基于SnO2/Fe3O4粒子电极的三维电极体系的电催化性能

通过水热法合成复合金属氧化物SnO_2/Fe_3O_4粒子电极,然后采用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、磁滞回线等技术分别对粒子电极的晶体组分、形貌、元素组成和分子结构以及粒子电极的磁性特征进行表征。采用循环伏安法分析了三维电极系统的电化学性能,并进行了电催化氧化降解罗丹明B(RhB)的实验。结果表明,SnO_2/Fe_3O_4粒子电极负载稳定、导电性强、便于回收再利用,有利于电催化氧化降解反应。三维电极降解罗丹明B的析氧电流高于其他电极体系,电催化活性效果明显,90min内罗丹明B的降解率为100%、TOC去除率为83%,反应中产生的·OH是降解有机物的主要活性基。粒子电极在重复利用5次的情况下,对罗丹明B的降解率仍保持93%以上、TOC去除率保持在77%以上,具有稳定的电催化性能。     

碳纳米管空气阴极的制备及其光电催化性能

采用CVD法制备了碳纳米管(CNTs),并用X-射线衍射、TEM等方法进行了表征.进一步得到碳纳米管空气阴极,用于降解活性艳红X-3B、处理农药废水和检测羟自由基的应用研究,并与碳黑空气阴极做了对比试验.结果表明:碳纳米管空气阴极较碳黑空气阴极有更强的光电催化性能,碳纳米管是一种具有很大发展潜力和广阔应用前景的新材料.     

活性炭在三维电极法处理染料废水中的应用

采用活性炭作为自制三维电极反应器中的第三极，并用此电极反应器对甲基橙模拟染料废水的降解进行了实验研究。重点讨论了电压、电解质浓度以及溶液pH等因素对CODCr去除率和甲基橙去除率的影响。研究结果表明：活性炭作为第三极的三维电极反应器对甲基橙模拟染料废水进行降解，甲基橙浓度去除率到达90％，CODCR去除率达到80％。并由此展望了活性炭在三维电极处理染料废水的应用前景。     

钛基Co中间层SnO2电催化电极的制备及性能研究

为提高钛基二氧化锡电极的稳定性,设计并制备了含Co中间层的钛基二氧化锡电催化电极Ti/Co/SnO2,以苯酚为目标有机物,考察了所制备Ti/Co/SnO2电极电催化氧化降解苯酚的性能,并采用SEM、EDX以及XPS等检测方法分析了Ti/Co/SnO2电极表面的形貌、元素组成及元素化学态.研究结果表明,含有中间层的Ti/Co/SnO2电极其使用寿命较不含中间层的钛基二氧化锡电极Ti/SnO2大幅度提高,但其对苯酚的电催化降解活性有所下降,氧化还原电对Co2 /Co3 的存在是所制备Ti/Co/SnO2电极稳定性及电催化活性改变的主要原因.     

改性PbO2 电极电催化降解水中硝基苯酚

为研究PbO2电极的性能,在酸性溶液中,以电沉积法制备了改性钛基PbO2电极,优化并确定了电极的制备工艺,并利用SEM对电极的表面形貌进行了检测.以硝基苯酚为目标有机物,考察了电极的电催化氧化性能.采用铋掺杂PbO2电极处理水中邻硝基苯酚、间硝基苯酚和对硝基苯酚,并对不同硝基苯酚的矿化过程以及降解动力学进行了比较.研究表明:改性PbO2电极的电催化性能优于传统的PbO2电极;邻硝基苯酚在本研究条件下更易被降解.     

电催化氧化处理难降解废水用电极材料的研究进展

随着石油化工、医药等工业的迅速发展,工业废水中难降解物质与日俱增,采用传统的水处理方法已难以达到环保要求。电催化氧化技术主要利用电极表面产生的活性物质羟基自由基进行氧化降解,具有氧化能力强、无需添加化学药剂、无二次污染的优势,而且电催化氧化工艺操作简单、处理条件温和,在处理难降解废水方面具有诸多优势。电催化氧化技术的核心部件是阳极,因此阳极材料的开发一直是研究人员关注的重点。一般要求阳极材料具有析氧电位高、电催化活性高、耐腐蚀、稳定性好、价格低廉等特点。目前常用的阳极材料有钛基金属氧化物阳极(SnO_2电极和PbO_2电极)和合成掺硼金刚石薄层电极,但是这些材料存在使用寿命短、制作成本高等问题。通过改性制备复合金属氧化物阳极可以改善上述问题,常用的改性方法包括掺杂离子、引入中间层、掺杂纳米颗粒、调控电极材料的微观形貌等。改性可以提高电极电催化性能、导电性及稳定性,增大电极的反应面积,延长电极寿命。因此复合金属氧化物阳极的制备是阳极材料研究的重点。在二维电极的基础上引入粒子电极可以构成三维电极系统。在三维电极系统中,粒子电极在电场作用下,会极化形成一个个微型电解槽,极大地增加了反应面积。因而三维电极相比于二维电极具有面体比大、电催化效率更高、能耗更低的优势,因此高催化活性、高稳定性的粒子电极的研制成为了电催化氧化技术领域新的研究方向。目前,常用的粒子电极材料主要有碳材料(活性炭、炭气凝胶等)、金属氧化物(Al_2O_3、Fe_3O_4等)、陶瓷和矿物类等。本文从电催化氧化的机理以及三维电极的工作原理出发,综述了在电催化氧化处理废水中广泛应用的电极材料,包括钛基金属氧化物阳极、合成掺硼金刚石薄层电极,重点介绍了在三维电极系统中使用的粒子电极。并对今后废水处理中电催化氧化电极材料的研究趋势进行了展望,指出提高电催化氧化效率不仅需改进电极材料,还需改善反应器构型及与其他工艺的耦合等,以实现电催化氧化技术的推广应用。     

Ni/AC膜电极-铝合金储氢电池的研究

采用化学还原法制备了以椰壳活性炭(AC)为载体的Ni/AC电催化剂. 将Ni/AC电催化剂制作成膜电极, 与铝合金一起组成了一种全新概念的高效、安全、廉价的Ni/AC膜电极-铝合金储氢电池. 运用SEM和XRD 对Ni/AC电催化剂的形貌和结构进行了分析, 通过稳态极化曲线研究了Ni/AC膜电极在中性电解液中的电催化活性, 将Ni/AC膜电极与铝合金组装成的模拟电池进行了恒流放电实验以研究其产氢量和放电性能. 结果表明, 镍在活性炭上的负载量为50%时, 活性炭上沉积的镍颗粒最小; 采用镍负载量为50%的Ni/AC电催化剂的Ni/AC膜电极的电催化活性最高, 将其作为正极的储氢电池不仅放电性能好, 产氢量也大.     

Fe掺杂钛基SnO2/Sb电催化电极的制备及表征

为了改进钛基SnO2/Sb电极的电催化性能,采用高温热氧化法制备了Fe掺杂钛基SnO2/Sb 电极.采用SEM、EDX以及XRD等方法对所制备电极的表面形貌、元素组成及结构进行分析,并以苯酚为目标有机物,研究了所制备电极对有机污染物的电催化降解能力.结果表明,适量Fe的掺杂有利于晶粒细化和导电性的提高;但过量Fe的掺杂可能导致SnO2晶格的混乱程度增大,甚至使晶格破坏,从而使电极性能降低;掺杂0.5?的SnO2/Sb电极对苯酚的降解效果优于未掺杂Fe的电极;电解3 h后,苯酚去除率和化学需氧量(COD)去除率分别达到100.0%和92.0%.     

碳纳米管的氧化还原控制及其电化学检测多巴胺

利用湿化学法制备出化程度不同的多壁碳纳米管,并采用红外光谱仪、X-射线光电子能谱仪、透射电子显微镜分析样品因氧化程度不同而引起的表面特征差异。通过循环伏安法和示差脉冲伏安法研究多巴胺,尿酸和抗坏血酸在氧化程度不同的碳纳米管修饰玻碳电极上的电化学行为。其中,样品MWNCTs-R修饰的玻碳电极与其它样品相比,不仅展现出对多巴胺,尿酸和抗坏血酸更好的电催化性能,而且解决了氧化峰相互重叠的问题,可以用于在尿酸和抗坏血酸共存的条件下检测多巴胺。同时,传感器的响应电流随着多巴胺含量的增加而线性增大,线性范围为2~100μM。结果表明,不同氧化程度导致碳纳米管表面的组成和形貌不同,表面含有羧基,并保持完整石墨层结构的碳纳米管对多巴胺有更好的电催化响应。     

含Mn中间层钛基二氧化锡电催化电极的性能

采用高温热氧化方法制备了含Mn中间层的钛基二氧化锡电催化电极Ti/Mn/SnO2.采用SEM、EDX以及XPS等检测方法对电极表面涂层的形貌、元素组成及元素化学态进行了分析,研究了所制备Ti/Mn/SnO2电极电催化氧化降解苯酚的性能.结果表明,Mn中间层的引入降低了电极对苯酚的电催化降解活性,使电极的使用稳定性大为提高.含Mn中间层的存在,可防止电化学反应过程中析出的氧向基体的扩散,离子对Mn2 /Mn4 与Sn2 /Sn4 的存在改变了SnO2电极表面催化剂的组成和结构,导致电极性能变化.     

Basal plane pyrolytic graphite modified electrodes: comparison of carbon nanotubes and graphite powder as electrocatalysts

The oxidations of NADH, epinephrine, and norepinephrine are studied using carbon nanotube and graphite powder-modified basal plane pyrolytic graphite electrodes. Immobilization is achieved in two ways: first, via abrasive attachment of multiwall carbon nanotubes or graphite powder by gently rubbing the electrode surface on a fine quality paper supporting the desired material; second, via "film" modification from dispersing either graphite powder or nanotubes in acetonitrile and pipeting a small volume onto the electrode surface and allowing the solvent to volatilize. While electrocatalytic behavior of both types of nanotube-modified electrodes is shown, with enhanced currents and reduced peak-to-peak separations in the voltammetry in comparison with naked basal plane pyrolytic graphite, similar catalytic behavior is also seen at the graphite powder-modified electrodes. Caution is, therefore, suggested in assigning unique catalytic properties to carbon nanotubes.     

Electric field-oriented growth of carbon nanotubes and Y-branches in a needle-pulsed arc discharge unit: mechanism of the production

Carbon nano-onions, multiwall carbon nanotubes and Y-branched nanotubes are synthesised in a simple production apparatus. A pulsed plasma is generated by discharging a high voltage needle pulse between two graphite electrodes. A strong electric field is presented along anode and cathode electrodes. The pulse width is 0.3 μs. Acetone vapour, as a precursor, is introduced to the plasma through a graphite nozzle in the cathode assembly. A magnetic field, perpendicular to the plasma path, is provided. The possibility of carbon nanotube production through a short-pulsed arc discharge technique is investigated in this article. The results show that adding an electric field between electrodes prevents carbon ions’ dispersion, facilitates charge transferring between ions and electrodes, orients the growth of carbon nanotubes along the applied electric field and finally makes it possible to produce functionalised carbon nanoparticles such as Y-branch nanotubes and nanoknees. In this work, the growth mechanism of carbon nanotubes in a needle-pulsed arc-discharge reactor is discussed. And a possible explanation is provided for the synthesis of Y-branch carbon nanotubes. The products are examined by using scanning probe microscopy technique.     

Carbon nanotube purification: preparation and characterization of carbon nanotube paste electrodes

Paste electrodes have been constructed using single-wall carbon nanotubes mixed with mineral oil. The electrochemical behavior of such electrodes prepared with different percentages of carbon nanotubes has been compared with that of graphite paste electrodes and evaluated with respect to the electrochemistry of ferricyanide with cyclic voltammetry. Carbon nanotubes were purified by a treatment with concentrated nitric acid, then oxidized in air. In addition, electrochemical pretreatments were carried out to increase the selectivity of carbon nanotube electrodes. Performances of carbon nanotube paste and carbon paste electrodes were evaluated by studying such parameters as current peak, deltaEp, anodic and cathodic current ratio, and charge density toward several different electroactive molecules. Data interpretation based on the carbon nanotubes and carbon surface area is presented. Carbon nanotube paste and carbon paste electrodes were tested as H2O2 and NADH probes, and several analytical parameters were evaluated. The oxidative behavior of dopamine was examined at these electrodes. The two-electron oxidation of dopamine to dopaminequinone showed an excellent reversibility in cyclic voltammetry that was significantly better than that observed at carbon paste electrodes.     

Carbon Nanotubes Grown on the Surface of Cathode Deposit by Arc Discharge

Carbon nanotubes prepared by de arc discharge of graphite electrodes in He and CH₄ gas took markedly different morphology. Thick nanotubes embellished with many carbon nanoparticles were obtained by evaporation under high CH₄ gas pressure and high arc current. Thin and long carbon nanotubes were obtained under a CH₄ gas pressure of 50Torr and an arc current of 20A for the anode with a diameter of 6mm.     

Synthesis of Heterogenous Multi-Walled Carbon Nanotubes in a Carbon Arc in Water

Boron-doped multi-walled carbon nanotubes (MWCNTs) were generated by arc discharge in water by using B-doped graphite electrodes. The product morphology was studied by SEM and HRTEM microscopy. The electronic features were determinated by Raman and EELS spectroscopy. Optical emission spectroscopy (OES) was used to evaluate the temperature and C₂ content distributions in arc plasma.     

Electrochemical assessment of the interaction of microbial living cells and carbon nanomaterials

This work considers the effects of various carbon nanomaterials and fibres on bioelectrocatalytic and respiratory activity of bacterial cells during the oxidation of ethanol in the presence of an electron transport mediator. Gluconobacter oxydans sbsp. industrius VKM B‐1280 cells were immobilised on the surfaces of graphite electrodes and had an adsorption contact with a nanomaterial (multi‐walled carbon nanotubes, thermally expanded graphite, highly oriented pyrolytic graphite, graphene oxide, reduced graphene oxide). The electrochemical parameters of the electrodes (the polarisation curves, the value of generated current at the introduction of substrate, the impedance characteristics) were measured in two‐electrode configuration. Modification by multi‐walled carbon nanotubes led to the increase of microbial fuel cell (MFC) electric power by 26%. The charge transfer resistance of modified electrodes was 47% lower than unmodified ones. Thermally expanded and pyrolytic graphites had a slight negative effect on the electrochemical properties of modified electrodes. The respiratory activity of bacterial cells did not change in the presence of nanomaterials. The data can be used in the development of microbial biosensors and MFC electrodes based on Gluconobacter cells.Inspec keywords: nanofabrication, catalysis, microorganisms, adsorption, charge exchange, microbial fuel cells, electrochemical electrodes, graphite, graphene, oxidation, multi‐wall carbon nanotubes, cellular biophysicsOther keywords: reduced graphene oxide, electrochemical parameters, two‐electrode configuration, multiwalled carbon nanotubes, microbial fuel cell, respiratory activity, bacterial cells, microbial biosensors, MFC electrodes, microbial living cells, electron transport mediator, graphite electrodes, adsorption contact, highly oriented pyrolytic graphite, Gluconobacter oxydans sbsp. industrius VKM B‐1280 cells, polarisation curves, bioelectrocatalytic activity, ethanol, thermally expanded graphite, charge transfer resistance, C     

不同原料气催化热解法制备碳纳米管的研究

以CH4和C3H6为原料气，Ni-SiO2为催化剂，采用催化裂解法制备了碳纳米管。考察了两种原料气在单位催化剂上的产量与碳纳米管的转化率，并运用TEM、XRD和Raman对所获碳纳米管的形貌结构性能进行了分析。结果表明：以CH4为原料气时单位催化剂上的产率虽低而转化率却较高。说明当C1H6发生分解时，分解出来的碳只有少部分转化成了碳纳米管，而大部分为副产物；当CH4分解时，副反应较少，因此转化率较高：同时微观结构的分析也表明：采用CH4为原料气时，产物的形貌比较均一，其有序程度较高，碳纳米管的结构缺陷也较少。     

Carbon Nanotubes Grown on the Surface of Cathode Deposit by Arc Discharge

Abstract

Carbon nanotubes prepared by de arc discharge of graphite electrodes in He and CH₄ gas took markedly different morphology. Thick nanotubes embellished with many carbon nanoparticles were obtained by evaporation under high CH₄ gas pressure and high arc current. Thin and long carbon nanotubes were obtained under a CH₄ gas pressure of 50Torr and an arc current of 20A for the anode with a diameter of 6mm.     

Nickel-cobalt nanoparticles supported on single-walled carbon nanotubes and their catalytic hydrogenation activity

Single-walled carbon nanotubes were synthesized from graphite using the arc discharge technique. A nickel/yttrium/graphite mixture was used as the catalyst. After purification by sonication in a Triton X-100 solution, nickel-cobalt metal nanoparticles were deposited on the surface of the single-walled carbon nanotubes. The resulting material and/or the nanotubes themselves were characterized by physisorption, Raman spectroscopy, high-resolution transition electron microscopy and X-ray diffraction. Raman spectroscopy indicates that the nanotubes, prepared by the arc discharge technique, are semi-conducting with a diameter centering at 1.4 nm. The average nickel-cobalt particle size is estimated to be in the region of 8 nm. The catalytic activity of the material was examined for the hydrogenation of unsaturated fatty acid methyl esters obtained from avocado oil. The carbon nanotube supported nickel-cobalt particles effectively hydrogenate polyunsaturated methyl linoleate to monounsaturated methyl oleate. In contrast to a conventional nickel on kieselghur catalyst, further hydrogenation of methyl oleate to undesired methyl stearate was not observed.