Search

Abstract: Trifluoroacetic acid (TFA) modified TiO2 (TFA-TiO2) hollow microspheres were prepared by one-pot hydrothermal treatment of Ti(SO4)2 in the presence of TFA at 180°C for 12h. The prepared samples were characterized by X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, N2 adsorption–desorption isotherms and Fourier transform infrared. The production rates of surface of UV-illuminated TiO2 were detected by a photoluminescence (PL) method using terephthalic acid (TA) as probe molecule. The photocatalytic activity was evaluated by the photocatalytic decomposition of acetone in air under UV light illumination. The results show that TFA not only induces the formation of hollow microspheres, but also enhances their crystallization. The molar ratios of TFA to Ti(SO4)2 (R) have a great influence on photocatalytic activity. When R is in the range of 0.5–5, the photocatalytic activity of the samples is higher than that of commercial Degussa P25 TiO2 powders (P25) and pure TiO2 samples. At R =2, the photocatalytic activity of the sample reaches the highest and exceeds that of P25 by a factor of more than two times. This is ascribed to the fact that the former has hollow interior and bimodal mesoporous shells enhancing harvesting of light and the transfer and transport of reactant and product molecules, also, the surface-adsorbed TFA can reduce the recombination of photo-generated electrons and holes. [Copyright &y& Elsevier]

Abstract: Bimodal mesoporous TiO2 microspheres with high photocatalytic activity were prepared by a hydrothermal method using titanium sulfate as precursor in the presence of urea. The results indicate that all prepared samples show bimodal pore-size distributions in the mesoporous region: smaller intra-aggregated pores with peak pore diameter of ca. 2nm and larger inter-aggregated pores with peak pore diameter of ca. 12.5nm. The molar ratio of urea to Ti(SO4)2 (R u) has an obvious influence on the morphology, microstructure and photocatalytic activity of TiO2. With increasing R u, specific surface areas and porosity increase, contrarily, the crystallite size and relative anatase crystallinity decrease. The photocatalytic activity first increases with R u. At R u =2.0, the photocatalytic activity reaches the highest and is obviously higher than that of Degussa P25. With further increasing R u, the photocatalytic activity decreases. The formation rate of hydroxyl radicals during photocatalysis has a positive correlation with the photocatalytic activity. [Copyright &y& Elsevier]

Abstract: Highly photoactive nano-sized TiO2 powder photocatalyst was prepared by a hydrothermal method at 180°C for 5h using tetrabutyl titanate (TBOT) as the precursor. The pH values of the starting suspensions were adjusted from 1 to 11 using a 1.0M HCl or 1.0M NH3·H2O solution. The obtained TiO2 powders were characterized with X-ray diffraction (XRD), N2 adsorption–desorption measurement, transmission electron microscopy (TEM), X-ray photoelectron spectra, Fourier transform infrared (FTIR), Raman spectra and UV–vis spectrophotometry. The photocatalytic activity was evaluated by photocatalytic oxidation decomposition of acetone in air. The results showed that the pH values of the solutions obviously influenced the microstructures and photocatalytic activity of the as-prepared TiO2 powders. With increasing pH values, the crystallization enhanced, crystallite size increased and BET specific surface areas decreased. The photocatalytic activity of TiO2 powders prepared at a pH range of 6–9 exceeded that of Degussa P-25 by a factor of more than two times. [Copyright &y& Elsevier]

Abstract: TiO2 powder (P25) was hydrothermally treated in pure water at 150°C for different times. The P25 powders before and after hydrothermal treatment were characterized with XRD, TEM, UV–vis, XPS and nitrogen adsorption–desorption isotherms. The results showed that a small amount of anatase was transformed into rutile phase and more aggregates of the TiO2 crystallites formed after hydrothermal treatment, resulting in the decrease of specific surface area of the TiO2 powders. The photocatalytic activity of the hydrothermally treated P25 powders was obviously higher than that of the P25 powder. This can be attributed to the formation of more hydroxyl groups in the surface of TiO2. The more hydroxyl groups would generate more hydroxyl radicals, enhance the adsorption of O2 molecules and reduce recombination of the photogenerated electrons and holes. Moreover, more hydroxyl was also beneficial to the activation of the rutile phase, leading to an enhanced photocatalytic activity. [Copyright &y& Elsevier]

Abstract: Anatase TiO2 nanoparticles were uniformly coated on the surface of the titanate nanorods using TiF4 and H3BO3 as the precursors via a simple solution route. The prepared samples were characterized with SEM, XRD, TEM, HRTEM and nitrogen adsorption–desorption isotherms and their photocatalytic activities were evaluated by photocatalytic decolorization of methyl orange aqueous solution. The effects of the precursor concentration, deposition time and deposition temperature on the morphology and phase structure of the TiO2 nanoparticle-coated titanate nanorods were investigated. Compared with the titanate nanorods, the novel TiO2 nanoparticle-coated titanate nanorods showed an obvious increase in the specific surface area and pore volume due to the formation of TiO2 nanoparticles (10–50nm) on the surface of the titanate nanorods. Moreover, the TiO2 nanoparticle-coated titanate nanorods, which could be readily separated after photocatalytic reaction, exhibited highly photocatalytic activity for the degradation of methyl orange aqueous solution. [Copyright &y& Elsevier]

Abstract: Titanate nanotubes were prepared via a hydrothermal treatment of TiO2 powders (P25) in a 10M NaOH solution at 150°C for 48h and then calcined at various temperatures. The as-prepared titanate nanotubes before and after calcination were characterized with XRD, TEM, HRTEM, SEM, FESEM, and nitrogen adsorption–desorption isotherms. The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic oxidation of acetone in air. The effects of calcination temperature on the phase structure, crystallite size, morphology, specific surface area, pore structures and photocatalytic activity of the titanate nanotubes were investigated. The results indicated that at 400 to 600°C, the calcined nanotube samples showed a higher photocatalytic activity than Degussa P25. Especially, at 400 and 500°C, the photocatalytic activity of the calcined nanotubes exceeded that of P25 by a factor of about 3.0 times. This could be attributed to the fact that the former had a larger specific surface area and pore volume. With further increase in the calcination temperature from 700 to 900°C, the photocatalytic activity of the calcined nanotube samples greatly decreased due to the formation of rutile phase, the sintering and growth of TiO2 crystallites and the decrease of specific surface area and pore volume. [Copyright &y& Elsevier]

Abstract: A simple method for preparing highly photoactive nanocrystalline mesoporous N,S-codoped TiO2 powders was developed by hydrolysis of Ti(SO4)2 in a NH3·H2O solution at room temperature. The as-prepared TiO2 powders were characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermalgravimetric and differential thermal analysis (TG–DTA), UV–vis diffuse reflectance spectra, N2 adsorption–desorption measurements, scanning electron microscope (SEM) and transmission electron microscopy (TEM). The photocatalytic activity was evaluated for the photocatalytic oxidation of acetone and formaldehyde under UV light and daylight irradiation in air, respectively. The results showed that the as-prepared TiO2 powders exhibited a stronger absorption in the UV–vis light region and a red shift in the band gap transition due to N,S-codoping. The photocatalytic activity of the as-prepared N,S-codoped TiO2 powders at a temperature range of 400–700°C were obviously higher than that of commercial Degussa P25. Especially, the daylight-induced photocatalytic activities of the as-prepared N,S-codoped TiO2 powders were about ten times greater than that of Degussa P25. The high activities of the N,S-codoped TiO2 can be attributed to the results of the synergetic effects of strong absorption in the UV–vis light region, red shift in adsorption edge, good crystallization, large surface area and two phase structures of undoped TiO2 and N,S-codoped TiO2. [Copyright &y& Elsevier]

Abstract: Mesoporous titanium dioxide nanocrystalline powders were synthesized by ultrasonic-induced hydrolysis reaction of tetrabutyl titanate (Ti(OC4H9)4) in pure water without using any templates or surfactants. The as-prepared samples were characterized with X-ray diffraction (XRD) and N2 adsorption–desorption measurements. The photocatalytic activity of the samples was evaluated using the probe reaction: the photocatalytic oxidation of mixture of formaldehyde and acetone at room temperature. It was found that the as-prepared products by the ultrasonic method were composed of anatase and brooktie phases. The photocatalytic activity of the samples prepared by ultrasonic method is higher than that of commercial Degussa P25 and the samples prepared by conventional hydrolysis method. [Copyright &y& Elsevier]

Highlights: [•] Oxidative decomposition of formaldehyde on Pt/TiO2 occurs at room temperature. [•] Fluoride poisoning phenomenon of Pt/TiO2 nanosheets is explained. [•] This poisoning is due to F-blocking of Pt catalytic active sites. [•] Pt/TiO2 nanosheet-type catalysts can be easily regenerated by washing with NaOH solution. [Copyright &y& Elsevier]

Abstract: Anatase TiO2 particles were uniformly and dispersedly deposited on the surface of glass fibers by a liquid phase deposition (LPD) method from a TiF4 aqueous solution upon addition of H3BO3 at 60°C and then calcined at 60, 300 and 500°C. The photocatalytic activity of the samples was evaluated by the photocatalytic oxidation of nitrogen monoxide (NO) in the gaseous phase. It was found that calcination temperatures obviously influenced the surface morphology and photocatalytic activity of the TiO2 particles deposited on the glass fibers. At 300°C, the TiO2 samples exhibited the highest photocatalytic activity for the photocatalytic oxidation of NO and for the further conversion of NO2 (from NO2 to HNO3) due to the enhancement of crystallization of anatase TiO2 particles. At 500°C, the photocatalytic activity of the sample decreased significantly due to the dropping of many TiO2 particles from the glass fibers. Compared with the TiO2 film photocatalyst, the TiO2 particles deposited on the glass fibers exhibited a lower deactivation rate. [Copyright &y& Elsevier]

Highlights: [•] Fe(III) cocatalyst was loaded on the TiO2−x N x surface by an impregnation method. [•] Fe(III)/TiO2−x N x showed an enhanced visible-light photocatalytic activity. [•] Fe(III) cocatalyst promoted the rapid separation of photogenerated charges. [•] The advantage of Fe(III) as a new cocatalyst is its low cost and abundant resource. [Copyright &y& Elsevier]

Highlights: [•] RGO-cocatalyst modification and AgCl nanonization were simultaneously realized. [•] AgCl nanoparticles with a size of 20–200nm are tightly grafted on the rGO surface. [•] Ag/AgCl-rGO photocatalyst shows an excellent photocatalytic activity. [•] Both rGO cocatalyst and AgCl nanonization contribute to an improved performance. [ABSTRACT FROM AUTHOR]

Abstract: Usually, it is difficult to get small AgCl nanoparticles by a conventional aqueous solution route owing to their high nucleation and growth rate. In this study, AgCl nanoparticles with a diameter of less than 30nm were uniformly coated on the surface of Ag8W4O16 nanorods to form Ag8W4O16/AgCl-nanoparticle core–shell heterostructures by a simple in situ anion-exchange route. It was found that the ion exchange reaction between Cl− and WO4 2− ions was preferable to occur on the surface of Ag8W4O16 nanorods rather than in the bulk solution, resulting in the formation of core–shell nanorods. The AgCl shell layer could be easily controlled by adjusting the concentration of NaCl solution. With increasing NaCl concentration, more Ag8W4O16 phase in the core transferred into AgCl-nanoparticle shell layer while the total size of the core–shell nanorods almost remained unchanged. The photocatalytic activity experiments of methyl orange aqueous solution under fluorescence light irradiation indicated that the AgCl nanoparticles coated on the surface of Ag8W4O16 nanorods, which could be readily separated from a slurry system after photocatalytic reaction, exhibited a much higher photocatalytic activity than the bulk AgCl photocatalyst. [Copyright &y& Elsevier]