Operation of an Oxygen Gas Diffusion Electrode in a Hybride Fuel Cell

The paper is devoted to the operation of a hybride fuel cell (i.e. in the course of simultaneous electrosynthesis of a chemical product), in particular, the polarization characteristic of an oxygen electrode and the ratio of the produced electric energy to the amount of the produced target product. An equation for the dependence of the polarization of an oxygen gas diffusion hydrophobized electrode of a hydrogen-oxygen fuel cell on the concentration of the produced electroactive soluble product H₂O₂ in an inner-kinetic regime is suggested. It is established that the polarization variation does not depend on its initial magnitude but does depend on the concentration of the target product and the ratio between currents of the side and target reactions. The ratio of the produced electric energy to the amount of the produced target product is found to depend on the concentration of the produced target product, the electrode polarization, and the ratio between exchange currents of the side and target reactions.     

Strategy and Construction of the Backbone Bistetrahydrofuran System Towards Synthesis of Rollinicin

Rollinicin¹ (I), uvaricin² (II) and cherimoline³ (III), the new antitumour, antibiotic agents, isolated from renewable resources having bistetrahydrofuran ring system in the molecules, have been recently reported. Bates² has postulated that uvaricin has been probably biosynthesised from 1,5,9-trienoic acid derivative. The central portion of I - III, a bistetrahydrofuran ring system, is apparently novel. This prompted us to develop a methodology for the construction of the central bistetrahydro-furan ring system (L) using acetylenic derivatives as the starting materials for the first time. In this communication, we report 4 its result.     

Effects of Oxygen and Water Vapor on Volatile Organic Compounds Decomposition Using Gliding Arc Gas Discharge

The combined effects of oxygen and water vapor on three typical volatile organic compounds, i.e. tetrachloromethane, n-butane and toluene, decomposition efficiency under gliding arc gas discharge conditions are studied. The electron density and the density of the reactive radicals such as O and OH are modified by addition of oxygen and water vapor. Consequently, the decomposition process can be enhanced or suppressed, depending on the involved chemical structures and reaction channels. The addition of oxygen and water vapor suppresses the tetrachloromethane decomposition which indicates that this process is mainly controlled by the electron dissociation reactions. By contrast, the n-butane and toluene decompositions are enhanced, which shows that they can be mainly ascribed to the radical induced reactions. Especially, in a moist atmosphere the OH radicals are supposed to play the most important role in the n-butane decomposition process.     

电位型传感器嵌入式遥测系统的研制

研制了一种应用于电位型传感器的嵌入式遥测系统。系统由采样发送端、接收端和计算机组成。采样发送端包括电流放大器、∑-Δ型模数转换器、微控制器和无线数据传输模块,接收端包括无线数据传输模块、微控制器和协议转换器,接收端通过通用串行总线( USB)接口和计算机连接。嵌入式软件用C语言编写,控制信号的采集和传输;上位机软件用 LabVIEW编写,用于数据存储和显示。系统采集电压信号范围为±1.17 V。为验证该系统的精度和可靠性,应用本套系统和数字多用表对一组电位值进行了对照测试,并用自制的氢离子选择性电极进行了酸度变化响应测试。结果表明,本系统电位测量值可以精确到0.1 mV,且抗噪能力良好,pH响应测量的线性相关系数R2=0.998,变化曲线和商品化的电化学分析仪的结果一致。此系统硬件均由标准芯片组成,采样发送端尺寸为29 mm×14 mm×11 mm,可以用于电位型传感器的远程实时检测。     

薄池吸收宽带紫外光度检测器的研制

设计和制作了利用宽带吸收技术进行宽带表观吸光度测定的薄池宽带紫外光度检测器(，large-bandwidth UV absorption detector，简称LBUAD)，并进行了性能表征。该检测器在光学系统上采用氘灯做为紫外光源，通过宽带紫外玻璃得到入射宽带光，并利用中心对称的双透镜聚焦光学系统对宽带光进行聚焦，聚好的光斑通过蓝宝石球进一步会聚后照射吸收池，然后进行检测。毛细管薄池中系列高锰酸钾溶液的表观吸光度测定结果表明：该仪器的动态范围为2-3个数量级，对硝基苯肼的表观吸光度测定结果表明，其检出限达到10^-6AU，基线漂移小于0．001AU／h。与商品DD2000紫外检测器的比较以及在实际电泳分离中的检测进一步表明：该仪器具有很好的检测性能。     

Local Activities of Hydroxide and Water Determine the Operation of Silver‐Based Oxygen Depolarized Cathodes

Local ion activity changes in close proximity to the surface of an oxygen depolarized cathode (ODC) were measured by scanning electrochemical microscopy (SECM). While the operating ODC produces OH^? ions and consumes O₂ and H₂O through the electrocatalytic oxygen reduction reaction (ORR), local changes in the activity of OH^? ions and H₂O are detected by means of a positioned Pt microelectrode serving as an SECM tip. Sensing at the Pt tip is based on the pH‐dependent reduction of PtO and obviates the need for prior electrode modification steps. It can be used to evaluate the coordination numbers of OH^? ions and H₂O, and the method was exploited as a novel approach of catalyst activity assessment. We show that the electrochemical reaction on highly active catalysts can have a drastic influence on the reaction environment.     

Effect of Oxygen Environment on the Decomposition and Crystallization of an Aqueous Sol-Gel Derived Zirconium Acetate Gel

A precursor gel was prepared by desiccation of an aqueous solution of zirconium acetate and pyrolyzed to form crystalline powders in selected gas environments. Thermal analysis, X-ray powder diffraction, mass spectrometry and Fourier transform infrared spectroscopy were used to investigate the decomposition of the gel and the transformations occurring during pyrolysis to 800°C in nitrogen, air and oxygen. Three transition temperatures were detected: the amorphous-to-cubic crystal transformation, cubic-to-tetragonal transformation, and the initiation of tetragonal-to-monoclinic transition. The presence of molecular oxygen decreased the crystallization temperature, increased the grain size of the tetragonal crystals formed and decreased the temperature at which the tetragonal-to-monoclinic transformation was initiated. The decrease in the crystallization temperature in the presence of oxygen occurred despite an increase in the temperature corresponding to the loss of the major portion of the organic component of the gel.     

The Design of an Automatic System for the Gravimetric Measurement of Water Sorption

An understanding of the mechanisms by which water molecules are held within a substance or at its surface, either by physical or chemical processes, is of importance in the formulation, preparation and storage of a wide variety of substances. The traditional experimental techniques which have been used to make measurements on samples exposed to specific levels of relative humidity, (e.g. using desiccators containing saturated salt solutions), are slow, laborious, inaccurate, and provide a limited amount of data. This paper describes the conception, operation, and facilities of a new system which by employing recently developed electronic components and transducers, significantly advances the performance capability for moisture sorption analysis. This revised version was published online in July 2006 with corrections to the Cover Date.     

高效催化氧还原及氧析出反应的掺杂石墨炔的设计与理论计算

在清洁和可再生能源的转化过程中, 氧还原反应和氧析出反应需要高效的电催化剂以克服其动力学限制. 本文设计了一系列掺杂杂原子的无金属石墨二炔, 以促进上述两类关键化学反应.为了评估电催化性能, 利用密度泛函理论研究了反应路径和吉布斯自由能变化. 计算结果表明, 掺杂剂可以优化中间体的吸附, 降低反应的过电位. 本文还得到了将催化剂性质与催化剂结构相关联的内在描述符, 该描述符可以加速开发和筛选新型电催化剂. 研究结果可为清洁能源技术(如燃料电池、 金属空气电池和电解水等)中碳基催化剂的设计提供指导.     

The First Crystal Structure of a Germanium(II) Amide with a Germanium - Lithium Bond and Its Behavior Towards Oxygen and Water

The Ge-Li bond in 1 reacts readily with water and oxygen to give 2 (Li/H exchange) and 3 (insertion), respectively. In both cases the partial charge and the oxidation state of the germanium atom changes. All compounds were characterized by X-ray crystallography.     

Assembly of Supramolecular Networks with the Inclusion of Water Chains,Cyclic Hepta and Octa Water Clusters

Three new supramolecular compounds were synthesized and characterized with the formula of [Zn₄(picO)₄(phen)₄]·11.25H₂O ( 1 ), [Zn₄(picO)₄(2,2′‐bpy)₄(H₂O)₄]·12H₂O ( 2 ), and [Zn₃(picO)₃(bpe)₅(H₂O)₃]_n·8.5nH₂O ( 3 ) (H₂picO = 6‐hydroxypicolinic acid; phen = 1,10‐phenanthroline; 2,2′‐bpy = 2,2′‐bipyridine; bpe = 1,2‐bis(4‐pyridyl)ethane). For complexes 1 and 2 , picO ligands adopt tridentate, tetradentate and bidentate coordination modes to link zinc(II) ions into dimers, which are extended into 3D supramolecular structures through hydrogen bonds. Water chains with cyclic page‐like octamer and boat‐like heptamer water clusters are included, respectively. Complex 3 is of a 2D brick‐wall structure. Triple interpenetration occurs, and there are still cyclic chair‐like octamer water clusters in the channels. The fluorescent properties of complexes 1‐3 have also been investigated.     

Photo-Induced Dihydroxylation of Alkenes with Diacetyl,Oxygen, and Water

Herein reported is a photo-induced production of vicinal diols from alkenes under mild reaction conditions. The present dihydroxylation method using diacetyl (= butane-2,3-dione), oxygen, and water dispenses with toxic reagents and intractable waste generation.     

多用途薄层光谱电化学池的设计和表征

设计并组装了一种简易薄层光谱电化学池.该池具有结构简单、操作方便、对工作电极无透光要求,且能适用于多种现场光谱电化学研究的特点.用该池记录了邻联甲苯胺高氯酸醋酸组成的氧化还原体系的荧光光谱电化学和紫外可见光谱电化学响应,并用吡啶氯化钾体系进行了喇曼光谱电化学表征.     

外电场作用下三元环状水分子团簇的特性研究

The influence of an external field on the ground states energy and dipole moment of the cyclic water trimer is investigated. Employing the Hartree-Fork method with basis sets 3-21G. The field-induced H-F force including the internal and external forces and clusters equilibrium structures under balance of this force are analyzed. The external field is varied in the 0.001~0.01 a.u. range. It is shown that the magnitude of the external electric field has important effects on these characteristics of the cyclic water trimer. The energy was found to decrease and the dipole moment to increase with the increasing external field. The change of the electronic population of every atom leads the electrostatic field to vary accordingly.     

Construction and Operation of Microbial Fuel Cell with Chlorella vulgaris Biocathode for Electricity Generation

In this study, a modified microbial fuel cell (MFC) with a tubular photobioreactor (PHB) configuration as a cathode compartment was constructed by introducing Chlorella vulgaris to the cathode chamber used to generate oxygen in situ. Two types of cathode materials and light/dark cycles were used to test the effect on MFC with algae biocathode. Results showed that the use of algae is an effective approach because these organisms can act as efficient in situ oxygenators, thereby facilitating the cathodic reaction. Dissolved oxygen and voltage output displayed a clear light positive response and were drastically enhanced compared with the abiotic cathode. In particular, carbon paper-coated Pt used as a cathode electrode increased voltage output at a higher extent than carbon felt used as an electrode. The maximum power density of 24.4 mW/m² was obtained from the MFC with algae biocathode which utilized the carbon paper-coated Pt as the cathode electrode under intermittent illumination. This density was 2.8 times higher than that of the abiotic cathode. Continuous illumination shortened the algal lifetime. These results demonstrated that intermittent illumination and cathode material-coated catalyst are beneficial to a more efficient and prolonged operation of MFC with C. vulgaris biocathode.