Shoumin Zhang

Synthesis and gas sensing properties of α-Fe2O3@ZnO core–shell nanospindles

α-Fe(2)O(3)@ZnO core-shell nanospindles were synthesized via a two-step hydrothermal approach, and characterized by means of SEM/TEM/XRD/XPS. The ZnO shell coated on the nanospindles has a thickness of 10-15 nm. Considering that both α-Fe(2)O(3) and ZnO are good sensing materials, we have investigated the gas sensing performances of the core-shell nanocomposite using ethanol as the main probe gas. It is interesting to find that the gas sensor properties of the core-shell nanospindles are significantly enhanced compared with pristine α-Fe(2)O(3). The enhanced sensor properties are attributed to the unique core-shell nanostructure. The detailed sensing mechanism is discussed with respect to the energy band structure and the electron depletion theory. The core-shell nanostructure reported in this work provides a new path to fabricate highly sensitive materials for gas sensing applications.

Synthesis, Characterization, and Photocatalytic Activity of N‐Doped TiO2 Nanotubes

N‐doped TiO2 nanotubes with high photocatalytic activity were prepared by the combination of sol‐gel process with hydrothermal treatment. The prepared materials are characterized with transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM), x‐ray diffraction (XRD), x‐ray photoelectron spectra (XPS), and UV‐vis spectra. Photocatalytic performance of the N‐doped TiO2 nanotubes is studied by testing the degradation rate of methyl orange under UV irradiation. Obtained results indicate that N‐doped TiO2 nanotubes have high catalytic activity for photocatalytic oxidation.

A comparative study of CuO/TiO2-SnO2, CuO/TiO2 and CuO/SnO2 catalysts for low-temperature CO oxidation

Abstract Nanometer SnO 2 particles were synthesized by sol-gel dialytic processes and used as a support to prepare CuO supported catalysts via a deposition-precipitation method. The samples were characterized by means of TG-DTA, XRD, H 2 -TPR and XPS. The catalytic activity of the CuO/TiO 2 -SnO 2 catalysts was markedly depended on the loading of CuO, and the optimum CuO loading was 8 wt.% ( T 100 = 80 °C). The CuO/TiO 2 -SnO 2 catalysts exhibited much higher catalytic activity than the CuO/TiO 2 and CuO/SnO 2 catalysts. H 2 -TPR result indicated that a large amount of CuO formed the active site for CO oxidation in 8 wt.% CuO/TiO 2 -SnO 2 catalyst.

The Preparation and Characterization of La Doped TiO2 Nanotubes and Their Photocatalytic Activity

La-doped TiO2 nanotubes (La/TiO2 NTs) were prepared by the combination of sol-gel process with hydrothermal treatment. The prepared samples were characterized by using transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectra, and ultraviolet-visible spectra. The photocatalytic performance of La/TiO2 NTs was studied by testing the degradation rate of methyl orange under ultraviolet (UV) irradiation. The results indicated La/TiO2 NTs calcined at 300°C consisted of anatase as the unique phase. The absorption spectra of the La/TiO2 NTs showed a stronger absorption in the UV range and a slight red shift in the band gap transition than that of pure TiO2 nanotubes. The photocatalytic performance of TiO2 NTs could be improved by the doping of lanthanum ions, which is ascribed to several beneficial effects the formation of Ti-O-La bond and charge imbalance, existing of oxygen defects and Ti3+ species, stronger absorption in the UV range and a slight red shift in the band gap transition, as well as higher equilibrium dark adsorption of methyl orange. 0.75 wt% La/TiO2 NTs had the best catalytic activity.

Promoting effects of lanthanum on the catalytic activity of Au/TiO2 nanotubes for CO oxidation

Lanthanum-modified TiO2 nanotube (NT) supported gold catalysts were prepared. The linear relationship between actual and nominal lanthanum concentrations was found. The possible formation mechanism of La-modified TiO2 NTs was suggested. The effects of calcination temperature, La concentration and gold loading on the catalytic activity for CO oxidation were investigated. Au/La2O3–TiO2-NTs (Au: 4.18%, La: 1.62%) calcined at 300 °C could completely convert CO at 30 °C. T100% of La-free catalyst was 60 °C. The catalytic activity of Au/TiO2-NTs could be improved by modification with lanthanum.

Au/BiPO4 nanorod catalysts: synthesis, characterization and their catalytic performance for CO oxidation

In this paper, monoclinic phase BiPO4 nanorods were successfully prepared by a one-pot solvothermal route. Au/BiPO4 catalysts were obtained by a deposition–precipitation method. The samples were characterized by X-ray diffraction, transmission electron microscopy techniques, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and UV-vis diffuse reflectance spectroscopy. The TEM results exhibited a good dispersion of gold nanoparticles over the support. The XPS spectra revealed that gold was in the metallic state and bismuth was in the +3 oxidation state. The catalysis results demonstrated that BiPO4 nanorods could be a good support for gold catalysts. Among the prepared catalysts, the 1.5% Au/BiPO4 pretreated at 300 °C showed the best performance in CO oxidation and could achieve 100% CO oxidation at 40 °C. It retained 100% conversion after continuous operation for 10 h at 40 °C, and showed no deactivation after 50 h at a selected high reaction temperature of 180 °C. The possible mechanism of Au/BiPO4 catalysts in the CO oxidation was also proposed.

CO oxidation over Cu2O deposited on 2D continuous lamellar g-C3N4

Cu2O deposited on 2D continuous lamellar g-C3N4 (Cu2O/g-C3N4) was prepared via a facile impregnation–chemical reduction procedure. The composition, structure and morphology of as-prepared Cu2O/g-C3N4 were characterized by XRD, SEM, TEM, CO-TPR, FT-IR and nitrogen adsorption, respectively. The influence of Cu2O loading on the performances of Cu2O/g-C3N4, e.g. adsorption ability for methyl orange (MO) and the stability as well as catalytic activity for CO oxidation, was investigated. The changing trend of adsorption ability and the catalytic activity of Cu2O/g-C3N4 moved in the same direction. When the mass ratio of Cu2O to g-C3N4 was 4 : 10, the as-prepared composite exhibited the strongest adsorption ability and the highest catalytic activity; it also showed excellent stability in CO oxidation and over it the 100% conversion of CO was kept for more than 12 h under reaction conditions. The strong adsorption ability and good catalytic performance of Cu2O/g-C3N4 were ascribed to the synergetic effects between g-C3N4 and Cu2O as well as the improved dispersibility and the decreased particle size of Cu2O.

Preparation and Characterization of Bismuth Doped TiO2 Thin Films

A series of Bismuth-doped titanium oxide (Bi-doped TiO2) thin films on glass substrates have been prepared by sol-gel dip coating process. The prepared catalysts were characterized by XRD and XPS. The photocatlytic activity of the thin film catalysts was evaluated through the photodegradation of aqueous methyl orange under UV illumination. The experiments demonstrated that the Bi-doped TiO2 prepared was anatase phase. The doped bismuth was in the 3+ oxidation state. The presence of Bi significantly enhanced the photocatalytic activity of TiO2 films. At calcination temperature of 500°C, with doping concentration of 2 wt %, Bi-doped TiO2 thin film showed the highest photocatalyic activity.

Synthesis and characterization of TiO2 nanotube supported Rh-nanoparticle catalysts for regioselective hydroformylation of vinyl acetate

Three procedures: the impregnation-borohydride reduction procedure, the impregnation-alcohol reduction procedure and the impregnation-photoreducing procedure, were utilized for preparing TiO2 nanotube supported rhodium nanoparticle catalysts, in which rhodium acetate was used as a rhodium source. Catalysts were characterized with TEM, ICP, XPS and XRD; their catalytic performances for hydroformylation of vinyl acetate were evaluated. Of these catalysts prepared by three different methods, the catalyst prepared by the impregnation-photoreducing procedure showed the highest catalytic activity under the same reaction conditions. The effects of pressure of syngas, solvents, temperature, Rh content and reaction time on the hydroformylation were examined in detail. Under the optimized reaction conditions, the conversion of vinyl acetate can reach at 100%; the chemoselectivity for aldehydes was 74.70% and the regioselectivity for the branched aldehyde was 95%.

Characterization of Pt catalysts supported by three forms of TiO2 and their catalytic activities for hydrogenation

Three forms of TiO2, commercial TiO2 powder, hydrogen titanate nanotubes obtained by hydrothermal treatment, and the thermally stable TiO2 nanotubes prepared by treating hydrogen titanate nanotubes with a sol containing titanium, were used as supports, and Pt nanoparticles were deposited on the supports via the photodeposition method. The catalytic performances of as-prepared and calcined Pt/TiO2 catalysts for the hydrogenation reaction of cyclohexene were evaluated. The results showed that the effects of the support and calcination temperature on the catalytic performances of Pt/TiO2 catalysts were obvious and significant. The thermally stable nanotubular TiO2-supported Pt catalyst exhibited better catalytic performance than the other TiO2-supported Pt catalysts. In addition, it was discovered that the calcination can enhance the catalytic activity of Pt/TiO2 for hydrogenation greatly.