Didier Gandini

Oxidation of carboxylic acids at boron-doped diamond electrodes for wastewater treatment

Thin boron-doped diamond films have been prepared by HF CVD (hot filament chemical vapour deposition technique) on conductive p-Si substrate (Si/Diamond). The morphology of these Si/diamond electrodes has been investigated by SEM and Raman spectroscopy. The electrochemical behaviour of the Si/diamond electrodes in 1 M H2SO4 and in 1 M H2SO4 + carboxylic acids has been investigated by cyclic voltammetry. Finally, the electrochemical oxidation of some simple carboxylic acids (acetic, formic, oxalic) has been investigated by bulk electrolysis. These acids can be oxidized at Si/diamond anodes to CO2, in the potential region of water and/or the supporting electrolyte decomposition, with high current efficiency.

Oxidation of organics by intermediates of water discharge on IrO2 and synthetic diamond anodes

IrO2 and boron-doped diamond electrodes were tested by preparative electrolysis of simple model compds. in acid medium. In oxidn. reactions of more complex mechanism than simple electron transfer, these electrodes are active only at potentials of simultaneous oxygen evolution. At IrO2 electrodes, the reaction is mediated by chemisorbed oxygen, probably forming IrO3-type active sites, and yield highly selective oxidn. products at low overpotentials and with moderate current efficiency. At diamond electrodes, mediation at high overpotentials is due to physisorbed OH radicals leading to complete combustion of the org. compd. with high current efficiency. [on SciFinder (R)]

Electrochemical Behavior of Synthetic Diamond Thin Film Electrodes

The inertness and unique electrochem. properties of diamond present great potential for a variety of applications in aggressive environments. Preliminary results showed the widest known electrochem. window before water decompn., allowing new possibilities for both anodic and cathodic reactions. Studies of the oxidn. of org. compds. was performed with alcs. such as isopropanol, phenol and org. acids. Cyclic voltammetry demonstrates no activity in the potential range where water is stable. In the potential region of oxygen evolution, the org. compds. are mainly oxidized to CO2. No deactivation or redn. in the thickness of the electrode was obsd. No fouling of the diamond surface was detected. Also, no hydrodynamic effects were obsd. Concd. (1 M) and dild. (3 * 10-4 M) cyanide solns. were oxidized on diamond electrodes both in the presence and in the absence of chloride ions. The results show a direct oxidn. with a current efficiency of .apprx.40% for concd. solns. At low cyanide concns., the current efficiency is strongly increased by the presence of Cl-. Electrochem. redn. of cadmium and copper was carried out on diamond electrodes. Nonadherent deposits were obtained on diamond cathodes. [on SciFinder (R)]

Preparation and characterization of Ti/Diamond electrodes

Boron doped diamond films were deposited on Ti substrates by CVD. Raman spectroscopy reveals small amts. of nondiamond carbon. According to SEM and XRD, the diamond films are polycryst. with preferential {112} crystallite orientation. Electrochem. measurements show that the Fe(CN)63-/4- couple behaves in a quasi-reversible manner at the Ti/diamond electrode. The main reason of the successful prepn. of the Ti/diamond electrode is the formation of an conductive TiC interlayer between the Ti substrate and the diamond coating. [on SciFinder (R)]

Diamond-sensing microdevices for environmental control and analytical applications

Abstract For the fabrication of microdevices with line widths approching 1 μm, a patterning methodology has been developed by the modification of an existing plasma etching process, which is suitable for any form and type of diamond. These microdevices have been tested as active sensing elements for both environmental control and metrological applications: voltammetric detection of chlorine, detection of atomic oxygen for space and terrestrial applications, the measurement of ultraviolet (UV) light, and finally, conductive atomic force microscopy (AFM), which is successfully performed today with microfabricated diamond tips.