Cyclic voltammetric and in situ Fourier transform infrared spectroelectrochemical studies on the reaction of Cd2+ on the plussian blue/platinum modified electrode

Plussian blue(PB)/Pt modified electrode Tvas studied in the CdCl2 electrolyte solution by cyclic voltammetry and in situ FTIR spectroelectrochemistry. It was found that Cadmium ion was capable of substituting the high-spin iron of PB in an electrochemically induced substitution reaction and hexacyanoferrate cadmium (CdHCF) can be formed in the PB film. But PB and CdHCF in mixture film showed their own electrochemistry properties without serious effect on each other. The mechanism of substitution reaction has been given in detail.

CYCLIC VOLTAMMETRIC STUDY OF QUININE DERIVATIVES TRANSFER ACROSS THE WATER NITROBENZENE INTERFACE

Quinine derivatives, quinine hydrochloride and 8-hydroxyquinoline, transfer across the water/nitrobenzene interface was studied by cyclic voltammetry. The effect of solution acidity on the transfer behaviour was observed. Transfer mechanism was discussed

CYCLIC VOLTAMMETRIC AND SPECTROELECTROCHEMICAL STUDIES OF COPPER IN ALKALINE-SOLUTION

The behaviour of the electroplated copper film electrode on tin oxide/glass or glassy carbon surface was studied in potassium hydroxide medium by cyclic voltammetry and in situ transmission spectroelectrochemistry. The results indicate that the electroplated copper film electrode is similar to a copper electrode and cyclic voltammetry with this electrode affords more resolution. The anodic peaks were found to correspond successively to the adsorption of oxygen, the formation of a surface layer of Cu2O, the formation of a surface layer of Cu(OH)2 or CuO and formation of a thick multilayer film of CuO. This is the first time it has been proposed that a surface layer of Cu(OH)2 or CuO is formed from the oxidation of the surface layer of Cu2O. Similarly, a clear interpretation is presented that the cathodic peaks correspond successively to the reduction of CuO to Cu2O, the reductions of Cu2O to Cu and the soluble Cu(II) species to Cu. On the other hand, a shoulder peak related to the chemical transformation of Cu(OH)2 to CuO was first observed.

CYCLIC VOLTAMMETRIC STUDY ON THE TRANSFER MECHANISM OF ALKALI-METAL IONS ACROSS LIQUID LIQUID INTERFACE FACILITATED BY TRITON X-100

The transfer behavior of alkali motal ions K~+ and Na~+ across the interfaces of water/nitrobenzene and water/1, 2-dichloroethane facilitated by Triton X-100 is investigated by cyclic voltammetry with four electrodes. The equations of interfacial half-wave potential derived in terms of the mechanism proposed isverified by the experimental data and consistent with the practical △_0~wφ_p-pM curves.

Synthesis of Ruthenium Dioxide Nanoparticles by a Two-Phase Route and Their Electrochemical Properties

Dissolvable, size- and shape-controlled ruthenium dioxide nanoparticles are successfully achieved through a two-phase route. The influence of reaction time, temperature, and monomer concentration and the nature of capping agents on the morphologies of nanoparticles are studied through transmission electron microscopy (TEM). A possible mechanism for the formation and growth of nanoparticles is also involved. X-ray powder diffraction (XRD) confirms the amorphous structure for as-prepared ruthenium dioxide nanoparticles. Samples are immobilized by simple dip-coating on a current collector, and the cyclic voltammetry measurement is utilized to investigate their electrochemical properties. The specific capacitance of one sample can teach as high as 840 F g(-1), which reveals the promising application potential to electrochemical capacitors.

Electrochemical deposition of silver in room-temperature ionic liquids and its surface-enhanced Raman scattering effect

The use of room-temperature ionic liquids (RTILs) as media for electrochemical application is very attractive. In this work, the electrochemical deposition of silver was investigated at a glassy carbon electrode in hydrophobic 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) and hydrophilic 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) RTILs and in KNO3 aqueous solution by cyclic voltammetric and potentiostatic transient techniques. The voltammograms showed the presence of reduction and oxidation peaks associated with the deposition and dissolution of silver from AgBF4 in both BMIMPF6 and BMIMBF4, resembling the redox behavior of AgNO3 in KNO3 aqueous solution. A crossover loop was observed in all the cyclic voltammograms of these electrochemical systems, indicating a nucleation process. From the analysis of the experimental current transients, it was shown that the electrochemical deposition process of silver in these media was characteristic of 3D nucleation with diffusion-controlled hemispherical growth, and the silver nucleation closely followed the response predicted for progressive nucleation in BMIMPF6 and instantaneous nucleation in KNO3 aqueous solution, respectively.

Electrochemical preparation of microelectrodes modified with non-stoichiometric mixed-valent molybdenum oxides

A compact non-stoichiometric molybdenum (VI, V) oxide of blue film was grown on carbon fiber (CF) microelectrode surface be cycling the potential between + 0.2V and - 0.70V in a freshly prepared Na2MoO4 solution containing 5 x 10(-3) mol/L H2SO4. The quantity-of the oxide is controlled by the charge passing the electrode. The electrochemical pretreatment of CF microelectrode not only mises the deposition velocity of molybdenum oxide on CF surface, but also improves greatly the cyclic voltammetric behavior of the molybdenum oxide film prior to the electrodeposition. The cathodic processes are believed to yield the hydrogen molybdenum oxide bronzes HxMoO3(0 < x < 2), or substoichiometric lower molybdenum oxides with the formula MoO3-y(0 < y < 1). The anodic response results from the reversible oxidation of molybdenum bronze/Mo(V) centers [or perhaps Mo(IV) in more reduced coatings], to Mo(VI). Further information was gained about the chemical composition and valent state of Mo from XPS and SEM.

ELECTRODEPOSITION OF PLATINUM PARTICLES ON GLASSY-CARBON MODIFIED WITH COBALT PORPHYRIN AND NAFION FILM AND THEIR ELECTROCATALYTIC REDUCTION OF DIOXYGEN

In this paper, five types of chemically modified electrode (CMEs) prepared with the deposition of platinum particles on various surfaces of glassy carbon (GC) modified with cobalt porphyrin and Nafion(R) solution are characterized using the electron scanning microscope (SEM). Their activities in the four-electron reduction of dioxygen to water on the basis of their electrochemical data from cyclic voltammetric and rotating ring-disk electrode (RRDE) experiments are examined and compared. Platinum particles dispersed on the GC surface adsorbed with the cobalt porphyrin exhibit the highest activity for the electrocatalytic reduction of dioxygen. However it is interesting that the cobalt ion is lost from the center of the porphyrin ring during the preparation of the cobalt porphyrin + Nafion mixture solution, while the porphyrin ring still remains in the Nafion film, as shown by EDX analysis. The incorporation of the porphyrin may change the structure of the Nafion film into a looser form, since the platinum particles dispersed in the film are more readily exposed, resulting in more favourable mass transfer and higher activity for the electrocatalytic reduction of dioxygen.

Electrochemical Hydrogen Storage in Ti1.6V0.4Ni1-xCox Icosahedral Quasicrystalline Alloys

The discovery of the icosahedral phase (i-phase) in rapidly quenched Ti1.6V0.4Ni1-xCox (x=0.02-01) alloys is described herein. The i-phase occurs in a similar amount relative to the coexisting beta Ti phase. The electron diffraction patterns show the distinct spot anisotropy, indicating that the i-phase is metastable. The electrochemical hydrogen storage performance of these five alloy electrodes are also reported herein. The hydrogen desorption of nonelectrochemical recombination in the cyclic voltammetric (CV) response exhibits the demand for electrocatalytic activity improvement.

Immobilization and direct electrochemistry of copper-containing enzymes on active carbon

Two typical and important copper-containing enzymes, laccase (Lac) and tyrosinase (Tyr), have been immobilized on the surface of active carbon with simple adsorption method. The cyclic voltammetric results indicated that the active carbon could promote the direct electron transfer of both Lac and Tyr and a pair of well-defined and nearly symmetric redox peaks appeared on the cyclic voltammograms of Lac or Tyr with the formal potential, E-0', independent on the scan rate. The further experimental results showed that the immobilized copper-containing oxidase displayed an excellent electrocatalytic activity to the electrochemical reduction of O-2. The immobilization method presented here has several advantages, such as simplicity, easy to operation and keeping good activity of enzyme etc., and could be further used to study the direct electrochemistry of other redox proteins and enzymes and fabricate the catalysts for biofuel cell.

Study of the ion channel behavior of didodecyldimethylammonium bromide formed bilayer lipid membrane stimulated by PF6-

Bilayer lipid membranes ( BLM) formed from didode-cyldimethylammonium bromide were made on the freshly exposed surface of a glassy carbon (GC) and were demonstrated by the ac impedance spectroscopy. The ion channels of membrane properties induced by PF6- were studied by the cyclic voltammetric methods. Experimental results indicated that the ion channel of BLM was open in the presence of the PF6- due to the interaction of PF6- with the BLM, while it was switched off in the absence of PF6-. Because the ion channel behavior was affected by the concentration of PF6-, a sensor for PF6- can be developed.

Carbon ceramic electrodes bulk-modified with nanoparticles of ferrocenebutyrate-intercalated Mg-Al layered double hydroxide

Ferrocenebutyrate-intercalated layered double hydroxide (FcLDH) was prepared by the coprecipitation method and characterized by PXRD, FTIR, TEM and elemental analysis. FcLDH nanoparticles in deionized water were deposited onto the surface of graphite powder to yield graphite powder-supported FcLDH, which was subsequently dispersed into methyltrimethoxysilane-derived gels to fabricate surface-renewable, stable, rigid carbon ceramic electrodes containing the electroactive ferrocenyl group. Cyclic voltammetric study revealed that peak currents of the FcLDH-modified electrode were diffusion-con trolled in 0.1 mol l(-1) KCl aqueous solution. In addition, the formal potential of the modified electrode is related to the activity of chloride ion with a Nernst slope of 56 mV per decade.

Carbon ceramic electrodes modified with sub-micron particles of new methylene blue (NMB) intercalated alpha-zirconium phosphate

New methylene blue-intercalated a-zirconium phosphate (NMBZrP) was synthesized in the presence of n-butylamine and characterized by powder XRD, FTIR, TEM and elemental analysis. Sub-micron particles of NMBZrP in deionized water were apt to deposit onto the surface of graphite powder to yield graphite powder-supported NMBZrP, which was subsequently dispersed into methyltrimethoxysilane-derived gels to fabricate surface-renewable, stable, rigid carbon ceramic electrodes containing new methylene blue. Cyclic voltammetric studies revealed that peak currents of the NMBZrP-modified electrode were surface-confined at low scan rates but diffusion-controlled. at high scan rates. In addition, NMBZrP immobilized in a carbon ceramic matrix presented a two-electron, three-proton redox process in acidic aqueous solution in the pH range from 0.52 to 3.95.

A study of tetraethylammonium ion transfer across a micro liquid/liquid interface

Tetraethylammonium (TEA(+)) ion transfer across micro-liquid/liquid interface has been studied with cyclic voltammetric measurements. The results showed that voltammetric responses of the currents obtained were peak and steady-state for TEA(+) transfer from inside and outside of the micropipette when the radius was bigger than 3 mum. However, the currents were pseudo-steady-state when the micropipette diameters were less than 3 mum. The values of i(p) decreased with decreasing concentration of TEA(+). Peak current was proportional to the square root of the scan rate and it obeyed a Randles-Sevcik type relationship. The mechanism of mass transport across a liquid/ liquid microinterface for TEA(+) system was aslo discussed.

In-situ microscopic FTIR spectroelectrochemistry of ascorbic acid in poly(ethylene glycol)/LiClO4 electrolyte paste and in the presence of dispersed cobalt hexacyanoferrate microcrystalline powder

In-situ microscopic FTIR spectroelectrochemical technique(MFTIRs) was applied to studying the electrochemical oxidation of ascorbic acid(AA) in poly(ethylene glycol)(PEG) paste at a 100 mu m diameter Pt disk electrode. Using this technique, the catalytic ability of cobalt hexacyanoferrate(CoHCF) microcrystalline toward AA oxidation was also studied, it was found that the dispersed CoHCF powder in the PEG paste can generate well-shaped thin-layer cyclic voltammetric waves with the peak height proportional to the scan rate, corresponding to the Fe centered redox reactions. This oxidation step catalyzed the AA oxidation. Also, this pasted CoHCF powder generated well-resolved in-situ MFTIRs spectra, by which a chemical interaction between C = C bond of AA ring and CoHCF lattice was revealed. A corresponding surface docking mechanism for the catalytic reaction has been proposed.