Ibrahim S. El-Hallag

ELECTROCHEMICAL OXIDATION OF IODIDE AT A GLASSY CARBON ELECTRODE IN METHYLENE CHLORIDE AT VARIOUS TEMPERATURES

ABSTRACT Anodic electrooxidation of iodide in 0.1 mol L -1 TBAP/ CH 2 Cl 2 was studied electrochemically via cyclic voltammetry, convolution transforms voltammetry, chronoamperometry and chronopotentiometry techniques at a glassy carbon electrode (GCE) at various temperatures ranging from -20 o C to 21 o C. It was found that at less positive potential triiodide (I -3 ) is formed followed by a moderate fast chemical process, while at more positive potential, the triiodide is oxidized to iodine (I 2 ) followed by another chemical process, i.e EC 1 EC 2 scheme. The effect of lowering the temperature on the heterogeneous electron transfer rate constant and the diffusion coefficient was discussed. The relevant chemical and electrochemical parameters of the electrode reaction were determined. The accurate test of the parameters evaluated experimentally was verified by comparing the experimental voltammograms with the simulated one. Keywords : Convolution transforms voltammetry, electrochemical parameters, digital simulation , chronoamperometry, chronopotentiometry.

ElEctrochEmical studiEs and Extraction of chEmical and ElEctrochEmical paramEtErs of Zn(ii) ion at mErcury ElEctrodE via convolutivE voltammEtry and digital simulation mEthods

aBstract The electrochemical behaviour of Zn(II) ion as example of C rev E irr system was studied at hanging mercury drop electrode in aqueous solution in the presence of 1M KCl using cyclic voltammetry and convolutive voltammetry methods. Digital simulation technique was used to test the chemical and electrochemical parameters of Zn(II) ion estimated experimentally as well as verifying the proposed electrode mechanism. Keywords: Electrochemical behaviour, C rev E irr system, cyclic voltammetry, convolutive Voltammetry, digital simulation. introduction The electroreduction of Zn(II) has been extensively studied in aqueous and non-aqueous solutions and found to be controlled by both diffusion and charge transfer. 1-6 At mercury electrode different mechanisms have been proposed for electrode reduction of metal cations, e.g., a simple electron transfer process 7,8 , stepwise electron transfer 9 , a CE or CEE mechanism. 10,11 Several literature reports a possible validity of a mechanism involving two one-electron transfer has been discussed.

Electrochemical Investigation of Some Ruthenium-Carborane Complexes at a Glassy Carbon Electrode

Summary. Ruthenium complexes of some carboranes were examined using cyclic voltammetry, chronoamperometry, chronopotentiometry, and digital simulation techniques derived from convolution-deconvolution voltammetry. The complexes under consideration are of the type X-RuC2B8H10 (X=hexamethylbenzene, para-cymene); all relevant electrochemical and chemical parameters were deduced and a mechanism is proposed.Zusammenfassung. Rutheniumkomplexe einiger Carborane wurden mit Hilfe zyklischer Voltammetrie, Chronoamperometrie, Chronopotentiometrie und digitaler Simulationstechniken im Zusammenhang mit Konvolutions-Dekonvolutions-Voltammetrie untersucht. Die Komplexe sind vom Typ X-RuC2B8H10 (X=Hexamethylbenzol oder Paracumol). Alle relevanten elektrochemischen und chemischen Parameter wurden abgeleitet; ein Reaktionsmechanismus wird vorgeschlagen.

Electrochemical investigation of N,N′-Propylene-bis-(salicylideneiminato) Mn(III) in phosphate buffer solutions

SummaryAn electrochemical study on N,N′-Propylene-bis-(salicylideneiminato) Mn(III) was performed using cyclic voltammetry with convolution-deconvolution and digital simulation in phosphate buffer solutions ofpH values ranging from 5–9.5 at a hanging mercury drop electrode (HMDE). The reduction pathway of the investigated complex shows that a moderately fast transfer of one electron is followed by a very fast chemical reaction (EqCirr scheme). The electrochemical parameters have been determined experimentally andvia digital simulation experiments.ZusammenfassungN,N′-Propylen-bis-(salicylideniminato)-Mn(III) wurde in Phosphatpufferlösungen mitpH-Werten im Bereich von 5–9.5 an einer Quecksilbertrofelektrode (HMDE) mittels cyclischer Voltammetrie (Konvolution-Dekonvolution, digitale Simulation) elektrochemisch untersucht. Ein mäßig schneller Transfer eines Elektrons wird von einer sehr schnellen chemischen Reaktion gefolgt (EqCirr-Schema). Die elektrochemischen Parameter wurden experimentell und durch Simulations-experimente bestimmt.

DATA ANALYSIS AND EVALUATION OF THE ELECTROCHEMICAL PARAMETERS FOR THE ET PROCESS VIA CONVOLUTIVE VOLTAMMETRY AND DIGITAL SIMULATION

Data treatment and determination of the standard heterogeneous rate constant of simple ET process (simple electron transfer) & number of electrons consumed in electrode reaction were carried out via convolution-deconvolution voltammetry and digital simulation methods. The working curves required for determination of the standard heterogeneous rate constant, k s , were constructed and discussed. The number of electrons, n, consumed in electrode reaction was calculated via simple method. The electro-reduction of Pb2+ was carried out at hanging mercury drop electrode while the redox behaviour of Fe3+ /Fe2+ couple was performed at glassy carbon electrode to confirm the validity of the reported method in calculation of k s and n in case of simple ET.

Electrochemical study of the hetero-bimetallic complex [MeNC(CO)2Mn(dppm)2Pt(H)(CNMe)]+PF 6 − at a glassy carbon electrode

SummaryCyclic voltammetry (CV), convolution-deconvolution transformation of current, chronopotentiometry (CP), and digital simulation studies were used to evaluate the kinetic parameters of the electrode reaction of the hetero-bimetallic complex [MeNC(CO)2Mn(dppm)2Pt(H)(CNMe)]+PF6− in dichloromethane at a glassy carbon electrode (GCE). It was found that the complex undergoes a reduction step at −0.895±0.01 V and two anodic steps at +0.903±0.01 V and 1.370±0.01 V. The reduction and oxidation steps are followed by a rapid chemical process. On the basis of the electrochemical results, an overall oxidation process was found to proceed as EEC, while the reduction process proceeds according to an ECEC scheme.ZusammenfassungCyclische Voltammetrie (CV), Strom-Konvolution-Dekonvolution, Chronopotentiometrie und digitale Simulation wurden zur Bestimmung der kinetischen Parameter der Reaktion des hetero-bimetallischen Komplexes [MeNC(CO)2Mn(dppm)2Pt(H)(CNMe)]+PF6− an einer Glaskohlenstoffelektrode (GCE) in Dichlormethan eingesetzt. Der Komplex zeigt eine Reduktionsstufe bei −0.895±0.01 V und zwei anodische Stufen bei 0.903±0.01 V und 1.370±0.01 V. Auf die Reduktions-und Oxidationsschritte folgt unmittelbar ein schneller chemischer Prozeß. Aus den elektrochemischen Ergebnissen läßt sich ein Gesamtoxidationsprozeß nach einem EEC — Schema ableiten, während die Reduktion nach einem ECEC — Schema verläuft.

Convolutive Cyclic Voltammetry, Chronopotentiometry, and Digital Simulation Studies of Chloride at a Glassy Carbon Electrode

Summary. The electrode reaction of chloride at a glassy carbon electrode (GCE) in 0.1 M tetrabutylammoniumperchlorate (TBAP)/dichloromethane (CH2Cl2) and its electrochemical parameters were determined via convolutive cyclic voltammetry and chronopotentiometric (CP) techniques. The parameters calculated from experimental data were tested by comparing the experimental voltammograms with the simulated data. Convolutive cyclic voltammetry was found to provide high sensitivity and better resolution than ordinary cyclic voltammetry.Zusammenfassung. Die Reaktion von Chlorid an einer Glaskohlenstoffelektrode (GCE) in 0.1 M Tetrabutylammoniumperchlorat (TBAP)/Dichlormethan (CH2Cl2) und seine elektrochemischen Kenngrößen wurden mittels konvolutiver cyclischer Voltammetrie und Chronopotentiometrie (CP) untersucht. Die experimentellen Ergebnisse wurden durch Vergleich der Voltammogramme mit simulierten Daten überprüft. Konvolutive cyclische Voltammetrie zeigt hohe Empfindlichkeit und ist bezüglich der Auflösung der konventionellen cyclischen Voltammetrie überlegen.