Boron doped diamond microelectrodes arrays (MEA) have been prepared in order to be used as new amperometric sensors in electrochemical cells for HPLC detectors. The following parameters were studied: number and diameter (15–40µm) of the electrodes, distance between them (50–240µm), and effect of the flow rate (0.1–3mL/min). It was thus possible to find the optimum value of the parameters which give a good signal/noise ratio in the chronoamperometric responses, with a size of the electrochemical sensors as small as possible.

Lead dioxide deposits have been prepared as thin films Fluorine-doped tin oxide (FTO) substrates from methanesulphonate or nitrate-based plating solutions. The resulting electrodes exhibit lower oxygen evolution overpotential than FTO and their flatband potential is considerably higher. In addition, it is possible to increase their donor density by incorporating fluoride anions in the PbO2 coating.The electrodes have been designed for the generation of oxygen. It is shown that a transparent electrocatalytic FTO/PbO2 thin film assembly can be prepared by such process. (C) 2013 Elsevier B.V. All rights reserved.

An original selective and quantitative detection method for direct access to reactive oxygen species (ROS) generated in near-neutral aqueous solutions during transient electrochemical experiments is described herein. Several chemiluminescent probes, which were selected for their high selectivity toward ROS were used and the selective electrogenerated chemiluminescence (SECL) method was validated on several electrocatalytic materials known to exhibit different behaviors toward the oxygen reduction reaction (ORR); the examined electrodes consisted of platinum, Au(1 1 1), glassy carbon and boron-doped diamond (BDD). We first selected appropriate molecular probes that are suitable for use under electrochemical polarization conditions and that are chemiluminescent in the chosen aqueous solutions. The roles of the concentration, solubility and possible activation of the molecular probes were identified. Then, the information obtained by the simultaneous recording of the amperometric signal was correlated with the chemiluminescence intensity, which was measured with a highly sensitive photomultiplier tube (PMT). The experimental results were interpreted by constructing a potential vs. pH diagram for the oxygenated species. The complementary nature of the information about the mechanistic path of the ongoing mechanism of ORR on the different electrode materials allowed us to propose a unified scheme. A coupled proton electron transfer (CPET) mechanism can be invoked to explain the major differences observed from the identified reactive intermediates in relation to the electrocatalytic activity of the electrode materials. (c) 2013 Elsevier Ltd. All rights reserved.

Titanium is a valve metal able to withstand corrosion due to the presence of a passivating layer of titanium oxide on its surface But due to that more or less insulating layer titanium cannot be used directly as an anodic material However modification of the surface of a Ti/TiO2 substrate may lead to the formation of new structures Ti/TiO2/M or Ti/TiO2/OX in which M is a metal such as platinum and OX a conducting oxide exhibiting electrocatalytic properties These structures have interesting electrochemical properties and may be used as efficient electrode materialsIn this paper after a review of the electrochemical behaviour of these structures we give new results concerning the selective electrodeposition of lead dioxide on Ti/TiO2 substrates and we propose an interpretation of the results taking into account the dielectric properties of the underlying TiO2 It is shown that there is a dramatic decrease of the resistance of the electrode when a PbO2 layer is electrodeposited onto a Ti/TiO2 structure That effect allows the preparation of electrodes (low-cost DSAs) that may be used as anodes in spite of the presence of the underlying TiO2 layer that layer being useful to avoid corrosion of the titanium substrate At last the effect of stabilization of the underlying TiO2 layer is discussed (C) 2010 Elsevier Ltd All rights reserved

Accurate and rapid determination of Ti(IV) at low or trace levels in HClO4, HClO4-NaClO3, H2SO4, H2C2O4, H2C2O4-NaClO3 and H3PO4 media can be done by voltammetry at the mercury drop electrode. New reliable procedures implementing square wave and differential pulse voltammetries are described. Kinetic peak currents resulting from slow complex formation are proportional to the analytical concentration of Ti(IV). Calibration lines, figures of merit and formulae for the calculation of concentrations are given. Limits of quantification are determined with an accuracy of about +/- 10% using standard solutions. In acid oxalate-chlorate medium, where a catalytic reduction of Ti(IV) occurs, the precision and sensitivity of differential pulse voltammetry compare very favourably with other modern microanalytical methods. The limit of quantification is 10(-7) M. In the other media, this limit lies between 10(-5) and 10(-6) M.An extremely simple mathematical formula for the contribution of the sphericity of the mercury drop on the peak current in square wave voltammetry in the case of slow charge-transfer reactions is incidentally given. (c) 2006 Elsevier B.V. All rights reserved.

Titanium is a valve metal that is reported to be corrosion-resistant in acid media ; that property is attributed to the formation of a passive TiO2 film at the surface of the metal. The chemical stability and the electrochemical properties of TiO2 layers are strongly dependent on their preparation process. A careful study of those properties is a necessary step to propose titanium as a substrate for anodes in industrial electrolytic cells. Deposition of an electronic conductor coating on Ti/TiO2 substrates leads to « modified titanium electrodes ». These deposits may be: a noble metal (platinum) or a metallic oxide (RuO2, IrO2, PbO2...), i.e. conducting compounds which exhibit an electrocatalytic behaviour vs specific electrochemical reactions. In the present chapter, a particular attention is given to the electrochemical behaviour of modified titanium electrodes in aqueous solutions. First, the properties of the substrate are recalled. The passive layer is composed of TiO2, a n-type semiconductor that may be formed by thermal oxidation, chemical oxidation, or anodisation. The composition, thickness and electrochemical properties of those films are reviewed. Their conductivity may be enhanced considerably by doping. Second, the modification of the substrates by cathodic electrodeposition of a metal is described. That procedure is useful for preparing anodes coated with a noble metal. For example, Ti/TiO2/Pt structures exhibit a very interesting reactivity that will be illustrated by cyclic voltammetry or impedance spectroscopy experiments. Third, the modification of titanium electrodes by a metallic oxide is reviewed. It leads to the preparation of the well-known Dimensionally Stable Anodes (DSA). Their chemical mode of preparation is given, as well as the mechanisms involved in the use of these anodes and their deactivation process. It is also possible to deposit metallic oxides by an anodic process. The present paper is focussed on PbO2 electrodeposition, leading to « low-cost DSA » that may be used for the oxidation of Cr(III) to Cr(VI) in sulphuric acid. The anodic electrodeposition of PbO2 on oxidised polycrystalline Ti electrodes has been observed locally in particular circumstances; it occurs selectively on the (0001) grains. The topics reviewed in this paper are described using a large amount of data that were obtained in our laboratory.

Electrochemistry plays a major role in the quest for the preparation and the study of submicrometer and nanometer scale structures. Electrochemical deposit ion of small metallic clusters (1) and nanowires (2) is an attracting possibility to obtain modified surfaces for heterogeneous catalysis and especially electrocatal ysis. Studies concerning the chemical reactivity at nanom eterscale structures takes an increasing interest in electrochemical science. Specifically, the case of metal electrodeposition on semiconducting surfaces has be en studied on H-terminated Si(100) (3).