Probing the Catalytic Activity of Reduced Graphene Oxide Decorated with Au Nanoparticles Triggered by Visible Light

Hybrid materials in which reduced graphene oxide (rGO) is decorated with Au nanoparticles (rGO–Au NPs) were obtained by the in situ reduction of GO and AuCl₄^?_(aq) by ascorbic acid. On laser excitation, rGO could be oxidized as a result of the surface plasmon resonance (SPR) excitation in the Au NPs, which generates activated O₂ through the transfer of SPR‐excited hot electrons to O₂ molecules adsorbed from air. The SPR‐mediated catalytic oxidation of p‐aminothiophenol (PATP) to p,p′‐dimercaptoazobenzene (DMAB) was then employed as a model reaction to probe the effect of rGO as a support for Au NPs on their SPR‐mediated catalytic activities. The increased conversion of PATP to DMAB relative to individual Au NPs indicated that charge‐transfer processes from rGO to Au took place and contributed to improved SPR‐mediated activity. Since the transfer of electrons from Au to adsorbed O₂ molecules is the crucial step for PATP oxidation, in addition to the SPR‐excited hot electrons of Au NPs, the transfer of electrons from rGO to Au contributed to increasing the electron density of Au above the Fermi level and thus the Au‐to‐O₂ charge‐transfer process.     

纳米累托石-TiO2光催化剂的制备及表征

以TiCl4和累托石为主要原料，制备出纳米累托石-TiO2粉末，并用X-衍射、透射电镜等对其进行表征．结果表明：纳米累托石-TiO2粉末平均直径为17．5nm当焙烧温度从500℃升至800℃时，累托石-TiO2粉末的比表面积从65．7m^2／g下降至3．3m^2／g，单位质量吸附剂的孔体积从0．1430cm。／u降到0．0213cm^3／g；当焙烧温度从300℃上升至500℃时，孔径变化不大，属中孔范围；当焙烧温度升至800℃时，一些孔道出现坍塌，不利于纳米累托石-TiO2粉末的光催化活性．     

Photocatalytic Synthesis of Oxygenates from Gaseous CO2 and CH4 over Semiconductor

Photoinduced synthesis of CO2 and CH4 was investigated using a batch reaction system on several photoactive materials supported on silicon dioxide. Single semiconductor showed higher selectivity to C1 compounds. The production of C2-C3 oxygenates took place preferentially on composite semiconductor photocatalysts. In particular, it was found that acetone was the primary product over Cu/CdS-TiO2/SiO2.     

TiO2 粉末催化剂光催化降解室内 空气中有机污染物

本文制备了一系列 TiO2粉末催化剂, 用光催化法降解室内空气中各种微量有机污染物,最终降解率 接近 100%. 考察了晶型对光催化剂性能的影响, 结果表明,锐钛矿型 TiO2 的催化性能最好. 最后,分析了 TiO2 光催化反应机理.     

Preparation of TiO2 Sol Using TiCl4 as a Precursor

A titanium dioxide sol with narrow particle size distribution was synthesized using TiCl₄ as the starting material. The sol was prepared by a process where HCl was added to a gel of hydrated titanium oxide to dissolve it. The resulting aqueous titanic acid solution was heated to form titanium dioxide sol. The effects of preparation parameters were investigated. TiCl₄ was slowly added to distilled water at 5°C. Aqueous solution of sodium hydroxide was added to adjust the pH of the system to 8–12. After aging for a period of time, the peptized sol was filtered and sufficiently washed. The filtered cake was repulped in water. Hydrochloric acid was slowly added to the solution with stirring. After condensation reaction and crystallization, a transparent sol with suspended TiO₂ was formed. XRD results show that the crystalline phase was anatase. The suspended TiO₂ particles were rhombus primary particles with the major axis ca. 20 nm and the minor axis ca. 5 nm. The TiO₂ particles prepared at pH 8 had the largest surface area of 141 cm³/g and it was microporous. The compositions of the solution which yielded the smallest suspended TiO₂ particles were TiO₂:HCl (35% HCl) = 1:1 (molar ratio), concentration of TiO₂ = 10%. Hydroxypropyl cellulose with viscosity of 150–400 cps was added as a dispersant. The sol was excellent in dispersibility and long-term stability. Transparent thin films could be obtained through dip-coating glass substrate in the sol. The dip-coating on glass can be less than three times to have one monolayer TiO₂. The transparent TiO₂ thin film had strong hydrophilicity after being illuminated by UV light.     

The Incorporation of Titania into Modified Silicates for Solar Photodegradation of Aqueous Species

A new class of sol-gel-derived photocatalytic materials has been synthesized and used in solar-assisted photodegradation studies. The materials are comprised of a homogeneous dispersion of commercial TiO₂ powder into silica and organically modified silicate (Ormosil) hosts. The efficiency of the photocatalytic properties of these TiO₂-containing materials was determined by their relative performance in the solar photodecomposition of aqueous rhodamine B. The improved adsorption properties of the modified materials compared to commercial TiO₂ increase the photodecomposition rate and the buoyancy properties, although excess hydrophobicity decreases the wetted section of the catalyst and its photocatalytic performance. These materials can be used as floatable catalysts for solar-assisted water purification.     

A mesoporous Pt/TiO2 nanoarchitecture with catalytic and photocatalytic functions

A novel metal/semiconductor nanocomposite with catalytic and photocatalytic functions has been prepared. The new material consists of highly dispersed platinum (Pt) nanoparticles embedded in a cubic mesoporous nanocrystalline anatase (meso-nc-TiO2) thin film. The porous thin film possesses a narrow pore-size distribution and a large surface area. The diameter of the Pt cluster can be controlled to below 5 nm, and the high dispersion of these clusters gives rise to catalytic activity for the oxidation of carbon monoxide, an important reaction for automobile exhaust treatment. This novel ordered mesoporous Pt/TiO2 nanoarchitecture is also a promising photochemical material, as demonstrated by the photo-driven killing of Micrococcus lylae cells on the film.     

Products of Ag+, Cu+ and Cu2+ Ion Implantation in the Surface of Polycrystalline Cadmium Sulfide as Photocatalysts for the Oxidation–Reduction Reaction of Methylene Blue with Formaldehyde

Semiconductor–semiconductor and molecule (molecular ion)–semiconductor products are formed upon the implantation of Ag⁺, Cu⁺, and Cu²⁺ ions in the CdS surface. Possible mechanisms were examined for their photocatalytic action in the reduction of methylene blue.     

Effect of carbon content on photocatalytic activity of C/TiO2 composite

A series of carbon-covered titania (CCT) were prepared via pyrolysis of sucrose highly dispersed on titania surface in flowing N₂. The samples were characterized by XRD, BET, DTA-TG, UV—Vis, and their photocatalytic properties were evaluated with two model pollutants, methylene blue (MB) and rhodamine B (RB), at room temperature. The effect of carbon content on photocatalytic activity of the C/TiO₂ composite was investigated. It was found that the effect of carbon content is different for different pollutants or different light sources. For three tested samples, under UV illumination CCT01 has the highest activity for MB photocatalytic degradation, while in the case of RB, CCT02 is the most active photocatalyst. Under visible light illumination, CCT005 has the highest activity for both MB and RB photocatalytic degradation. Translated from Chinese Journal of Catalysis, 2006, 27(1): (in Chinese)     

Preparation and Characterization of Nanotitanium Dioxide Coating Film Doped with Fe^3＋ Ions on Porous Ceramic

The nanotitanium dioxide （TiO2） photocatalytic and porous ceramic filtering technique is one of the advanced methods to effectively treat organic wastewater. The TiO2 sol doped with Fe^3＋ ions was prepared by sol-gel processing. The influences of the process conditions of coating nanophotocatalytic material- Fe^3＋-TiO2 film on the surface of porous ceramic filter by dipping-lift method on the performance of porous ceramic filter were studied. The porous ceramic filters have two functions at the same time, filtration and photocatalytic degradation. The results of this study showed that the pH and viscosity of the sol, amount of Fe^3＋ ions doped as well as the coating times greatly affect the quality of coating film, the performance parameters and the photocatalytic activity of the porous ceramic filter. When the pH of the sol is 3-4, the viscosity is about 6 mPa.S, the amount of doped Fe^3＋ ions is about 2.0 g/L, the porous ceramic filter has been shown to have the best filtering performance and photocatalytic activity. In this condition, the porosity of porous ceramic is about 42.5%, the pore diameter is 8-10μm. The degradation of methyl-orange is 74.76% under lighting for 120 rain.