正极集流体对可充镁电池电化学性能的影响

以目前常用的Chevrel相Mo₆S₈作为正极材料, 涂覆在不同集流体(不锈钢、镍、铜、钛) 上, 以镁为负极,研究了在(PhMgCl)₂-AlCl₃/四氢呋喃(简称THF)“二代”电解液中集流体对可充镁电池电化学性能的影响. 恒流放电-充电结果显示在不锈钢集流体上电池电压极化最小, 并且具有较好的循环稳定性; 镍、铜次之; 钛集流体上的极化最大, 循环稳定性也最差. 并通过对比放电-充电循环前后电极和集流体表面的微观结构, 探讨了集流体对电池性能显著影响的原因. 电解液对集流体会造成腐蚀, 不同集流体在电解液中的稳定性有差异; 正极材料涂覆在不同集流体上, 电极表面状况有差异; 负载活性材料后集流体发生腐蚀的电位有所降低, 使集流体更易受到电解液的腐蚀.     

[SiCu(H2O)W11O39]6-在玻碳电极上的多层组装及电催化性能

The electrochemical behavior of SiCu W11 heteropolyacide in acidic aqueous solution was studied. The effect of solution pH on the electrochemical behavior of SiCu W11 was discussed and the mechanism was suggested. New electrode was modified by muhilayer films composed of heteropolyanion (SiCu W11 and cationic polymer poly (diallyldimethylammonium chloride). Cyclic vohammetry showed the uniform growth of the film. The modified electrodes exhibited some special electrochemical properties in the films, different from those in homogeneous aqueous solutions. The effect of pH on the redox behavior of SiCu W11 in the films was discussed in details. The muhilayer film electrodes have an excellent electrocatalytic response to the reduction of BrO3^- and NO2^-.     

POLYMERIZATION OF PYRROLE ON POLYACRYLAMIDE ELECTRODES

Polymerization of pyrrole on a polyacrylamide (PAA) coated electrode was carried out in acetonitrile. Different compositions of semi-conducting, composite films of PAA/Polypyrrole (PP_y), were prepared by the electrochemical polymerization of pyrrole on PAA electrodes. The polymerization was possible only for a certain thickness of the polyacrylamide on the platinum. Conductivites of PAA/PP_y films at different compositions were obtained. The electrochemical properties of polypyrrole-poly-acrylamide (PP_y/PAA) composite films have been investigated by using cyclic voltammetry. The PP_y/PAA composite film is suitable as the electroactive material due to its stable and controllable electrochemical properties. The films were examined by FTIR spectroscopy. The topography of surface films were analyzed by scanning electron microscope (SEM). The response behavior of PP_y/PAA films at different compositions when exposed to Ar, C₃H₈ and H₂ gases indicated that these films were only slightly sensitive to H₂ gas.     

The effect of nondiamond carbon admixture on the electrochemical behavior of polycrystalline CVD-diamond films

The effect of nondiamond (sp ²-) carbon admixture on the surface of polycrystalline boron-doped CVD-diamond electrodes on their electrochemical behavior was studied by comparing the films grown under similar conditions, yet of different thickness. It is shown that with the decreasing of the film thickness (hence, with the increasing of the nondiamond carbon content therein) its surface acquired electrochemical activity: the transfer coefficients of reactions in the [Fe(CN)₆]^3−/4− redox system increased, the oxygen anodic evolution overvoltage decreased, the differential capacitance increased; on the whole, the diamond electrode demonstrated increasingly better pronounced metal-like behavior.     

Effect of crystallization route on the properties of LiMn2O4 thin films prepared by spin coating

LiMn₂O₄ thin films were prepared by spin coating through intermediate amorphous layer route (IALR) and intermediate crystallized layer route (ICLR). The phase identification, surface morphology, and electrochemical properties of the films prepared by different crystallization routes were studied by X-ray diffraction, scanning electron microscopy, and galvanostatic charge–discharge experiments. The results show that both films prepared by different crystallization routes are homogeneous and crack free. Compared with the film prepared by IALR, the film prepared by ICLR shows smaller grain size and is smoother and denser. The LiMn₂O₄ film prepared by ICLR delivers the specific capacity of 39.8 μAh?cm^?2?μm^?1, which is higher than 35.6 μAh?cm^?2?μm^?1 for the one prepared by IALR. The capacity loss of the film prepared by ICLR after being cycled 100 times is 3.4 %, which is smaller than that of 5.5 % for the film prepared by IALR. The film prepared by ICLR shows higher specific capacity and better cycling behavior than the one prepared by IALR.     

Synthetic Semiconductor Diamond Electrodes: Electrochemical Characteristics of Homoepitaxial Boron-doped Films Grown at the (111), (110), and (100) Faces of Diamond Crystals

Electrode behavior of homoepitaxial (single-crystal) boron-doped diamond films deposited onto differently orientated faces of dielectric diamond single crystals is studied by the electrochemical impedance and potentiodynamic curve methods. It is shown that the acceptor concentration determined from the slope of Mott–Schottky plots decreases, in the epitaxial films grown under the same conditions, in the series: (111) > (110) > (100). This is explained by different intensity of boron incorporation, from gas phase, into differently orientated faces of the diamond crystals during their growth. The rate of electrode reactions in the Fe(CN)₆ ^3–/4– and Ru(NH₃)₆ ^2+/3+ redox systems decreases in the above series, which obeys the earlier found interrelationship between the electrochemical kinetics at diamond electrodes and their doping level.     

Electron transfer kinetics on composite diamond (sp3)–graphite (sp2) electrodes

The concept of non-diamond sp² impurity states as charge transfer mediators on boron-doped diamond (BDD) surface was suggested as an explanation for the electrochemical behavior of synthetic diamond based electrodes. In order to verify this concept, graphite particles (sp²) were deposited on diamond electrodes (sp³) by mechanical abrasion. The behavior of the so prepared diamond–graphite composite electrodes were compared with those of as-grown (BDD_ag) and those after mild anodic polarization (BDD_mild).Outer-sphere electron transfer processes such as ferri/ferrocyanide (Fe(CN)₆III/II) and inner-sphere charge transfer reactions such as 1,4-benzoquinone/hydroquinone (Q/H₂Q) were chosen in order to investigate the electrochemical properties of these composite electrodes. Both redox systems became more reversible as the graphite (sp²) loading increased. A strong analogy existed between as-grown diamond electrodes and diamond–graphite composite electrodes.Finally a model is proposed which describes the BDD electrode surface as a diamond matrix in which non-diamond (sp²) impurity states are dispersed. These non-diamond sp² states on BDD surface acts as charge mediators for both inner-sphere and outer-sphere reactions.     

Preparation,Characterization, and Electrocatalytic Properties of Cobalt Oxide and Cobalt Hexacyanoferrate Hybrid Films

Polynuclear mixed‐valent films of cobalt oxide and cobalt hexacyanoferrate (CoOCoHCF) have been deposited on electrode surfaces from a solution of Co²⁺ and Fe(CN)₆^3? ions by repetitive potential cycling method. Simultaneous cyclic voltammetry and electrochemical quartz crystal microbalance measurements demonstrate the steady growth of modified film. The effect of type of monovalent cations as well as acidity of the supporting electrolyte on film growth and redox behavior of resulting film was investigated. In pure supporting electrolyte, electrochemical responses of modified electrode resemble with that of a surface immobilized redox couple. The hybrid film electrodes showed electrocatalytic activity toward oxidation of NADH, hydrazine and hydroxylamine. The feasibility of using our modified electrodes for analytical application was also explored.     

Al Electrode Modified by Au Atoms as a Novel Electrode for Electrocatalytic Oxidation of Thiosulfate

An aluminum electrode modified with gold atoms was introduced as a novel electrode. Gold atoms were deposited both chemically and electrochemically onto the aluminum electrode to make an aluminum/gold (Al/Au) modified electrode (ME). The experimental results showed that the Al/Au modified electrode prepared by chemical deposition, exhibits much more current than the electrochemical deposition method. The electrochemical behavior of the Al/Au modified electrode was studied by cyclic voltammometry. This modified electrode showed two pairs of peaks, a₁c₁ and a₂c₂, with surface‐confined characteristics in a 0.5 M phosphate buffer. The dependence of E_pa of the second peak (a₂c₂) on pH shows a Nernestian behavior with a slope of 55 mV per unit pH. The effect of different supporting electrolytes, solution's pH and different scan rates on electrochemical behavior of Al/Au modified electrode was studied. Au deposited electrochemically on a Pt electrode (Pt/Au) was also used as another modified electrode. A comparative study of electrochemical behavior of bare Al, Pt/Au and Al/Au modified electrodes showed that both Pt/Au and Al/Au electrodes have the ability of electrocatalytic oxidation of S₂O₃^2?, but the electrocatalytic oxidation on the latter was better than the former. The kinetics of the catalytic reaction was investigated by using cyclic voltammetry and chronoamperometry techniques. The average value of the rate constant for the catalytic reaction and the diffusion coefficient were evaluated by means of chronoamperometry technique.     

Preparation of lead and tin oxide thin films by spin coating and their application on the electrodegradation of organic pollutants

In this work, lead and tin oxide films (Pb _x O _y /SnO₂) were prepared, using the spin coating technique. The influence of the temperature and duration of the thermal treatment on the final film composition were analysed. The metallic oxide films that were prepared, Pb _x O _y /SnO₂, were characterized by means of XRD, SEM/EDS and cyclic voltammetry. When different experimental preparation conditions were used different lead oxide phases were obtained. The electrochemical studies show that the films are stable and can be used as electrodes. Finally the films were tested as electrodes for the electrochemical degradation of a CHCl₃ aqueous solution.     

Electrochemical comparison between IrO2 prepared by thermal treatment of iridium metal and IrO2 prepared by thermal decomposition of H2IrCl6 solution

The surface redox activities, the oxygen evolution reaction (OER), the oxidation of formic acid (FA) and the anodic stability have been investigated and compared on IrO₂ electrodes prepared by two techniques: the thermal decomposition of H₂IrCl₆ precursor (TDIROF) and the thermal treatment of metallic iridium (TOIROF). It was found, that the surface redox activities involved on both IrO₂-based electrodes are similar. Concerning the oxygen evolution reaction and the oxidation of formic acid, both films show similar mechanism.The electrode stability measurements have shown that both films are not corroded under strong OER or organics oxidation conditions and therefore, to summarize, both IrO₂-based films exhibit similar electrochemical behaviours.     

Electrochemical Biosensing for Cancer Cells Based on TiO2/CNT Nanocomposites Modified Electrodes

Both TiO₂ nanoparticles and carbon nanotubes have been usually utilized to modify the electrodes to enhance the detection sensitivity of biomolecular recognition. In this research, novel TiO₂/CNT nanocomposites have been prepared and doped on the carbon paper as the modified electrodes. Subsequently, the redox behavior of the ferricyanide probe and the surface properties of the cancer cells coated on the modified electrodes have been investigated by using electrochemical and contact angle measurements. Compared with electrochemical signals on bare carbon paper and nanocomposite modified substrates, the significantly enhanced electrochemical signals on the modified electrodes covered with cancer cells have been observed. Meanwhile, different leukemia cells (i.e., K562/ADM cells and K562/B.W. cells) could be also recognized because of their different electrochemical behavior and hydrophilic/hydrophobic features on the modified electrodes due to the specific components on the plasma membranes of the target cells. This new strategy may have potential application in the development of the biocompatible and multi‐signal responsive biosensors for the early diagnosis of cancers.     

Fabrication and the electrochemical activation of network-like MnO<Subscript>2</Subscript> nanoflakes as a flexible and large-area supercapacitor electrode

Porous network-like MnO₂ thick films are successfully synthesized on a flexible stainless steel (SS) mesh using a simple and low-cost electrodeposition method followed by an electrochemical activation process. Morphology, chemical composition, and crystal structure of the prepared electrodes before and after the activation process are determined and compared by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analyses. The results show that the implementation of the electrochemical activation process does not change the chemical composition and crystal structure of the films, but it influences the surface morphology of the MnO₂ thick layer to a flaky nanostructure. Based on the electrochemical data analysis, the maximum specific capacitance of 1400 mF (381 F g^?1) and 3700 mF (352 F g^?1) are measured for small (2.6 cm²) and large (10 cm²) surface area electrodes, respectively. In addition, a flexible symmetric MnO₂//MnO₂ solid-state supercapacitor shows a capacitance of 0.3 F with about 98% retention at different bending angles from 0 to 360°.     

Preparation of grain size controlled boron-doped diamond thin films and their applications in selective detection of glucose in basic solutions

Boron-doped diamond (BDD) thin films with different crystal grain sizes were prepared by controlling the reacting gas pressure using hot filament chemical vapor deposition (HFCVD). The morphologies and structures of the prepared diamond thin films were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. The electrochemical responses of K₄Fe(CN)₆ on different BDD electrodes were investigated. The results suggested that electron transfer was faster at the boron-doped nanocrystalline diamond (BDND) thin film electrodes in comparison with that at other BDD thin film electrodes. The prepared BDD thin film electrodes without any modification were used to directly detect glucose in the basic solution. The results showed that the as-prepared BDD thin film electrodes exhibited good selectivity for detecting glucose in the presence of ascorbic acid (AA) and uric acid (UA). The higher sensitivity was observed on the BDND thin film grown on the boron-doped microcrystalline diamond (BDMD) thin film surface, and the linear response range, sensitivity and the low detection limit were 0.25–10 mM, 189.1 μA mmo^?1 cm^?2 and 25 μM (S/N=3) for glucose in the presence of AA and UA, respectively.     

The hydrodesulfurization activity and characterization of cobalt Chevrel phase sulfides

Hydrodesulfurization activity of cobalt Chevrel phase sulfide catalysts has been investigated in a fixed-bed flow reactor. Single phase cobalt Chevrel phase sulfides exhibited catalytic activity for hydrodesulfurization. Supported cobalt Chevrel phase sulfides catalysts indicated much higher hydrodesulfurization activity and even higher than commercial CoMoS/Al₂O₃ catalysts. The existence of Mo₆S₈ and the reduced oxidation state of Mo in the cobalt Chevrel phase sulfides has been observed by XRD, LRS, and XPS. This revised version was published online in August 2006 with corrections to the Cover Date.     

Capacitive and Charge Transfer Effects of Single-Walled Carbon Nanotubes in TiO2 Electrodes

The transfer of nanoscale properties from single-walled carbon nanotubes (SWCNTs) to macroscopic systems is a topic of intense research. In particular, inorganic composites of SWCNTs and metal oxide semiconductors are being investigated for applications in electronics, energy devices, photocatalysis, and electroanalysis. In this work, a commercial SWCNT material is separated into fractions containing different conformations. The liquid fractions show clear variations in their optical absorbance spectra, indicating differences in the metallic/semiconducting character and the diameter of the SWCNTs. Also, changes in the surface chemistry and the electrical resistance are evidenced in SWCNT solid films. The starting SWCNT sample and the fractions as well are used to prepare hybrid electrodes with titanium dioxide (SWCNT/TiO₂). Raman spectroscopy reflects the optoelectronic properties of SWCNTs in the SWCNT/TiO₂ electrodes, while the electrochemical behavior is studied by cyclic voltammetry. A selective development of charge transfer characteristics and double-layer behavior is achieved through the suitable choice of SWCNT fractions.     

Structure–reactivity relationships in Chevrel phase electrocatalysts for small-molecule reduction reactions

Chevrel phases, M_xMo₆X₈ (M = metal intercalant, X = chalcogen), constitute a family of materials with composition-dependent physicochemical properties that have shown promising electrocatalytic activity for various small-molecule reduction reactions. The wide range of possible compositions among the Chevrel phase family offers the opportunity to tune the local and electronic structure of discrete Mo₆X₈ cluster units within the extended M_xMo₆X₈ framework. Thus, making them an ideal platform for studying structure–function relationships and generating design principles for improved electrocatalytic reactivity. This review summarizes the state of the art in experimental and computational evaluations of Chevrel phases as electrocatalysts for hydrogen evolution, CO₂ reduction, and nitrogen reduction reactions. We aim to elucidate the uncharted small-molecule electrochemical reactivity of Chevrel phases as a function of composition and consequently guide the design of promising multinary chalcogenides for energy conversion reactions.     

Platinum nanoparticle-modified electrodes, morphologic, and electrochemical studies concerning electroactive materials deposition

The present work describes the synthesis of platinum nanoparticles followed by their electrophoretic deposition onto transparent fluorine-doped tin oxide electrodes. The nano-Pt-modified electrodes were characterized by voltammetric studies in acidic solutions showing a great electrocatalytic behavior towards H⁺ reduction being very interesting for fuel cell applications. Morphological characterization was performed by atomic force microscopy on different modified electrodes showing a very rough surface which can be tuned by means of time of deposition. Also, nickel hydroxide thin films were galvanostatically grown onto these electrodes showing an interesting electrochemical behavior as sharper peaks, indicating a faster ionic exchange from the electrolyte to the film.     

Electrosynthesis of the poly(N-vinyl carbazole)/carbon nanotubes composite for applications in the supercapacitors field

Electrochemical polymerization of N-vinyl carbazole (VK) on carbon nanotube (CN) films was studied by cyclic voltammetry in LiClO₄/acetonitrile solutions. Cyclic voltammograms recorded on a blank Pt electrode were compared with those obtained when single or multi-walled CN films were deposited on the Pt electrode; in the latter case, a down-shift of the VK reduction peak potential was observed. Functionalization of CNs with poly(N-vinyl carbazole) (PVK) was invoked by Raman scattering and UV-VIS-NIR spectroscopic studies. The influence of sweep rate on the electrochemical properties of the PVK/CN nanocomposite and the performance of supercapacitors constructed using PVK-functionalized single-walled carbon nanotube electrodes were also evaluated.     

Nanocrystalline FeWO4 as a pseudocapacitive electrode material for high volumetric energy density supercapacitors operated in an aqueous electrolyte

Iron tungstate (FeWO₄) has been synthesized using two low-temperature synthetic routes and investigated as a new pseudocapacitive electrode material for supercapacitors operating in a neutral aqueous electrolyte. Its electrochemical properties are clearly related to the specific surface area and seem to originate from Fe^3 +/Fe^2 + fast surface reactions. For FeWO₄ obtained by polyol-mediated synthesis, a high volumetric capacitance of 210 F·cm^− 3 (i.e. more than two times higher than that of activated carbon) was measured at 20 mV·s^− 1 with less than 5% fade over 10,000 cycles. Furthermore, unlike most of the previously investigated iron based electrodes, a unique pseudocapacitive behavior is observed, thus emphasizing the role of the crystallographic structure on the electrochemical signature.