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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. 0.8 V 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 toNi(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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In this work, the structural and textural properties of the SiO2/Nb2O5 system prepared by the sol-gel method and then modified by phosphoric acid were studied. The different materials were prepared, with three different mol % Nb2O5 (2.5, 5.0, and 7.5 mol %), and calcined in the temperature range of 423-1273 K. BET specific surface area determinations, scanning electron microscopy connected to a X-ray emission analyzer, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS) were used for the investigation. For the lowest temperature of calcination (423 K), the mesopores and micropores of the modified material were blocked, resulting in a decrease of the specific surface area compared to the SBET values obtained for the SiNb matrix. Under intermediate temperatures of calcination (423-873 K), the modified material acquired textural stability. By XPS analysis, the presence of the dihydrogenphosphate species was identified, the P/Nb atomic ratios being independent of the thermal treatment. 31P magic angle spinning NMR confirmed the XPS data and also showed that the chemical shift of the (H2PO4)- ions strongly depended on the crystallization degree of the Nb2O5. Structural thermal stability was also shown by the presence of Brønsted acid sites in the modified material calcined at high temperature (1273 K). The thermal stability is directly associated with obtainment of the same value for K+ exchange capacity (0.74 mmol g(-1), average value) for the modified materials calcined at 423 and 1273 K. The chemical analyses of phosphorus for the modified materials were made by using the inductively coupled plasma. The value was 0.36 mmol g(-1), corroborating the presence of (H2PO4)- ions. The ion exchange isotherms presented an S-shaped form characteristic of energetically heterogeneous ion exchangers, permitting application of a model of fixed polydentate centers, in which ion exchange took place.

A ruthenium (III) hexacyanoferrate (Ru(HCF)) film coated on a glassy carbon electrode was explored as an electrocatalyst for hydrazine oxidation. Surface cyclic voltammograms of Ru(HCF) film showed four reversible one-electron redox waves. Two, which corresponded to the redox processes of Ru(III)/Ru(IV) and Fe(II)/Fe(III), were identified to be responsible for the catalytic activity of hydrazine oxidation. Kinetic studies using potential scan rate dependency, Tafel plots, and rotating disk electrode technique found that this catalyzed hydrazine oxidation was a complete four-electron/four-proton process producing N 2 , with the rate determining step possibly a one-electron process with a transfer coefficient (a) of *0.31-0.36. In addition, based on kinetic analysis and findings in the literature, we propose a possible reaction mechanism for catalyzed hydrazine oxidation in order to facilitate further understanding.