1,721,094 research outputs found
ELECTRODEPOSITION OF COBALT FILMS FROM CARBONATE SOLUTIONS CONTAINING Co-(II) TARTRATE COMPLEXES.
No full textAn electrochemical procedure of anodic deposition of cobalt oxyhydroxide film on a glassy carbon substrate in an alkaline medium (i.e. pH 11.6) is described. The electrodeposited film was obtained either by voltage cycling or by potentiostatic conditions using non-deaerated 0.1 M Na2CO3 solutions containing 40 mM tartrate ions and 4 mM CoCl2. The effects on the film formation and growth, such as tartrate-cobalt ratio, pH, applied potential, etc. were widely evaluated. The electrodeposition process, under anodic conditions and moderately alkaline solutions, most likely involves a redox transition Co(II) --> Co(III)/Co(IV) with destruction of the tartrate complex and formation of insoluble oxide/hydroxide cobalt species on the glassy carbon surface. The resulting cobalt oxyhydroxide films were characterised by cyclic voltammetry (CV) in 0.1 M NaOH solutions and by scanning electron microscopy (SEM) analysis after different strategies of preparation and various electrochemical treatments. The electrochemical activity of the deposited films was checked using various organic molecules as model compounds
PLATINUM/GLASSY CARBON ELECTRODE AS DETECTOR FOR LIQUID CHROMATOGRAPHIC DETERMINATION OF HYDROXYL-CONTAINING COMPOUNDS.
No full textA platinum-modified glassy carbon electrode was investigated as an amperometric sensor for the determination of alcoholic species in acidic medium. The described electrode was tested in liquid chromatography and flow-injection analysis by pulsed amperometric detection. It showed a promising combination among catalytic activity, detection limits and reproducibility for the determination of alcoholic species. The electrode response was stable; over 8 h a signal loss of less than 5% was observed. Linear responses at low concentrations yielded detection limits in the 0.6-1.8 mu g ml(-1) ranges for the various aliphatic alcohols. Typical relative standard deviations were comprised between 1.2% and 3.8% for all mono- and polyhydric compounds investigated. Linear plots of 1/I-p, and 1/C indicated Langmuir-type adsorption of analytes on the electrode surface. The Pt chemically modified electrode showed a few important differences with the bulk platinum electrode: i.e., a greater extension of linear range for relatively high concentrations and different trend of sensitivity towards the catalytic oxidation of mono-and polyhydric species
ELECTROOXIDATION OF ALIPHATIC ALCOHOLS ON PALLADIUM OXIDE CATALYST PREPARED BY PULSED ELECTRODEPOSITION TECHNIQUE.
No full textPalladium film can be deposited on gold polycrystalline electrodes, from a deoxygenated alkaline solution containing 50 mM NaOH plus 0.5 mM K(2)Pd(CN)(4). A multipulse sequence of potentials of equal amplitude and duration was used for the palladium deposition process. In particular, an optimized waveform of potentials of E(1) = 1.0V vs. SCE and E(2) = -1.0V VS. SCE for the relevant pulse duration of t(1) = 0.05 s and t(2) = 0.05 s, for 30 s, Was used. Cyclic voltammetry and scanning electron microscopy (SEM) were employed to characterize the gold-palladium modified electrode (Au-Pd) towards the electrooxidation of aliphatic alcohols in alkaline solutions. The voltammetric Study suggests that the kinetics involved in the alcohol electrooxidation at the Pd-Au electrode are sensibly higher than those observed on the bare Pd and Au electrodes. In addition, the most interesting aspect of the electrooxidation of aliphatic alcohols at the Au-Pd electrode was that as the number of methylene groups on the homologous series of aliphatic alcohols increased, the molar response also increased. Under pulsed chronoamerometric conditions (PCC), using an optimized triple pulse waveform of potentials the modified electrode exhibits interesting catalytic currents without any apparent poisoning effects during the oxidation of aliphatic alcohols. (C) 2009 Elsevier Ltd. All rights reserved
AN ELECTROCHEMICAL AND XPS STUDY OF Ag-Pb BINARY ALLOYS INCORPORATED IN NAFION COATINGS.
No full textGlassy carbon electrodes coated with thin films of Nafion(R) metalized with silver and lead species were investigated by cyclic voltammetry, chronoamperometry and X-ray photoelectron spectroscopy (XPS). Metalization of Nafion(R) film was accomplished by dipping the coated electrodes in 3 mM AgNO3 + 3mM Pb(NO3)(2) solution for 10 min. The resulting chemically modified electrodes were electrochemically characterized toward the oxidation of amino compounds in carbonate solutions buffered at pH 10. Under chronoamperometric experiments carried out at a constant applied potential of 0.95 V vs SCE, the linear range (r(2)>0.995) was determined to be at least three decades and the limit of detection range from 26 muM (ethylamine) and 65 muM (tert-butylamine), for the investigated amino compounds. The perm-selective properties of the Nafion(R) film with respect to anion species were investigated toward the electrooxidation of ethylamine in presence of large concentration of chloride ions. The XPS analysis revealed heterogeneous distribution of the catalytic species dispersed in the metalized Nafion(R) film. Thus, a comparison of the spectra of Ag3d and Pb4f acquired at various take-off angles, indicates an increase in the atomic ratio Ag:Pb and a notable enrichment of lead oxide species in the outer surface of the film when compared with the bulk membrane coated electrode
ELETTRODEPOSIZIONE DI FILMS A BASE DI OSSIDI DI RAME-TALLIO: LORO CARATTERIZZAZIONE ELETTROCHIMICA E SPETTROSCOPICA.
No full textPULSED ELECTRODEPOSITION OF PALLADIUM THIN-FILM FROM ALKALINE SOLUTIONS CONTAINING Pd(II)-CYANIDE COMPLEXES: AN ELECTROCHEMICAL AND XPS INVESTIGATION.
No full textA pulsed bipolar electrodeposition procedure of palladium film onto polycrystalline gold surfaces from alkaline solution containing dianion Pd(CN)(4)(2-) complex was investigated. Several experimental parameters such as pulse amplitude, pulse frequencies, pH, K(2)Pd(CN)(4) concentration, time of deposition, and electrode substrate, were evaluated and critically discussed. The palladium electrodeposition on the gold electrode substrates was performed using a multipulse of potentials. The optimized waveform should consist of oxidation potentials, E(1) = 1.0 V vs saturated calomel electrode (SCE) and a reduction potential, E(2) = - 1.0 V vs SCE. The relevant pulse duration of t(1) = 0.05 s and t(2) = 0.05 s (repetition rate of 10 Hz) for 30 or 60 s has to be chosen to give maximum efficiency of palladium electrodeposition. The deposited palladium film was characterized by using electrochemical and X-ray photoelectron spectroscopy (XPS) techniques. The probable mechanism of palladium electrodeposition involves in the first instance a strong and direct adsorption of Pd(CN)(4)(2-) complex on the gold surface at negative potentials, while during the subsequent anodic sweep, palladium oxide formation (PdO(n)) passes through the intermediate Pd(CN)(2) product and the simultaneous formation of a stable Au(CN)(2)(-) complex. The reduction process of palladium oxide species to form Pd(0) particles is simultaneously accompanied by the gold complex reduction process. The XPS analysis confirms the presence on the electrode surface of Pd(0), PdO, and PdO(2) species, while the oxygen-containing species increase significantly with increasing the palladium surface concentration
CARBOHYDRATE AND ALDITOL ANALYSIS BY HIGH-PERFORMANCE ANION-EXCHANGE CHROMATOGRAPHY COUPLED WITH ELECTROCHEMICAL DETECTION AT A COBALT-MODIFIED ELECTRODE.
No full textA cobalt oxyhydroxide film dispersed on a carbon electrode surface was characterized and proposed as an amperometric sensor for determination of alditols and carbohydrates in flowing streams. Complex mixtures of carbohydrates were separated by anion-exchange chromatography using a moderately alkaline solution as mobile phase. The cobalt modified electrode (GC-Co) was employed under a constant applied potential of 0.5 V (vs Ag/AgCl). Under these experimental conditions the detection limits (S/N=3) for all analyzed electroactive molecules ranged between 0.3 mumol L-1 and 1.5 mumol L-1 and the dynamic linear ranges spanned generally three orders of magnitude above the relevant detection limits. Analytical determinations of carbohydrates and alditols in red and white wines, are reported
Composite electrodes based on nanotubes/polydispersed metal particles. A voltammetric and morphological study.
No full textCobalt oxide electrodeposition on various electrode substrates from alkaline medium containing Co-gluconate complexes: a comparative voltammetric study
No full textAbstract: A study regarding the electrodeposition of Co oxides from alkaline medium containing 12 mM gluconate ligand and 12 mM Co2+ on glassy carbon, Au, Pt, Ni, Ti and ITO electrode substrate was carried out through cyclic voltammetry technique. Films of cobalt oxides were deposited either anodically by voltage cycling (100 mV s(-1)) between -0.3 and 0.6 V (SCE) or by potentiostatic conditions at potential comprised between 0.2 and 0.6 V for a fixed time of deposition. Analysis of the voltammetric experimental data clearly showed that the rate of cobalt oxide electrodeposition process decreases in the order Au > Pt > GC, Ni > Ti, ITO and the massive cobalt electrodeposition does not proceed to an appreciable extent until potentials of 0.3-0.4 V (SCE) is reached. The effect of the scan rate on the peak potential, peak current, an
STUDIES ON THE FORMATION OF THE METAL ION COMPLEXES IN PROPILENE CARBONATE. I: COMPLEX FORMATION BETWEEN COBALT (II) AND THIOCYANATE IONS.
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