Structural Changes of Activated Carbon Electrodes for EDLCs in the Manufacturing Process

Supercapacitors,or electric double-layer capacitors(EDLCs),are the new generation of energy storage devices to store electrical charges and provide high power densities and long cyclic life compared to other storage devices.EDLC mainly consists of activated carbon electrodes and an electrolyte,and the performance of EDLC depends on the activated carbon electrodes.In this work,the structural changes of activated carbon electrodes are analyzed using commercial 2.7 V/9500 F EDLCs in its manufacturing process.It is found that there is no significant change in morphology and crystal structure of the activated carbon,but its specific surface area(SSA) reduced greatly.The SSA of activated carbon was decreased by 23% after they were manufactured or converted into electrodes and finally retained only 40% of SSA after the capacitance test.Besides,the SSA of the positive electrodes was found to decrease critically than that of the negative electrodes.The SSA of the external positive electrodes is only 14.3% after floating test at 65℃.     

Electroless Co-Zn Surface-Modified Nickel Hydroxide as an Active Matedrial for Pasted Nickel Electrodes

Chemically precipitated β-type nickel hydroxide powder was surface-modified by electroless deposition of Co-Zn coatings,and physical properties of both the modified and unmodified nickel hydroxide were characterized by scanning electron microscopy (SEM), specific surface area (BET), X-ray diffraction (XRD) and Xray photoelectron spectroscopy (XPS). It has been found that Co and Zn components of the surface electroless coatings exist in the oxidized state. Electrochemical performances of pasted nickel electrodes using the modified nickel hydroxide as an active material were investigated, and compared with those of the electrodes prepared with the unmodified nickel hydroxide. Charge/discharge tests show that the modified nickel hydroxide electrodes exhibit better performances in the charge efficiency, specific discharge capacity and active material utilization.Their resistance to swelling with cycling is also superior to that of the unmodified nickel hydroxide electrodes.Cyclic voltammetric (CV) studies indicate that the modified electrodes have a higher electrochemical activity,and the porous pasted nickel electrodes have some distinguished CV characteristics in comparison with those of the thin film nickel electrodes.     

IR study on surface chemical properties of catalytic grown carbon nanotubes and nanofibers

In this study, the surface chemical properties of carbon nanotubes （CNTs） and carbon nanofibers （CNFs） grown by catalytic decomposition of methane on nickel and cobalt based catalysts were studied by DRIFT （Diffuse Reflectance Infrared Fourier Transform） and transmission Infrared （IR） spectroscopy. The results show that the surface exists not only carbon-hydrogen groups, but also carboxyl, ketene or quinone （carbonyl） oxygen-containing groups. These functional groups were formed in the process of the material growth, which result in large amount of chemical defect sites on the walls.     

Application of corncob-based activated carbon as electrode material for electric double-layer capacitors

To investigate the influence of expansion pretreatment for materials on carbon structure, activated carbons (ACs) were prepared from corncob with/without expansion pretreatment by KOH activation, the structure properties of which were determined based on N 2 adsorption isotherm at 77 K. The results show that the expansion pretreatment for corncobs is beneficial to the preparation of ACs with high surface area. The specific surface area of the AC derived from corncob with expansion pretreatment (AC-1) is 32.5% larger than that without expansion pretreatment (AC-2). Furthermore, to probe the potential application of corncob-based ACs in electric double-layer capacitor (EDLC), the prepared ACs were used as electrode materials to assemble EDLC, and its electrochemical performance was investi- gated. The results indicate that the specific capacitance of AC-1 is 276 F/g at 50 mA/g, which increases by 27% com- pared with that of AC-2 (217 F/g). As electrode materials, AC-1 presents a better electrochemical performance than AC-2, including a higher voltage maintenance ratio and a lower leakage current.     

Preparation and Electrochemical Application of Praseodymium Modified TiO_2-NTs/SnO_2-Sb Anode by Cyclic Voltammetry Method

A Pr-doped TiO_2-NTs/SnO_2-Sb electrode was prepared by a simple method, cyclic voltammetry(CV). The methyl orange(MO)aqueous solution was selected as a simulated wastewater. The ordered microstructural TiO_2-NTs substrate was synthesized by an electrochemical method to obtain large specific surface area and high space utilization. The phase structure, electrode surface morphology and electrochemical properties of electrodes were characterized by XRD, SEM and electrochemical technology, respectively. The results showed that praseodymium oxide was successfully doped into the SnO_2-Sb film by CV method. Due to the doped Pr, the oxygen evolution potential increased from 2.25 V to 2.40 V. The degradation of MO was investigated by UV-vis. The C_t /C_0(φ)was studied as a function to obtain the optimal parameters, such as the amount of doped Pr, current density and initial dye concentration. In addition, the degradation process followed pseudo-first-order reaction kinetics and the rate constant was 0.0993 min~(-1). The result indicated that the introduction of Pr reduced the formation of oxygen vacancies or enhanced the formation of adsorbed hydroxyl radical groups on the surface, thus leading to better activity and stability.     

Effect of substrates and underlayer on CNT synthesis by plasma enhanced CVD

Due to their unique thermal, electronic and mechanical properties, carbon nanotubes （CNTs） have aroused various attentions of many researchers. Among all the techniques to fabricate CNTs, plasma enhanced chemical vapor deposition （PECVD） has been extensively developed as one growth technique to produce verticallyaligned car bon nanotubes （VACNTs）. Though CNTs show a trend to be integrated into nanoelectromechanical system （NEMS）, CNT growth still remains a mysterious technology. This paper attempts to reveal the effects of substrates and un derlayers to CNT synthesis. We tried five different substrates by substituting intrinsic Si with high resistivity ones and byincreasing the thickness of SiO2 insulativity layer. And also, we demonstrated an innovative way of adjusting CNT den sity by changing the thickness of Cu underlayer.     

Unperturbed dimensions of atactic poly（dibenzyl itaconate）s

The unperturbed dimension and temperature character of poly(dibenzyl itaconate)s (PDBzI) are studied by a revised rotational isomeric state (RIS) method. The improved formulas of the mean-square radius of gyration, deduced by the pseudo-stereochemical equilibrium approach, may be used to investigate the configurational-conformational properties of atactic polymers with large side groups [poly(itaconates) for instance]. The calculated results showed that poly(itaconates) have larger dimension of the molecule than other vinyl polymers. Comparison of the dimension between considering and without considering side groups showed that the effect of large side groups on the unperturbed dimension for short-chain polymers is more obvious than that of long-chain polymers and, if the dimension of side groups increases, the effect also increases. The dimension differences of PDBzI between short-chain and long-chain polymers are investigated by the relation of characteristic ratios and temperature coefficients with temperature. Moreover, the dependence between the temperature coefficients and the tacticity of chains shows that the temperature characters of the isotactic, syndiotactic and atactic PDBzI chains have remarkable difference.     

Molecular and crystal assembly inside the carbon nanotube： encapsulation and manufacturing approaches

Encapsulation of different guestspecies such as molecules and ions inside carbon nanotubes （CNTs） has been reported in the literatures during the last 15 years and repre sents an exciting development of nanoengineering of novel materials and composites. The reported nanocomposite mate rials show the semiconducting properties with potential applications in nanosensors, nanounits and nanocircuits as well as advanced energy transfer and storage properties, and encompass manufacturing for novel nanowires, nanoelectronic devices with properties designed with optoelectronic, spin tronic and nanomagnetic qualities. This review reports on a wide range of encapsulation references with particular focus on single molecules, atomic chains, metal halides and polymers encapsulated inside CNTs. The encapsulation methods and the chemical and physical qualities of these novel materials are crucial for the future manufacturing of novel innovations in nanotechnology, and represent therefore the current stateof theart of encapsulation methods in advanced manufacturing.     

Electrochemical behavior of insulin on pretreated carbon black electrode enhanced with silicon carbide nanostructure

We previously reported the direct electrochemical detection of insulin at bare carbon electrodes. Here a novel modified acetylene carbon black paste electrode(SiC/CB-CPE), based on the outstanding characteristics of silicon carbide nanostructure,was developed for the electrooxidation of insulin in alkaline solution and it was characterized by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) in 5 mmol/L Fe(CN)63-/4- solution. It is found that silicon carbide nanostructure doped into the CB-CPE greatly facilitates the redox electrochemistry of Fe(CN)63-/4- probe and the electrochemical oxidation of insulin. The electrooxidation of insulin is a one-electron and one-proton reaction and an irreversible adsorption-controlled electrode process. The anodic oxidation current increases linearly with the concentration of insulin from 1×10-7mol/L to1.2×10-6mol/L in 0.1 mol/L Na2CO3-NaHCO3 buffer solution(pH 10.0) and the detection limit was 50 nmol/L. In addition, the SiC/CB-CPE shows good sensitivity, reproducibility, renewability and capacity of resisting disturbance.     

Oxidation Characteristics of the Reactivity Between Pyrite and Aqueous Arsenate

Natural pyrites contain high levels of adsorbed and structurally incorporated arsenic(As),which may simultaneously result in the release of As and affect the oxidation process of pyrite.However,the oxidation and electrochemical behaviors of As on the oxidation reactivity of pyrites are still not clear.In this study,pyrite was prepared by a hydrothermal method and applied to study the oxidation mechanism between pyrite and aqueous arsenate.Analyses of X-ray diffraction,X-ray photoelectron spectroscopy,and scanning electron microscopy demonstrate that the as-prepared sample is an octahedron-like pyrite with high purity and crystallinity.The interaction between As(V)and pyrite as well as the electrochemical behaviors of pyrite oxidation in the presence of aqueous arsenate were investigated under acidic conditions by an ion analysis method,cyclic voltammetry(CV),Tafel,and electrochemical impedance spectroscopy(EIS).The results of the chemical reaction indicate that electrons are transferred from S _2~(2-)to dissolved oxygen with the formation of SO _4~(2-)in the initial As(V)concentration range of 0–0.3 mmol/L.In the initial As(V)concentration range of 0.4–1.2 mmol/L,electrons are transferred from S _2~(2-)to As(V)with the formation of elemental S ~(0 )and As(III).The CV,the Tafel plot and EIS analyses indicate that aqueous arsenate in an electrolyte promotes oxidation reactivity and passivation of the pyrite electrode.Moreover,the electron transfer rate increases with increasing aqueous arsenate concentration in the electrolyte.     

Electrochemical potential at the interface between carbon nanotubes and electrolyte

IntroductionaCarbonnanotube(CNT)isakindofcarbonallotrope,whichwasfoundin1991[1].Carbonnanotubes,particularlysingle-walledcarbonnanotubes(SWNTs),areprototypeone-dimensionalnano-materialfortheirlargeaspectratio.Theyexhibitgoodconductorandsemiconductorbehaviorsbaseontheirstructures[2].Sincetheirdiscovery,carbonnanotubeshaveattractedmuchattentionfortheirnovelstructureandmarvelousproperties.Scientistshavetakenalotofeffortstomakenano-circuitsandmolecularelectroniccomponentswithCNTs,includingfie…     

多壁碳纳米管修饰电极电化学传感器测定尿酸

基于羧基化多壁碳纳米管的催化作用,建立了一种测定体液中尿酸含量的新方法．通过扫描电子显微镜和电化学手段对传感器的表面形貌和性能进行了表征,并且优化了检测条件,研究了传感器对尿酸的响应．结果表明,多壁碳纳米管对尿酸的氧化有明显的催化作用．在最优实验条件下,尿酸在修饰电极表面的峰电流与其浓度在8．0×10^－7-8．0×10^－4 mol·L^－1内呈良好线性关系,检测限为5×10^－8 mol·L^－1,该传感器已经应用于实际样品中的测定,测定的回收率在94％-105％．     

碳纳米管粉末微电极对NO2-的催化还原

采用粉末微电极来研究修饰和未修饰的碳纳米管电极的电化学特性 ,结果显示经阳极极化的碳纳米管比未极化的碳纳米管具有明显的催化效果 .TEM和SEM显示阳极极化能有效切断碳纳米管成长度更短 ,管口更多的碎片 .同时其电化学表面积和吸附中继体Os(bpy) 2 + 3的量增加 ,从而导致其在酸性溶液中对NO- 2 具有较高的催化活性     

采用改进的湿化学方法提纯多壁碳纳米管

采用改进的湿化学方法提纯多壁碳纳米管。在强酸回流处理多壁碳纳米管之前，在30％双氧水中超声分散多壁碳纳米管。提纯后的碳纳米管的纯度较高，而且分散性较好，为其后期应用奠定了基础。     

碳纳米管负载单（双）核四硝基铁酞菁的制备和催化性能

制备出了碳纳米管负载单（双）核硝基铁酞菁,采用电化学手段研究了碳纳米管与金属酞菁的最佳配比,最佳热处理温度以及它们催化氧还原反应的动力学特征。结果表明：对于单核硝基铁酞菁而言,其与碳纳米管的最佳比例为2：3,而双核硝基铁酞菁与碳纳米管的最佳比例为1：4：样品的最佳热处理温度为500℃,催化剂催化氧还原反应的电极过程均受表面吸附所控制。     

碳纳米管／纳米TiO2复合膜电极与纳米TiO2电极电化学性能比较

本文采用TEM、循环伏安、阻抗-电位等方法,研究比较了碳纳米管／纳米TiO2复合膜（CNT／nano—TiO2）修饰电极与纯纳米TiO2（nano—TiO2）膜电极电化学性能的差异。大量细小的碳纳米管的存在,可起到阻碍TiO2纳米粒子的团聚作用,从而提高了CNT／nano-TiO2修饰电极的电化学性能。     

纳米碳粒的石墨碎片微结构及电化学性质

文章采用HRTEM（高分辨透射电镜）、XRD（X射线衍射）表征了三种不同纳米碳粒的石墨碎片微结构及其石墨化程度,并采用CV（循环伏安）、EIS（交流阻抗图谱）方法对由纳米碳粒制备的电极的电化学性质进行了研究。结果发现：随纳米碳粒石墨化度的减小,石墨碎片卷曲形态的清晰度增加,对应电极的电化学反应速率常数及电容值增大。作者认为：石墨碎片的卷曲和石墨化属于两种不同形式的碳原子有序化,二者均可对纳米碳粒的电化学性质产生影响。     

催化剂种类对PECVD制备碳纳米管的影响

采用PEVCD技术,分别用Fe、Ni、Co作为催化剂,在Si基底上沉积出了不同形貌的碳纳米管．并用扫描电镜对碳纳米管的形貌进行了表征．而且深入研究了不同催化剂种类对碳纳米管生长的影响机理．结果表明：Ni是这3种催化剂中最适合沉积碳纳米管的催化剂．     

氯霉素在羧基化单壁碳纳米管修饰电极上的电催化还原

利用扫描电镜（SEM）和交流阻抗谱法（EIS）对以滴涂法制备的羧基化单壁碳纳米管（SWCNTs-COOH）修饰玻碳电极进行纳米膜特性表征,并采用循环伏安法（CV）研究了氯霉素（CAP）在其上的电化学行为.结果表明,SWCNTs-COOH修饰的玻碳电极对CAP的还原有良好的电催化作用,根据实验结果推测为双质子双电子还原过程,CAP在修饰电极上的扩散系数及反应速率常数分别为8.76×10-4cm2/s及1.64×10-3s-1.在实验优化选定的测试条件下,还原峰（-0.602 V）电流与CAP的浓度在1.55×10-7-1.97×10-5mol/L范围内呈良好线性关系,检出限达2.02×10-8mol/L.相对标准偏差（n=10）为2.24%,可用于氯霉素的含量测定.     

氮在碳纳米管结构变化中的作用

利用等离子体增强热丝化学气相沉积制备了碳纳米管，并用扫描电子显微镜和透射电子显微镜对生长的碳纳米管进行了表征。发现用CH4和H2制备的是空芯碳纳米管，而在反应气体中加入NH3后，生长的碳纳米管是竹节型结构的碳纳米管，表明氮在碳纳米管的结构变化过程中起到了重要的作用。根据氮对碳在催化剂中的扩散影响，分析了氮在碳纳米管结构发生变化过程中的作用。