Showing papers on "Cyclic voltammetry published in 1978"

Microelectrode Studies of Electrochemically Coprecipitated Cobalt Hydroxide in Nickel Hydroxide Electrodes

Abstract: The role of electrochemically coprecipitated cobalt hydroxide and nickel hydroxide has been investigated at a nickel microelectrode for purposes of elucidating the effect of cobalt hydroxide on the electrode reactions of battery active nickel hydroxide. Hydroxide films were deposited onto the electrode surface from boiling ethanol solutions of in the presence and absence of ; their behavior in 30% solution was studied by cyclic voltammetry, chronoamperometry, and chronocoulometry. In general, the presence of coprecipitated cobalt hydroxide appears to render the charge‐discharge reaction more reversible thereby allowing charging to occur at less positive potentials, this apparently increases the charging efficiency by minimizing concurrent oxygen evolution. The microelectrode was also used to characterize the cathodic deposition process for the nickel hydroxide.

Anodic Voltammetry and Its Analytical Application to the Detection and Simultaneous Determination of Hypoxanthine, Xanthine, and Uric Acid

Abstract: The voltammetric oxidation of hypoxanthine, xanthine, and uric acid was investigated by means of linearsweep voltammetry, cyclic voltammetry, and controlled-potential coulometry Hypoxanthine, xanthine, and uric acid each gave a single oxidation peak at a different potential, with a stationary glassy carbon electrode, over the wide pH range of 0–13 Hypoxanthine was initially oxidized in a two-electron step to xanthine, which was then further oxidized in a two-electron step to uric acid, as well as the enzymatic oxidation All three substances were strongly adsorbed on the surface of the glassy carbon electrode, so that the concentration vs anodic peak current curves were not linear The adsorption on the electrode was very dependent on the pH, and especially at pH values around neutrality the anodic peaks were ill-defined However, in such acid solutions as H3PO4 and H2SO4, the voltammetric oxidation was a diffusion-controlled process and the differences between the peak potentials were most pronounced

Chemically derivatized n-type semiconducting germanium photoelectrodes. Persistent attachment and photoelectrochemical activity of ferrocene derivatives

Abstract: Attachment of trichlorosilylferrocene (I) and (1,1'-ferrocenediyl)dichlorosilane (II) to pretreated n-type Ge surfaces by hydrolytic reaction is described. Characterization of the derivatized surface by cyclic voltammetry in C/sub 2/H/sub 5/OH or CH/sub 3/CN solutions of 0.1 M (n-Bu/sub 4/N)ClO/sub 4/ shows persistently attached electroactive groups. Cyclic waves persist for hundreds of scans between oxidized and reduced form of the attached electroactive species. The position of the anodic current peak depends on the illumination intensity, though an anodic peak does obtain in the dark at approximately 0.5 V vs. SCE for attached I or II. Illumination moves the anodic peak by up to approximately 200 mV more negative, consistent with expected photoeffects for an n-type semiconductor. Comparison of the derivatized electrode with a naked n-type Ge photoelectrode exposed to electrolyte solutions of ferrocene shows that the interface energetics and kinetics are essentially unchanged by the surface derivatization. Conversion of light to electricity using an n-Ge-based photoelectrochemical cell is possible, but output parameters are very low for an electrolyte solution containing ferrocene and ferricenium. 10 figures.

Nickel‐Based Alloys as Electrocatalysts for Oxygen Evolution from Alkaline Solutions

Abstract: The oxygen evolution reaction on the alloys of Ni with Ir, Ru, or W and on Ni‐Ti intermetallic compounds was studied in at 80°C using steady‐state potentiostatic and slow potentiodynamic (at 0.1 mV/sec) methods. Since this reaction always takes place on film‐covered surfaces, the nature of oxide films formed on these alloys was investigated using cyclic voltammetry. The peaks for the formation and reduction of oxygen‐containing layers appearing on the pure metals are not always found on these alloys. Oxygen overpotentials at an apparent current density of 20 mA/cm2, on the alloys of 50Ni‐50Ir and 75Ni‐25Ru (in atomic percent, a/o) and the intermetallic compound were less than on Ni by about 40, 30, and 20 mV, respectively. On long‐term polarization at potentials in the oxygen evolution region, the oxygen‐containing films on Ni‐Ir and Ni‐Ru alloys are predominantly composed of nickel oxide and independent of the bulk composition of the alloys themselves. This accounts for the absence of any direct dependence of electrocatalytic activities for oxygen evolution on their electronic properties. The effects of relative activities of the individual components in the alloys are however detectable on the oxide formation reactions on the surfaces of freshly prepared electrodes.

Analysis of oxidized layers on pyrite surfaces by X-ray emission spectroscopy and cyclic voltammetry

Abstract: X-Ray emission spectroscopic analysis of the surface of the iron sulphide mineral, pyrite, has demonstrated the presence of an oxygen- containing layer. Differences between the quantity of oxygen detected after grinding the pyrite on 600 grade silicon carbide paper and polishing it to the 10 μm or 0.25 μm diamond stage are considered to be due to differences in surface roughness. Triangular potential sweep voltammograms display current peaks which have been identified with the oxidation and reduction of the oxide layer between iron(II) and iron(III) valence states. The quantities of oxide on the surface determined from the charge passed on a potential sweep correlate with the X-ray emission measurements for the three surface preparations.

Anodic oxidation of organophosphorus compounds. Part 1. Anodic alkylamination of triphenylphosphine

Abstract: Anodic oxidation of triphenylphosphine has been investigated by cyclic voltammetry and controlled potential electrolysis at a glassy-carbon electrode in acetonitrile. Electrolyses of triphenylphosphine in the presence of various primary amines result in the formation of monoalkylaminotriphenylphosphonium salts in 50–70% yield. The reaction sequence is suggested to be one-electron oxidation of the phosphine, nucleophilic attack of primary amine on the resulting cation radical, and a further one-electron transfer and loss of a proton.

Electro-organic chemistry. Part 2. Structure and anodic peak potential relationships. Cyclophanes. Cyclic voltammetric studies of cation-radical formation and reactions

Abstract: The peak potentials for a series of cyclophanes were measured and compared with those of model compounds. Measurements were performed by cyclic voltammetry in acetonitrile–tetrabutylammonium perchlorate. Cyclic voltammetry revealed that the first electron-transfer step was not reversible and that the rate of electron transfer dominated. Peak potentials measured at 250 mV s–1 were used for comparison. Compared with xylene the anodic peak potentials were lowered as follows: [2.2]meta-(ΔO1 0.75 V), [2.2]para-(0.51 V), and [2,2]meta-, para-cyclophanes (0.29 V). Electron-withdrawing substituents increased the potential of one-electron abstraction from the opposite benzene ring for [2.2]para- and [2.2]metapara-cyclophane reflecting π-π interactions. 5,13-Dialkyl[2.2]metacyclophane had an anomalously low peak potential with ΔO1 almost 1 V. Other dialkyl derivatives showed no such anomaly indicating the dependence on the position of substitution. Homologous compounds were found to be less anomalous. The geometrical isomers of [2.2](2,7)naphthalenophane behaved differently and the trans-isomer showed two oxidation peaks instead of one with lower O1 than for the cis-isomer. The possible involvement of a transannular cation-radical from [2.2]metacyclophane is suggested for electrophilic and photolytic reactions as well as for reactions with metal salts.