Juntao Yan

MoS 2 修饰ZnIn 2 S 4 微米球复合光催化剂的制备及光催化制氢活性增强研究

Abstract MoS2/ZnIn2S4 composites with MoS2 anchored on the surface of ZnIn2S4 microspheres were synthesized by a two-step hydrothermal process. The obtained samples were characterized by X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, ultraviolet–visible diffuse reflectance absorption spectroscopy, nitrogen adsorption–desorption measurements, photoluminescence spectroscopy, and photoelectrochemical tests. The influence of the loading of MoS2 on the photocatalytic H2 evolution activity was investigated using lactic acid as a sacrificial reagent. A H2 evolution rate of 343 μmol/h was achieved under visible light irradiation over the 1 wt% MoS2/ZnIn2S4 composite, corresponding to an apparent quantum efficiency of about 3.85% at 420 nm monochromatic light. The marked improvement of the photocatalytic H2 evolution activity compared with ZnIn2S4 can be ascribed to efficient transfer and separation of photogenerated charge carriers and facilitation of the photocatalytic H2 evolution reaction at the MoS2 active sites.

Solid phase extraction with titanium dioxide nanofibers combined with dispersive liquid-liquid microextraction for speciation of thallium prior to electrothermal vaporization ICP-MS

AbstractThe authors describe a method for speciation of thallium that is based on solid phase extraction (SPE) combined with dispersive liquid-liquid microextraction (DLLME) prior to electrothermal vaporization ICP-MS determination. The method is shown to be applicable to the determination of total, suspended, soluble, organic and inorganic Tl, and of Tl(I) and Tl(III) in tea leaves and tea infusion. The SPE step involves the use of titanium dioxide nanofibers for preconcentration of the Tl analytes and simultaneous removal of the matrix components such as polyphenols, soluble sugars, catechin, caffeine and tea pigments. Following elution of Tl with dilute HNO3, the eluate was further preconcentrated and separation by DLLME. After optimization of the method, it has a detection limits of 0.015xa0pg mL−1 for Tl(I) and of 0.020xa0pg mL−1 for Tl(III), with relative standard deviations of 6.5% and 7.3% (at 0.10xa0ng mL−1; for nxa0=xa09), respectively. The technique has an enrichment factor of 450 and is highly selective. It was successfully applied to the speciation and distribution of thallium in tea leaves and tea infusions. A certified reference material of tea leaves was analyzed by this method, and the obtained values were in good agreement with the certified values.n Graphical abstractSchematic of a new method for solid phase extraction (SPE)xa0of thallium. Titanium dioxide nanofiber-based extraction was combined with dispersive liquid-liquid microextraction (DLLME) for speciation of thallium and its distribution in tea leaves and tea infusion, including total, suspended, soluble, organic and inorganic Tl, and of Tl(I) and Tl(III).

Investigation on the morphology of hierarchical mesoporous ZSM-5 zeolite prepared by the CO2-in-water microemulsion method

A series of hierarchical mesoporous ZSM-5 zeolites with different morphology were successfully synthesized by the CO2-in-water microemulsion method, and mesoporosity was formed without organotemplate. The different synthesis conditions, including silica alumina molar ratio, stirring time and compressed CO2 pressure, were systematically investigated to discuss the influence of these conditions on the morphology of ZSM-5 zeolite. The resulting samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), inductively coupled plasma (ICP) and nitrogen adsorption-desorption measurement. XRD results indicated that compressed CO2 route for the synthesis of MFI zeolites had a fast crystallization rate and good crystallinity. SEM images showed that the ZSM-5 hierarchical mesoporous ZSM-5 zeolite had a uniform chain-like crystal morphology, whereas silicalite-1 displayed a monodisperse crystal morphology. In addition, the nitrogen adsorption-desorption measurement provided sufficient evidence for the presence of hierarchical mesopores in ZSM-5 zeolite.

Synthesis of 5-hydroxymethyl furfural from cellulose via a two-step process in polar aprotic solvent

The synthesis of 5-hydroxymethyl furfural (HMF) from cellulose via a two-step process was investigated. To optimize reaction conditions, the separate conversion of cellulose and glucose was first performed in tetrahydrofuran (THF) and N, N-dimethylformamide (DMF) via a one-step process using hosphotungstic acid (PHA) as catalyst. The direct conversion of cellulose to HMF was then performed via the two-step process. The first step and the second step were carried out in THF and the mixture solvent composed of THF/DMF, respectively. Cellulose was converted to HMF and glucose in the first step in THF. Both of cellulose and the as-formed glucose were then converted to HMF in the second step. The conversion of cellulose to HMF and glucose were significantly improved by the two-step process, and the total yield of HMF and glucose was elevated from 52.1 to 97.0%. A possible mechanism for the formation of HMF from cellulose via the two-step process was also proposed.

Synthesis and Characterization of Magnetic TiO2 Hollow Nanofibers via Electrospinning Assisted Sol-Gel Process

The PVP/Fe3O4/TBT composite nanofibers have been successfully fabricated via a facile electrospinning assisted sol-gel process, and magnetic TiO2 hollow nanofibers are obtained by the calcination process. The effects of TBT and Fe3O4 dosage on the morphologies and hollow structure of nanofibers are systematically investigated. Scanning electron microscopy (SEM) demonstrated that the magnetic TiO2 nanofibers had a hollow structure with the average diameter of 200 nm. XRD results exhibited that magnetic TiO2 hollow nanofibers with well crystallized anatase phase were obtained. Both the hollow structure and well crystallized anatase phase of TiO2 nanofibers play very important role in photocatalytic activity. Moreover, the magnetic test demonstrated TiO2 hollow nanofibers possessed an excellent magnetic responsiveness, which facilitated the separation of TiO2 hollow nanofibers.

Facile Synthesis of Fluorine Doped Graphitic Carbon Nitride with Enhanced Visible Light Photocatalytic Activity

Fluorine doped graphitic carbon nitride (g-C3N4) was successfully synthesized by a convenient co-polycondensation of urea and ammonium fluoride (NH4F) mixtures, and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FTIR), UV-Vis diffuse reflectance absorption spectra (UV-DRS), nitrogen adsorption–desorption, photoelectrochemical measurement and photoluminescence (PL) spectra. The photocatalytic activities of fluorine doped g-C3N4 samples were evaluated by the degradation of Rhodamine B (RhB) solution under visible light irradiation. The results showed that the fluorine doped g-C3N4 had a better photocatalytic activity than that of undoped g-C3N4, which was attributed to the favorable textural, optical and electronic properties derived from the fluorine atoms substituting nitrogen atoms of g-C3N4 frameworks. The photoelectrochemical measurements confirmed that the charges separation efficiency was improved by fluorine doping g-C3N4. Moreover, the tests of radical scavengers demonstrated that the holes (h+) and superoxide radicals (⋅O2−) were the main active species for the degradation of RhB.