Showing papers by "Ch. Comninellis published in 2003"

Electrogeneration of Hydroxyl Radicals on Boron-Doped Diamond Electrodes

Abstract: The electrogeneration of hydroxyl radicals was studied at a synthetic B-doped diamond (BDD) thin film electrode. Spin trapping was used for detection of hydroxyl radicals with 5,5-dimethyl-1-pyrroline-N-oxide and with salicylic acid using ESR and liq. chromatog. measurements, resp. The prodn. of H2O2 and competitive oxidn. of formic and oxalic acids were also studied using bulk electrolysis. Oxidn. of salicylic acid gives hydroxylated products (2,3- and 2,5-dihydroxybenzoic acids). The oxidn. process on BDD electrodes involves hydroxyl radicals as electrogenerated intermediates. [on SciFinder (R)]

Electrochemical oxidation of water on synthetic boron-doped diamond thin film anodes

Abstract: Electrolysis in aqueous 1 M HClO4 and 1 M H2SO4 solutions has been carried out under galvanostatic conditions using boron-doped diamond electrodes (BDD). Analyses of the oxidation products have shown that in 1 M HClO4 the main reaction is oxygen evolution, while in H2SO4 the main reaction is the formation of H2S2O8. In both electrolytes small amounts of O3 and H2O2 are formed. Finally, a simplified mechanism involving hydroxyl radicals formed by water discharge has been proposed for water oxidation on boron-doped diamond anodes.

Electrochemical Behavior of Fluorinated Boron-Doped Diamond

Abstract: The surface properties and the electrochem. behavior of a fluorinated B-doped diamond (F-BDD) electrode prepd. by plasma treatment in CF4-He mixt. was studied by XPS and cyclic voltammetry in acidic media. The results showed C-F bonding (C-CF and C-F) on the surface of F-BDD, which made the surface more hydrophobic. Also hydrogen evolution was shifted to more cathodic potentials for fluorinated diamond, as compared with untreated BDD. Finally, the higher cathodic overpotential for hydrogen evolution permitted Ni deposition and nitrate redn. [on SciFinder (R)]

Dimensionally Stable Anode-Type Anode Based on Conductive p-Silicon Substrate

Abstract: In the search for a good dimensionally stable anode-type electrode, p-silicon (1-3 mW cm) has been chosen as the substrate material due to its high anodic stability and its reasonable cost compared to titanium and tantalum. Several p-Si/IrO2 electrodes have been prepd. by thermal decompn. at different temp. The effect of prepn. temp. on the morphol. and electrochem. properties has been investigated by SEM anal., X-ray diffraction, and cyclic voltammetry in 1 M HClO4 showing that p-Si/IrO2 prepd. at 450 DegC presents a high surface area and a low degree of crystallinity, while increasing the calcination temp. resulted in a decrease of true area and an increase in crystallite size. The activity of p-Si/IrO2 electrodes for simple electron transfer reactions and for complex electrode reactions has been also studied by cyclic voltammetry and linear polarization in solns. contg. the hydroquinone/benzoquinone redox couple and various org. compds. (isopropanol, tert-butanol, methanol). Finally, the anodic stability of a p-Si/IrO2 electrodes prepd. at 450 DegC has been tested by an accelerated service life test. p-Silicon based electrodes were shown to have the highest standardized service life compared with that of titanium- or tantalum-based electrodes. [on SciFinder (R)]