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Full-Text Articles in Chemical Engineering
Mathematical Modeling Of A Nickel-Cadmium Battery: Effects Of Intercalation And Oxygen Reactions, Deyuan Fan, Ralph E. White
Mathematical Modeling Of A Nickel-Cadmium Battery: Effects Of Intercalation And Oxygen Reactions, Deyuan Fan, Ralph E. White
Faculty Publications
Extensions are presented for a previously published (1) mathematical model of a nickel-cadmium (Ni-Cd) cell. These extensions consist of intercalation thermodynamics for the nickel electrode and oxygen generation and reduction reactions during charge and overcharge. The simulated results indicate that intercalation may be important in the nickel electrode and that including the oxygen reactions provides a means of predicting the efficiency of the cell on charge and discharge.
Effect Of Ohmic, Mass-Transfer, And Kinetic Resistances On Linear-Sweep Voltammetry In A Cylindrical-Pore Electrode, John W. Weidner, Peter S. Fedkiw
Effect Of Ohmic, Mass-Transfer, And Kinetic Resistances On Linear-Sweep Voltammetry In A Cylindrical-Pore Electrode, John W. Weidner, Peter S. Fedkiw
Faculty Publications
Extracting quantitative kinetic information from linear-sweep voltammograms (LSV) on porous electrodes is more difficult than on planar electrodes since the electrode surface is not uniformly accessible to the bulk supply of reactant or the counterelectrode. We present here a means to account for the effect of ohmic, mass-transfer, and kinetic resistances on LSV by modeling a pore in a porous matrix as a cylindrical-pore electrode, and solving the mass and charge conservation equations in the context of this geometry for the simply redox reaction O + ne– <=> R where both O and R are soluble species. Both analytical …
Electrochemical Behavior Of Graphite And Ni-Cr Electrodes In Sodium Polysulfide In The Absence And Presence Of Hydrogen Sulfide, Z. Mao, Ralph E. White, B. Dandapani, A. Anani, S. Srinivasan, A. J. Appleby
Electrochemical Behavior Of Graphite And Ni-Cr Electrodes In Sodium Polysulfide In The Absence And Presence Of Hydrogen Sulfide, Z. Mao, Ralph E. White, B. Dandapani, A. Anani, S. Srinivasan, A. J. Appleby
Faculty Publications
The electrochemical behavior of graphite and Ni-Cr electrodes in sodium tetrasulfide melt has been investigated using voltammetric, chronoamperometric, and chronopotentiometric techniques in the presence and absence of hydrogen sulfide. Two continuous phases, namely, Na2S2 and Na2S, are apparently formed at different potentials during the cathodic polarization. The blocking effect by these layers was much less significant on the Ni-Cr electrode than on graphite. The presence of H2S did not appear to influence the electrode reactions, but it significantly reduced the rate of formation of the continuous phases (Na2S2 or Na …
Oxygen Reduction In A Proton Exchange Membrane Test Cell, S. J. Ridge, Ralph E. White, Y. Tsou, R. N. Beaver, G. A. Eisman
Oxygen Reduction In A Proton Exchange Membrane Test Cell, S. J. Ridge, Ralph E. White, Y. Tsou, R. N. Beaver, G. A. Eisman
Faculty Publications
Oxygen reduction in a gas-fed porous electrode attached to a proton exchange membrane is discussed. Experimental data and a mathematical model are presented for the test cell used. Various membrane and electrode assemblies were tested at different levels of platinum loading and Teflon® content. The model accounts for the diffusion and reaction of oxygen and the diffusion and reaction of hydrogen ions. Sulfuric acid was placed above the membrane in the test cell reservoir to provide a source of protons for the reduction of oxygen at the cathode. Based upon model predictions, it is shown that the transport of the …
Estimation Of Electrode Kinetic Parameters Of The Lithium/Thionyl Chloride Cell Using A Mathematical Model, T. I. Evans, Ralph E. White
Estimation Of Electrode Kinetic Parameters Of The Lithium/Thionyl Chloride Cell Using A Mathematical Model, T. I. Evans, Ralph E. White
Faculty Publications
A one-dimensional mathematical model for the lithium/thionyl chloride primary cell is used in conjunction with a parameter estimation technique, in order to estimate the electrode kinetic parameters of this electrochemical system. The electrode kinetic parameters include the anodic transfer coefficient and exchange current density of the lithium oxidation, a,1 and i0,1,ref; the cathodic transfer coefficient and the effective exchange current density of the thionyl chloride reduction, c,4 and a0i0,4,ref, and a morphology parameter, . The parameter estimation is performed on simulated data first in order to gain confidence in the method. Data reported in …
A Mathematical Model Of A Lithium/Thionyl Chloride Primary Cell, T. I. Evans, T. V. Nguyen, Ralph E. White
A Mathematical Model Of A Lithium/Thionyl Chloride Primary Cell, T. I. Evans, T. V. Nguyen, Ralph E. White
Faculty Publications
A one-dimensional mathematical model for the lithium/thionyl chloride primary cell has been developed to investigate methods of improving its performance and safety. The model includes many of the components of a typical lithium/thionyl chloride cell such as the porous lithium chloride film which forms on the lithium anode surface. The governing equations are formulated from fundamental conservation laws using porous electrode theory and concentrated solution theory. The model is used to predict one-dimensional, time dependent profiles of concentration, porosity, current, and potentialas well as cell temperature and voltage. When a certain discharge rate is required, the model can be used …
A Two-Dimensional Mathematical Model Of A Porous Lead Dioxide Electrode In A Lead-Acid Cell, E. C. Dimpault-Darcy, T. V. Nguyen, Ralph E. White
A Two-Dimensional Mathematical Model Of A Porous Lead Dioxide Electrode In A Lead-Acid Cell, E. C. Dimpault-Darcy, T. V. Nguyen, Ralph E. White
Faculty Publications
A two-dimensional mathematical model is presented for a lead dioxide electrode in a lead-acid cell. It is used to simulate the time dependent behavior of the electrode during discharge. The model contains six dependent variables: the concentration of the acid electrolyte, the porosity, the electrical potentials of the solid and solution phases, and the two directional components of the current density in the electrolyte. The effect of the electrode grid was included by varying the conductivity of the solid. Parameters such as electrode conductivity, electrode dimensions, and temperature are investigated to understand their effects on electrode discharge performance.
Analysis Of Electrokinetic Data By Parameter Estimation And Model Discrimination Techniques, Prosper K. Adanuvor, Ralph E. White
Analysis Of Electrokinetic Data By Parameter Estimation And Model Discrimination Techniques, Prosper K. Adanuvor, Ralph E. White
Faculty Publications
An alternative approach to classical methods of electrochemical data analysis is presented. This alternative method is based on nonlinear parameter estimation and model discrimination techniques. The method is used to obtain the relevant kinetic and transport parameters and to elucidate the kinetic mechanism of O2 reduction at carbon and silver electrodes in alkaline electrolytes.
A Mathematical Model For Predicting Cyclic Voltammograms Of Electronically Conductive Polypyrrole, Taewhan Yeu, Trung V. Nguyen, Ralph E. White
A Mathematical Model For Predicting Cyclic Voltammograms Of Electronically Conductive Polypyrrole, Taewhan Yeu, Trung V. Nguyen, Ralph E. White
Faculty Publications
Polypyrrole is an attractive polymer for use as a high energy density secondary battery because of its potential as an inexpensive, lightweight, and noncorrosive electrode material. A mathematical model to simulate cyclic voltammograms for polypyrrole is presented here. The model is for a conductive porous electrode film on a rotating disk electrode (RDE) and is used to predict the spatial and time dependence of concentration, overpotential, and stored charge profiles within a polypyrrole film. The model includes both faradaic and capacitive charge components in the total current density expression.
Electrodeposition Of Copper-Nickel Alloys From Citrate Solutions On A Rotating Disk Electrode, Ramona Y. Ying, Patrick K. Ng, Z. Mao, Ralph E. White
Electrodeposition Of Copper-Nickel Alloys From Citrate Solutions On A Rotating Disk Electrode, Ramona Y. Ying, Patrick K. Ng, Z. Mao, Ralph E. White
Faculty Publications
A mathematical model is developed to simulate the electrodeposition of Cu-Ni alloy from citrate solutions onto a rotating disk electrode under potentiostatic control. The model includes the influence of diffusion, ionic migration, forced convection, and homogeneous equilibria. The three major electrochemical reactions treated in the model are copper deposition, nickel deposition, and hydrogen evolution. Using experimental parameters when available, the model was fitted and tested against experimentally-obtained results for different bath compositions and operating conditions. The model agreed reasonably well with the experimental results particularly in the codeposition region, –1.0 to –1.2V vs. SCE, where hydrogen evolution is not the …
A Mathematical Model For The Initial Corrosion Rate Of A Porous Layer On A Rotating Disk Electrode, William E. Ryan, Ralph E. White, S. L. Kelly
A Mathematical Model For The Initial Corrosion Rate Of A Porous Layer On A Rotating Disk Electrode, William E. Ryan, Ralph E. White, S. L. Kelly
Faculty Publications
A mathematical model is presented for the initial corrosion rate of a porous layer on a rotating disk electrode. The model is used to predict the corrosion potential and corrosion current density for a porous electrode made of pure iron in aerated caustic solutions. The dependence of these predictions on some of the properties of the porous layer is presented. It is shown that the corrosion rate depends significantly on the specific surface area of the porous electrode.
The Effect Of The Tribromide Complex Reaction On The Oxidation/Reduction Current Of The Br2/Br– Electrode, P K. Adanuvor, Ralph E. White, S. E. Lorimer
The Effect Of The Tribromide Complex Reaction On The Oxidation/Reduction Current Of The Br2/Br– Electrode, P K. Adanuvor, Ralph E. White, S. E. Lorimer
Faculty Publications
The Br2/Br– electrode reaction with tribromide complex formation reaction in the solution, a chemical-electrochemical (C-E) type reaction, has been investigated in order to determine the effect of the chemical reaction on the electrode kinetics. It is shown that the chemical reaction has little effect on the electrode kinetics at very slow homogeneous reaction rates, but has a more drastic effect on the electrode kinetics at faster homogeneous reaction rates. Also, the kinetics at the electrode are affected by changes in the concentrations of the active species (Br2, Br–, and Br3–) …
Modeling The Rotating Disk Electrode For Studying The Kinetics Of Electrochemical Reactions, P K. Adanuvor, Ralph E. White, S E. Lorimer
Modeling The Rotating Disk Electrode For Studying The Kinetics Of Electrochemical Reactions, P K. Adanuvor, Ralph E. White, S E. Lorimer
Faculty Publications
A general mathematical model for studying the kinetics of electrochemical reactions at a rotating disk electrode under steady-state potentiostatic conditions is presented. The model, apart from predicting the net and partial current densities at given values of the applied potential, the ohmic potential drop, and the concentration and potential profiles in the solution, also accounts for homogeneous reactions of any order in the solution and noncharge transfer reactions at the electrode surface. The versatility of the model is demonstrated by the application of the model to a variety of complex reaction schemes.
Simulation Of The Polarization Curves For Oxygen Reduction At A Rotating Disk Electrode, P. K. Adanuvor, Ralph E. White
Simulation Of The Polarization Curves For Oxygen Reduction At A Rotating Disk Electrode, P. K. Adanuvor, Ralph E. White
Faculty Publications
The electrochemical reduction of oxygen in 1M NaOH solution is simulated at a rotating disk electrode. Steady-state polarization curves are presented for possible reaction schemes for the reduction process. The effect of changes in the kinetic parameters on the polarization curves is demonstrated and special attention is focused on the production of hydrogen peroxide.
A Mathematical Model Of A Lead-Acid Cell: Discharge, Rest, And Charge, Hiram Gu, T. V. Nguyen, Ralph E. White
A Mathematical Model Of A Lead-Acid Cell: Discharge, Rest, And Charge, Hiram Gu, T. V. Nguyen, Ralph E. White
Faculty Publications
A mathematical model of a lead-acid cell is presented which includes the modeling of porous electrodes and various physical phenomena in detail. The model is used to study the dynamic behavior of the acid concentration, the porosity of the electrodes, and the state of charge of the cell during discharge, rest, and charge. The dependence of the performance of the cell on electrode thicknesses and operating temperature is also investigated.
A Model Of The Bromine/Bromide Electrode Reaction At A Rotating Disk Electrode, Ralph E. White, S. E. Lorimer
A Model Of The Bromine/Bromide Electrode Reaction At A Rotating Disk Electrode, Ralph E. White, S. E. Lorimer
Faculty Publications
A mathematical model is presented for the Br2/Br– electrode reaction at a rotating disk electrode. The model includes current density-overpotential expressions for the electrode reaction according to either the Volmer-Heyrovsky (V-H) or the Volmer-Tafel (V-T) mechanism and the transport equations including the effect of ionic migration. The model is used to predict current-overpotential curves for various cases of interest. Qualitative comparison of the model predictions to literature data shows that either the V-H or the V-T mechanism, with V controlling, may be acceptable for the Br2/Br– reaction.
An Analysis Of A Back Fed Porous Electorde For The Br2/Br- Redox Reaction, John W. Van Zee, Ralph E. White
An Analysis Of A Back Fed Porous Electorde For The Br2/Br- Redox Reaction, John W. Van Zee, Ralph E. White
Faculty Publications
No abstract provided.
Prediction Of The Current Density At An Electrode At Which Multiple Electrode Reactions Occur Under Potentiostatic Control, Ralph E. White, S. E. Lorimer, R. Darby
Prediction Of The Current Density At An Electrode At Which Multiple Electrode Reactions Occur Under Potentiostatic Control, Ralph E. White, S. E. Lorimer, R. Darby
Faculty Publications
It is often desirable to be able to predict the total current density at an electrode when multiple electrochemical reactions occur there under potentiostatic control. It is also sometimes desirable to include the effect of ionic migration within the diffusion layer upon the predicted total (1) and partial current densities (2). A procedure for doing this can be illustrated by considering the rotating disk electrode (RDE) system and the associated potential distribution near the RDE as shown in Fig. 1 and 2.
An Analysis Of A Back Fed Porous Electrode For The Br2/Br Reaction, John Van Zee, Ralph E. White
An Analysis Of A Back Fed Porous Electrode For The Br2/Br Reaction, John Van Zee, Ralph E. White
Faculty Publications
An experimental analysis of the Br2/Br– redox reaction in a porous back fed ruthenium-coated titanium electrode is described. A mathematical model of the steady-state process is presented. Nonlinear regression of the model against the experimental data gives physically meaningful parameter estimates; these parameters and the model provide a design equation for the porous electrode current as a function of specific surface area, bulk Br2 concentration, average total overpotential, and the Reynolds number. The design equation shows that the back fed electrode could reduce the loss of Br2 across the separator and the ohmic loss in …