Understanding Voltammetry

by Compton, Richard G.; Banks, Craig E.

• ISBN13: 9789812706256
• ISBN10: 9812706259
• Format: Hardcover
• Copyright: 2007-09-10
• Publisher: World Scientific Pub Co Inc

Summary

The power of electrochemical measurements in respect of thermodynamics, kinetics and analysis is widely recognized but the subject can be unpredictable to the novice even if they have a strong physical and chemical background, especially if they wish to pursue quantitative measurements. Accordingly, some significant experiments are perhaps wisely never attempted while the literature is sadly replete with flawed attempts at rigorous voltammetry.

Table of Contents

Preface	p. V
Equilibrium Electrochemistry and the Nernst Equation	p. 1
Chemical Equilibrium	p. 1
Electrochemical Equilibrium: Introduction	p. 5
Electrochemical Equilibrium: Electron Transfer at the Solution-Electrode Interface	p. 9
Electrochemical Equilibrium: The Nernst Equation	p. 11
Walther Hermann Nernst	p. 17
Reference Electrodes and the Measurement of Electrode Potentials	p. 19
The Hydrogen Electrode as a Reference Electrode	p. 26
Standard Electrode Potentials and Formal Potentials	p. 27
Formal Potentials and Experimental Voltammetry	p. 30
Electrode Processes: Kinetics vs. Thermodynamics	p. 32
Electrode Kinetics	p. 35
Currents and Reaction Fluxes	p. 35
Studying Electrode Kinetics Requires Three Electrodes	p. 37
Butler-Volmer Kinetics	p. 40
Standard Electrochemical Rate Constants and Formal Potentials	p. 43
The Need for Supporting Electrolyte	p. 45
The Tafel Law	p. 46
Julius Tafel	p. 47
Multistep Electron Transfer Processes	p. 49
Tafel Analysis and the Hydrogen Evolution Reaction	p. 52
B. Stanley Pons	p. 57
Cold Fusion-The Musical!	p. 58
Why are Some Standard Electrochemical Rate Constants Large but Others Slow? The Marcus Theory of Electron Transfer: An Introduction	p. 60
Marcus Theory: Taking it Further. Inner and Outer Sphere Electron Transfer	p. 66
Marcus Theory: Taking it Further. Adiabatic and Non-Adiabatic Reactions	p. 67
Marcus Theory: Taking it Further. Calculating the Gibbs Energy of Activation	p. 70
Relationship between Marcus Theory and Butler-Volmer Kinetics	p. 73
Marcus Theory and Experiment. Success!	p. 74
Diffusion	p. 77
Fick's 1st Law of Diffusion	p. 77
Fick's 2nd Law of Diffusion	p. 79
The Molecular Basis of Fick's Laws	p. 81
How Did Fick Discover His Laws?	p. 83
The Cottrell Equation: Solving Fick's 2nd Law	p. 88
The Cottrell Problem: The Case of Unequal Diffusion Coefficients	p. 92
The Nernst Diffusion Layer	p. 94
Mass Transfer vs. Electrode Kinetics: Steady-State Current-Voltage Waveshapes	p. 97
Mass Transport Corrected Tafel Relationships	p. 100
Cyclic Voltammetry at Macroelectrodes	p. 107
Cyclic Voltammetry: The Experiment	p. 107
Cyclic Voltammetry: Solving the Transport Equations	p. 109
Cyclic Voltammetry: Reversible and Irreversible Kinetics	p. 111
What Dictates 'Reversible' and 'Irreversible' Behaviour?	p. 119
Reversible and Irreversible Behaviour: The Effect of Voltage Scan Rate	p. 120
Reversible versus Irreversible Voltammetry: A Summary	p. 126
The Measurement of Cyclic Voltammograms: Three Practical Considerations	p. 127
The Effect of Unequal Diffusion Coefficients, D[subscript A not equal] D[subscript B]	p. 129
Multiple Electron Transfer: Reversible Electrode Kinetics	p. 133
Multiple Electron Transfer: Irreversible Electrode Kinetics	p. 142
The Influence of pH on Cyclic Voltammetry	p. 147
Voltammetry at Microelectrodes	p. 153
The Cottrell Equation for a Spherical or Hemispherical Electrode	p. 153
Potential Step Transients at Microdisc Electrodes	p. 158
Microelectrodes have Large Current Densities and Fast Response Times	p. 159
Applications of Potential Step Chronoamperometry Using Microdisc Electrodes	p. 161
Double Potential Step Microdisc Chronoamperometry Exploring the Diffusion Coefficient of Electrogenerated Species	p. 164
Cyclic and Linear Sweep Voltammetry Using Microdisk Electrodes	p. 172
Steady-State Voltammetry at the Microdisc Electrode	p. 182
Microelectrodes versus Macroelectrodes	p. 183
Ultrafast Cyclic Voltammetry: Megavolts per Second Scan Rates	p. 187
Ultrasmall Electrodes: Working at the Nanoscale	p. 188
Voltammetry at Heterogeneous Surfaces	p. 193
Partially Blocked Electrodes	p. 193
Microelectrode Arrays	p. 209
Voltammetry at Highly Ordered Pyrolytic Graphite Electrodes	p. 215
Electrochemically Heterogeneous Electrodes	p. 219
Electrodes Covered with Porous Films	p. 222
Voltammetric Particle Sizing	p. 224
Scanning Electrochemical Microscopy (SECM)	p. 228
Cyclic Voltammetry: Coupled Homogeneous Kinetics and Adsorption	p. 233
Homogeneous Coupled Reactions: Notation and Examples	p. 233
Modifying Fick's Second Law to Allow for Chemical Reaction	p. 235
Cyclic Voltammetry and the EC Reaction	p. 236
How Do The Parameters K[subscript 1] and [Lambda] Emerge?	p. 240
Cyclic Voltammetry and the EC[subscript 2] Reaction	p. 243
Examples of EC and EC[subscript 2] Processes	p. 246
ECE Processes	p. 254
ECE vs DISP	p. 262
The CE Mechanism	p. 264
The EC' (Catalytic) Mechanism	p. 266
Adsorption	p. 268
Voltammetric Studies of Droplets and Solid Particles	p. 277
Hydrodynamic Electrodes	p. 285
Convection	p. 285
Modifying Fick's Law to Allow for Convection	p. 287
The Rotating Disc Electrode: An Introduction	p. 288
The Rotating Disc Electrode - Theory	p. 289
Osborne Reynolds (1842-1912)	p. 293
The Rotating Disc Electrode - Further Theory	p. 293
Chronoamperometry at the Rotating Disc Electrode: An Illustration of the Value of Simulation	p. 300
The Rotating Disc and Coupled Homogeneous Kinetics	p. 303
The Channel Electrode: An Introduction	p. 306
The Channel Electrode: The Levich Equation Derived	p. 309
Channel Flow Cells and Coupled Homogeneous Kinetics	p. 310
Chronoamperometry at the Channel Electrode	p. 316
The Channel Electrode is not "Uniformly Accessible"	p. 318
Channel Microelectrodes	p. 319
Channel Microband Electrode Arrays for Mechanistic Electrochemistry	p. 321
The High Speed Channel Electrode	p. 325
Hydrodynamic Electrodes Based on Impinging jets	p. 327
Sonovoltammetry	p. 329
Voltammetry for Electroanalysis	p. 341
Potential Step Voltammetric Techniques	p. 341
Differential Pulse Voltammetry	p. 342
Square Wave Voltammetry	p. 344
Stripping Voltammetry	p. 345
Sono-electroanalysis	p. 352
Simulation of Electrode Processes	p. 361
Fick's First and Second Laws	p. 361
Boundary Conditions	p. 362
Finite Difference Equations	p. 362
Backward Implicit Method	p. 363
Conclusion	p. 365
Index	p. 367
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