Jul 24, 2007 this paper demonstrates the application of a modified levich equation for chemical systems with varying viscosity. Application of koutecky levich method to the analysis of steady state voltammograms with ultramicroelectrodes jiyeon kim and allen j. This practice is based on the kouteckylevich equation derived for a. We demonstrate a new experimental approach to measure heterogeneous electron transfer rates. The limiting current for reduction of ferricyanide ion at. A modified kouteckylevich equation for the analysis of electrochemical flow cells with complex geometries s.
The koutecky levich equation is a powerful and versatile tool that is commonly used for the correction of mass transport effects in rde testing to obtain kinetic current densities. Dec 23, 2015 we demonstrate a new experimental approach to measure heterogeneous electron transfer rates. A general data analysis protocol based on the reversible kouteckylevich equation is developed to obtain accurate kinetic information of. Hydrodynamic voltammetry department of chemical engineering. For that, we shall solve the diffusion equation in the case of an homogeneous production of rfh 2, which allows to obtain the evolution of the current density over time. The available viscocapillary model is based on the landau. As the potential at the disk is swept from high to low values, the onset of orr gives rise to a negative cathodic signal that is observable at approximately 0. Rotating disc electrode an overview sciencedirect topics. Levich analysis is a frequently used method for extraction of diffusional properties of electrochemical active species. Schmidt2 1paul scherrer institut, villigen, switzerland 2eth zurich, zurich, switzerland abstract electrochemical flow cells have found widespread use in analytical chemistry due to their. The levich equation predicts that a plot of the limiting current vs. In this cell it is the volume flow rate vf that controls the convection to the surface and the corresponding levich equation for a reversible electron transfer is predicted by h, d, w,and xe are constants for the cell size and vf is the volume flow rate.
Application of kouteckylevich method to the analysis of. The levich equation models the diffusion and solution flow conditions around a rotating disk. Bard supporting information table of contents page the derivation for irreversible, onestep one electron transfer reduction reaction equations s1. The analysis is based on plotting current versus the square root of the rotation rate of a rotating disc electrode. We adapted the classical koutecky levich model for a rotating disk electrode rde to a general heterogeneous electrochemical kinetic study with ultramicroelectrodes umes even for fast redox systems, where different sizes of umes are used to modulate the mass transfer rate m. The levich equation models the diffusion and solution flow conditions around a rotating disc electrode. From the slope of this plot, the levich b factor and the. Inspire a love of reading with prime book box for kids discover delightful childrens books with prime book box, a subscription that delivers new books every 1, 2, or 3 months new customers receive 15% off your first box. Oxygen reduction reaction with the rotating ring disk. From the above equation, the value of kobs can be determined from intercept of the kouteckylevich plots11, i. Jun 19, 2009 the objective was to investigate the applicability and limitations of a novel approach for measuring intrinsic dissolution rates idr of very small quantities of compounds introduced as powders to buffered solutions and comparing these results to disk idr obtained using the traditional woods apparatus. The k obs values were evaluated from the intercepts of kouteckylevich plots at infinite rotation speed, on the basis of the known number of electrons 2 and the surface.
The derivation for reversible, onestep one electron transfer reaction. The steadystate convectiondiffusion equation at high. Computational modelling of fluid dynamics in electropolishing. Building upon the kouteckylevich equation for evaluation. Building upon the kouteckylevich equation for evaluation of. The average mass transport boundary layer thickness along the wafer under combined flow due to different rotation rates and impinging fountain flow of 4 gpm. In the case a rotating disk electrode setup is used and the electrode is flat and smooth, the i mt can modeled using the levich equation.
Subrahmanyan chandrasekhar 19101995 is justly famous for his lasting contributions to topics such as white dwarfs and black holes which led to his nobel prize, stellar structure and dynamics, general relativity, and other facets of astrophysics. Rotating disk electrode rde method is widely employed in studies on the hydrogen oxidationevolution reaction horher owing to its welldefined mass transport behaviors. Levich koutecky levich electrochemistry application note 56 latest updated. Limiting current values can show large deviations from the values predicted by the levich equation for laminar flow to a polished. If u is the speed of withdrawal of a vertical plate, is the viscosity of the. Pdf extensions of the kouteckylevich equation to channel. Levich koutecky levich electrochemistry application note. Numerical modelling and simulation of kouteckylevich. The steadystate convectiondiffusion equation at high peclet numbers for a cluster of spheres. The powder dissolution profiles of model drugs were determined at 37c in usp. The solid red line corresponds to the levich equation for the rotating disk.
A modified kouteckylevich equation for the analysis of. Powder dissolution method for estimating rotating disk. Correcting the hydrogen diffusion limitation in rotating. The author excuses his omission of turbulence, rheology, natural convection and compressible flows on the grounds that his aim is selfcontained coverage of the necessary fundamentals. Mechanism of the electrocatalytic reduction of ferricyanide. The steadystate convectiondiffusion equation at high peclet. Download fulltext pdf extensions of the kouteckylevich equation to channel electrodes article pdf available in electrochemical and solidstate letters 112 january 2008 with 283 reads. Correcting the hydrogen diffusion limitation in rotating disk. Kouteckylevich equation for the diagnosis of charge transfer the levich equation 1 applies to the totally mass transfer mechanisms when various multi step. A modified koutecky levich equation for the analysis of electrochemical flow cells with complex geometries s. Typically a levich plot would be constructed to ensure that the system behaves correctly and to gain better accuracy, but this calc allows a onepoint rough calculation. A commonly used technique to analyze rotating disc electrode rde experiments is to fit the data to the levich equation assuming a constant effective diffusion coefficient which may be valid for conditions where the viscosity does not vary significantly less than an order of. This practice is based on the kouteckylevich equation derived for a onestep electrontransfer mechanism.
Application of the kouteckylevich method to the analysis of steady. Application of kouteckylevich method to the analysis of steady state voltammograms with ultramicroelectrodes jiyeon kim and allen j. Supplementary information hydrodynamic chronoamperometry for. Application of the kouteckylevich method to the analysis. The precision of several koutecky levich type equations is evaluated and it is shown that differences between the most commonly applied equations are negligible within. Pdf kinetics of surface reactions on rotating disk electrodes.
Levich equation for rotating disk electrode wolfram. This calc uses it to find the diffusion coefficient of a redox probe. Effects of viscositydependent diffusion in the analysis of. Rde rotating disk electrode levich kouteckylevich analytical electrochemistry diffusion coefficient redox reaction kinetic parameters this note describes these analysis tools that can be used to analyse data obtained with a rotating disk electrode rde.
Extensions of the kouteckylevich equation to channel electrodes. The value for ik can be related to the rate of electron transfer as follows. Levich equation, which is limited to small capillary and reynolds numbers. Pdf a consideration of the application of koutecky. Levich plot is assumed to be a reciprocal function of the heterogeneous rate constant k h, cm s. For the tafel plot, the kinetic current jk was calculated from the masstransport correction of rde by equation 4. Kouteckylevich equation metadata this file contains additional information such as exif metadata which may have been added by the digital camera, scanner, or software program used to create or digitize it. Levich analysis and the apparent potential dependency of the. Oxygen reduction reaction with the rotating ring disk electrode page 2 of 3. Application of the kouteckylevich method to the analysis of. Ii a when surface active impurities were either unintentionally or intentionally added. Dip coating in the presence of a substrateliquid interaction. We adapted the classical kouteckylevich model for a rotating disk electrode rde to a general heterogeneous electrochemical kinetic study with ultramicroelectrodes umes even for fast redox systems, where different sizes of umes are used to modulate the mass transfer rate m. We will present a novel numerical approach to obtain a modified kouteckylevich equation for electrochemical flow cells with complex geometries containing elements of both fluid profiles of walljet and channel electrodes.