I. Duo

Platinum particles deposited on synthetic boron-doped diamond surfaces. Application to methanol oxidation

Two methods have been used for the deposition of Pt particles on synthetic boron-doped diamond (BDD) surfaces: chemical deposition and electrodeposition under potentiostatic conditions. However, electrodeposition leads much higher platinum dispersion than chemical deposition. The mechanism of nucleation and growing of the electrodeposited platinum was investigated by means of chronoamperometric studies in acid medium. The electrodeposition on diamond surfaces shows a mechanism of progressive nucleation as deduced from the chronoamperometric studies in acid medium. The stability of the deposited platinum is very low and the platinum particle are dissolved/detached by cycling. The modified BDD electrodes by deposition of platinum have been tested for the oxidation of methanol, showing that multi-step deposition results in higher values of surface and mass activities for methanol oxidation than one-step deposition process.

Electron Transfer Kinetics on Boron-Doped Diamond Part I: Influence of Anodic Treatment

Boron-doped diamond electrodes, both as-grown and polarized anodically under different conditions, were prepared in order to study the chemical and electrochemical changes of diamond and clarify the role played by the surface-state density. Many different treatments were employed: as-grown (BDDag), mildly polarized (BDDmild), strongly polarized in perchloric acid (BDDsevererpar;, and strongly polarized in a sulphuric acid-acetic acid mixture (BDDAcOHrpar;. Charge transfer processes at the electrode surface were studied by cyclic voltammetry. Simple electron transfer processes such as the outer-sphere redox system ferri/ferrocyanide (FeIII/II;(CN)6rpar; and complex charge transfer reactions such as the inner-sphere 1,4-benzoquinone/hydroquinone (Q/H2Q) redox reaction were chosen to test the electrochemical properties of the electrodes. The properties of the diamond electrodes were found to undergo strong modification as a function of surface treatment. The active surface area and the reaction rate constants decreased significantly upon anodic polarization. Important drops in the charge carrier concentration on the surface and in true surface area led to hindrance of electron transfer at the electrode.

Electrochemical Generation of Silver (II) at Boron‐Doped Diamond Electrodes

Synthetic boron-doped diamond (BDD) thin film electrodes were tested for the electrogeneration of silver(II). In nitric acid, the kinetics of the silver(I)/silver(II) couple were studied by cyclic voltammetry. The results demonstrate that silver(II) can be produced with high current efficiency by silver(I) oxidn. at BDD electrodes. At low concn. of nitric acid and high concn. of silver(I), AgO is formed on the electrode surface. [on SciFinder (R)]

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

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)]

Electrochemical Polishing of Boron-Doped Diamond in Organic Media

The electropolishing of a B-doped diamond (BDD) film deposited by CVD was studied in HOAc-H2SO4 media. The electropolished surface was characterized by SEM, XPS, and electrochem. measurements. In 1 M H2SO4 no polishing of the surface occurred even after prolonged time; on the contrary, in electrolyte contg. 3 M HOAc in 1 M H2SO4 the morphol. changed rapidly. The surface became smoother and the roughness decreased as the typical results of a polishing process. All the nondiamond impurities were also removed by the electropolishing treatment in HOAc media. [on SciFinder (R)]