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The electrochemical behaviour of mixtures of phenazine (P) with iodine (I2) in the solid state was investigated. Three types of electrochemical experiments were conducted: (i) EMF measurements of the Ag/AgI/I2:P system for various I2 : P ratios, (ii) cyclic voltammetric (CV) experiments and (iii) potentiometric measurements of the open cell potentials after different cathodic charges were injected into the I2 : P pellets. In the first case, a detailed analysis of the observed electromotive force was presented. The Gibbs free energy of the I2 : P complex determined was in good agreement with earlier results. In the second case, the CV curves corresponding to the electrode processes of phenazine mixed with graphite in the solid state indicate that the mass and charge transfer, which occur in the pellets, are faster than expected. The potentiometric experiments confirm this conclusion. Additional experiments, conducted with pellets of different thickness, indicate that although, in comparison with an equilibrated pellet, the concentration profiles are modified in small layers (diffusion layers) neighbouring the electrodes, the electrode reaction probably occurs in the whole pellet. A tentative mechanism of these processes is discussed. Copyright © 2003 John Wiley & Sons, Ltd.

The electroreduction of nitromethane and 1-nitrohexane in both the absence and in the presence of n-octanol and n-decanol was studied. It was found that, under comparable conditions at smaller concentrations of inhibitors, nitromethane is inhibited more strongly than 1-nitrohexane by the n-alcohol adsorbed monolayer on the mercury electrodes. This was explained by the larger affinity of nitrohexane to the alcohol-rich surface phase and of nitromethane to the aqueous solution phase. Through the increased affinity of both reactants to the electrode surface phase at the inhibitor concentration, c/cs, exceeding 0.6, the independence of the electroreduction rate constant of both reactants was explained. When the bulk concentration of inhibitors approached saturation even the increase of the rate constant was observed. The change of the solvent composition, from pure water to 10 vol. % ethanol, increases the inhibition by increasing the affinity of the reactant to the solution phase.

The electrooxidation of in situ produced electrolytically radical anion of 3-nitrophthalic acid in various water—ethanol solutions containing 0.5 M NaCIO4, 0.05 M NaOH and inhibitor has been studied. The inhibition of the electrode kinetics in the presence of n-octanol and n-decanol, used as inhibitors, at relative concentrations not exceeding c/cs ≤ 0.5 could be interpreted in terms of the competitive monolayer adsorption of reactant, inhibitor and solvent on the electrode surface. At c/cs > 0.8, on the capacitance-potential curves, a subtle minima caused by formation of two layers adsorbed on the mercury electrode were observed. The kinetics of the electrooxidation of the 3-nitrophthalic acid anion radical was additionaly influenced by this multilayer. An equation which describes the inhibition of the electrode process by two adsorbed layers of inhibitor is presented and used in the estimation of the surface coverage in the second layer.

The parameters α, β and γ of the equation WΔsGf(MX) = αBKT + βET + γ were calculated and analysed for different salts (MX) in pure solvents and in non-aqueous solvent–water mixtures (S). Among 109 different equations, only 64 were taken for the final analysis since in the case of 38 equations the parameters BKT and ET were highly correlated. After a statistical analysis and normalization, on the basis of the coefficients α and β obtained, it was found that the ions analysed may be divided into three classes characterized by the different dependences of α on β: class I, H+, Li+, Na+, Rb +, Cs+, Me4N+, Cl−, Br− and I−, where αN = 1.074βN + 1.639; class II, Ag+, Cl−, Br−, I−, OAc−, SCN− and N where αN = 2.057βN + 2.147; and class III, Ph4As+, BPh, Ph4C and Ph4Ge, where αN is variable and βN is almost constant. Two main conclusions can be drawn out from the results obtained: the behaviour of ions considered as Lewis acids and bases reflects different hard–soft properties of the ions, and the behaviour of the Ph4As+ ion is different from that of BPh.

The sections in this article are Double-layer Properties of Cadmium Electrodes Electrochemical Properties and Kinetics of the Cd(II)/Cd(Hg) Systems Electrochemistry in Aqueous Solutions Kinetics of Simple Ions Influence of a Catalyst Influence of Inhibitors Electrochemistry in Mixed and Nonaqueous Solvents Electrochemical Properties of the Cadmium Complexes Determination of Stability Constants Electrochemical Preparation of Cadmium Complexes Preparation and Electrochemical Properties of Cadmium Chalcogenides CdS CdSe CdTe Properties of Cadmium Intermetallic Compounds Cadmium Underpotential Deposition and Electrodeposition on Solid Electrodes Deposition of Cd on Cadmium Electrode Electrodeposition of Cd on Other Solid Substrates Gold Platinum Silver Copper Silicon Other Substrates Passivation and Corrosion of Cadmium Passivation of Cadmium Electrode Corrosion of Cadmium Applied Electrochemistry Batteries Cadmium–Mercuric Oxide Primary Cells Cadmium–Nickel Oxide (Ni–Cd) Secondary Cells Cadmium–Silver Oxide Secondary Cells Application in Electrochemical Sensors Potentiometric Sensors Amperometric-voltammetric Sensors

The sections in this article are Double-layer Properties of Pb Electrodes Properties of Solid Electrodes Properties of Liquid Electrodes Adsorption on Solid Electrodes Electrochemical Properties and Kinetics of Lead and Lead Compounds Pb(II)/Pb(Hg) System Studies in the Presence of Inhibitors and Organic Solvents Other Phenomena Complexes of Pb(II) and Related Phenomena Electrochemical Processes of Liquid Lead in Molten Salts Voltammetric Behavior of Lead Sulfuric Acid Solutions Nitric Acid Solutions Phosphoric Acid Solutions Sodium Hydroxide Solutions Different Salt Solutions Voltammetric Behavior of Several Lead Compounds PbO PbO2 Pb chalcogenides Electrodeposition and Underpotential Deposition of Lead on Solid Substrates Platinum Gold Silver Copper Carbon Silicon Germanium Other Materials Corrosion and Passivation Applied Electrochemistry Lead-acid Batteries Electrocatalytic Properties Pb PbO2 Electrochemical Sensors Potentiometric Sensors Amperometric/Voltammetric Sensors

The sections in this article are Double-layer Properties of Zinc Electrodes Pc-Zinc in Aqueous Solutions Zn Single Crystals in Aqueous Solutions Electrochemical Properties and Kinetics of the Zn(II)/Zn(Hg) and Zn(II)/Zn Systems Electrochemistry in Aqueous Solutions Electrochemistry in Water-organic Solvent Mixtures Electrochemistry in Nonaqueous Solvents The Influence of Organic Compounds on the Electrode Processes The Electrochemical Properties of the Zinc Complexes Properties of Zinc Oxide Electrode Electrode Processes in Molten Salts Deposition and Underpotential Deposition of Zn on Solid Electrodes Underpotential Deposition of Zinc Zn UPD on Pt Zn UPD on Au Zinc Electrodeposition on Solid Electrodes Electrodeposition on Zn Electrodes Electrodeposition on Other Electrodes Passivation and Corrosion of Zinc Anodic Dissolution and Passivation of Zinc Corrosion Applied Electrochemistry Batteries Ni–Zn Cells Zn–Air Batteries Zn–MnO2 Batteries Zn–Ag Batteries Other Cells Electrowinning Zinc Electroplating Zinc Alloys Electroplating Electrochemical Sensors and Modified Electrodes Potentiometric Sensors Voltammetric/Amperometric Sensors Modified Electrodes

The sections in this article are Double-layer Properties of Hg/Water Interface Potential of Zero Charge Surface Charge Density and Capacitive Current Experimental and Theoretical Studies of the Hg/Water Interface Double-layer Properties of Hg/Nonaqueous Media Interface Adsorption and Electrode Reactions at Hg Surface Deposition and Underpotential Deposition of Hg on Various Electrodes Underpotential Deposition of Mercury on Gold Electrodes Film Electrodes and Related Hg Electrodes Adsorption and Electrode Reactions of Inorganic Ions and Coordination Compounds of Metal Ions Analytical Applications Adsorption and Electrode Reactions Involving Organic Compounds Organic Compounds Containing Sulfur, Selenium, and Tellurium Organic Nitrogen Compounds Indicators and Dyes Vitamins and Antibiotics Enzymes and Coenzymes Other Organic Compounds Analytical Aspects of Adsorption of Organic Compounds Ammonium and Quaternary-substituted Ammonium Amalgams

The sections in this article are Preparation of Au Surfaces and Double-layer Properties Polycrystalline (pc-Au) and Single-crystal Au/H2O Interface pc-Au and Single-crystal Au/Nonaqueous Solutions Interface Adsorption of Inorganic Compounds on Gold Electrodes Sulfate Hydroxide Nitrate Chloride Bromide Iodide Cyanide Thiocyanate Other Inorganic Species Adsorption of Organic Compounds on Gold Electrodes Adsorption of Sulfur-containing Compounds Adsorption of Thiols Adsorption of Modified Thiols Adsorption of Thiourea Adsorption of Disulfides and Related Compounds Other Sulfur Compounds and Complex Adsorption Layers Adsorption of Selenium-containing Compounds Adsorption of Nitrogen-containing Compounds Pyridine and its Derivatives Pyrazine Amines and Other Nitrogen-containing Compounds Adsorption of Other Organic Compounds Alcohols Aminoacids Other Organic Acids Nucleic Bases and Other Biochemical Compounds Other Compounds Reconstruction of the Surface of Gold Electrodes Formation of Oxides on Gold Electrodes Underpotential Deposition of Various Metals on Au Cu Cd Pd S, Se, and Te Sulfur Selenium Tellurium Bi Pt Ni Co Sb Sn Al Tl Pb Zn Ge Rh Li Fe Ag Hg Electrochemistry of Coordination Compounds of Gold. Electrodissolution and Electrodeposition of Au Au Electrodeposition Au Electrodissolution Gold Clusters

The sections in this article are Properties of Ag Electrodes Polycrystalline Ag Electrodes Preparation Surface and Double-layer Properties Single-crystal Ag Electrodes Preparation Surface and Double-layer Properties Surface Dynamics Affinity of Water and Nonaqueous Solvent Molecules to Ag Surfaces Adsorption of Inorganic Species on Ag Electrodes Halide Ions pc-Ag Electrodes Single-crystal Ag Electrodes Pseudohalide Oxygen and its Compounds Sulfur Compounds Inorganic Carbon Compounds Fullerenes Other Inorganic Compounds Metalocenes Adsorption of Organic Species on Ag Electrodes Hydrocarbons Pyridine and Other Nitrogen Compounds Carboxylic Acids Alcohols Sulfur Compounds Thiourea (TU) Alkanethiols and Self-assembled Monolayers Biochemically Important Compounds Adsorption on Modified Ag Electrodes Other Organic Compounds Electrode Processes with Participation of Silver Electrodes Reactions Involving Oxidation of Ag Surface Oxygen and its Compounds Sulfur Compounds Carbon Compounds Electrode Reactions of Selected Organic Compounds, Adsorbed on Ag Electrodes Biochemically Important Species Underpotential Deposition Processes Ag UPD on Ag Ag UPD on Au and Pt Pb Tl Ni Chalcogenides Other Elements and Compounds Electrodeposition and Electrodissolution Processes of Ag Electrodeposition Processes Electrodissolution Processes Silver Compounds at the Oxidation States Higher Than I

Voltocoulometric, chronocoulometric and cyclic voltammetric studies of the electrode reaction of Tl(2,2,2)+ cryptate at mercury electrodes are described. This process occurs via two parallel pathways – from the solution and from the adsorbed states which are energetically close. The kinetic and adsorption parameters of thallium(I) cryptate electroreduction were found by analysis of the normal pulse voltocoulometric curves recorded with a 1 ms delay after the application of the potential pulse. Such Qt−1-E dependences are characterized by a maximum that originates from the electroreduction of the adsorbed reactant. The model for numerical simulation of such curves was developed. Comparison of experimental and simulated curves allowed to determine apparent standard rate constant of Tl(2,2,2)+/Tl(Hg) couple as equal to 8×10−3 cm s−1, thus significantly lower than that for noncomplexed Tl+ /Tl(Hg) system. The stability constant of the Tl(2,2,2)+ complex (log K=6.70) and the surface coverage of the electrode by Tl+ were determined.

On the basis of potentiometric measurements, the solubility product of PtZn2 in mercury was found to be 1×10−14 M3 at 298 K. The stoichiometry of this compound was also confirmed in voltammetric experiments using the hanging mercury drop (HMDE) and carbon paste electrodes Analysis of one-cycle chronopotentiometric results, based on precipitation of PtZn2 in saturated Pt amalgam and electroreduced Zn, enabled the solubility of platinum in mercury to be estimated as (5±1)×10−4 at. % or 3×10−4 M at 298 K.

The kinetics of the Eu(III)/Eu(II) system at mercury electrodes has been investigated in water, acetonitrile (AN), N,N-dimethylformamide (DMF) dimethylsulphoxide (DMSO) and hexamethylphosphoramide (HMPA). Formal potentials Efo move towards more negative values in the order AN

Durch cyclische Chronovoltammetrie wird die Elektroreduktion von V(IV) in angesaurerten CaCl2-Losungen an Hg-Elektroden untersucht.

The electrode process Bi(III)+ 3e = Bi(Hg) has been investigated in weakly acidic, neutral and alkaline solutions by means of amalgam polarography and cyclic voltammetry and chronopotentiometry with the use of hanging amalgam drop electrode. It has been found that in weakly acidic and neutral solutions, oxidation of bismuth amalgam goes through aquocomplexes of bismuth. In the cathodic step on cyclic voltammetry curves four peaks of reduction are observed, with magnitude and shape strongly dependent on pH of the solution. These peaks have been ascribed to the reduction of Bi3+, Bi(OH)+2, Bi(OH)+2 and Bi(OH)3. In alkaline solutions, oxidation of bismuth amalgam leads to Bi(OH)3. In cathodic scan on cyclic voltammetry curves only one peak is observed, which corresponds to Bi(OH)3 reduction. Formal potentials of electrode process and solubility product of Bi(OH)3 have been calculated and discussed. The step-wise nature of the overall electrode reaction has been ascertained and discussed. At higher concentrations of OH− ions, Bi(OH)3 dissolves.

Summary A mechanism for the electroreduction of nitrosobenzene in DMF is proposed. A multistep electrode reaction has been found with two paths: (a) direct reduction of PhNO∸, and (b) reduction via the intermediate azoxybenzene formed and chemical reaction. The mechanism of transformation of PhNO∸ formed in the first step into azoxybenzene, and ion pairing effects are also described and discussed. Experimental association constants for ion pair formation are correlated with simple quantum chemical calculations of association energies.

At high ionic strength the ion pair (NiPy2+4, nX−) or complex (NiPy4X2), n = 0, 1, 2; X− = Cl−, Br−, SCN−, N−3, F−, NO−3, ClO−4; is adsorbed at the surface of mercury electrode. Under specified conditions in chloride, bromide, and thiocyanates solutions the electroreduction is preceded by a crystallization of a complex on the electrode surface. The inductive role of specifically coadsorbed Cl− ions is discussed.

Chronovoltammetrisch werden Kinetik und Mechanismus der Reaktion Ti(IV) e - Ti(III) an der Hg-Elektrode in NaClO4- oder Ca(ClO4)2-Losung untersucht.