APPLICATIONS AND MANUFACTURE OF THE MICROSCALE LONG-OPTICAL-PATH ELECTROCHEMICAL CELL WITH A PLUG-IN THIN-LAYER ELECTRODE

The construction and characteristics of a microscale long-optical-path electrochemi- cal cell with a plug-in thin-layer electrode are described.Using ferricyanide as the test species,the thermodynamic parameters of electron transfer processes are determined at car- bon,plantinum,and gold electrodes.

Influence of TiO_2 on the electrochemical performance of pasted typeβ-nickel hydroxide electrode in alkaline electrolyte

Nickel hydroxide was used as the positive electrode material in rechargeable alkaline batteries, which plays a significant role in the field of electric energy storage devices. β-nickel hydroxide（β-Ni（OH）2 ） was prepared from nickel sulphate solution using potassium hydroxide as a precipitating agent. Pure β-phase of nickel hydroxide was confirmed from XRD and FT-IR studies. The effects of TiO2 additive on the β-Ni（OH）2 electrode performance are examined. The structure and property of the TiO2 added β-Ni（OH）2 were characterized by XRD, TG-DTA and SEM analysis. A pasted–type electrode is prepared using nickel hydroxide powder as the main active material on a nickel sheet as a current collector. Cyclic voltammetry and electrochemical impedance spectroscopy studies were performed to evaluate the electrochemical performance of the β-Ni（OH）2 and TiO2 added β-Ni（OH）2 electrodes in 6 M KOH electrolyte. Anodic（Epa） and cathodic（Epc）peak potentials are found to decrease after the addition of TiO 2 into β-Ni（OH）2 electrode material. Further,addition of TiO2 is found to enhance the reversibility of the electrode reaction and also increase the separation of the oxidation current peak of the active material from the oxygen evolution current. Compared with pure β-Ni（OH）2 lectrode,TiO2 added β-Ni（OH）2 electrode is found to exhibit higher proton diffusion coefficient（D） and lower charge transfer resistance. These findings suggest that the TiO2 added β-Ni（OH）2 electrode possess improved electrochemical properties and thus can be recognized as a promising candidate for the battery electrode applications.

DIRECT ELECTROCHEMICAL BEHAVIOUR OF CYTOCHROME C AT A BARE GLASSY CARBON ELECTRODE

A reversible electron transfer between horse heart cytochrome c and a bare glassy carbon electrode was found and the dependence of direct electrochemical behaviotw on the electrode surface state was discussed.

First-principles calculations and experimental studies of Sn-Zn alloys as negative electrode materials for lithium-ion batteries

The physical characters and electrochemical properties of various phases in a Sn-Zn electrode, such as formation energy, plateau potential, specific capacity, as well as volume expansion, were calculated by the first-principles plane-wave pseudo-potential method based on the den- sity functional theory. Sn-Zn films were also deposited on copper foils by an electroless plating technique. The actual composition and chemical characters were explored by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, plasma atomic emission spectrometry （ICP）, and constant current charge/discharge measurements （CC）. The results show that separation phases with tin and zinc including a small quantity of Cu6Sn5 phase were obtained, the initial lithium insertion capacity of the Sn-Zn film was 661 mAh/g, and obvious potential pla- teaus of about 0.4 V and 0.7 V were displayed, which is in accordance with the results of theoretical calculations. The capacity of the Sn-Zn film decreased seriously with the increase of cycle number.

RE-Ni Based Alloys Used in Ni Hydride Batteries

The characteristics of LaNi5 and RE-Ni base alloys were systematically reviewed. The hydrogen-storage electrode materials made of RE-Ni base alloys, the operating characteristics of hydrogen-storage electrodes and the operating principle of Ni-hydride batteries were described in detail. Besides, the methods for preparing RE-Ni base alloys were outlined.

Electrochemical behavior and analytical detection of Imidacloprid insecticide on a BDD electrode using square-wave voltammetric method

A sensitive square-wave voltammetric method for the determination of lmidacloprid （IMD） was developed using electrochemically pretreated boron-doped diamond （BDD） electrode. Aqueous solutions were prepared with Confidor 200 SL as the commercial formulation of IMD. Sodium sulfate （Na2SO4） was used as supporting electrolyte. The influence of operating parameters, such as the pH of the medium, frequency, pulse amplitude, scan increment and the concentration of IMD was investigated. An irreversible cathodic peak, corresponding to the reduction oflMD is observed at 1.21 V （vs. SCE） and the electrode reaction was controlled by adsorption. Under optimized conditions, the square-wave reduction peak current was linear over the concentration range of （30-200 μmol L 1） with a detection and quantification limits of 8.60 μmol L 1 and 28.67 μmol L 1, respectively. The results were compared with spectrophotometry and HPLC methods under some conditions and found to be in good agreement. To investigate applicability to real samples, the proposed method was applied to the determination of IMD in plum juice.

Graphene oxide/multi-walled carbon nanotubes/gold nanoparticle hybridfunctionalized disposable screen-printed carbon electrode to determine Cd(II)and Pb(II)in soil

Cadmium(Cd)and lead(Pb)in soil or water environment cause the ecological destruction and environmental deterioration when their contents exceed the natural background values.To trace the concentrations of Cd(II)and Pb(II),a sensitive and selective electrode was developed using disposable screen-printed carbon electrode(SPE)immobilized with a composite film of reduced graphene oxide/carboxylation multi-walled carbon nanotubes/gold nanoparticle hybrid(RGO-MWNT-AuNP)throughπ-πbind.This highly conductive nano-composite layer,“RGO-MWNT-AuNP,”was characterized by scanning electron microscopy,UV-visible spectrometer,cyclic voltammetry,and electrochemical impedance spectroscopy.Square wave stripping voltammetry was applied to RGO-MWNT-AuNP/SPE to electroplate bismuth film and monitor the Cd(II)and Pb(II)simultaneously.To obtain high current responses,the detecting parameters were optimized.Under optimized conditions,the current responses showed a linear relationship with the concentrations of Cd(II)and Pb(II)in the range from 1.0 to 80.0μg/L with a lower detection limit of 0.7μg/L and 0.3μg/L(S/N=3),respectively.Finally,the prepared electrode was further employed to detect Cd(II)and Pb(II)in soil samples with good results.

Electroanalytical method for determination of shikonin based on the enhancement effect of cyclodextrin functionalized carbon nanotubes

A simple and sensitive electroanalytical method for determination of shikonin, a widely used antitumoral agent, using β-cyclodextrin-functionalized multiwalled carbon nanotubes composite modified glassy carbon electrodes （MWCNTs/β-CD/GCE） was presented. CDs are water-soluble and environmentally friendly and can improve the dispersibility of MWCNTs/βCD functional materials, which was confirmed by SEM. The electrochemical behaviors of shikonin on different electrodes were investigated by cyclic voltammetry （CV） and differential pulse voltammograms （DPVs）. The results demonstrated that the redox peak currents of shikonin obtained at MWCNTs/fl-CD/GCE were much higher than those at the βCD/GCE and MWCNTs/GCE, which can be attributed to the combination of the excellent electrocatalytic properties of MWCNTs and the molecular recognition ability of βCD. At MWCNTs/ βCD/GCE, the response current exhibits a linear range from 5.0 nmol/L to 10.0 μmol/L with a detection limit of 1.0nmol/L （S/N=3）. As a practical application, the proposed method was applied to quantitatively determine shikoninin urine samples with satisfying results.

A nanosilica/exfoliated graphene composite film-modified electrode for sensitive detection of methyl parathion

Graphene nanosheets （GS） were easily prepared through liquid-phase exfoliation of graphite powder in N,N-dimethylformamide （DMF） with the assistance of sodium citrate. Then, GS was coated onto a glassy carbon electrode （GCE） surface by drop to fabricate a GS]GCE nanointerface. Subsequently, by using tetraethylorthosilicate sol as precursor, nanosilica was electrochemically deposited onto the GS]GCE surface to produce a nanocomposite film electrode （nanosilicaJGSJGCE）. Electrochemical behaviors of methyl parathion （MP） on the nanosilica/GS/GCE surface were investigated thoroughly. It was found that the nanosilicaJGS nanocomposites can improve the redox peak currents of MP significantly due to the synergetic effect. The oxidation peak current was linearly related to MP concentration in the range from 0.0005 μmol/L to 5.6 μmol/L. The detection limit was calculated to be 0.07 nmol/L （SJN = 3）. The developed method was used to determine MP in real samples. The recoveries were in the range from 95.4% to 104.2%, demonstrating satisfactory results.

Electrocatalytic reduction of ortho nitrobenzaldehyde using modified aluminum electrode and its determination

A simple, cost effective and rapid electrochemical method has been developed for the determination of micro level ortho nitrobenzaldehyde（ONB） based on outstanding properties of modified aluminum electrode tin nanorods/anodic aluminum oxide/aluminum（SnNR/AAO/Al） for the first time. The SnNR/AAO/Al electrode was fabricated by a second step anodization, followed by electrodeposition and its electrochemical behavior was investigated in detail. The cyclic voltammetry results indicated that the SnNR/AAO/Al electrode exhibited efficient electrocatalytic activity toward reduction of ONB in the acidic solution. It provides an appreciable improvement of reduction peak for ONB at-0.721 V.Furthermore, various kinetic parameters such as transfer electron number, transfer proton number and standard heterogeneous rate constant were calculated from the scan rates.The electrocatalytic behavior was further exploited as a sensitive detection scheme for the ONB determination by differential pulse voltammetry. Under the optimized conditions, the concentration range and detection limit are 0.1-100 μmol/L and 0.05 μmol/L, respectively,for ONB. The analytical performance of this modified sensor has been evaluated for detection of real sample such as river water and recovery of ONB was achieved all-out up to102.3% under standard addition method.