Nickel-dimethylglyoxime complex modified graphite and carbon paste electrodes: preparation and catalytic activity towards methanol/ethanol oxidation

Journal of Applied Electrochemistry (Impact Factor: 1.84). 12/2008; 39(1):55-64. DOI: 10.1007/s10800-008-9636-x

ABSTRACT Nickel-dimethylglyoxime complex (abbreviated as Ni(II)(DMG)2) modified carbon paste and graphite electrodes were prepared by mixing Ni(II)(DMG)2 with graphite paste, and coating Ni(II)(DMG)2 to the graphite surface. It is necessary to cycle the electrode potential to a high value (e.g. 0.8V versus SCE) for the
preparation of the modified electrodes. The electrochemical reaction was originally assumed to be a one-electron process converting
Ni(II)(DMG)2 to [(DMG)2(H2O)Ni(III)ONi(III)(OH)(DMG)2]−. [(DMG)2(H2O)Ni(III)ONi(III)(OH)(DMG)2]− showed a strong catalytic activity toward electro-oxidation of methanol and ethanol. The electrocatalytic oxidation currents
consistently increase with the increase in Ni(II)(DMG)2 loading, OH−, and alcohol concentrations. Rotating disk electrode results obtained with a Ni(II)(DMG)2 coated graphite disk electrode showed that the electrocatalytic oxidation of alcohol is a 4-electron process producing formate
anion (methanol oxidation) or acetate anion (ethanol oxidation). A mechanism for the electrocatalytic oxidation of methanol/ethanol
was proposed, and a rate-determining step was also discussed.

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    ABSTRACT: A Ni(II)-dimethylglyoxime ion-imprinted polymer {Ni(II)-DMG IIP} was synthesised by the bulk polymerisation method. The morphology of the Ni(II)-DMG IIP and non-imprinted polymer were observed by scanning electron microscopy and the chemical structures were evaluated by infrared spectroscopy. Selectivity of the Ni(II)-DMG IIP was studied by ana-lysing, using an inductively coupled plasma-optical emission spectrometer, for Ni(II) ions that were spiked with varying concentrations of Co(II), Cu(II), Zn(II), Pd(II), Fe(II), Ca(II), Mg(II), Na(I) and K(I) in aqueous samples. The studies revealed Ni(II) recoveries ranging from 93 to 100% in aqueous solutions with minimal interference from competing ions. Enrichment factors ranged from 2 to 18 with a binding capacity of 120 µg • g −1 . Co(II) was the only ion found to slightly interfere with the determination of Ni(II). Selectivity studies confirmed that the Ni(II)-DMG IIP had very good selectivity, characterised by %RSD of less than 5%. The limits of detection and quantification were 3x10 -4 µg • mℓ −1 and 9x10 -4 µg • mℓ −1 , respectively. The accuracy of the method was validated by analysing a custom solution of certified reference material (SEP-3) and the concentration of Ni(II) obtained was in close agreement with the certified one. The Ni(II)-DMG IIP was successfully employed to trap Ni(II) ions from a matrix of sea, river and sewage water. It is believed that the Ni(II)-DMG IIP has potential to be used as sorbent material for pre-concentration of Ni(II) ions from aqueous solutions by solid-phase extraction.
    Water S.A 11/2010; 4738(37). · 0.88 Impact Factor
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    ABSTRACT: Ni(II)-dimethylglyoxime ion-imprinted polymer (Ni(II)-DMG IIP) was encapsulated in polysulphone and electrospun into nanofibres with diameters ranging from 406 to 854 nm. The structures of the Ni(II)-DMG encapsulated-IIP nanofi-bre, non-imprinted encapsulated-polymer nanofibre and polysulphone nanofibre mats were observed by scanning electron microscopy and evaluated by infrared spectroscopy. Electrospinning increased the specific surface area of the Ni(II)-DMG encapsulated-IIP nanofibre mats, as was evidenced by the low masses of the Ni(II)-DMG encapsulated-IIP nanofibre mats used. The accuracy of the method was validated by analysing a custom solution of certified reference material (SEP-3); the concentration of Ni(II) obtained was close to the certified one. The limit of detection was found to be 4.0x10 -4 µg • mℓ −1 while the limit of quantification was found to be 1.2x10 -3 µg • mℓ −1 . The recovery of Ni(II) achieved using the Ni(II)-DMG imprinted nanofibre mats in water samples was found to range from 83 to 89%, while that of non-imprinted nanofibre mats was found to range from 59 to 65%, and that of polysulphone from 55 to 62%.
    01/2011; 4738(37).
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    ABSTRACT: The electrocatalytic oxidation of methanol was studied on Ni–P and Ni–Cu–P supported over commercial carbon electrodes in 0.1 M KOH solution. Cyclic voltammetry and chronoamperometry techniques were employed. Electroless deposition technique was adopted for the preparation of these catalysts. The effect of the electroless deposition parameters on the catalytic activity of the formed samples was examined. They involve the variation of the deposition time, pH and temperature. The scanning electron micrography showed a compact Ni–P surface with a smooth and low porous structure. A decreased amount of nickel and phosphorus was detected by EDX analysis in the formed catalyst after adding copper to the deposition solution. However, an improvement in the catalytic performance of Ni–Cu–P/C samples was noticed. This is attributed to the presence of copper hydroxide/nickel oxyhydroxide species. It suppresses the formation of γ-NiOOH phase and stabilizes β-NiOOH form. Linear dependence of the oxidation current density on the square root of the scan rate reveals the diffusion controlled behaviour.
    International Journal of Hydrogen Energy. 01/2010;


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