Showing papers on "Electrode potential published in 2005"

Electrochemical ostwald ripening of colloidal ag particles on conductive substrates.

Abstract: Thermally evaporated silver nanoparticles on conducting substrates spontaneously evolve in size when immersed in pure water. The process was studied using scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and optical absorption spectroscopy. The particles are proposed to reform through an electrochemical Ostwald ripening mechanism driven by the size dependence of the work function and standard electrode potential. We also discuss prior literature experiments where this process appears to occur. Our results show the sensitivity of the electrochemical properties of metallic nanoparticles at relatively large sizes (∼50 nm).

Lithium-ion capacitor

Abstract: A lithium ion capacitor includes a positive electrode made of a material capable of reversibly carrying either one or both of a lithium ion and an anion, a negative electrode made of a material capable of reversibly carrying a lithium ion, and an electrolytic solution made of a non-protonic organic solvent electrolytic solution of a lithium salt. A negative electrode active material is non-graphitizable carbon having a ratio of number of hydrogen atoms to number of carbon atoms of zero or more and less than 0.05. The lithium ion is doped in advance to either one or both of the negative electrode and the positive electrode so that a negative electrode potential when a cell is discharged to a voltage one half a charging voltage of the cell is 0.15 V or less relative to a lithium ion potential.

Electrodeposition of Manganese and Molybdenum Mixed Oxide Thin Films and Their Charge Storage Properties

Abstract: Manganese and molybdenum mixed oxides in a thin film form were deposited anodically on a platinum substrate by cycling the electrode potential between 0 and +1.0 V vs Ag/AgCl in aqueous manganese(II) solutions containing molybdate anion (MoO42-). A possible mechanism for the film formation is as follows. First, electrooxidation of Mn2+ ions with H2O yields Mn oxide and protons. Then, the protons being accumulated near the electrode surface react with MoO42- to form polyoxomolybdate through a dehydrated condensation reaction (by protonation and dehydration). The condensed product coprecipitates with the Mn oxide. Cyclic voltammetry of the Mn/Mo oxide film-coated electrode in aqueous 0.5 M Na2SO4 solution exhibited a pseudocapacitive behavior with higher capacitance and better rate capability than that of the pure Mn oxide prepared similarly, most likely as a result of an increase in electrical conductivity of the film. Electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy clearly...

Lithium secondary cell with high charge and discharge rate capability

Abstract: A high capacity, high charge rate lithium secondary cell includes a high capacity lithium-containing positive electrode in electronic contact with a positive electrode current collector, said current collector in electrical connection with an external circuit, a high capacity negative electrode in electronic contact with a negative electrode current collector, said current collector in electrical connection with an external circuit, a separator positioned between and in ionic contact with the cathode and the anode, and an Electrolyte in ionic contact with the positive and negative electrodes, wherein the total area specific impedance for the cell and the relative area specific impedances for the positive and negative electrodes are such that, during charging at greater than or equal to 4C, the negative electrode potential is above the potential of metallic lithium. The current capacity per unit area of the positive and negative electrodes each are at least 3 mA-h/cm2, the total area specific impedance for the cell is less than about 20 Ω-cm2, and the positive electrode has an area specific impedance r1 and the negative electrode has an area specific impedance r2, and wherein the ratio of r1 to r2 is at least about 10.

Electrochemical and PM-IRRAS studies of the effect of the static electric field on the structure of the DMPC bilayer supported at a Au(111) electrode surface.

Abstract: Differential capacity, charge density measurements, and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) were employed to study the fusion of small unilamellar vesicles of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) on a Au(111) electrode surface. The differential capacity and charge density data showed that the vesicles fuse onto the gold surface at charge densities between -10 microC/cm(2) < sigma(M) < 10 microC/cm(2) to form a bilayer. When sigma(M) < -10 microC/cm(2), the film is detached from the surface but it remains in close proximity to the surface. PM-IRRAS experiments provided IR spectra for the bilayer in the adsorbed and the desorbed state. Ab initio normal coordinate calculations were performed to assist interpretation of the IR spectra. The IR bands were analyzed quantitatively, and this analysis provided information concerning the conformation and orientation of the acyl chains and the polar head region of the DMPC molecule. The orientation of the chains, hydration, and conformation of the headgroup of the DMPC molecule strongly depend on the electrode potential.

Ion-selective electrodes

Abstract: An ion-selective electrode (10) including a water-impermeable, non-conductive substrate (12); an electrically conductive layer including a metal/metal salt mixture (14) supported on a surface of the substrate; a hydrophobic, conductive intermediate layer (16) in contact with the metal/metal salt layer and including a salt having suitable ionic mobility such that an electrode potential is rapidly established; a layer (18) including an ion-specific ligand in contact with the intermediate layer; and a water-impermeable barrier layer (20) which overlays the layer including the ion-specific ligand such that a portion of this layer is uncovered, and a method for preparing same, is described. The present ion-selective electrode permits rapid, reproducible measurements of ion concentrations to be made without requiring electrode calibration and in the absence of liquid electrolytes.

pH-Sensitive Solid-State Electrode Based on Electrodeposited Nanoporous Platinum

Abstract: The nanoporous platinum oxide (H1-ePtO) as a hydrogen ion-selective sensing material is reported. Bare nanoporous platinum oxides exhibit near-Nernstian behavior (e.g., -55 mV/pH in PBS), ignorable hysteresis, a short response time, and high precision, which are remarkably better than those of flat platinum oxides. The electrode potential of a nanoporous platinum oxide responds exclusively to hydrogen ion, which implies its usefulness as a solid-state pH sensor. In the present study, the performance of nanoporous platinum oxide was investigated and compared with that of IrOx in terms of selectivity and the influences of ionic strength, temperature, complexing ligands, and surfactants. H1-ePtO functions well as a pH-sensing solid-state material, and it is viewed as a promising alternative to IrOx. Interference by redox couples was successfully suppressed by covering the H1-ePtO surface with a protective layer, e.g., an electropolymerized polyphenol thin film. Since the nanoporous platinum oxide with such a protective layer is particularly suitable for miniaturization and micropatterning, our findings suggest its usefulness in applications such as solid-state pH sensors embedded in chip-based microanalysis systems.

Liquid crystal display apparatus, driving method for same, and driving circuit for same

Abstract: The liquid crystal display apparatus is provided with a display unit, a video signal driving circuit, a scanning signal driving circuit, a common electrode potential controlling circuit, and a synchronizing circuit. The display unit has a scanning electrode, a video signal electrode, a plurality of pixel electrodes arranged in matrix form, a plurality of switching elements which transmit video signals to the pixel electrodes, and a common electrode. After the scanning signal driving circuit scans the entire scanning electrodes and transmits video signals to the pixel electrodes, the common electrode potential controlling circuit changes the potential of the common electrode into a pulse shape, overdrives video signals, or increases a torque required to return to a state in which no voltage is applied.

Electro-Oxidation of Carbonate in Aqueous Solution on a Platinum Rotating Ring Disk Electrode

Abstract: The kinetics of electro-oxidation of carbonate aqueous solution on a platinum electrode were examined by a rotating ring (platinum) – disk (platinum) electrode in aqueous sodium carbonate/bicarbonate solutions (25 °C, pH = 10.75) with the peroxide stabilizing additives sodium silicate, magnesium sulphate and sodium DTPA such as are used in brightening mechanical wood pulp. A theoretical model based on the experimental data is proposed to describe this electro-oxidation process. The model shows consistency between the experimental results and the expectation from the proposed reaction sequence. The first-order rate constants at 25 °C, pH = 10.75 in 1.13 M (Na2CO3 + NaHCO3) for carbonate electro-oxidation to percarbonate (a.k.a. peroxidicarbonate C2O62-), percarbonate hydrolysis to hydrogen peroxide and hydrogen peroxide electro-oxidation to oxygen are estimated from the experimental data, respectively, as (1.43±0.1) × 10−11cm s−1 (extrapolated to the equilibrium electrode potential which is estimated as ca. 0.21 (vs SCE)), (1.1 ± 0.2) × 10−2 s−1 and (5.6±0.5) × 10−8cm s−1 (extrapolated to the equilibrium electrode potential of −0.019 V (vs SCE)).

Electrochemical sensor for superoxide anion radical using polymeric iron porphyrin complexes containing axial 1-methylimidazole ligand as cytochrome c mimics

Abstract: A needle-type electrochemical sensor for the facile detection of superoxide anion radical (O - . 2 ) was devised using an electrodeposited film of a polymeric porphyrin complex attached to a carbon microelectrode which wasplaced in a stainless steel 18G needle tube as an auxiliary electrode. The sensing element was prepared by means of electropolymerization of bromoiron(III) mesotetra(3-thienyl)porphyrin in the presence of 1-methylimidazole in CH 2 Cl 2 containing 100 mM tetrabutylammonium perchlorate (TBAP) as a supporting electrolyte, which gave a smooth film of the corresponding polymer. The film was electrochemically active to give a redox response near -0.05 V versus Ag/AgCl due to the iron(II/III) couple. The microsensor was applied to detect O 2 produced by xanthine oxidation catalyzed by xanthine oxidase. The amperometric response for O 2 was monitored at an electrode potential of 0.5V versus the auxiliary electrode in a 10 mM phosphate buffer. The microsensor displayed a high catalytic activity for the oxidation of O - . 2 and showed a linear relationship between the current and the O - . 2 concentration. Axial coordination of an imidazole ligand to the iron porphyrin center enhanced selectivity for O - . 2 by impeding the undesired coordination of H 2 O 2 that resulted from the dismutation of O - . 2 .

Redox shuttle for overdischarge protection in rechargeable lithium-ion batteries

Abstract: A battery of series-connected rechargeable lithium ion cells each of which contains a negative electrode; a negative electrode current collector; a positive electrode; a positive electrode current collector; and an electrolyte comprising charge carrying medium, lithium salt and cyclable redox chemical shuttle. The negative electrode has a larger irreversible first cycle capacity loss than that of the positive electrode, and is driven to a potential above that of the positive electrode if the cell is discharged to a state of cell reversal. The shuttle has an electrochemical potential above the positive electrode maximum normal operating potential, and prevents the negative electrode potential from reaching even higher and more destructive positive values during overdischarge. The current collector has a lithium alloying potential below the negative electrode minimum normal operating potential. The battery chemically limits or eliminates cell damage due to repeated overdischarge, and may operate without electronic overdischarge protection circuitry.