Preparation of dendritic bismuth film electrodes and their application for detection of trace Pb(Ⅱ)and Cd(Ⅱ)

In this paper,dendritic Bi film electrodes with porous structure had successfully been prepared on glassy carbon electrode using a constant current electrolysis method based on hydrogen bubble dynamic templates.The electrode prepared using a large applied current density showed an increased internal electroactive area and a significantly improved electrochemical performance.The analytical utility of the prepared dendritic Bi film electrodes for the determination of Pb(Ⅱ)and Cd(Ⅱ)in the range of 5–50 μg·L~(-1)were presented in combination with square wave stripping voltammetry in model solution.Compared with non-porous Bi film electrode,the dendritic Bi film electrode exhibited higher sensitivity and lower detection limit.The prepared Bi film electrode with dendritic structure was also successfully applied to real water sample analysis.     

Carbon-coated lithium titanate: effect of carbon precursor addition processes on the electrochemical performance

In this paper,two carbon-coated lithium titanate(LTO-C1 and LTO-C2)composites were synthesized using the ball-milling-assisted calcination method with different carbon precursor addition processes.The physical and electrochemical properties of the as-synthesized negative electrode materials were characterized to investigate the effects of two carbon-coated LTO synthesis processes on the electrochemical performance of LTO.The results show that the LTO-C2 synthesized by using Li2CO3 and TiO2 as the raw materials and sucrose as the carbon source in a one-pot method has less polarization during lithium insertion and extraction,minimal charge transfer impedance value and the best electrochemical performance among all samples.At the current density of 300 mA·h·g^-1,the LTO-C2 composite delivers a charge capacity of 126.9 mA·h·g^-1,and the reversible capacity after 300 cycles exceeds 121.3 mA·h·g^-1 in the voltage range of 1.0–3.0 V.Furthermore,the electrochemical impedance spectra show that LTO-C2 has higher electronic conductivity and lithium diffusion coefficient,which indicates the advantages in electrode kinetics over LTO and LTO-C1.The results clarify the best electrochemical properties of the carbon-coated LTO-C2 composite prepared by the one-pot method.     

电化学还原硝基甲烷合成N-甲基羟胺盐酸盐的工业化试验

An industrial electrolytic cell was designed for the electrochemical synthesis of N-methylhydroxylamine hydrochloride （N-MHA）. Copper was used as the cathode, graphite as the anode, and a cation membrane as the separator. The results show that N-MHA with a high purity of 99% can be electrosynthesized directly from nitromethane in HC1 solution. Under a constant current of 1000-2500A.m^-2 in the temperature of 30-50℃, the average yield, current efficiency, and reaction selectivity were 65%, 70%, and 99%, respectively. Graphite electrode and membrane material can be used continuously in the preparative electrolysis for 5000h. Moreover, the effects of the electrode and membrane materials, current intensity, electrolyte temperature, and other associated parameters on the electrosynthesis results were investigated. The direct current power consumption was 8151.3kW-h-（1000kg N-MHA）^ -1. This method is a simple separation process with limited contamination and hence, is a new green synthesis method for the industrial production of N-MHA.     

PTFE-F-PbO2 电极在H2SO4溶液中的析氧行为

F-PbO2 electrode and polytetrafluoroethylene （PTFE） doped F-PbO2 electrode （PTFE-F-PbO2） were prepared on a plexiglas sheet substrate by a series of procedure including chemical and electrochemical depositions. The electrochemical activities of these two electrodes for oxygen evolution （OE） reaction were examined by electrochemical tests. In comparison with F-PbO2, PTFE-F-PbO2 electrode exhibited larger active surface area and higher oxygen vacancy deficiency, which resulted in its higher electrocatalytic activity for OE. In addition, both exchange current density and activation energy of the electrodes for OE were calculated in terms of active surface area. The values of exchange current density and activation energy in 0.5 mol·L^-1 H2SO4 aqueous solution were 1.125×10^ -3 mA·cm^-2 and 18.62 kJ·mol^-1 for PTFE-F-PbO2, and 8.384×10^-4 mA·cm^- 2 and 28.98 kJ·mol^-1 for F-PbO2, respectively. Because these values are calculated on the basis of the active surface areas of the electrodes, the enhanced activity of PTFE-F-PbO2 can be attributed to an increase in oxygen vacancy deficiency of PbO2 due to doping by PTFE. The influence of PTFE adulteration on the activity of PbO2 film electrode for OE was investigated in detail in this study.     

CoO AS ADDITIVE IN POSITIVE ELECTRODE OF NICKEL-METAL HYDRIDE BATTERY

A series of positive electrodes for Ni/MH battery were fabricated by addition of CoO.The morphology and microstructure of the electrodes were examined by SEM and EDS, and electrochemical behavior was investigated in three-compartment appliances at room temperature.The electrochemical performance of the positive electrodes with CoO was improved. Under the same charge-discharge cycle, the electrodes with CoO showed higher specific capacity, lower charge mean voltage and higher discharge mean voltage. But further increasing the content of CoO in the electrodes contributed negative effect on the overall performance. Addition of 8% (mass) CoO was suggested to be a suitable content for the positive electrode.     

Electrochemical analysis and convection-enhanced mass transfer synergistic effect of MnOx/Ti membrane electrode for alcohol oxidation

The different electrocatalytic reactors could be constructed for the electrocatalytic oxidation of 2,2,3,3-tetrafluoro-1-propanol(TFP) with two typical MnO_x/Ti electrodes, i.e.the electrocatalytic membrane reactor(ECMR) with the Ti membrane electrode and the electrocatalytic reactor(ECR) with the traditional Ti plate electrode.For the electro-oxidation of TFP, the conversion with membrane electrode(70.1%) in the ECMR was 3.3 and 1.7 times higher than that of the membrane electrode without permeate flow(40.8%) in the ECMR and the plate electrode(21.5%) in the ECR, respectively.Obviously, the pore structure of membrane and convection-enhanced mass transfer in the ECMR dramatically improved the catalytic activity towards the electro-oxidation of TFP.The specific surface area of porous electrode was 2.22 m~2·g~(-1).The surface area of plate electrode was 2.26 cm~2(1.13 cm~2× 2).In addition, the electrochemical results showed that the mass diffusion coefficient of the MnO_x/Ti membrane electrode(1.80 × 10~(-6) cm~2·s~(-1)) could be increased to 6.87 × 10~(-6) cm~2·s~(-1) at the certain flow rate with pump, confirming the lower resistance of mass transfer due to the convection-enhanced mass transfer during the operation of the ECMR.Hence, the porous structure and convection-enhanced mass transfer would improve the electrochemical property of the membrane electrode and the catalytic performance of the ECMR,which could give guideline for the design and application of the porous electrode and electrochemical reactor.     

Rapid regeneration of chelated iron desulfurization solution using electrochemical reactor with rotating cylindrical electrodes简

A new electrochemical reactor with rotating cylindrical electrodes was designed and used to increase the regeneration efficiency of chelated iron desulfurization solution. The influence of operating parameters, such as the rotation speed of electrode, voltage, and inlet air and liquid flow rates, on the regeneration rate was investigated. Compared with the traditional tank-type reactor, the regeneration rate with the new electrochemical reactor was in- creased significantly. Under the optimum conditions, the regeneration rate was increased from 45.3% to 84.8%. Experimental results of continuous operation indicated that the new electrochemical regeneration method had some merits including higher regeneration efficiency, smaller equipment size and good stability in operation.     

直接和间接电合成制备出的高铁酸钾的物理和电化学性能

K2FeO4 powders were synthesized by the ex-situ and in-situ electrochemical methods, respectively, and characterized by infrared spectrum （IR）, scanning electron microscopy （SEM）, X-ray powder diffraction （XRD） and BET. Their electrochemical performances were investigated by means of galvanostatic discharge and electrochemical impedance spectroscopy （EIS）. The results of physical characterization showed that the two samples have simi- lar structural features, but their surface morphologies and oriented growth of the crystals are different, which results in smaller specific surface area and lower solubility of the ex-situ electrosynthesized K2FeO4 sample. The results of discharge experiments indicated that the ex-situ electrosythesized K2FeO4 electrode has much larger discharge capacity and lower electrode polarization than the in-situ electrosynthesized K2FeO4 electrode. It was found from the results of EIS that lower electrochemical polarization might be responsible for the improvement on the discharge performance of the ex-situ electrosynthesized K2FeO4 electrode.     

水热合成二硫化钼纳米片及在锂离子电池中的应用(英文)

Molybdenum disulfide nanoflakes were synthesized by a simple hydrothermal process using sodium molybdate and thiourea as reactants at a relatively low temperature. X-ray diffraction(XRD) and transmission elec-tron microscopy(TEM) indicate that the samples have the structure of 2H-MoS2 and the morphology of nanoflakes with the average thickness around 5-10 nm. The results of electrochemical properties indicate that the morphology and size of MoS2 particles have effects on their capacity when they are used as the anode for lithium ion battery. The as-prepared MoS2 samples have high reversible discharge capacity up to 994.6 mA·h·g-1 for the MoS2-1 elec-trode and 930.1 mA·h·g-1 for the MoS2-2 electrode and show excellent cycling performances. The MoS2-1 electrode has a better cycling stability than the MoS2-2 electrode due to their difference in the uniformity of the samples.     

Diamond-derived microelectrodes array for electrochemical analysis

Two types of diamond electrodes were fabricated and characterized for electrochemical analysis; diamond ultramicroelectrode arrays (D-UMEAs) and nano-diamond-coated microprobes. Array parameters such as electrode geometry, electrode–electrode spacing, and array size are established through design and fabrication, and their relation to electrochemical analysis is evaluated. The superior detection figures of merit for diamond, particularly the limits of detection and sensitivity, have been achieved by shrinking electrode geometries with microfabrication techniques. The D-UMEAs were shown to display ultramicroelectrode (UME) behavior when individual active electrode was placed at a sufficient distance from each other. The D-UMEAs were also found to display higher current density for detection of analyte in comparison with a conventional diamond planar macroelectrode. Diamond ultramicroelectrodes in array configurations have potential applications in electrochemical analysis including the study of fast electron transfer reactions, electrocatalysis, and as a sensor in flow systems. The boron-doped nano-diamond-coated microprobe was fabricated with plasma-enhanced chemical vapor deposition (PECVD). The nano-diamond-coated microprobe showed good sensitivity to analytes with reversible electron transfer and a large potential window.     

Effect of electronic structures on electrochemical behaviors of surface-terminated boron-doped diamond film electrodes

In order to analyze the electrochemical behaviors of hydrogen-terminated and oxygen-terminated boron-doped diamond film electrodes, experiments of the cyclic voltammetry and AC impedance spectroscopy have been performed. For the purpose of clarifying the detailed electronic structures of these diamond films, current–voltage spectroscopy curves and XPS spectra have been investigated by scanning probe microscopy and X-ray photoelectron spectroscopy, respectively. For the hydrogen-terminated boron-doped diamond film electrode, its potential window is narrower than that of the oxygen-terminated boron-doped diamond. The impedance results indicate that the diamond film resistances and capacitances corresponding to different surface-terminated boron-doped diamond electrodes vary significantly. The surface band gap of hydrogen-terminated diamond film is narrow with empty surface states in it. In contrast, the surface band gap of oxygen-terminated diamond film is wide and clean. Compared with hydrogen-terminated diamond film, the surface energy bands of oxygen-terminated diamond film bend downwards. Based on their electronic structures, the electrochemical behaviors of the two boron-doped diamond film electrodes have been discussed.     

New directions in structuring and electrochemical applications of boron-doped diamond thin films

Conductive boron-doped diamond electrodes have been shown to be highly suitable as electrochemical detectors in flow injection analysis and high performance liquid chromatographic analysis, achieving high sensitivity and stability for certain species that cannot be detected at other electrodes due to electrode deactivation or high electrochemical oxidation potential. The use of this electrode material for the detection of chlorophenols and theophylline is demonstrated. Apart from the electrochemistry of diamond, various methods have been developed to fabricate well-aligned nanocylindrical diamond films and periodic bulb-like structures, which may be useful for sensors and electronic devices such as field emission displays.     

The underlying electrode causes the reported ‘electro-catalysis’ observed at C60-modified glassy carbon electrodes in the case of N-(4-hydroxyphenyl)ethanamide and salbutamol

The reported ‘electro-catalysis’ of C₆₀-film-modified electrodes for the electrochemical oxidation of N-(4-hydroxyphenyl)ethanamide and salbutamol has been explored at boron-doped diamond and glassy carbon electrodes. Using both C₆₀-film-modified boron-doped diamond and glassy carbon as underlying electrode substrates no electro-catalytic response is observed using the target analytes but rather the C₆₀ serves to block the electrode surface.A common experimental protocol used by researchers in this field is to electrochemically pre-treat the C₆₀-film-modified electrode. The response of employing this electrochemical pre-treatment at both bare glassy carbon and boron-doped diamond electrodes using the target analytes reveals that no effect on the electrochemical responses obtained at the boron-doped diamond electrode whereas a slight but significant effect occurs on glassy carbon which is attributed to the likely introduction of surface oxygenated species.Consequently the previously reported ‘electro-catalysis’ using C₆₀-film-modified electrode is not due to C₆₀ itself being catalytic, but rather that substrate activation through electrode pre-treatment is responsible for the observed ‘electro-catalysis’ likely through the introduction of surface oxygenated species.This work clearly shows that substrate activation is an important parameter which researchers studying C₆₀-film-modified electrodes, especially in electro-analysis needs to be considered.     

Recent advances in electrochemistry of diamond

Conductive boron-doped chemically vapour-deposited diamond thin film and honeycomb electrodes were examined for various possible applications in electroanalysis and electric double layer capacitor applications, respectively. The possibility of voltammetric study of electrochemical reactions occurring at high oxidation and high reduction potentials was demonstrated at diamond electrodes, taking histamine and carbon tetrachloride as respective examples. High sensitivity and high stability of this electrode were demonstrated for the determination of histamine and sulfadiazine by flow injection analysis method. Nanostructured honeycomb diamond electrodes, prepared by oxygen plasma etching, exhibited a wide potential window similar to that of as-grown film but a capacitance 200 times higher than that of the as-grown film. These results indicate the usefulness of diamond electrode for electroanalysis and double layer capacitor applications.     

Electrochemical studies of ganciclovir at boron-doped nanocrystalline diamond electrodes

The electrochemical oxidation of ganciclovir was investigated at boron-doped nanocrystalline diamond (BDND) electrodes by the use of cyclic voltammetry and differential pulse voltammetry. The optimization of the experimental variables including supporting electrolyte and pH value was studied, and the 0.04-M Britton-Robinson buffer solution (pH 2.5) was selected. The relationship of the oxidation peak potential to scan rate and pH value was also investigated, and 2 electron transfer and 2 proton participation for the oxidation process of ganciclovir at BDND electrode were obtained. Compared with boron-doped microcrystalline diamond and glassy carbon electrodes, the BDND electrode demonstrated the wider linear range of 0.5-350 μM, lower limit of detection of 0.2 μM, and higher reproducibility and stability for the determination of ganciclovir under the optimum conditions. For the analysis of ganciclovir in human serum at the BDND electrodes, precision and accuracy were checked by recovery experiments.     

掺硼金刚石薄膜电极电催化降解染料废水的研究

通过测试新型掺硼金刚石薄膜电极的电化学性质,发现掺硼金刚石薄膜电极具有较高的析氢析氧过电位,有效地抑制了析氧副反应,具有较高的催化氧化效率。在研究活性艳红模拟染料废水在该电极上的催化降解过程中,考察了不同工艺条件:活性炭投加、电解质、电流密度、pH值和染料废水的初始浓度对染料降解脱除的影响。实验结果表明:在酸性介质中,投加一定量的活性炭和2gL-1硫酸钠电解质,选用电流密度为0.08Acm-2,来处理高浓度染料废水色度去除率可达到99%。由染料废水处理前后的紫外可见光谱表明电解不仅破坏了染料分子中的偶氮共轭发色基团,达到去色的目的,还可以断裂其他难降解小分子基团。     

Kinetic modelling of the electrochemical mineralization of organic pollutants for wastewater treatment

The electrochemical mineralization of organic pollutants is a new technology for treatment of dilute wastewater (COD < 5 g L⁻¹). In this method, use of the electrical energy can produce complete oxidation of pollutants on high oxidation power anodes. An ideal anode for this type of treatment is a boron-doped diamond electrode (BDD) characterized by a high reactivity towards oxidation of organics. In the present work kinetic aspects of organic mineralization is discussed. The proposed theoretical kinetic model on boron-doped diamond anodes is in excellent agreement with experimental results. In addition economic aspects of electrochemical organic mineralization are reported.     

金微粒修饰的电极对细胞色素C的直接电化学响应

采用循环伏安法制备了金微粒修饰的金刚石膜电极。用循环伏安法、电化学交流阻抗法对得到的修饰电极进行了表征。同时考查了细胞色素C在修饰电极上的电化学行为,发现细胞色素C在修饰电极上有显著的直接电化学响应,其氧化还原峰电流与扫描速度呈良好的线性关系,表明细胞色素C在修饰电极上呈现吸附控制的电极反应过程。     

Anodic behaviour of fulvestrant and its voltammetric determination in pharmaceuticals and human serum on highly boron-doped diamond electrode using differential pulse adsorptive stripping voltammetry

The electrochemical oxidation of fulvestrant was made on highly boron-doped diamond electrode using differential pulse adsorptive stripping voltammetry. The highest current intensities were obtained by applying +1.10 V during 150 s for boron-doped diamond electrode. For boron-doped diamond electrode, linear responses were obtained for the concentrations between 1 × 10⁻⁶ and 8 × 10⁻⁵ M in standard samples and between 1 × 10⁻⁶ and 4 × 10⁻⁵ M in serum samples. The repeatability of the method was 0.55 RSD% for differential pulse adsorptive stripping voltammetry. The analytical values of the method are demonstrated by quantitative determination of fulvestrant in pharmaceutical formulations and human serum, without the need for separation or complex sample preparation, since there was no interference from the excipients and endogenous substances. Selectivity, reproducibility, and accuracy of the developed methods were demonstrated by recovery studies.