Synthesis and electrocatalytic oxygen reduction properties of truncated octahedral Pt3Ni nanoparticles

Pt₃Ni nanoparticles have been obtained by shape-controlled synthesis and employed as oxygen reduction electrocatalysts for proton exchange membrane fuel cells (PEMFC). The effects of varying the synthesis parameters such as the types of the capping agent and the reducing agent, and the reaction time have been systematically studied. The as-prepared Pt₃Ni nanoparticles were subjected to a butylamine-based surface treatment in order to prepare carbon-supported electrocatalysts. The Pt₃Ni electrocatalysts show an areaspecific activity of 0.76 mA/cm²(Pt) at 0.9 V in an alkaline electrolyte, which is 4.5 times that of a commercial Pt/C catalyst (0.17 mA/cm² (Pt)). The mass activity reached 0.30 A/mg(Pt) at 0.9 V, which is about twice that of the commercial Pt/C catalyst. Our results also show that the area-specific activities of these carbon-supported Pt₃Ni electrocatalysts depend strongly on the (111) surface fraction, which is consistent with the results of a study based on Pt₃Ni extended single-crystal surfaces.     

纳米二氧化钛的晶型转变及光催化性能研究

采用溶胶-凝胶法制得稳定的TiO2透明溶胶．凝胶经焙烧制备了纳米TiO2粉体,利用FT-IR、XRD和原子力显微镜(AFM)技术对其进行了结构和形貌表征,考察了其对水杨酸的光催化活性。研究结果表明,醇胺不同的加入量,对TiO2从锐钛矿转变为金红石型的晶相转变温度(600～800℃)有很大影响．FT-IR谱的423cm^-1处吸收峰为金红石型TiO2的特征Ti-O键振动峰,采用310nm的紫外光波长照射时锐钛矿型TiO2粉体具有较高的光催化活性。     

A facile method for fabrication of highly ordered hollow Ag/TiO2 nanostructure and its photocatalytic activity

This letter reports a facile and efficient strategy for the designed preparation of highly ordered hollow Ag/TiO₂ nanostructure. Different from previous reports, the presently proposed method conveniently combines the long-range ordering porosity and the property of Ag nanoparticles by a general colloidal crystal-templating technique. The sample was characterized by SEM and XRD. The results show that such hollow nanostructured material is composed of anatase TiO₂ and metal Ag. The as-prepared sample shows a good photocatalytic activity for photodegradation of methyl orange compared with the reference samples, which was attributed to its long-range ordering porosity and the addition of Ag nanoparticles.     

Anatase-TiO2 nano-particle preparation with a micro-mixing technique and its photocatalytic performance

A micro-mixing method named membrane dispersion precipitation technology has been developed, and used to prepare titanium oxide nano-particles in this work. Titanium sulfate and ammonia bicarbonate were selected as reactants. The microcrystal structure of the TiO₂ was characterized by an X-ray diffractometer, and morphology by a transmission electron microscopy (TEM). In addition, the photocatalytic performance of these TiO₂ ultra-fine particles were evaluated by the methylic orange photocatalytic degradation. The experimental results showed that the particles were anatase and amorphous phase, the average diameters were in range of 10–20 nm. The particles have excellent photocatalytic efficiencies, and more than 90% methylic orange was degraded in an hour. The kinetic behavior of photocatalysis belongs to zero order. It is found that the reaction constant is directly proportional to the diameter of particles, by investigating the influence of the particle size on the photocatalysis.     

Synthesis and photocatalytic properties of BiOCl nanowire arrays

Bismuth oxychloride (BiOCl) nanowire arrays have been successfully prepared employing the Anodic Aluminum Oxide (AAO) template assisted sol-gel method. Nanowires of 100 nm diameter and length 2-6 μm, assembled in the porous of AAO templates, were formed. XRD and HRTEM results show that the nanowires are pure BiOCl polycrystal phase without Bi₂O₃ or BiCl₃. The photocatalytic activity of BiOCl nanowire arrays was investigated by the degradation of Rhodamine B dye solution under UV irradiation.     

Bi4Ti3O12光催化粉体的制备及性能研究

采用溶胶-凝胶法制备Bi4Ti3O12粉体,通过DSC-TGA、XRD以及光催化降解甲基橙的分析,研究了热处理温度、蒸馏水加入量及溶胶陈化时间等制备条件对光催化活性的影响.结果表明,通过优化制备条件后,所制备样品的带隙能约为2.89eV,在普通日光灯下对甲基橙的降解率普遍大于相同条件下P25的降解率.     

TiO2薄膜的制备及光催化性能研究

采用溶胶－凝胶法在玻璃衬底上制备了均匀透明牢固的TiO2光催化薄膜,利用XRD、SEM分光光度计及椭圆偏光测厚仪对薄膜进行了分析。利用光催化降解乙醛气体实验研究了TiO2薄膜的光催化活性。结果表明膜的特性及孔隙度同水解条件密切相关。孔隙度及薄膜厚度对催化活性有大的影响。     

Optical and photocatalytic properties of arginine-stabilized cadmium sulfide quantum dots

Currently, environmental pollution caused by organic compounds leads to severe negative consequences in the human society. Therefore, the removal of these pollutants from aqueous media has become one of the most important issues in environmental science. In the present study, CdS QDs were successfully prepared under aqueous conditions using l-arginine as the stabilizing agent. Optical property determination results reveal that the CdS QDs exhibited strong absorption and photoluminescence in a visible wavelength region. Moreover, the CdS QDs could effectively degrade two organic dyes under visible light irradiation. This suggested that the CdS QDs prepared in this work might be used as the potential photocatalyst to effectively treat the organic pollutants under visible light irradiation.     

碳化硅微粉的低温合成与制备

以硅溶胶为硅源,淀粉为碳源,采用低温碳热还原法合成了SiC微粉.实验结果表明:淀粉热解得到的碳颗粒和硅溶胶中的SiO2能形成较好的包覆,增大了接触面积,促进了反应的进行.在1700℃下反应1h,反应前驱体全部转化为β-SiC,产物为SiC颗粒和纳米棒的混合物.升高反应温度和延长反应时间都能显著增加转化率.但温度过高会导致晶粒长大.     

Study of photocatalytic properties of pure and doped ZnO powders

In this paper pure ZnO and doped Bi–ZnO powders annealed at 200 °C were prepared using conventional solid state reaction and were applied as photocatalysts for Cr(VI) reduction. Structural properties were studied using X‐ray diffraction (XRD) and optical properties were investigated using photoluminescence (PL) spectrophotometry and ultraviolet‐visible (UV‐vis) absorbance spectroscopy. Based on the obtained results, it was found that bismuth (Bi) had a strong impact in varying the electronic structure of ZnO. This was mainly referred to Bi that existed in different states as an acceptor, donor and plasmonic nanostructure metal. According to the literature Bi was known to be acted as an acceptor and donor without knowing how it acted in this manner. A new mechanism was proposed describing the different states of Bi as waves having different orientations when interacting within ZnO. The time at which an interaction of incident UV light with the oriented Bi wave within ZnO occurred must be less than the duration of existence of such wave at this orientation.     

Synthesis and photocatalytic oxidation properties of titania hollow spheres

The hollow spheres of anatase TiO₂ with higher photocatalytic activity have been fabricated by spherical CaCO₃ nanoparticles as a template, and titanium sulfate (Ti(SO₄)₂) as a precursor, and the CaCO₃ templates were dissolved subsequently in dilute HNO₃ solution. The TiO₂ hollow spheres samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and N₂ adsorption-desorption isotherms. The characterization results indicate that as prepared TiO₂ hollow spheres sample was transformed to anatase phase in calcined at 400 °C, and the anatase TiO₂ hollow spheres have a higher specific surface area and show much better photocatalytic activity than commercial P25 in the photodegradation of Rhodamine B under the UV irradiation.     

Controllable synthesis and enhanced photocatalytic properties of Cu2O/Cu31S16 composites

The controlled synthesis of Cu₂O/Cu₃₁S₁₆ microcomposites with hierarchical structures had been prepared via a convenient sonochemical route. Ultrasonic irradiation of a mixture of Cu₂O and (NH₂)₂CS in an aqueous medium yielded Cu₂O/Cu₃₁S₁₆ composites. The content of Cu₃₁S₁₆ in the Cu₂O/Cu₃₁S₁₆ can be easily controlled by adjusting the synthesis time. The Cu₃₁S₁₆ layer not only protected and stabilized Cu₂O particles, but also prohibited the recombination of photogenerated electrons–holes pair between Cu₃₁S₁₆ and Cu₂O. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) spectra, ultraviolet–visible (UV–Vis) spectroscopy and photoluminescence (PL) spectroscopy were used to characterize the products. Photocatalytic performance of the Cu₂O/Cu₃₁S₁₆ hierarchical structures was evaluated by measuring the decomposition rate of methyl orange solution under natural light. To the best of our knowledge, this is the first report on the preparation and photocatalytic activity of Cu₂O/Cu₃₁S₁₆ microcomposite. Additionally, the Cu₂O/Cu₃₁S₁₆ core/shell structures were more stable than single Cu₂O particles during photocatalytic process since the photocatalytic activity of the second reused architecture sample was much higher than that of pure Cu₂O. The Cu₂O/Cu₃₁S₁₆ microcomposites may be a good promising candidate for wastewater treatment.     

Cu2ZnGeS4 nanorods by solvothermal method: physical and photocatalytic properties

In the present study, we synthesized Cu₂ZnGeS₄ (CZGS) nanorods by simple solvothermal method. The physical properties, such as crystalline structure, band gap, morphology, and chemical composition, were studied using different characterization techniques. The structural characterization by X-ray diffraction showed predominantly orthorhombic phase which was additionally verified by Raman analysis. The estimated crystalline size of the nanorods was approximately 14–17 nm. Scanning electron microscopy images revealed typically nanorod-like structures. The orthorhombic symmetry of CZGS has been further confirmed from high-resolution TEM results. The nanorods demonstrated good UV–Vis light absorption with optical band gap 2.01 eV. The photocatalytic efficiency of CZGS nanoparticles was evaluated from the photodegradation of methylene blue (MB) using H₂O₂ in the solution; almost 90% of the MB was degraded in 180 min.

     

Applications of Cu2O octahedral particles on ITO glass in photocatalytic degradation of dye pollutants under a halogen tungsten lamp

Cu₂O octahedral microcrystals were prepared on the ITO glass by galvanostatic electrodeposition in CuSO₄ solution with poly(vinylpryrrolidone) as the surfactant. By controlling the electrodeposition time, the microcrystals could be randomly distributed on the ITO glass and separated from each other, resulting in as many as possible {1 1 1} crystalline planes were exposed. Such microcrystals immobilized on ITO glass were employed in photodegradation of dye pollutants in the presence of H₂O₂ under a 150 W halogen tungsten lamp. The photodegradation of methylene blue was taken as an example to evaluate the photocatalytic activities of the octahedral Cu₂O microcrystals. Effects of electrodeposition time and H₂O₂ amount on the degradation efficiency was discussed, giving the optimum conditions and the corresponding degradation mechanism. The catalyst showed high ability in degradation of methylene blue, methyl orange, rhodamine B, eosin B and their mixtures under identical conditions.     

1D sub 10 nm nanofabrication of ultrahydrophobic Ag@TiO2 nanowires and their photocatalytic,UV shielding and antibacterial properties

Here we report the synthesis of 1D TiO₂ sub 10 nm nanowires through one pot hydrothermal method in an alkaline NaOH medium at 95 °C for 36 h. Further, these TiO₂ nanowires were embellished with silver (Ag) using polyvinylpyrrolidone (PVP) and ethylene glycol (EG) based solvothermal route at 160 °C for 4 h. With Ag decoration the photocatalytic activity was enhanced and the complete photooxidation of Methylene Blue (MB) was achieved in 35 min under optimized conditions. Super- and ultra-hydrophobic coating on cotton fabric exhibited a consistent antibacterial activity with enhanced UV-blocking property. Enhanced multifunctional properties observed were primarily attributed to the formation of Ag decorated 1D sub 10 nm TiO₂ nanowires heterojunctions achieved using facile chemical route. Hence, such multiple functionalities make the 1D sub 10 nm TiO₂ nanowires good candidate for industrial and domestic wastewater treatment.     

Physico-chemical, photoelectrochemical and photocatalytic properties of electrodeposited nanocrystalline titanium dioxide thin films

Crystal structure and microstructural properties of titanium dioxide (TiO₂) thin films prepared by cathodic electrodeposition on indium-tin-oxide coated glass substrates from aqueous peroxo-titanium complex solutions have been investigated. The electrodeposited TiO₂ thin film electrode exhibited anodic photocurrent upon visible light irradiation, indicating the typical behavior of n-type semiconductor. The photodecomposition of CH₃CHO by such thin films on exposure to ultraviolet light illumination was also observed.     

Au/TiO2复合纤维的制备及其光催化性能研究

采用溶胶-凝胶法制备了TiO2纤维和Au/TiO2复合纤维,利用XRD、SEM、TEM等手段对纤维样品的结晶性能及其表面形貌进行了表征,并以光催化降解甲基橙为模型反应考察了样品的光催化活性。结果表明,热处理后的TiO2呈锐钛矿结构,Au的颗粒尺寸范围为7～15nm,纤维直径范围为5～20μm,长度为5～50cm。Au的掺入可以显著地提高TiO2的光催化活性,且其光催化活性随着Au掺入量的增加而变大。