CuO／活性炭和Fe2O3／活性炭催化还原NO

ＣｕＯ／活性炭和Ｆｅ_２Ｏ_３／活性炭催化还原ＮＯ高志明，赵震，杨向光，吴越（中国科学院长春应用化学研究所长春１３００２２）关键词活性炭，还原，ＮＯ，氧化铜，氧化铁目前，对固定源的ＮＯ处理是采用Ｖ２Ｏ５／ＴｉＯ２作催化剂，ＮＨ３作还原剂的选择催化还原方...     

Zerovalent metal polymer composites. III. Metallization of metal oxide surfaces with the aid of metallized functional polymer microdispersions

The adsorption of poly[N-(m- and p-vinylbenzyl)-N,N,N-trimethylammonium tetrachloropal-ladate] complex on inorganic oxide surfaces followed by reduction of the palladium salt to form a catalytically active zerovalent metal polymer composite dispersed on the oxide surface and further deposition of transition metals, e.g., nickel, cobalt, and copper, by “additive” or “subtractive” deposition from electroless plating solutions is described. γ-Ferric oxide was used as a template for such intermetallic replacement reactions, providing materials with controlled amounts of metal. Multimetallic catalysts based on aluminum oxide, zinc oxide, lanthanum oxide, magnesium oxide, and silica were prepared. Iron oxide modified by subtractive deposition of rhodium and iridium on nickel-clad iron oxide were evaluated in Fischer–Tropsch carbonylation reactions leading from synthesis gas to alkanols.     

The effect of iodide on the electrochemical reduction of thick oxide films formed on platinum electrodes in sulfuric acid solution

The reduction of thick oxide films formed on Pt under severe anodic conditions was studied in the presence of adsorbed I^?. The Pt electrode covered with a thick oxide film does not adsorb I^?. However, when a superficial monolayer oxide on the thick oxide has been reduced, I^? is irreversibly adsorbed. Iodide adsorbed on its surface blocks the adsorption of hydrogen and retards markedly the cathodic reduction of the inner thick oxide remaining. It was found that the reduction rate of the inner oxide depends only on the coverage by hydrogen, which coexists with adsorbed I^?. These results support the proton-electron theory which has previously been proposed for the explanation of the characteristic reduction of the thick oxide films.     

An investigation of anodic film formation on electrodeposited ruthenium by potential sweep techniques

Potential sweep techniques were used to investigate the anodic behaviour of reduced ruthenium surfaces, prepared by electrodeposition on gold-plated substrates, as a function of sweep rate, temperature and pH. The most important factor appeared to be pH as this strongly influenced the oxide layer thickness and both the number and location of the peaks on the voltammogram. The formation of thin oxide films on ruthenium at intermediate pH values (3.5–9.5) is attributed to the growth of a compact amorphous film with significant metal-oxygen-metal bridging in the structure. Heavier oxide growth in strong acid is attributed to protonation of the oxide lattice resulting in the formation of a more porous anodic film. Thicker oxide growth in strong base is attributed to the growth of a higher (+6) oxide under these conditions. The effects of both sweep rate and temperature on anodic behaviour in strong acid are attributed to activation-controlled rearrangement of the oxide film.     

氧化石墨烯吸附亚甲基蓝的分子动力学模拟

采用分子动力学方法研究了亚甲基蓝在不同氧化度的氧化石墨烯表面的吸附行为及其动力学性质, 从微观角度讨论了亚甲基蓝由体相到氧化石墨烯表面的吸附过程及主要作用机制, 并通过亚甲基蓝分子动力学性质解释了氧化石墨烯的氧化度和含氧官能团类型对吸附行为的影响. 结果表明, 吸附过程中, 亚甲基蓝主要受氧化石墨烯表面含氧官能团的静电作用, 以近似垂直氧化石墨烯表面的方向进入, 并以平行的方式吸附于氧化石墨烯表面; 亚甲基蓝不易脱离高氧化度氧化石墨烯的吸附位点; 吸附平衡过程中, 相对于低氧化度的氧化石墨烯, 高氧化度氧化石墨烯对亚甲基蓝的束缚性更强, 同时与亚甲基蓝间相互作用更强; 含氧官能团中的环氧基与亚甲基蓝间的作用势能更强, 且羟基能够与亚甲基蓝间形成氢键结构, 共同保障了亚甲基蓝吸附层的稳定性.     

A novel hydrogen peroxide sensor based on Ag nanoparticles electrodeposited on chitosan-graphene oxide/cysteamine-modified gold electrode

A novel strategy to fabricate a hydrogen peroxide sensor based on Ag nanoparticles electrodeposited on chitosan-graphene oxide nanocomposites/cysteamine-modified gold (Au) electrode was reported. The chitosan-graphene oxide nanocomposites were first assembled on a cysteamine-modified Au electrode to produce chitosan-graphene oxide/cysteamine/Au electrode. Then Ag nanoparticles were electrodeposited on the modified Au electrode and formed Ag nanoparticles/chitosan-graphene oxide/cysteamine/Au electrode. The chitosan-graphene oxide nanocomposites and the electrodeposited Ag nanoparticles were characterized by atomic force microscopy and scanning electron microscopy. The results showed the Ag nanoparticles were uniformly dispersed on the chitosan-graphene oxide/cysteamine/Au electrode. The cyclic voltammagrams and amperometric method were used to evaluate electrocatalytic properties of the Ag nanoparticles/chitosan-graphene oxide/cysteamine/Au electrode. The results showed that the modified electrode displayed good electrocatalytic activity to the reduction of hydrogen peroxide with a detection limit of 0.7 μM hydrogen peroxide based on a signal-to-noise ratio of 3. The sensor has good reproducibility, wide linear range, and long-term stability.     

Study on microarc oxidation of AZ31B magnesium alloy in alkaline metal silicate solution

The effects of pulsating current and voltage sources with different magnitudes on an oxide film formed by microarc oxidation (MAO) of AZ31B magnesium alloy in alkaline metal silicate solution were investigated. The thickness of an oxide film increased with increasing current source but the uniformity of the surface of an oxide film became worse. The unstable oxidation process represented by fluctuating voltage established across an oxide film was discussed and related to the surface roughness and the melting down of magnesium alloy. By comparing the surface of an oxide film a pulsating current source produced more uniform oxide film on magnesium alloy than a pulsating voltage source.     

Effect of silicon oxidation on long-term cell selectivity of cell-patterned Au/SiO2 platforms

Cellular patterning on silicon platforms is the basis for development of integrated cell-based biosensing devices, for which long-term cell selectivity and biostability remain a major challenge. We report the development of a silicon-based platform in a metal-insulator format capable of producing uniform and biostable cell patterns with long-term cell selectivity. Substrates patterned with arrays of gold electrodes were surface-engineered such that the electrodes were activated with fibronectin to mediate cell attachment and the silicon oxide background was passivated with PEG to resist protein adsorption and cell adhesion. Three types of oxide surfaces, i.e., native oxide, dry thermally grown oxide, and wet thermally grown oxide, were produced to illustrate the effect of oxide state of the surface on long-term cell selectivity. Results indicated that the cell selectivity over time differed dramatically among three patterned platforms and the best cell selectivity was found on the dry oxide surface for up to 10 days. Surface analysis results suggested that this enhancement in cell selectivity may be related to the presence of additional, more active oxide states on the dry oxide surface supporting the stability of PEG films and effectively suppressing the cell adhesion. This research offers a new strategy for development of stable and uniform cell-patterned surfaces, which is versatile for immobilization of silane-based chemicals for preparation of biostable interfaces.     

纳米氧化亚铜的制备及其电化学性质

研究了纳米氧化亚铜的软模板制备法,并用XRD和TEM对所制备的纳米氧化亚铜进行了表征.试验表明,利用十六烷基三甲基溴化胺为软模板制备的纳米氧化亚铜呈直径为10 nm左右,长度为250 nm左右的纳米晶须.利用Nafion将新制备的纳米氧化亚铜固定在玻碳电极表面,研究了纳米氧化亚铜的电化学性质.结果表明,纳米氧化亚铜在电极表面表现出一对对称性良好的氧化还原峰,对应于纳米氧化亚铜中心的Cu(Ⅱ)/Cu(Ⅰ)的氧化还原,峰电流随扫描速度的增大呈现线性关系,根据峰电位与扫速对数的线性关系,计算出了电子转移系数.表明纳米氧化亚铜在电极表面的反应是受表面控制的部分不可逆过程.     

纳米TiO2-SiO2复合氧化物的制备与性质

采用溶胶-凝胶结合CO2超临界干燥方法制备了比表面积大、热稳定性好的纳米TiO2-SiO2复合氧化物.考察了原料组成和焙烧温度对复合氧化物比表面积、热稳定性和酸性的影响,通过加氢脱硫反应考察了该复合氧化物作为加氢精制催化剂载体的可行性.结果表明,采用该方法制备的复合氧化物为纳米颗粒,在n(Ti)/n(Si)=1时,其比表面积和孔容最大;与纯TiO2相比,引入SiO2明显提高了复合氧化物的热稳定性和晶型稳定性;以此复合氧化物为载体的加氢精制催化剂具有很好的低温脱硫活性,TiO2-SiO2复合氧化物载体的酸性特征影响了催化剂的加氢脱硫活性.     

Influence of structural transformations over the electrochemical behavior of Ti anodic films grown in 0.1 M NaOH

In this work, the structural transformation during the anodic growth of Ti oxide films and its influence on the resistive properties of the film are studied. The voltammetric characterization of Ti/0.1 M NaOH indicates that the oxide film composition depends on potential. Depending on the anodic switching potential, the oxide film can produce up to three cathodic peaks, and the peaks can be related to different Ti oxides. During the early stages of potentiostatic formation, the oxide film seems to have the same initial structure regardless of the film formation potential; however, after increasing growth time, the oxide structure depends on the formation potential. The evaluation of the resistive properties of Ti oxide films determined by electrochemical impedance spectroscopy shows that despite the chemical transformations within the film, there is a linear dependence between the capacitance of the Ti oxide film with formation potential.     

Synthesis of reduced graphene oxide and its electrocatalytic properties

The method of the chemical synthesis of reduced graphene oxide was developed. Sodium hypophosphite and sulfi te were used as reducing agents. The formation of reduced graphene oxide was confi rmed by several methods. Volt-ampere characteristics of electrodes based on reduced graphene oxide were investigated in an experimental model of an oxygen fuel cell with an alkaline electrolyte. Characteristics of oxygen electrodes based on reduced graphene oxide were stable over semiannual tests. The resulting reduced graphene oxide is a promising material for oxygen electrodes of chemical current sources.     

外延定向生长氧化铌模型催化剂的制备

为用现代表面科学技术研究金属氧化物催化剂，在Pt（111）上于超高真空系统中原位蒸镀制备了NbO、NbO2、NbO2、单晶薄膜（＞2nm）．通过AES、ISS、LEED、ILS等手段研究了单晶薄膜的成长模式、化学计量和几何结构．表明通过选择合适的废物和控制制备条件，可制备出确定结构的金属氧化物单晶薄膜表面作为体相氧化物催化剂的模型表面．这种方法克服了电子能谱技术研究金属氧化物表面的困难，为研究金属氧化物催化剂的表面化学物理性质提供了方法     

担载型钴镍金属氧化物催化剂上CH4还原NO反应研究

ＮＯｘ是大气的主要污染物之一,近年来,利用甲烷选择还原ＮＯｘ引起了广泛关注,研究发现,Ｃｏ、Ｍｎ和Ｎｉ离子交换的ＺＳＭ－５分子筛具有较高的活性［１～３］．但金属离子交换的分子筛催化剂有热稳定性差、易失活等缺点．最近已有金属氧化物用作甲烷还原ＮＯｘ反应...     

木质素磺酸钠在氧化铁表面的吸附驱动力

研究吸附介质的pH值、 尿素及盐类对木质素磺酸钠(SL)在氧化铁表面吸附性能的影响规律, 结果表明, 络合能力较强的柠檬酸钠使SL的吸附量几乎减少至零, 较弱络合能力的亚硫酸钠使SL的吸附量具有一定程度的降低, 而无络合能力的硫酸钠增大了SL的吸附量. 说明SL的羧基与氧化铁之间的络合吸附驱动力对吸附起主导作用, 磺酸基对其在氧化铁上吸附的影响很弱. 采用氯化锂屏蔽部分羧基后SL在氧化铁上的吸附量也有所降低, 进一步证明了羧基与氧化铁表面的络合作用是其吸附的主要驱动力.     

Kinetics and mechanism of electrochemical reduction of multilayer oxides on a smooth platinum electrode surface in acidic electrolyte

The electrochemical reduction of multilayer oxides which were formed on a smooth Pt electrode surface under severe anodic conditions was investigated using a galvanostatic transient, a linear potential sweep and a potential step technique. Four regions of the surface oxide reduction were distinguished in the galvanostatic E?t curve and four corresponding cathodic current peaks were observed in the potentiodynamic i?E profile. These four regions or peaks are attributed to the reduction of four O-containing layers: an oxygen monolayer adsorbed on the oxide surface, two oxide layers in a first and a second lattice and a multilayer oxide in the deeper lattices having a phase property. The reduction rate of the first lattice oxide layer is determined by a second electron transfer. Under a rapid stripping condition, the reduction of the second oxide layer is considered to be controlled by the place exchange reaction. The extremely large reduction rate of the multilayer oxide compared with the formation rate is explained in terms of the proton-electron model.     

Effects of the polarizability and packing density of transparent oxide films on water vapor permeation

The tin oxide and silicon oxide films have been deposited on polycarbonate substrates as gas barrier films, using a thermal evaporation and ion beam assisted deposition process. The oxide films deposited by ion beam assisted deposition show a much lower water vapor transmission rate than those by thermal evaporation. The tin oxide films show a similar water vapor transmission rate to the silicon oxide films in thermal evaporation but a lower water vapor transmission rate in IBAD. These results are related to the fact that the permeation of water vapor with a large dipole moment is affected by the chemistry of oxides and the packing density of the oxide films. The permeation mechanism of water vapor through the oxide films is discussed in terms of the chemical interaction with water vapor and the microstructure of the oxide films. The chemical interaction of water vapor with oxide films has been investigated by the refractive index from ellipsometry and the OH group peak from X-ray photoelectron spectroscopy, and the microstructure of the composite oxide films was characterized using atomic force microscopy and a transmission electron microscope. The activation energy for water vapor permeation through the oxide films has also been measured in relation to the permeation mechanism of water vapor. The diffusivity of water vapor for the tin oxide films has been calculated from the time lag plot, and its implications are discussed.     

Parameters affecting carbofuran photocatalytic degradation in water using ZnO nanoparticles

Carbofuran photodegradation in water using zinc oxide nanoparticles as a catalyst was examined as well as some parameters influencing its percentage degradation rate such as zinc oxide load, initial concentration of carbofuran, the temperature of the reaction, the initial pH of the solution, and doping of zinc oxide nanoparticles with 5% (w:w) silver. Zinc oxide and Ag-doped zinc oxide nanoparticles were produced using solvothermal and photoreduction methods, respectively, and silver doping effects on the structural, optical, and photocatalytic properties of zinc oxide nanoparticles were investigated using XRD, UV-VIS spectrophotometer, TEM, SEM, SEM/EDX, and FTIR. The average diameter of the synthesized samples was 26.6, 30.55 nm for undoped zinc oxide and Ag-doped zinc oxide, respectively. Zinc oxide doping with silver did not change the shape of the zinc oxide crystal, but decreased the reflection in the visible region, as well as the energy of the bandgap, and increased the zinc oxide photocatalytic activity.     

臭氧化物生成机理研究综述

以Criegee三步反应机理为核心对烯烃臭氧化反应中的臭氧化物生成机理进行了综述。论述了初级臭氧化物的生成与分解和臭氧化物生成过程的选择性和立体化学。讨论了烯烃结构和反应各步骤的选择性和立体化学的关系。