碳化钨和天然沸石复合材料在水溶液中的电催化活性(英文)

Tungsten carbide and zeolite nanocomposite was prepared by combining a mechanochemical approach with a reduction and carbonization approach,using natural zeolite and ammonia metatungstate as precursors.The sample was characterized by X-ray diffraction and scanning electron microscope.The results showed that the crystal phase of the sample is composed of zeolite,monotungsten carbide and bitungsten carbide.The mass percentage and the crystallite diameter of tungsten carbide change along with the reacted time.Its electrocatalytic activity was measured with a microelectrode system with three electrodes.The results show that its electrocatalytic property is related to its crystal phase and the mass percentage of tungsten carbide,and its electrocatalytic activity is connected with the property of electrolyte,in which it is measured.Synergistic effect between tungsten carbide and zeolite is found during electrocatalysis.     

Pt、Rh及Pt-Rh合金电极上氢的吸附

The hydrogen adsorption on Pt-Rh alloys in sulfuric acid aqueous solutions was studied by the method of cathode pulses. Hydrogen adsorption on the electrode with all ratio of alloy components (ωRh = 0-100%) is well described by the Temkin logarithmic isotherm. The surface coverage by adsorbed hydrogen at the same potential is decreased with increasing content of rhodium in the system. A linear dependence of adsorption peak potential on the alloy compositions in the case of weakly bonded adsorbed hydrogen is established. Hydrogen adsorption heat as a function of surface coverage for Pt-Rh-electrodes was obtained. The shape of the current-potential curve and position of the weakly bonded hydrogen adsorption on the potential scale are all related to alloy compositions, thus can serve as the basis for the determination surface composition of allovs.     

Cathodic Hydrogen as Electron Donor in Enhanced Reductive Dechlorination

In situ capping is an attractive and cost-effective method for remediation of contaminated sediments, but few studies on enhancing contaminant degradation in sediment caps have been reported, especially for chlorinated benzenes. Electrically enhanced bioactive barrier is a new process for in situ remediation for reducible compounds in soil or sediments. The primary objective of this study is to determine if electrodes in sediment could create a redox gradient and provide electron acceptor/donor to stimulate degradation of chlorinated contaminant. The results demonstrate that graphite electrodes lead to sustainable evolution of hydrogen, displaying zero-order kinetics in the initial stages with different voltages. The constant rates of hydrogen evolution at 3, 4, and 5 V are 1.05, 2.54, and 4.3 nmol·L 1·d 1, respectively. Even higher voltage can produce more hydrogen, but it could not keep long time because the over potentials on electrode surfaces prevent its function. The study shows that 4 V is more appropriate for hydrogen evolution. The measured and evaluated concentration of 1,2,3,5-tetrachlorobenzene in pore water of sediment and concentration of sulfate show that dechlorination is inhibited at higher concentration of sulfate.     

羟基氧化镍的电解制备，结构表征和电化学性能研究

NiOOH was prepared by one-step electrolysis of spherical Ni（OH）2 and the effects of electrolysis parameters were examined. The highly pure NiOOH was obtained after electrolysis at a current density of 60mA.g^-1 and 30℃ with anodic potential controlled in the range of 1.73-1.85V （vs. Zn/ZnO） for 360min. The NiOOH samriles were characterized bv X-ray oowder diffraction （XRD） and scanning electron microscope （SEM） analysis.Resuits indicate that the electrolysis product is spherical NiOOH doped with graphite. Charge and discharge tests show that the prepared NiOOH offers a discharge capacity of over 270mAh·g^-1 at current density of 30mA·g^-1 and can be directly used as cathode material of alkaline Zn/NiOOH batteries. Galvanostatic charge/discharge and cyclic voltammetry （CV） tests reveal good cycling reversibility, of the NiOOH electrode.     

电流中断法在线测定直接甲醇燃料电池的欧姆阻抗

Electrochemical impedance spectroscopy (EIS) is widely used in fuel cell impedance analysis. However, for ohmic resistance (RΩ), EIS has some disadvantages such as long test period and complex data analysis with equivalent circuits. Therefore, the current interruption method is explored to measure the value of RΩ in direct methanol fuel cells (DMFC) at different temperatures and current densities. It is found that RΩ decreases as temperature increase, and decreases initially and then increases as current density increases. These results are consistent with those measured by the EIS technique. In most cases, the ohmic resistances with current interruption (RiR) are larger than those with EIS (REIS), but the difference is small, in the range from –0.848% to 5.337%. The errors of RiR at high current densities are less than those of REIS. Our results show that the RiR data are reliable and easy to obtain in the measurement of ohmic resistance in DMFC.     

Effect of silver-nanoparticles generated in poly(vinyl alcohol)membranes on ethanol dehydration via pervaporation

Pervaporation is an important membrane separation method of chemical engineering. In this work,silver-nanoparticles-poly(vinyl alcohol) nanocomposite membranes(AgNPs-PVA) are produced for the sake of improving its potentials for pervaporation of ethanol–water mixture so that the usual opposite trend between membrane selectivity and permeation can be reduced. The nanocomposite membranes are fabricated from an aqueous solution of poly(vinyl alcohol) with silver nanoparticles via the in-situ generation technique in the absence of any reducing agent. Successful generation of the nano size silver is measured by the UV–vis spectrum showing a single peak at 419 nm due to the plasmonic effect of silver nanoparticles. Our nanocomposite AgNPs-PVA membranes are characterized using scanning electron microscope(SEM), Fourier-transform infrared(FT-IR) spectroscopy, X-ray diffraction and thermogravimetric analysis(TGA). The pervaporation tests of our new AgNPs-PVA membranes show good results since at a higher temperature and higher ethanol concentration in the feed, the prepared membranes are highly permeable for the water having stable selectivity values and therefore our membranes show better performance compared to that of the other PVA-based nanocomposite membranes.     

喷动床中气体停留时间分布的研究

In a spouted bed of 80mm in ID and 1700mm in height, the gas residence time distributions at different radial positions in both spout and annular area were measured with five different kinds of particles as spouting material, air as spouting gas, and hydrogen as tracer. The effects of superficial gas velocity, operating pressure, particle size and its category on gas residence time distribution were discussed. It was found that the gas velocity profile in spout was more uniform than that in annulus. It could be concluded that the gas flow in the spout could be treated as a plug-flow, while that in the annulus inhibited a strong non-ideal flow behavior. Increasing the superficial gas velocity and decreasing the operating pressure, the particle density and its size gave rise to spouting disturbance, thus the measured tracer concentrations vs. time curves fluctuated. The variances of residence time distribution curves could be taken as a measure of the gas fluctuation degree.     

High tap density of Ni3(PO4)2 coated LiNi1/3Co1/3Mn1/3O2 with enhanced cycling performance at high cut-off voltage

The LiNi1/3Co1/3Mn1/3O2 is first obtained by the control ed crystallization method and then coated with Ni3(PO4)2 particles. The effects of the coating on rate capability and cycle life at high cut-off voltage are investigated by elec-trochemical impedance spectroscopy and galvanostatic measurements. The element ratio of Ni:Mn:Co is tested by inductively-coupled plasma spectrometer (ICP) analysis and it testified to be 1:1:1. It is indicated that Ni3(PO4)2-coated LiNi1/3Co1/3Mn1/3O2 has an outstanding capacity retention, where 99%capacity retention is maintained after 10 cycles at 5C discharge rate between 2.7 V and 4.6 V. The electrochemical impedance spectroscopy (EIS) results show that the current exchange density i0 of the coated sample is higher than that of LiNi1/3Co1/3Mn1/3O2, which is beneficial to its electrochemical performances. All the conclusions show that the Ni3(PO4)2 coating can prominently enhance the high rate performance of the LiNi1/3Co1/3Mn1/3O2, especially at high cut-off voltage.     

Integration of coal pyrolysis process with iron ore reduction:Reduction behaviors of iron ore with benzene-containing coal pyrolysis gas as a reducing agent☆

An integrated coal pyrolysis process with iron ore reduction is proposed in this article. As the first step, iron oxide reduction is studied in a fixed bed reactor using simulated coal pyrolysis gas with benzene as a model tar compound. Variables such as reduction temperature, reduction time and benzene concentration are studied. The carbon deposition of benzene results in the retarded iron reduction at low temperatures. At high temperatures over800 °C, the presence of benzene in the gas can promote iron reduction. The metallization can reach up to 99% in20 min at 900 °C in the presence of benzene. Significant increases of hydrogen and CO/CO2 ratio are observed in the gas. It is indicated that iron reduction is accompanied by the reforming and decomposition of benzene. The degree of metallization and reduction increases with the increasing benzene concentration. Iron oxide can nearly completely be converted into cementite with benzene present in the gas under the experimental conditions. No sintering is found in the reduced sample with benzene in the gas.     

Energy and economic analysis of a hydrogen and ammonia co-generation system based on double chemical looping

In this work, a model of hydrogen production by double chemical looping is introduced. The efficiency benefit obtained was investigated. The chemical looping hydrogen generation unit is connected in series to the downstream of a chemical looping gasification unit as an additional system for 100 MW·h coal gasification, with the function of supplementary combustion to produce hydrogen. Using Aspen Plus software for process simulation, the production of H_2 and N_2 in the series system is higher than that in the independent Chemical looping gasification and Chemical looping hydrogen generation systems, and the production of hydrogen is approximately 25.63% and 12.90% higher, respectively; The study found that when the gasification temperature is 900 °C, steam-carbon ratio is 0.84 and oxygen-carbon ratio is 1.5,the hydrogen production rate of the system was the maximum. At the same time, through heat exchange between logistics, high-pressure steam at 8.010×10~4 kg·h~(-1) and medium-pressure steam at 1.101×10~4 kg·h~(-1) are generated, and utility consumption is reduced by 61.58%, with utility costs decreasing by 48.69%. An economic estimation study found that the production cost of ammonia is 108.66 USD·(t NH_3)~(-1). Finally, cost of equipment is the main factors influencing ammonia production cost were proposed by sensitivity analysis.     

Preparation of cerium and nitrogen co-doped titania hollow spheres with enhanced visible light photocatalytic performance

N,Ce-codoped titania hollow spheres were prepared using carbon spheres as template and using N,Ce-codoped titania nanoparticles as building blocks. The N,Ce-codoped titania nanoparticles were synthesized at low temperature. The prepared hollow spheres were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse reflectance spectrum (DRS). The effect of N and Ce content on the physical structure and photocatalytic properties of the as-prepared hollow sphere samples was investigated. The mechanism of photocatalytic degradation of dyes under visible light irradiation was also discussed.     

TiO2/碳管纳米复合材料的制备与表征

以四氯化钛溶胶为前驱体,硝化后的碳管为载体,采用溶胶-水解法制得TiO2/碳管纳米复合材料。运用红外光谱、X射线衍射和透射电子显微镜等手段分别对硝化后的碳管和复合材料的晶相组成、形貌特征和显微结构等进行表征,结果表明,CNTs表面修饰了羟基、羧基等基团;样品由TiO2和碳管组成,且TiO2主要以锐钛矿晶型为主;TiO2颗粒呈椭圆形均匀负载在碳管外表面,平均粒径在7nm左右。     

掺铁二氧化钛纳米晶的制备及其光催化性能

通过溶胶-凝胶法室温制备了掺杂铁二氧化钛纳米晶光催化剂。采用透射电子显微镜、X射线衍射仪、能谱元素分析仪、紫外-可见分光光度计等对所得产物进行表征。以甲基橙为目标降解物,对未掺杂的二氧化钛纳米晶及掺杂铁的二氧化钛纳米晶进行了光催化降解性能研究,并对其降解机理进行了分析。结果表明:适量的铁掺杂有利于提高二氧化钛纳米晶的光催化性能和对甲基橙的降解率。铁的最佳掺杂量为25%[Fe占(Ti+Fe)的摩尔分数]。掺杂铁的二氧化钛纳米晶光催化性能优于纯二氧化钛纳米晶,在光照150min后,甲基橙的降解率达75%以上。     

用水量对溶胶-凝胶法制备氮掺杂纳米二氧化钛的影响

采用两种用水量的溶胶-凝胶工艺制备了氮掺杂二氧化钛(N-TiO2)纳米颗粒粉末,对样品进行了X射线衍射、透射电子显微镜、X射线光电子能谱及紫外-可见漫反射谱分析,并以甲基橙的光催化降解实验研究了样品的可见光催化性能。结果表明:采用用水多的溶胶-凝胶工艺可获得可见光催化活性高的N-TiO2,且N-TiO2的颗粒粒径较小;由于溶胶中过量的N掺杂剂可在N-TiO2前驱体凝胶离心分离时被去除,可进行较低温度的煅烧,易于获得N掺杂浓度较高的N-TiO2。另外,采用用水多的工艺时,氮掺杂剂对TiO2颗粒的氮化及凝胶化过程也有很大的影响,有些含氮化合物作为掺杂剂可能会明显降低N-TiO2的可见光催化活性。     

Hydrothermal-assisted liquid phase deposition synthesis and photocatalytic activities of titania nanocrystals

Herein, we firstly used hydrothermal-assisted liquid phase deposition (HT-LPD) approach to prepare anatase titania nanocrystals, with γ-Al₂O₃ as the fluorion scavenger. The as-prepared products were characterized by X-ray powder diffraction, UV–vis diffuse reflectance spectrometer, and transmission electron microscope. Compared with titania nanocrystal prepared by LPD method, titania nanocrystals prepared by HT-LPD method exhibited better photocatalytic activity, especially the nanocrystal prepared by HT-LPD method at 200 °C for 3 h. The possible reason for the enhanced photocatalytic activity was investigated.     

Support Effects on Thiophene Hydrodesulfurization over Co-Mo-Ni/Al2O3 and Co-Mo-Ni/TiO2-Al2O3 Catalysts

A carbon-based sulfonated catalyst was prepared by direct sulfonation and carbonization （in moderate conditions：200 ＆#176;C, 12 h） of red liquor solids, a by-product of paper-making process. The prepared sulfonated cata-lyst （SC） had aromatic structure, composed of carbon enriched inner core, and oxygen-containing （SO3H, COOH, OH） groups enriched surface. The SO3H, COOH, OH groups amounted to 0.74 mmol·g^-1, 0.78 mmol·g^-1, 2.18 mmol·g^-1, respectively. The fresh SC showed much higher catalytic activity than that of the traditional solid acid catalysts （strong-acid 732 cation exchange resin, hydrogen type zeolite socony mobile-five （HZSM-5）, sulfated zir-conia） in esterification of oleic acid. SC was deactivated during the reactions, through the mechanisms of leaching of sulfonated species and formation of sulfonate esters. Two regeneration methods were developed, and the catalytic activity can be mostly regenerated by regeneration Method 1 and be fully regenerated by regeneration Method 2, respectively.     

Room temperature synthesis of spherical mesoporous titania

This work reports a facile hydrolysis method for the synthesis of spherical mesoporous titania particles using titanium tetrachloride under mild conditions. The method can be easily controlled or expanded. The influences of various reaction conditions including concentration of Ti⁴⁺ ions and water content on the formation of mesoporous titania particles were systematically investigated. The titania particles were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM) and Brunauer-Emmett-Teller (BET) surface areas. Experimental results showed that the mesoporous titania particles have special surface structure and excellent thermally stable mesoporous structure after annealing at high temperatures (500 °C). The effects of various reaction conditions, such as concentration of Ti⁴⁺, H₂O/n-butanol volume ratio and reaction temperature, on formation, crystal phase, morphology of titania particles were investigated.     

超声分散法制备含锰的二氧化钛光催化剂及其表征

以钛酸四丁酯为主要原料,硫酸锰溶液为掺杂剂,采用超声分散法制备了含锰的二氧化钛光催化剂。并用X射线衍射(XRD)和透射电镜(TEM)对粉体的结构、粒径大小、物相、形貌等进行了表征。经500℃焙烧2h后,锰掺杂的二氧化钛粉末为锐钛型结构,其平均粒径为13nm,由于在XRD图谱上未发现有新相的生成,因此,可知锰离子是经过焙烧渗入到了二氧化钛的晶格中,掺杂所引起的变化主要是由于锰离子渗入二氧化钛晶格引起的。     

纳米二氧化钛溶胶的光催化活性及细胞毒性试验

利用低温合成法制备了分散有锐钛矿纳米颗粒的二氧化钛(TiO2)溶胶,该溶胶均一、透明。利用X射线衍射和透射电镜对该溶胶内纳米颗粒的结构和形貌进行研究。结果显示:颗粒呈梭形,分散性良好,其尺寸小于50nm,晶型为锐钛矿型。通过对TiO2溶胶光催化活性和老鼠内皮细胞毒性进行研究,发现该溶胶在日光照射下光催化活性较高,具有良好的生物相容性和安全性。     

Morphology and Microstructure of As-Synthesized Anodic TiO2 Nanotube Arrays

The as-grown structure of electrochemically synthesized titania nanotube arrays is investigated by scanning electron microscope (SEM) in combination with transmission electron microscope (TEM) as well as X-ray diffraction (XRD). The analysis reveals a preferred growth direction of the nanotubes relative to the substrate surface and the well control on the nanotube arrays morphology. The crystal structure of the anatase phase is detected and exists in the tube walls without any thermal treatment, which makes it possible to realize the application of as-formed TiO₂ nanotubes avoiding the degradation of the nanotube structures when sintering. In addition, a new growth, layered model of the anodic TiO₂ nanotubes is presented to obtain further understanding of the growth mechanism.