Levich Analysis Research Articles

Cathodic electrodeposition of CuSCN thin films

Cathodic electrodepositon of CuSCN thin films on F-doped SnO2 (FTO) substrates has been investigated in aqueous mixed solution of copper perchlorate and lithium thiocyanate. Cathodic current arose around +0.5 V vs. Ag/ AgCl and reached a plateau below ca. +0.3 V in the mixed solution. Levich analysis of the plateau current confirmed limitation of CuSCN deposition by mass transport. The current was proportional almost symmetrically to the concentrations of Cu2+ and SCN-, suggesting that transport of their complex was responsible. Absorption spectrum of the mixed solutions indeed revealed an appearance of a new peak only when both Cu2+ and SCN- were present. Job plot for this peak elucidated formation of 1 to l complex. As the concentration of this active species could be determined from the absorption spectra, Levich analyses at different temperatures made it possible to determine the frequency factor (Do) of and the activation energy (Ea) for the diffusion of (Cu2+)(SCN-) complex as 3.24 x 10-2 cm2 s-1 and 20.1 kJ mol-1 , respectively.

Oxygen reduction reaction on spontaneously and potentiodynamically formed Au/TiO 2 composite surfaces

From aqueous solutions, gold was deposited on freshly polished titanium surface either by displacement reaction or by potentiodynamic polarization. Both of these procedures resulted in the formation of Au/TiO 2 composite layer over the titanium surface, although with quite different Au content. The electrochemical behaviour of these composite layers was examined in 0.1 M NaOH solution, both oxygen free and oxygen saturated, using rotating disc technique. In the potential region of oxygen reduction reaction, the Au/TiO 2 layer obtained by potentiodynamic polarization, displayed the voltammetric curve similar to that observed on (1 0 0) plane of Au monocrystal. The Koutecky–Levich analysis evidenced that 4e − route of oxygen reduction dominates on both type of composite layers.

Electrocatalytic reduction of oxygen at platinum particles photodeposited on polyaniline/Nafion film

AbstractPlatinum based electrocatalyst for oxygen reduction reaction was prepared by photodeposition of platinum (Pt) particles on the surface of polyaniline/Nafion (PANI/Nafion) composite film. Polyaniline (PANI) acts as a convenient catalyst for the photodeposition of Pt particles and thus gives extremely low platinum loading, from 3 to 32 µg/cm2, on the surface of the PANI/Nafion composite film. Normal cyclic voltammetry (CV) studies were carried out to investigate the influence of different photodeposition conditions. Rotating disc electrodes (RDEs) were used to affirm the oxygen reduction mechanism of these catalytic membranes. Parameters such as the total transferred electrons, limiting reduction current density were determined by Koutecky–Levich analysis of the RDE results. Copyright © 2006 John Wiley & Sons, Ltd.

Water diffusion coefficients during copper electropolishing

Cu electropolishing was studied using a rotating disc electrode in a variety of phosphoric acid-based electrolytes, including several with ethanol and other species added as diluents. Diluents allow a wider range of water concentrations and electrolyte viscosities to be accessed and also reduce the removal rate during Cu electropolishing, simplifying possible application to damascene processing. Transient and steady state currents in the mass transfer limited regime are shown to depend on both the number of water acceptor molecules associated with each dissolving Cu ion and on the effective diffusion coefficient of water. Transient analysis samples the bulk transport properties, whereas steady state analysis integrates them through the diffusion layer. Assuming that the effective diffusion coefficients appropriate to transient and steady state behavior are the same, about one water molecule is associated with each dissolving Cu ion. This analysis yields effective diffusion coefficients for water on the order of 10−9cm2s−1. However, the data is also consistent with an assumption that six water molecules are associated with each dissolving Cu ion, but the effective diffusion coefficient appropriate for a Levich analysis is somewhat lower than that in the bulk electrolyte. This analysis yields effective diffusion coefficients for water on the order of 10−8–10−7cm2s−1. The latter interpretation, that six water molecules are associated with each dissolving Cu ion, appears more likely since it provides almost exact agreement with the effective diffusion coefficient reported previously by Vidal and West. In combination with previously published impedance results ruling out a salt film mechanism, the good agreement between the transient and steady state analyses confirm that water is the acceptor species that complexes dissolving Cu ions in phosphoric acid-based electropolishing baths.

Mechanistic Studies of Cu Electropolishing in Phosphoric Acid Electrolytes

Electropolishing of Cu and Cu/Ta/Si wafer samples were studied using a rotating disk electrode in a variety of phosphoric acid-based electrolytes, including several with ethanol and other species added as diluents. Diluents allow a wide range of water concentrations to be accessed and also reduce the dissolution rate during Cu electropolishing, simplifying possible applications to damascene processing. The measured limiting current densities are subject to a Levich analysis, demonstrating that water is the acceptor species involved in the rate-determining step. The effective diffusion coefficient that is determined is in almost exact agreement with that previously obtained from the electrohydrodynamic impedance, which does not require knowledge of the limiting species. © 2004 The Electrochemical Society. All rights reserved.

連続自動測定マクロ言語を装備したオープンソース電気化学測定システムの開発

An open-source electrochemical measurement system called ECHAN (ElectroCHemical ANalyzer) has been developed with Visual Basic Language. This software enables automated measurement of electrode samples with macro language successively through various electrochemical methods. Cyclic voltammetry, rotating ring-disk voltammetry, potential step chronoamperometry, current vs. rotation speed measurement and multipotentiostat measurement are all carried out with this single software. It is also equipped with a searching function by keywords and measurement conditions. After measurement, data can be processed by FFT (Fast Fourier Transform) low pass filter, smoothing by the simple moving average or the Savitzky-Golay method and operations between two data sets. It makes possible the evaluation of electro-catalysis by the Koutecky-Levich analysis, the Levich analysis, the electron number concerned with oxygen reduction reaction, chronoamperometry analysis by Cottrell's equation, coulomb number calculation and the Tafel analysis. Since an A/D board is used for data sampling, this program is applicable to a conventional potentiostat, which is usually connected to an X-Y recorder.

Synthesis and characterization of osmium carbonyl cluster compounds with molecular oxygen electroreduction capacity

A transition metal cluster electrocatalyst based on Os x (CO) n was synthesized by pyrolysis of Os 3(CO) 12 in 1,2-Dichlorobenzene (b.p.≈180°C) under inert atmosphere (N 2). The electrocatalytic parameters of the oxygen reduction reaction (ORR) for an Os x (CO) n catalyst were studied with a rotating disk electrode in 0.5 M H 2 SO 4 electrolyte. The diffusion coefficient and solubility of O 2 in 0.5 M H 2 SO 4 were calculated. Koutecky–Levich analysis of the linear voltamperometry data showed that the reaction follows first-order kinetics and the value of the Koutecky–Levich slope indicates a multielectron charge transfer during the ORR. The value of the Tafel slope obtained from the mass transfer corrected Tafel plots is 131 mV/ decade . The performance of the catalyst in a H 2/O 2 PEM fuel cell cathode was evaluated and found to be nearly as good as that of Pt.

Electrohydrodynamic Impedance in the Presence of Nonuniform Transport Properties

A numerical model is described for electrohydrodynamic impedance spectroscopy (EHDIS) in the presence of viscosity and diffusivity gradients near the electrode. The viscosity is assumed to depend on the concentration of a diffusion-limited reaction product raised to a power. An effective diffusion coefficient measured from a Levich analysis is shown to approach the near-surface value of the diffusion coefficient when the near-surface kinematic viscosity is greater than in the bulk. Similarly, EHDIS measurements can lead to quick estimates of near-surface viscosity. The model is applied to interpret experimental data for the steady-state limiting current and electrohydrodynamic impedance of the zinc-KOH system. © 2001 The Electrochemical Society. All rights reserved.

Electrochemical characterization of tungsten carbonyl compound for oxygen reduction reaction

The results of electrochemical studies carried out on W x (CO) n electrocatalyst are presented in this article. W x (CO) n was synthesized from W(CO) 6 in xylene at 140°C. The kinetic studies were carried out in 0.5 M H 2SO 4 solution under a three-electrode configuration. Linear voltametry studies on W x (CO) n reveal significant catalytic activity of the material for oxygen reduction. Koutecky–Levich analysis of the voltametry data shows that the reaction follows first-order kinetics and the value of the Koutecky–Levich slope indicates a multi-electron charge transfer in the oxygen reduction reaction. The value of Tafel slope is found to be −120 mV/ decade from the mass-transfer-corrected Tafel plots. The charge transfer coefficient and exchange current density were found to be 0.66 and 8.4×10 −5 A/cm 2 , respectively.

Electrocatalytic reduction of dioxygen at platinum particles dispersed in a polyaniline film

Platinum based electrocatalysts for the oxygen reduction reaction were prepared by electrodeposition of Pt particles in a polyaniline film acting as a convenient matrix to achieve low Pt loadings (from 11 to 600 μg cm −2). Using a rotating disc electrode or a rotating ring disc electrode allowed us to separate the different contributions in the overall reaction : diffusion of molecular oxygen in the electrolyte solution, diffusion inside the PAni film, adsorption process, and electron transfer. Koutecky–Levich analysis made possible to evaluate the kinetics parameters (total number of exchanged electrons, limiting current density, Tafel slope and exchange current density). These parameters vary with the Pt loading, displaying a steep increase at around 200 μg.cm −2, above which the behavior of bulk platinum is found. At lower Pt loadings, the kinetics is controlled by a Temkin isotherm, and a large amount of hydrogen peroxide is formed.

Electrochemical Studies of the Automotive Lubricant Additive Zinc n‐Dibutyldithiophosphate

Zinc dialkyldithiophosphates (ZDTPs) are widely incorporated in lubricant formulations as antioxidant and antiwear additives. Using the model compound zinc n dibutyldithiophosphate (Bu-ZDTP) in dimethylformamide (DMF) solution, cyclic voltammetry is applied to a detailed study of Bu-ZDTP electro‐oxidation. Bu-ZDTP is shown to be oxidized in a chemically irreversible electron transfer process under diffusionf‐limited conditions. A similar study of Bu-ZDTP reduction revealed nucleation of zinc at the electrode surface. A chronoamperometric investigation of zinc deposition classified the nucleation according to a progressive mechanism with the diffusion coefficient for Bu‐ZDTP in (DMF) solution as . By comparison with diffusion coefficients obtained via Levich analysis of Bu-ZDTP oxidation, the oxidation process is assigned as a two‐electron transfer. The use of atomic force microscopy as a means of directly visualizing zinc nuclei formed as a result of Bu-ZDTP reduction is described. © 1999 The Electrochemical Society. All rights reserved.

Copper Electropolishing in Concentrated Phosphoric Acid: II . Theoretical Interpretation

A theory for copper electropolishing in concentrated phosphoric acid is compared to ac‐impedance and electrohydrodynamic (EHD)‐impedance spectra. A water‐acceptor mechanism is hypothesized. Agreement between experiment and theory is good. Curve fits of the EHD‐impedance data estimate that the Schmidt number of the system is at room temperature. At temperatures near 90°C, . The plausibility of these high values of is discussed. These estimates of the Schmidt number are obtained without any assumptions about the bulk concentration of the acceptor. With a known viscosity and diffusion coefficient, the Levich analysis of the variation of the limiting current with rotation speed is subsequently used to estimate the bulk concentration of acceptor. The value obtained is in agreement with the known water content in phosphoric acid which indicates that water is the acceptor species.

The electrocatalytic enzyme function of adsorbed cytochrome c peroxidase on pyrolytic graphite

Cytochrome c peroxidase (CCP) is a well characterized redox enzyme which can serve as a model for understanding the electrocatalytic function of adsorbed enzymes. Rotating disk electrode (RDE) voltammetry and cyclic voltammetry were used to show that CCP adsorbed on edge-oriented pyrolytic graphite reduces H 2O 2 electrocatalytically in a manner similar but not identical to solution CCP. Bulk electrolysis and Koutecky—Levich analysis of RDE data proved that the observed amperometric signal corresponds to the unmediated 2e − reduction of H 2O 2 to water. The pH dependence of the enzyme—substrate kinetics of adsorbed CCP were similar to those for solution CCP at pH ≤ 6 but showed some differences at pH > 6. RDE studies in solutions of varying ionic strength show that CCP remains strongly adsorbed to pyrolytic graphite even at high ionic strength. Preliminary cyclic voltammetry experiments revealed that adsorbed CCP is reversibly inhibited by inhibitors of solution CCP.

Electrodeposition of Copper‐Nickel Alloys from Citrate Solutions on a Rotating Disk Electrode: I . Experimental Results

Steady‐state polarization measurements on stationary and rotating disk electrodes were performed in Cu‐Ni‐citrate plating baths as well as in single metal ion‐citrate solutions. The polarization curves were used to identify the different electrode reactions occurring during the plating process. Five electrochemical reactions were found dominant in different potential regions. They were the reduction of hydrogen ion from the dissociation of hydrogenated citrate ion, oxygen reduction, copper deposition, nickel deposition, and reduction of water. Codeposition of Cu‐Ni alloy occurred in a fairly narrow electrode potential region (−1.0 to −1.2V vs. SCE), where the effects of the side reactions were relatively small. A Levich analysis of the rotating disk data was used to determine the overall kinetic and mass transport parameters of the Cu‐Ni alloy electrodeposition process. Finally, compositional and morphological analyses of the alloy plated at constant potentials were also performed.

An improved cell for in-situ electrochemical ESR

An improved cell for simultaneous electrochemical ESR based on a coaxial cylindrical cavity is described and shown to have high sensitivity whilst behaving as a satisfactory hydrodynamic electrode as evidenced by Tafel analysis, by Levich analysis and comparison with theory for the dependence of the ESR signal on electrode currents and electrolyte flow rate.

Film absorption in liquids of different viscosities

Experimental results on absorption of CO2 in liquid film flowing downwards the string of spheres are presented for liquids with viscosities in the range from 1 to 10.1 mPa s. The results correspond qualitatively to the Levich's analysis of mass transfer into the flowing film with wavy surface. Equation relating dimensionless numbers is proposed for calculation of the volumetric mass transfer coefficient.

The liquid film left behind by a large bubble in a sloping channel

Measurements have been made of the shape and final thickness of the water film left behind by large air bubbles moving into stationary water in rectangular channels sloping at angles of up to 21° to the horizontal. A theory due to Landau and Levich predicts the final thickness for bubble velocities up to 0·15 m/sec, but account must be taken of the momentum flux of the liquid in the film at higher velocities. The shape of the liquid meniscus is given approximately by the Landau and Levich analysis if the distance parallel to the channel wall is stretched by a parameter which is dependent upon the bubble velocity and which is theoretically predicted.