Search

Abstract: A magnetically separable photocatalyst Bi12TiO20/SiO2/NiFe2O4 (BSN) with a typical ferromagnetic hysteresis was prepared by a simple process: the magnetic 200wt% SiO2/NiFe2O4 (SN) dispersion prepared by a liquid catalytic phase transformation method and the visible-light-active photocatalyst Bi12TiO20 prepared by a simple coprecipitation processing were mixed, sonificated, dried, and calcined at 550°C. The prepared photocatalyst showed high photocatalytic activity for the degradation of methyl orange in water under UV irradiation and visible-light irradiation (λ>400nm), and it was easy to be separated from a slurry-type photoreactor under the application of an external magnetic field, being one of promising photocatalysts for wastewater treatment. Transmission electron microscope (TEM) and X-ray diffractometer (XRD) were used to characterize the structure of the photocatalyst, indicating that the magnetic SN particles adhered to the surface of the Bi12TiO20 congeries. SiO2 layer round the surface of NiFe2O4 nanoparticles prevented effectively the injection of charges from TiO2 particles to NiFe2O4, which gave rise to the increase in photocatalytic activity. [Copyright &y& Elsevier]

Abstract: Nitrogen (N)-doped TiO2 samples with high specific surface areas were directly prepared by heating the mixture of urea and TiO2, where the TiO2 was obtained with titanium tetrachloride as precursor. The absorption spectrum of the N-doped TiO2 shifted to wavelength up to 600nm with increasing urea contents. X-ray photoelectron spectroscopic measurements showed that the N presented in TiO2 was in the state of both molecularly chemisorbed N2 and substituted N. While both of them contribute to the response to visible light, the latter gave the prepared samples with hydrogen evolution under visible light. The apparent photocatalytic activity of water splitting demonstrated as high amount of H2 evolution was partly due to the phase transformation from anatase to rutile for the N-doped TiO2. [Copyright &y& Elsevier]

Abstract: M-ZSM-5 (M=Zn, Cu, Mn) catalysts were prepared by ion-exchange of M ions with H+ in H-ZSM-5. TiO2 loading on M-ZSM-5 was realized by dipping method. All the catalysts were characterized by ultraviolet and visible spectroscopy (UV–vis), X-ray diffraction (XRD) and nitrogen isothermal adsorb-desorption measurement. The catalytic activities of the samples were investigated under UV, ozone and UV–ozone for acetaldehyde degradation. The results showed that the application of photocatalytic ozonation (UV–ozone) produced the improved efficiency for acetaldehyde removal, indicating a combined effect occurred when photocatalysis and ozonation were carried out simultaneously. Transition metal ions exchanged catalyst TiO2/M-ZSM-5 increase the apparent catalysis activity by increasing acetaldehyde adsorption and ozonation at the sites of M ions. TiO2/Mn-ZSM-5 presented the highest activity with acetaldehyde conversion among the prepared samples, which was higher than that of simple additive under UV and O3. The improvement was attributed to the exchanged Mn ions and the integrated effect among adsorption, ozonation and photocatalytic reactions. [Copyright &y& Elsevier]

Abstract: TiO2 photocatalysts coated on foam nickel were prepared by sol–gel method. Al2O3–SiO2 films introducing as transition interlayer between TiO2 and nickel metal foam were used to promote the photocatalytic activity of TiO2. The results show that TiO2/Al2O3–SiO2 composite films have much higher photocatalytic activity and stability for degradation of gaseous acetaldehyde than TiO2 films. The significant enhancement effect arises from the large specific surface area of Al2O3–SiO2, which provides more active sites for subsequent TiO2 loading and photocatalytic reaction. The Al2O3–SiO2 interlayer also inhibits the transfer of photo-generated electron from TiO2 to Ni metal and improves the photocatalytic activity of photocatalysts. Furthermore, Pt loading on TiO2 by photo-deposition was carried out to improve photocatalytic efficiency. The acetaldehyde degradation rate on Pt-loaded TiO2 photocatalyst is more than three times than that of TiO2 without Pt loading. The optimum Pt concentration is 0.3wt%. XRD, UV–vis and SEM were used to characterize the structural, physical and chemical features of all the samples and to reveal the mechanism of the improvement of the photocatalytic activity. The effects of photocatalyst preparation parameters along with their photocatalytic behavior in deactivation and reactivation are also presented in the present study. [Copyright &y& Elsevier]

Anatase TiO2 films were obtained on glass substrates using a sol–gel method using titanium isopropoxide as a precursor. The thickness of the film was about 140 nm for one coating, and the thickness is controlled by the number of coating cycles. The spectra of UV-VIS absorption indicated that the absorption edge of the TiO2 films is ca. 385 nm, corresponding to the band gap energy of 3.20 eV. We obtained TiO2 films having a high activity for the hydrogen evolution from photocatalytic water cleavage. By loading with 0.3 wt% Pt rate of hydrogen production increases. No influence of film thickness and calcination temperature on the photocatalytic property is observed. [Copyright &y& Elsevier]

The gradient-doping technique has been widely applied to induce an oriented built-in electric-field. However, it is still not efficient enough for charge mobility especially for particulate semiconductors, as the field is primarily in one direction from inner to surface. Here, we propose a multilocal gradient-doping technique that a nano-capsule is designed to store dopants and then release them into semiconductors nonuniformly. As an illustration, scattered pyrochlore-type K 2 Ta 2 O 6 nanoparticles have been validated the capability of storing and releasing K+, which subsequently diffuse into the substrate PCN. Multi point-radiative gradient in K+ concentration, confined within the K 2 Ta 2 O 6 's vicinity, will construct several 3D potential wells which can not only accelerate the carrier separation but also offer more migration channels for both photo-induced electrons and holes to the surface. Consequently, the multilocal K+ gradient-doping PCN shows the longest carriers' lifetime and highest AQY (∼21.8% at 400 nm) compared with the other uniformly doping techniques. [Display omitted] • Multilocal gradient-doping technique is firstly proposed. • Nano-capsule is designed to store dopants and then release them into semiconductors. • Pyrochlore-type K 2 Ta 2 O 6 is proved to be a nano-capsule for alkali metal ion. • Multilocal K+ gradient-doping PCN has been successfully synthesized. • Multilocal gradient-doping results in the longest carriers' lifetime and highest AQY. [ABSTRACT FROM AUTHOR]

Abstract: TiO2 (P25)–graphene (P25–GR) hybrids were prepared via solvothermal reaction of graphene oxide and P25 using ethanol as solvent. The as-prepared P25–GR nanocomposites were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence emission spectroscopy and ultraviolet-visible (UV–vis) diffuse reflectance spectroscopy. The results indicated that P25–GR nanocomposites possessed enhanced light absorption ability and charge separation efficiency. As photocatalysts, P25–GR hybrids were much better than the bare P25, when they were used in the hydrogen evolution from aqueous methanol solution under Xe-lamp illumination. A significant enhancement in the rate of hydrogen production was achieved through using P25–GR as photocatalysts, comparing to bare P25. The optimum mass ratio of GR to P25 in the hybrids was 0.5wt%. The higher mass ratio of GR in P25–GR would decrease the photocatalytic activity of P25. [Copyright &y& Elsevier]

Abstract: A visible-light-active photocatalyst Bi12TiO20 with sillenite structure was prepared by a simple co-precipitation method. The spectrum of UV–vis absorption indicated that the absorption edge of the Bi12TiO20 was at 450nm, corresponding to the band gap energy of 2.75eV. The prepared Bi12TiO20 showed high photocatalytic activity for the degradation of phenol in water either under UV (300nm< λ <400nm) or visible light (λ >400nm) irradiation. The photodegradation experiments of phenol indicated that the prepared photocatalyst calcined at 550°C had the best photocatalytic activity. [Copyright &y& Elsevier]