Fundamentals of Electrochemistry V. S. Bagotzky A. N. Frumkin Institute of Electrochemistry Russian Academy of Sciences Moscow, Russia

Translated from Russian by Klaus Müller

Plenum Press • New York and London

CONTENTS

Part 1. Basic Concepts

Chapter 1. Electric Current in Galvanic Cells. The Electrodes 3

1.1. Free Charges in Conductors 3 1.2. Electric Current in Conductors 5 1.3. Brief Characterization of the Different Kinds

ofConductor 8 1.4. Circuits Involving Galvanic Cells 15 1.5. Electrodes and Electrode Reactions 17 1.6. Faraday's Laws 24 1.7. Mass Transport in Electrolytes 25 1.8. The Sign Convention for the Current and the Fluxes . . . . 26

Chapter 2. Electrode Potentials 29 2.1. Electrostatic Fields and Potentials 29 2.2. Interfacial Potential Differences (Galvani Potentials) . . . . 33 2.3. Open-Circuit Voltages 37 2.4. Defining the Concept of "Electrode Potential" 41 2.5. Nonequilibrium Electrode Potentials 44 2.6. Potentials at the Conductor/Insulator (or Vacuum)

Interphase 47

Chapter 3. Thermodynamics of Electrochemical Systems . . . 53 3.1. Ways to Describe Compositum 53 3.2. Conventional and Undefined Parameters 54 3.3. Thermodynamic Functions in Electrochemistry 55 3.4. Thermodynamic Activity 60

xiii

xiv CONTENTS

3.5. Equations for the emf of Galvanic Cells 63 3.6. Concentration Dependence of Electrode Potentials 66 3.7. Special Thermodynamic Features of Electrode Potentials . . 72

Chapter 4. Diffusion Processes in Electrochemistry 81 4.1. Basic Laws oflonic Diffusion in Solutions 81 4.2. Diffusion During Current Flow in Electrolytes 85 4.3. Ionic Transport by Migration and Diffusion 88 4.4. Convective Transport 94

Chapter 5. Phase Boundaries (Interfaces) between Electrolytes 105

5.1. Types of Interfaces between Electrolytes 105 5.2. Diffusion Potentials 107 5.3. Distribution of the Ions between Dissimilar Electrolytes . . . 112 5.4. Distribution of Ions in Cells with Membrane 115 5.5. Galvanic Cells with Transference 117

Chapter 6. Polarization of Electrodes 121 6.1. Basic Concepts 121 6.2. The Laws of Activation Polarization 125 6.3. Diffusional Concentration Polarization 135 6.4. Superposition of Concentration and Activation

Polarization 140

Chapter 7. Transient Processes 147 7.1. Evidence forTransient Conditions 147 7.2. Transient Diffusion to Electrodes of Large Size 149 7.3. Transient Diffusion to Electrodes of Finite Size 155

Chapter 8. Types of Electrodes Used 157 8.1. Nonconsumable Electrodes . 158 8.2. Reacting Electrodes 160 8.3. Reference Electrodes 161

Chapter 9. Electrochemical Research Techniques 167 9.1. Voltage and Electrode Potential Measurements

(Potentiometry) . . . 170 9.2. Steady-State Polarization Measurements 170 9.3. Transient (Pulse) Measurements 174

CONTENTS xv

9.4. Alternating-Current Measurements 184 9.5. Polarography 193

Part 2. Properties of Electrolytes and Interfaces

Chapter 10. Aqueous Electrolyte Solutions 203 10.1. The Properties and Structure of Water 203 10.2. Thermodynamic Properties of Solutions 206 10.3. Electrolytic Dissociation 208 10.4. Conductivity of Electrolyte Solutions 214 10.5. Ionic Transport Numbers 221 10.6. Ionic Solvation (Hydration) in Solutions 227 10.7. Activity of Real Electrolyte Solutions 236 10.8. Physical Theories of Ion-Ion Interactions 243 10.9. Ionic Reactions and Equilibria 258

Chapter 11. Polyelectrolytes and Nonaqueous Electrolytes 267

11.1. Polyelectrolytes 267 11.2. Nonaqueous Electrolyte Solutions 269 11.3. Ionically Conducting Melts 273 11.4. Solid Electrolytes 278

Chapter 12. Structure and Properties of Surface Layers . . . 283 12.1. General Concepts 283 12.2. Adsorption 287 12.3. Excess Surface Energy. Wetting 292 12.4. Thermodynamics of Surface Phenomena 294 12.5. Structure of the Electric Double Layer 299 12.6. Methods for Studying Electrode Surfaces 311 12.7. The Mercury Electrode Surface 316 12.8. The Platinum Electrode Surface 320 12.9. Surfaces of Other Electrodes 330 12.10. Two Problems in Electrochemistry 334

Part 3. Electrochemical Kinetics

Glfapter 13. Multistep Electrode Reactions 339

xvi CONTENTS

13.1. Intermediate Reaction Steps 339 13.2. Rate-Determining Step 341 13.3. Two-Step Electrochemical Reactions 343 13.4. Complex Electrochemical Reactions 349 13.5. Reactions with Homogeneous Chemical Steps 351 13.6. Reactions with Mediators 355 13.7. Parallel Electrode Reactions 357

Chapter 14. The Elementary Reaction Act 361 14.1. The Energy of Activation 361 14.2. Kinetic Influence of the Electric Double Layer 369 14.3. Kinetic Infiuence of Adsorption 371 14.4. Infiuence of the Electrode Material 374

Chapter 15. Reactions Producing a New Phase 385 15.1. Intermediate Stages in the Formation of New Phases . . . . 385 15.2. Formation of Gas Bubbles 387 15.3. Crystal Phase Formation (Metal Deposition) 392

Part 4. Scientific Principles of Applied Electrochemistry

Chapter 16. Main Areas of Applied Electrochemisty 397

Chapter 17. Electrochemical Reactors 409 17.1. Design Principles 409 17.2. Separators 414 17.3. Macrokinetics of Electrochemical Processes 418

Chapter 18. Reactions Involving Metals or Other Solids . . . 427 18.1. Reacting Metal Electrodes 427 18.2. Anodic Metal Dissolution 429 18.3. Surface-Layer Formation 432 18.4. Passivation of Electrodes 437 18.5. Corrosion of Metals 443 18.6. Electrochemical Metal Treatments 451 18.7. Cathodic Metal Deposition 454 18.8. Reacting Nonmetal Electrodes 460

Chapter 19. Reactions at Nonconsumable Electrodes 465

CONTENTS xvii

19.1. Hydrogen Evolution and Ionization 465 19.2. Reactions Involving Oxygen 476 19.3. Reactions Involving Chlorine and Other Halogens 483 19.4. Reactions Involving Organic Substances 486 19.5. Reactions at High Anodic Potentials 493 19.6. Electrocatalysis 497

Chapter 20. Electrochemical Methods of Analysis 499 20.1. Conductometry 500 20.2. Coulometry 501 20.3. Voltammetry 503 20.4. Potentiometry 510

Chapter 21. Photoelectrochemistry 519 21.1. Energy Levels of Electrons in Electrodes and

in the Electrolyte 521 21.2. Electron Photoemission into Solutions 526 21.3. Photoexcitation of Semiconductor Electrodes 529 21.4. Photoexcitation of Reacting Species 536

Chapter 22. Electrokinetic Processes 539 22.1. Electrokinetic Potential 542 22.2. Basic Equations of Electrokinetic Processes 546 22.3. Practical Use of Electrokinetic Processes 551

Chapter 23. Bioelectrochemistry 553 23.1. Transmission of the Nervous Impulse 554 23.2. Bioenergetics 566 23.3. Electrochemical Methods in Biology and Medicine . . . . 572

Bibliography 579

Author Index 583

Subject Index 585