading (0–5.2wt.%) were prepared by the sol–gel technique from nonionic surfactant Triton X-114, cyclohexane, water (or water solution of AgNO3) and metal precursor. Calcination at 400°C for 4h was applied to convert prepared gels to pure anatase crystalline powders. Effects of silver doping on titanium photocatalyst properties were evaluated by nitrogen physical adsorption, X-ray diffraction, elemental analysis, transmission electron microscopy, Raman spectroscopy, TGA analysis and UV–vis spectroscopy. Two“green” photocatalytic reactions were chosen for photocatalytic experiments: photocatalytic reduction of CO2 and photocatalytic oxidation of 4-chlorophenol (4-CP) water solution. Both photocatalytic reactions were carried at mild conditions (room temperature and ambient pressure or pH 7). The activity of titania catalysts for photocatalytic reduction of CO2 was evaluated individually with respect to various UV lamps (254 and 365nm). The UV lamp with wavelength in the range 250–420 with highest maxima at 254 and 365nm was used for photocatalytic oxidation of 4-CP. The dependence of the photocatalytic activity on increase of Ag content was evaluated for both reactions and compared with the photocatalytic activity of Degussa catalyst P25. [Copyright &y& Elsevier]

Highlights: [•] ZnS nanoparticles deposited on montmorillonite forming ZnS-MMT nanocomposite. [•] Catalyst for photocatalytic decomposition of N2O. [•] Better catalytic performance in fluidized bed than fixed bed. [•] Presence of water vapor inhibited N2O decomposition by photocatalysis. [•] Presence of water vapor improved N2O photolysis. [ABSTRACT FROM AUTHOR]

Abstract: TiO2 and Ag-TiO2 (0.05, 0.25 and 1wt% of Ag) thin films were prepared by the sol–gel method. The prepared films were characterized using SEM-EDAX, XRD, Raman spectroscopy, atomic force microscopy and UV–Vis spectrometry. Photocatalytic decomposition of N2O was performed in an annular batch reactor illuminated with an 8W Hg lamp (254nm wavelength). The photoreactivity of Ag-TiO2 increases with the Ag amount to 0.25wt% Ag. Further increase of Ag loading to 1wt% Ag did not change N2O conversion. The Ag particles deposited on the TiO2 surface can act as electron–hole separation centers. The presence of water vapor and oxygen in the reaction mixture slightly improved N2O conversion. [Copyright &y& Elsevier]