Electrochemical properties of lanthanum nickel oxide

Electrochemical properties of lanthanum nickel oxide, LaNiO₂₈₄, were studied in alkaline solutions. It was concluded that redox reactions of Ni⁴⁺/Ni³⁺ and Ni³⁺/Ni²⁺ in a solid surface layer took place at 0.4 V and ?0.4 V (vs. Hg/HgO), respectively. As the conductivity of the oxide is a function of the oxygen concentration due to σ^* bond formation, the resistivity of the electrode was changed depending on polarization potentials. The catalytic activity for oxygen reduction of a preoxidized electrode seemed to be higher than that of an electrode not intentionally oxidized, and the activity depended on the concentration of the alkaline solution. It was presumed that Ni³⁺ cations which form the σ^* bond with oxygen have an important role in the electrocatalysis of oxygen reduction on lanthanum nickel oxide.     

Electrochemical capacitance of nickel oxide nanotubes synthesized in anodic aluminum oxide templates

Nickel oxide (NiO) nanotubes for supercapacitors were synthesized by chemically depositing nickel hydroxide in anodic aluminum oxide templates and thermally annealing at 360 °C. The synthesized nanotubes have been characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The capacitive behavior of the NiO nanotubes was investigated by cyclic voltammetry, galvanostatic charge–discharge experiment, and electrochemical impedance spectroscopy in 6 M KOH. The electrochemical data demonstrate that the NiO nanotubes display good capacitive behavior with a specific capacitance of 266 F g⁻¹ at a current density of 0.1 A g⁻¹ and excellent specific capacitance retention of ca. 93% after 1,000 continuous charge–discharge cycles, indicating that the NiO nanotubes can become promising electroactive materials for supercapacitor.     

Electrochemical capacitance performance of polyaniline/tin oxide nanorod array for supercapacitor

Journal of Solid State Electrochemistry - A binary nanocomposite of polyaniline/tin oxide nanorod array (PANI/SnO2 NRA) was developed as an electrode material for energy storage. SnO2 NRA supported...     

Electrochemical stability of polyaniline

The kinetics of the electrochemical degradation of polyaniline (PANI) films has been investigated in 0.5 M sulfuric acid solution at different electrode potentials ranging from 0.3 to 1.0 V vs. Ag/AgCl. Two kinds of PANI films were used, one doped with poly(styrene sulfonate) (PSS), and the other—with indigotetrasulfonate (ITS). Within a range of relatively low electrode potential (0.3-0.6 V), the degradation was found to proceed at a first-order rate constant of 4×10⁻⁵ to 5×10⁻⁵ s⁻¹, corresponding to degradation half-period of 4-5 h. A sharp increase in the degradation rate proceed by extending the electrode potential to higher values, with a maximum rate constant of ≈2.5×10⁻³ s⁻¹ for PANI-PSS, and ≈1.2×10⁻³ s⁻¹ for PANI-ITS films, obtained at a higher potential of 0.9-1.0 V. The data obtained are interpreted by different degradation rate for two distinct redox forms of PANI—emeraldine (slow degradation), and pernigraniline (fast degradation).     

Electrochemical and photocatalytic investigation of nickel oxide for energy storage and wastewater treatment

Nickel oxide (NiO) was synthesized via a one-step facile method. X-ray diffraction analysis confirmed the face-centered cubic structure of NiO. The bonding nature and surface purity were confirmed via Fourier-transform infrared spectroscopy. NiO revealed partial spherical morphology with less particle aggregation. The optical bandgap of NiO was found to be 3.75 eV. Cyclic voltammetry revealed well-defined oxidation and reduction peaks for NiO. The charge–discharge curve exhibited specific capacitance of 184.6 F/g at current density of 0.3 A/g. NiO electrode exhibited longer cyclic stability of 93 % up to 1500 cycles. In addition, NiO + H₂O₂ revealed efficient photocatalytic degradation of methylene blue (organic pollutant) under visible-light irradiation with degradation efficiency of ~88 %. These results confirm that nanosized NiO is more suitable for dual application.

     

Electrochemical synthesis of polyaniline nanoparticles

Polyaniline nanoparticles were prepared on a highly oriented pyrolytic graphite (HOPG) surface from dilute polyaniline acidic solution (1 mM aniline+1 M HClO₄) using a pulsed potentiostatic method. Electrochemistry, Fourier transform infrared external reflection spectroscopy (FT-IR-ERS), X-ray photoelectron spectroscopy (XPS) and tapping-mode atomic force microscopy (TMAFM) were used to characterize the composition and structure of the polyaniline nanoparticles. FT-IR-ERS and XPS results revealed that the polyaniline was in its emeraldine form. TMAFM measurement showed that the electropolymerized polyaniline nanoparticles dispersed on the HOPG surface with a coverage of about 10¹⁰ cm⁻². These nanoparticles were disk-shaped having a height of 10–30 Å and an apparent diameter varying from 200 to 600 Å. The particle dimensions increased with the electropolymerization charge (Q) over the interval from 5.7 to 19.3 μC cm⁻².     

Electrochemical property of graphene oxide/polyaniline composite prepared by in situ interfacial polymerization

Graphene oxide–polyaniline composites were synthesized by an interfacial method using two green solvents, water and an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate), as the two phases. The interfacial polymerization of aniline was carried out at room temperature in the presence of graphene oxide dispersed in the aqueous phase. The analysis revealed the surface of the graphene sheets to be coated with a smooth thin layer of polyaniline. The thermal stability of the composites was much better than that of bare graphene oxide. The composites were used to modify the glass carbon electrodes for the chemical detection of hydrogen peroxide in aqueous media. This method is a facile, efficient, and green route for the development of doped polyaniline materials suitable for chemical sensors.     

Electrochemical characterization of Ni–Fe alloy codeposition under MHD control

The nickel–iron alloy electrodeposition is affected by a superimposed magnetic field. Some previous papers [Msellak et al., Magnetohydrodynamics, 39:487–493, 2003 and Msellak et al., J Magn Magn Mat, 281:295–304, 2004] have exhibited some dramatic changes in iron amount and morphology of these deposits. As it is usual for a magnetic field up to 1 T, no charge transfer effect can be expected, and the observed modifications can be explained by the magnetohydrodynamic convection that controls the iron species flux during the electrochemical reaction. By electrochemical impedance spectroscopy and physical investigations (scanning electron microscopy, X-ray diffraction, and inductively coupled plasma), the reduction process is analyzed, the characteristic parameters of the mechanism are determined, and the magnetic field effects can be quantified. Contribution to special issue on “Magnetic field effects in Electrochemistry”.     

基于钨酸镍与氧化锌复合材料的电化学传感平台检测吲哚美辛EI北大核心CSCD

采用一锅法制备了钨酸镍与氧化锌复合材料(NiWO_(4)-ZnO),并对其进行了形貌表征、元素分析及比表面积测试,构筑了一种吲哚美辛电化学传感器。研究发现,NiWO_(4)-ZnO复合材料修饰玻碳电极对吲哚美辛表现出较高的检测灵敏度,在最优的实验条件下,吲哚美辛浓度与氧化峰电流成正比,在250~1082 pmol/L范围内呈现良好的线性关系,线性相关系数为0.9970,检出限为66.6 pmol/L。吲哚美辛电化学传感器应用于实际样品中吲哚美辛的测定,回收率为95.1%~98.3%,相对标准偏差为2.3%~3.8%,该传感器可用于药物分析领域。     

Electrochemical properties of rhodium- and gold-containing polyaniline films

Graphite-supported polyaniline films (PANI) containing rhodium particles were obtained by two procedures: metal electrodeposition on a prepared PANI film and electropolymerization. The adsorption/desorption and electrowinning of hydrogen on these films were observed for both types of synthesized composite films. PANI/Au composites were synthesized using the PANI films deposited onto a gold electrode. High anode potentials were further applied to the electrode in the presence of chloride ions, leading to a dissolution of gold and its transfer to the films during subsequent electroreduction. The amounts of the chloride complexes of gold formed in this procedure were determined by cyclic voltammetry of their electroreduction.     

Electrochemical deposition and characterization of polyppyrrole coatings doped with nickel cobalt oxide for environmental applications

Electrochemical depositions of hybrid polypyrrole/nickel cobalt oxide (PPy/NiCoO) coatings onto ferritic stainless steel surface were carried out with different electrochemical techniques from 0.1 M pyrrole (Py) in 0.2-M oxalic acid (OA) solution and less than 150-nanometer-sized NiCoO particles. The structural properties of the composite were investigated by using different methods such as transmission electron microscopy (TEM), scanning electron microscopy (SEM) with energy-dispersive X-ray spectrometer (EDS) and Raman spectroscopy. The embedded NiCoO particles, uniformly distributed onto the surface of the PPy film, have similar oxide ratios corresponding to a mixed oxide structure. The electrochemical characterization was done using polarization curves and linear sweep voltammetry (LSV) related to oxygen reduction reaction (ORR) in alkaline solution and hydrogen peroxide as an oxygen source. Concerning the exchange current densities for ORR, the obtained values (between 1.06 and 1.45?×?10^?3 mA cm^?2 for a total amount of NiCoO of 0.1 mg cm^?2) are comparable with other polymer films with Pt.     

多级树状纳米结构聚苯胺的电化学制备

建立一种无模板的恒电位电聚合方法,可在室温下制备对甲基苯磺酸（p-TSA）掺杂的多级树状纳米结构聚苯胺（PANI）.根据电聚合曲线分析了PANI的聚合机理.扫描电镜（SEM）、透射电镜（TEM）观察表明制备的PANI具有均匀的多级树状纳米结构.紫外可见吸收光谱（UV-Vis）和红外光谱（FTIR）则显示所制备的PANI为掺杂态.该电沉积方法具有简便、易操作的特点,还可应用于其他纳米结构导电聚合物的可控制备.     

Electrochemical fluorination using porous nickel and foam nickel anodes

This work set out to examine the reasons behind some of the problems associated with ECF, namely, lack of reproducibility, low chemical yields, poor selectivity and low current densities, with a view to ameliorating these shortcomings and making the process more attractive to the chemical industry.The approach was to study the chemistry under controlled conditions of potential, reactant concentration, temperature, etc., and to analyse the results in terms of product structure, distribution and yield.Two distinct stages in the process were identified, i) the conditioning of the electrode, and, ii) the fluorination of the organic substrate.These stages are described in detail in relation to two model systems investigated, the fluorination of propene using porous and foam nickel anodes, and the fluorination of the octanoyl chloride using nickel foam anodes. The scales of experiments ranged from 100ml to 100 1 cell capacities.General conclusions are derived and recommendations made for the more efficient operation of the process.     

Electrochemical behavior of polyaniline films in acetonitrile

The electro-oxidation and electroreduction behavior of polyaniline films in acetonitrile in the absence and presence of added acid or base were investigated using cyclic voltammetry. A general mechanism is proposed that enables the interpretation of the electroactivity loss and the catalytic and autocatalytic properties of the film. The electroactivity loss was found to be a reversible phenomenon which is accelerated in alkaline solutions through deprotonation. Electroactivity was recovered when the electroinactive films were reduced in an acidic solution. The films that lose their electroactivity on electro-oxidation were found to be conducting, and various cation radicals in the structure are believed to be responsible for this nonprotonic conductivity. The proton content of the polyaniline film was found to be crucial in determining its electrochemical and physical properties. Autocatalysis was detected when protons were produced electrolytically in situ during electropolymerization.     

Electrochemical doping of polyaniline with the tetracyanoquinodimethane anion

A new complex of aniline (An) with tetracyanoquinodimethane (TCQM) An(TCQM)₄ has been obtained and studied. The redox cycling of polyaniline (PAni-sulfo) in a neutral electrolyte containing Cl^– and ClO₄^? anions led to a replacement of the sulfate anion by the Cl^– and ClO₄^? anions. The TCQM anion can also replace the sulfate anions in polyaniline (PAni) during the cycling of the latter in a neutral electrolyte containing TCQM anions. The introduction of TCQM in PAni creates conditions for generating nanocrystalline regions inside the polymer.     

Electrochemical behavior of polyaniline synthesized by chemical oxidation

The slow voltammetry was taken on the paste electrode consisting of polyaniline powder and Teflon binder which was applied to pyrographite disc electrode. The potential cycle range was +0.6V→ ? 0.2V→+0.8V→+0.6V vs. SCE. It was found that the voltammetry curves are similar for both polyanilines obtained chemically and electrochemically. The difference of the voltammetry curves in various acids might be attributed to some exchange of doping anions in polyaniline. The first redox couple peaks shifted to positive potential direction with increase of pH and it might be associated with the proton addition-elimination reaction. It was shown that polyaniline prepared from very dilute or concentrated acid solution was electrochemically inactive.     

Graphene oxide doped polyaniline for supercapacitors

A novel high-performance electrode material based on fibrillar polyaniline (PANI) doped with graphene oxide sheets was synthesized via in situ polymerization of monomer in the presence of graphene oxide, with a high conductivity of 10 S cm^?1 at 22 °C for the obtained nanocomposite with a mass ratio of aniline/graphite oxide, 100:1. Its high specific capacitance of 531 F/g was obtained in the potential range from 0 to 0.45 V at 200 mA/g by charge–discharge analysis compared to 216 F/g of individual PANI. The doping and the ratio of graphene oxide have a pronounced effect on the electrochemical capacitance performance of the nanocomposites.     

Electrochemical and Raman spectroscopic study of polyaniline; influence of the potential on the degradation of polyaniline

The polymerization of aniline has been studied employing in-situ electrochemical and Raman spectroscopical techniques. Aniline was polymerized by cyclic voltammetry on a Pt surface in sulfuric acid solutions of aniline. The Raman bands were assigned for degradation products of the overoxidized form of polyaniline. A discussion of the degradation mechanism is given. Received: 12 November 1997 / Accepted: 20 January 1998