Investigation on Cyclic Reciprocal Derivative Chronopotentiometry. Part II. Theoretical Equation for an Irreversible Reaction

2000 ◽  
Vol 65 (6) ◽  
pp. 971-978 ◽  
Author(s):  
Shuping Bi ◽  
Jian Chen ◽  
Tao Chen
Keyword(s):  
Transfer Coefficient ◽  
Rate Constant ◽  
Current Density ◽  
Mathematical Analysis ◽  
Electrode Reaction ◽  
Theoretical Equation ◽  
Irreversible Reaction ◽  
Reactant Concentration ◽  
Electrochemical Parameters ◽  
Rigorous Mathematical Analysis

A rigorous mathematical analysis is presented for an irreversible electrode process in the cyclic reciprocal derivative chronopotentiometry. Influences of basic electrochemical parameters, such as transfer coefficient α, rate constant ks, current density j, number of the electrons involved in the electrode reaction n and reactant concentration c0• on the properties of the dt/dE-E chronopotentiogram are described.

POLAROGRAPHY OF URANIUM: III. URANIUM(VI) IN FLUORIDE MEDIA

1957 ◽  
Vol 35 (10) ◽  
pp. 1225-1236 ◽  
Author(s):  
David J. McEwen ◽  
Thomas De Vries
Keyword(s):  
Electron Transfer ◽  
Transfer Coefficient ◽  
Rate Constant ◽  
Transfer Process ◽  
Rate Constants ◽  
Electrode Reaction ◽  
Electron Transfer Process ◽  
Fold Excess

The uranium(VI) and (V) polarographic waves were studied in chloride and perchlorate supporting electrolytes of 0.1 M to almost neutral acidities and containing 0 to 100 fold excess of fluoride. The concentrations of the uranium(VI)–fluoride species (UO2Fn+2−n, n = 1 − 4) were calculated and it is shown that the first two species, UO2F+ and UO2F2, are either reduced reversibly at the D.M.E., or dissociate rapidly to the uncomplexed ion, UO2++, which is known to reduce reversibly. The UO2F4− species, and possibly also UO2F3− is reduced irreversibly, and the rate constant of the electron transfer process, kf°, and the transfer coefficient, α, were calculated by two methods. The electrode reaction is proposed as UO2Fn+2−n+e− = UO2++nF−. The rate of disproportionation of uranium(V) was found to depend upon the F/U ratio, and the rate constants for the reaction were calculated.

scholarly journals Defining the transfer coefficient in electrochemistry: An assessment (IUPAC Technical Report)

2014 ◽  
Vol 86 (2) ◽  
pp. 245-258 ◽  
Author(s):  
Rolando Guidelli ◽  
Richard G. Compton ◽  
Juan M. Feliu ◽  
Eliezer Gileadi ◽  
Jacek Lipkowski ◽  
...  
Keyword(s):  
Transfer Coefficient ◽  
Current Density ◽  
Electrode Reaction ◽  
Elementary Step ◽  
Rate Theory ◽  
Common Source ◽  
Anodic Current Density ◽  
Transfer Coefficients ◽  
Electrode Reactions ◽  
Experimental Quantity

Abstract The transfer coefficient α is a quantity that is commonly employed in the kinetic investigation of electrode processes. In the 3rd edition of the IUPAC Green Book, the cathodic transfer coefficient αc is defined as –(RT/nF)(dlnkc/dE), where kc is the electroreduction rate constant, E is the applied potential, and R, T, and F have their usual significance. This definition is equivalent to the other, -(RT/nF)(dln|jc|/dE), where jc is the cathodic current density corrected for any changes in the reactant concentration at the electrode surface with respect to its bulk value. The anodic transfer coefficient αa is defined similarly, by simply replacing jc with the anodic current density ja and the minus sign with the plus sign. It is shown that this definition applies only to an electrode reaction that consists of a single elementary step involving the simultaneous uptake of n electrons from the electrode in the case of αc, or their release to the electrode in the case of αa. However, an elementary step involving the simultaneous release or uptake of more than one electron is regarded as highly improbable in view of the absolute rate theory of electron transfer of Marcus; the hardly satisfiable requirements for the occurrence of such an event are examined. Moreover, the majority of electrode reactions do not consist of a single elementary step; rather, they are multistep, multi-electron processes. The uncritical application of the above definitions of αc and αa has led researchers to provide unwarranted mechanistic interpretations of electrode reactions. In fact, the only directly measurable experimental quantity is dln|j|/dE, which can be made dimensionless upon multiplication by RT/F, yielding (RT/F)(dln|j|/dE). One common source of misinterpretation consists in setting this experimental quantity equal to αn, according to the above definition of the transfer coefficient, and in trying to estimate n from αn, upon ascribing an arbitrary value to α, often close to 0.5. The resulting n value is then identified with the number of electrons involved in a hypothetical rate-determining step or with that involved in the overall electrode reaction. A few examples of these unwarranted mechanistic interpretations are reported. In view of the above considerations, it is proposed to define the cathodic and anodic transfer coefficients by the quantities αc = –(RT/F)(dln|jc|/dE) and αa = (RT/F)(dlnja/dE), which are independent of any mechanistic consideration.

scholarly journals Electrochemical Investigation of Some Pharmaceutical Compounds at Mercury Electrode

2018 ◽  
Vol 34 (6) ◽  
pp. 2851-2858
Author(s):  
A. A. Al-Owais ◽  
I. S. El-Hallag
Keyword(s):  
Rate Constant ◽  
Digital Simulation ◽  
Supporting Electrolyte ◽  
Mercury Electrode ◽  
Simulation Method ◽  
Electrode Reaction ◽  
Cyclic Voltammograms ◽  
Triazole Derivatives ◽  
Aqueous Buffer ◽  
Electrochemical Parameters

The present work aims to report the investigation of the electrochemical behavior of 3- arylazomethine-1,2,4-triazole derivatives in universal aqueous buffer series at mercury electrode. The electrode behavior of the studied compounds was performed via voltammetric studies, chronoamperometry, convoluted transforms, and dp polarography techniques. The relevant chemical and electrochemical parameters of 3- aryl azomethine -1,2,4- triazole derivatives were determined experimentally in universal aqueous buffer series as supporting electrolyte at mercury electrode. CPC was used for determination of the number of electrons to elucidate the mechanistic pathway of electrode reaction of aryl azomethine triazole compounds. Digital simulation method was used to confirm the accuracy of the experimental chemical parameters (homogeneous chemical rate constant) and electrochemical parameters (heterogeneous rate constant, symmetry coefficient and redox potential) via matching between the experimental and theoretical cyclic voltammograms.

Spectrochemical Behavior of Carcinogenic Polycyclic Aromatic Hydrocarbons in Biological Systems. Part II: A Theoretical Rate Model for BaP Metabolism in Living Cells

1996 ◽  
Vol 50 (11) ◽  
pp. 1352-1359 ◽  
Author(s):  
Ping Chiang ◽  
Kuang-Pang Li ◽  
Tong-Ming Hseu
Keyword(s):  
Rate Constant ◽  
Living Cells ◽  
Rate Model ◽  
Number Density ◽  
Order Process ◽  
Irreversible Reaction ◽  
First Order ◽  
Metabolism Rate ◽  
Polycyclic Aromatic ◽  
Kinetics Of

An idealized model for the kinetics of benzo[ a]pyrene (BaP) metabolism is established. As observed from experimental results, the BaP transfer from microcrystals to the cell membrane is definitely a first-order process. The rate constant of this process is signified as k1. We describe the surface–midplane exchange as reversible and use rate constants k2 and k3 to describe the inward and outward diffusions, respectively. The metabolism is identified as an irreversible reaction with a rate constant k4. If k2 and k3 are assumed to be fast and not rate determining, the effect of the metabolism rate, k4, on the number density of BaP in the midplane of the microsomal membrane, m3, can be estimated. If the metabolism rate is faster than or comparable to the distribution rates, k2 and k3, the BaP concentration in the membrane midplane, m3, will quickly be dissipated. But if k4 is extremely small, m3 will reach a plateau. Under conditions when k2 and k3 also play significant roles in determining the overall rate, more complicated patterns of m3 are expected.

scholarly journals A Ni(OH)2 nanopetals network for high-performance supercapacitors synthesized by immersing Ni nanofoam in water

2019 ◽  
Vol 10 ◽  
pp. 281-293 ◽  
Author(s):  
Donghui Zheng ◽  
Man Li ◽  
Yongyan Li ◽  
Chunling Qin ◽  
Yichao Wang ◽  
...  
Keyword(s):  
Power Density ◽  
Current Density ◽  
High Performance ◽  
Low Cost ◽  
Electrode Reaction ◽  
Commercial Application ◽  
Ion Diffusion ◽  
Symmetric Supercapacitor ◽  
Red Led ◽  
A Current

Developing a facile and environmentally friendly approach to the synthesis of nanostructured Ni(OH)2 electrodes for high-performance supercapacitor applications is a great challenge. In this work, we report an extremely simple route to prepare a Ni(OH)2 nanopetals network by immersing Ni nanofoam in water. A binder-free composite electrode, consisting of Ni(OH)2 nanopetals network, Ni nanofoam interlayer and Ni-based metallic glass matrix (Ni(OH)2/Ni-NF/MG) with sandwich structure and good flexibility, was designed and finally achieved. Microstructure and morphology of the Ni(OH)2 nanopetals were characterized. It is found that the Ni(OH)2 nanopetals interweave with each other and grow vertically on the surface of Ni nanofoam to form an “ion reservoir”, which facilitates the ion diffusion in the electrode reaction. Electrochemical measurements show that the Ni(OH)2/Ni-NF/MG electrode, after immersion in water for seven days, reveals a high volumetric capacitance of 966.4 F/cm3 at a current density of 0.5 A/cm3. The electrode immersed for five days exhibits an excellent cycling stability (83.7% of the initial capacity after 3000 cycles at a current density of 1 A/cm3). Furthermore, symmetric supercapacitor (SC) devices were assembled using ribbons immersed for seven days and showed a maximum volumetric energy density of ca. 32.7 mWh/cm3 at a power density of 0.8 W/cm3, and of 13.7 mWh/cm3 when the power density was increased to 2 W/cm3. The fully charged SC devices could light up a red LED. The work provides a new idea for the synthesis of nanostructured Ni(OH)2 by a simple approach and ultra-low cost, which largely extends the prospect of commercial application in flexible or wearable devices.

Application of BDD thin film electrode for electrochemical decomposition of heterogeneous aromatic compounds

Open Physics ◽  
2012 ◽  
Vol 10 (5) ◽  
Author(s):  
Justyna Czupryniak ◽  
Aleksandra Fabiańska ◽  
Piotr Stepnowski ◽  
Tadeusz Ossowski ◽  
Robert Bogdanowicz ◽  
...  
Keyword(s):  
Current Density ◽  
Aromatic Compounds ◽  
Vapour Deposition ◽  
Microwave Plasma ◽  
Chemical Vapour ◽  
Grain Structure ◽  
Average Roughness ◽  
Bdd Electrode ◽  
Electrochemical Parameters ◽  
Initial Ph

AbstractThe aim of the presented study is to investigate the applicability of electrochemical oxidation of aromatic compounds containing heteroatoms, e.g. waste from production of pesticides or pharmaceutics, at a borondoped diamond (BDD) electrode. The BDD electrodes were synthesized by microwave plasma enhanced chemical vapour deposition (MW PE CVD). Investigation of the electrode surface by optical microscopy and scanning electron microscopy (SEM) confirmed that the synthesized layer was continuous and formed a densely packed grain structure with an average roughness of less than 0:5 μm. The influence of important electrochemical parameters: current density, kind of reactor, pH or mixing operation, on the efficiency of the oxidation was investigated. The fouling of electrode’s surface caused by the deposition of organic material was observed during CV and galvanostatic experiments. At low current density the oxidation rate constant k was low, but the current efficiency was relatively high. The BDD can be used successfully to remove heterogeneous aromatic compounds existing either as molecules or cations. During 4 h of electrolysis 95% of aromatic compounds were electrochemically decomposed to mineral forms. It was observed that the influence of the initial pH on mineralization was marginal.

Voltammetric investigation of the kinetics of alkali metal cation reduction in N,N-dimethylformamide

1975 ◽  
Vol 28 (2) ◽  
pp. 237 ◽  
Author(s):  
JW Diggle ◽  
AJ Parker ◽  
DA Owensby
Keyword(s):  
Electron Transfer ◽  
Alkali Metal ◽  
Propylene Carbonate ◽  
Rate Constant ◽  
Alkali Metal Cation ◽  
Electrode Reaction ◽  
Amalgam Electrode ◽  
Kinetics Of ◽  
Dipolar Aprotic Solvents

The standard electron-transfer heterogeneous rate constant of lithium, potassium, sodium and caesium amalgams in N,N-dimethylformamide was ascertained employing cyclic voltammetry in an effort to relate the presence of a non-equilibrium electrode reaction at the dropping lithium amalgam electrode to the variation of the lithium amalgam electrode potential with amalgam electrode con- figuration, i.e. whether streaming, dropping or stationary. Such variations are not observed at other alkali metal amalgam electrodes. ��� In the dipolar aprotic solvents the standard electron-transfer heterogeneous rate constant for the Li(Hg) electrode increases as the solvating power for Li+ decreases, i.e. dimethyl sulphoxide < di- methylformamide < propylene carbonate. Water is a much stronger solvator of Li+ than is propylene carbonate, but the electron transfer is faster in water than in propylene carbonate; the important role of entropic contributions in ion solvation is discussed as an explanation.

Electrochemical studies of Schiff base compounds derived from antipyrine nucleus in ethanolic buffer solutions

2000 ◽  
Vol 78 (9) ◽  
pp. 1170-1177 ◽  
Author(s):  
Ibrahim S El-Hallag ◽  
Gad B El-Hefnawy ◽  
Youssef I Moharram ◽  
Enass M Ghoneim
Keyword(s):  
Schiff Base ◽  
Electrochemical Behaviour ◽  
Electrochemical Techniques ◽  
Mercury Electrode ◽  
Electrode Reaction ◽  
Limiting Current ◽  
Electron Transfer Process ◽  
Buffer Solutions ◽  
Mechanistic Pathway ◽  
Electrochemical Parameters

The electrochemical behaviour of Schiff base compounds derived from an antipyrine nucleus was investigated in 30% (v/v) ethanolic buffer solutions (pH 3-11) using various electrochemical techniques at mercury electrode. The results showed that, the total limiting current of each of the studied compounds corresponds to 2-electron transfer process. The mechanistic pathway of the electrode reaction of the investigated compounds at mercury electrode, the effect of the medium, and the evaluation of the electrode reaction parameters were illustrated and discussed.Key words: Schiff base, antipyrine nucleus, electrode reaction, electrochemical parameters, cyclic voltammetry.

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