Carl H. Hamann:
Following his studies in mathematics, physics, biology and economics in Hamburg and Bonn, graduating in 1966 as a physicist, Carl H. Hamann gained his doctorate in 1970, becoming Professor for Applied Physical Chemistry at the University of Oldenburg in 1975. He has since concentrated mainly on fuel cells, electrochemical metrology, passage and adsorption kinetics, turbulent flows, the thermodynamics of irreversible systems, preparative electroorganic chemistry and technical electrochemistry. Professor Hamann has thus far published some 80 articles in journals and books.

Wolf Vielstich:
As Heinz Gerischer's first student, in Gottingen in 1952/53, Wolf Vielstich was concerned with developing a fast Potentiostaten while determining exchange current densities. Upon starting work at the Institute for Physical Chemistry, Bonn University, in 1960 he demonstrated that, apart from mercury, reproducible cyclic voltamograms, such as for the oxidation of hydrogen and methanol, are contained in solid electrodes, including Pt, Ir, Rh, Au and Pd. There then followed experiments with methanol/air and NiMH cells, among others. He was always interested in developing novel methods, such as the rotating ring electrode, on-line MS (DEMS), in-situ FTIRS and UHV analysis of adsorbants. Between 1986 and 1993, Wolf Vielstich was the Coordinator of the first European project to develop a DMFC, and in 1998 he was awarded the Faraday Medal by the Royal Chemical Society. Since 1999 he has been working as a guest of the Universidade de Sao Paulo, and edited Wiley's Handbook of Fuel Cells (2003).

Professor Hamnett graduated from the University of Oxford with a BA (Chemistry) in 1970 and a [...]. (Chemistry) in 1973. He has held research and academic positions at the University of British Columbia, Canada, and at Oxford and Newcastle Universities, England, before his appointment in January 2001 as Principal and Vice-chancellor of the University of Strathclyde. He has nearly 200 publications in books and scientific journals, covering areas of spectroscopy, quantum theory and electrochemistry. His primary academic interests in recent years include the development and utilisation of spectro-electrochemical techniques in electrochemistry, and the development of improved fuel cells and solar-energy conversion devices.

Preface xiii

List of Symbols and Units xv

1 Foundations, Definitions and Concepts 1

1.1 Ions, Electrolytes and the Quantisation of Electrical Charge 1

1.2 Transition from Electronic to Ionic Conductivity in an Electrochemical Cell 3

1.3 Electrolysis Cells and Galvanic Cells: The Decomposition Potential and the Concept of EMF 4

1.4 Faraday's Laws 7

1.5 Systems of Units 9

2 Electrical Conductivity and Interionic Interactions 13

2.1 Fundamentals 13

2.1.1 The Concept of Electrolytic Conductivity 13

2.1.2 The Measurement of Electrolyte Conductance 14

2.1.3 The Conductivity 18

2.1.4 Numerical Values of Conductivity 19

2.2 Empirical Laws of Electrolyte Conductivity 21

2.2.1 The Concentration Dependence of the Conductivity 21

2.2.2 Molar and Equivalent Conductivities 22

2.2.3 Kohlrausch's Law and the Determination of the Limiting Conductivities of Strong Electrolytes 23

2.2.4 The Law of Independent Migration of Ions and the Determination of the Molar Conductivity of Weak Electrolytes 26

2.3 Ionic Mobility and Hittorf Transport 27

2.3.1 Transport Numbers and the Determination of Limiting Ionic Conductivities 28

2.3.2 Experimental Determination of Transport Numbers 29

2.3.3 Magnitudes of Transport Numbers and Limiting Ionic Conductivities 31

2.3.4 Hydration of Ions 32

2.3.5 The Enhanced Conductivity of the Proton, the Structure of the H 3 O þ Ion and the Hydration Number of the Proton 34

2.3.6 The Determination of Ionic Mobilities and Ionic Radii: Walden's Rule 36

2.4 The Theory of Electrolyte Conductivity: The Debye-Hückel-Onsager Theory of Dilute Electrolytes 38

2.4.1 Introduction to the Model: Ionic Cloud, Relaxation and Electrophoretic Effects 38

2.4.2 The Calculation of the Potential due to the Central Ion and its Ionic Cloud: Ionic Strength and Radius of the Ionic Cloud 39

2.4.3 The Debye-Onsager Equation for the Conductivity of Dilute Electrolyte Solutions 44

2.4.4 The Influence of Alternating Electric Fields and Strong Electric Fields on the Electrolyte Conductivity 46

2.5 The Concept of Activity from the Electrochemical Viewpoint 46

2.5.1 The Activity Coefficient 46

2.5.2 Calculation of the Concentration Dependence of the Activity Coefficient 48

2.5.3 Extensions to More Concentrated Electrolytes 51

2.6 The Properties of Weak Electrolytes 61

2.6.1 The Ostwald Dilution Law 61

2.6.2 The Dissociation Field Effect 63

2.7 The Concept of pH and the Idea of Buffer Solutions 64

2.8 Non-aqueous Solutions 66

2.8.1 Ion Solvation in Non-aqueous Solvents 67

2.8.2 Electrolytic Conductivity in Non-aqueous Solutions 68

2.8.3 The pH-Scale in Protonic Non-aqueous Solvents 70

2.9 Simple Applications of Conductivity Measurements 71

2.9.1 The Determination of the Ionic Product of Water 71

2.9.2 The Determination of the Solubility Product of a Slightly Soluble Salt 72

2.9.3 The Determination of the Heat of Solution of a Slightly Soluble Salt 72

2.9.4 The Determination of the Thermodynamic Dissociation Constant of a Weak Electrolyte 73

2.9.5 The Principle of Conductivity Titrations 73

3 Electrode Potentials and Double-Layer Structure at Phase Boundaries 77

3.1 Electrode Potentials and their Dependence on Concentration, Gas Pressure and Temperature 77

3.1.1 The EMF of Galvanic Cells and the Maximum Useful Energy from Chemical Reactions 77

3.1.2 The Origin of Electrode Potentials, Galvani Potential Difference and the Electrochemical Potential 78

3.1.3 Calculation of the Electrode Potential and the Equilibrium Galvani Potential Difference between a Metal and a Solution of its Ions - The Nernst Equation 81

3.1.4 The Nernst Equation for Redox Electrodes 82

3.1.5 The Nernst Equation for Gas-electrodes 83

3.1.6 The Measurement of Electrode Potentials and Cell Voltages 84

3.1.7 Schematic Representation of Galvanic Cells 86

3.1.8 Calculation of Cell EMF's from Thermodynamic Data 88

3.1.9 The Temperature Dependence of the Cell Voltage 90

3.1.10 The Pressure Dependence of the Cell Voltage - Residual Current for the Electrolysis of Aqueous Solutions 91

3.1.11 Reference Electrodes and the Electrochemical Series 93

3.1.12 Reference Electrodes of the Second Kind 98

3.1.13 The Electrochemical Series in Non-aqueous Solvents 102

3.1.14 Reference Electrodes in Non-aqueous Systems and Usable Potential Ranges 104

3.2 Liquid-junction Potentials 105

3.2.1 The Origin of Liquid-junction Potentials 105

3.2.2 The Calculation of Diffusion Potentials 106

3.2.3 Concentration Cells with and without Transference 108

3.2.4 Henderson's Equation 109

3.2.5 The Elimination of Diffusion Potentials 111

3.3 Membrane Potentials 112

3.4 The Electrolyte Double-Layer and Electrokinetic Effects 115

3.4.1 Helmholtz and Diffuse Double Layer: the Zeta-Potential 116

3.4.2 Adsorption of Ions, Dipoles and Neutral Molecules - the Potential of Zero Charge 120

3.4.3 The Double-Layer Capacity 121

3.4.4 Some Data for Electrolytic Double Layers 123

3.4.5 Electrocapillarity 124

3.4.6 Electrokinetic Effects - Electrophoresis, Electro-osmosis, Dorn-effect and Streaming Potential 128

3.4.7 Theoretical Studies of the Double Layer 130

3.5 Potential and Phase Boundary Behaviour at Semiconductor Electrodes 133

3.5.1 Metallic Conductors. Semiconductors and Insulators 133

3.5.2 Electrochemical Equilibria on Semiconductor Electrodes 136

3.6 Simple Applications of Potential Difference Measurements 139

3.6.1 The Experimental Determination of Standard Potentials and Mean Activity Coefficients 139

3.6.2 Solubility Products of Slightly Soluble Salts 141

3.6.3 The Determination of the Ionic Product of Water 141

3.6.4 Dissociation Constants of Weak Acids 142

3.6.5 The Determination of the Thermodynamic State Functions (r G 0 , r H 0 and r S 0) and the Corresponding Equilibrium Constants for Chemical Reactions 144

3.6.6 pH Measurement with the Hydrogen Electrode 145

3.6.7 pH Measurement with the Glass Electrode 148

3.6.8 The Principle of Potentiometric Titrations 153

4 Electrical Potentials and Electrical Current 157

4.1 Cell Voltage and Electrode Potential during Current Flow: an Overview 157

4.1.1 The Concept of Overpotential 159

4.1.2 The Measurement of Overpotential; the Current-Potential Curve for a Single Electrode 160

4.2 The Electron-transfer Region of the Current-Potential Curve 162

4.2.1 Understanding the Origin of the Current-Potential Curve in the Electrontransfer-limited Region with the Help of the Arrhenius Equation 162

4.2.2 The Meaning of the Exchange Current Density j 0 and the Asymmetry Parameter b 166

4.2.3 The Concentration Dependence of the Exchange-current Density 169

4.2.4 Electrode Reactions with Consecutive Transfer of Several Electrons 170

4.2.5 Electron Transfer with Coupled Chemical Equilibria; the Electrochemical Reaction Order 173

4.2.6 Further Theoretical Considerations of Electron Transfer 179

4.2.7 Determination of Activation Parameters and the Temperature Dependence of Electrochemical Reactions 184

4.3 The Concentration Overpotential - The Effect of Transport of Material on the Current-Voltage Curve 185

4.3.1 The Relationship between the Concentration Overpotential and the Butler-Volmer Equation 186

4.3.2 Diffusion Overpotential and the Diffusion Layer 187

4.3.3 Current-Time Behaviour at Constant Potential and Constant Surface Concentration c s 189

4.3.4 Potential-Time Behaviour at Constant Current: Galvanostatic Electrolysis 191

4.3.5 Transport by Convection, Rotating Electrodes 192

4.3.6 Mass Transport Through Migration - The Nernst-Planck Equation 199

4.3.7 Spherical Diffusion 200

4.3.8 Micro-electrodes 201

4.4 The Effect of Simultaneous Chemical Processes on the Current Voltage Curve 203

4.4.1 Reaction Overpotential, Reaction-limited Current and Reaction Layer Thickness 204

4.5 Adsorption Processes 207

4.5.1 Forms of Adsorption Isotherms 208

4.5.2 Adsorption Enthalpies and Pauling's Equation 211

4.5.3 Current-Potential Behaviour and Adsorption-limited Current 211

4.5.4 Dependence of Exchange Current Density on Adsorption Enthalpy, the Volcano Curve 212

4.6 Electrocrystallisation - Metal Deposition and Dissolution 213

4.6.1 Simple Model of Metal Deposition 214

4.6.2 Crystal Growth in the Presence of Screw Dislocations 218

4.6.3 Under-potential Deposition 219

4.6.4 The Kinetics of Metal Dissolution and Metal Passivation 220

4.6.5 Electrochemical Materials Science and Electrochemical Surface Technology 222

4.7 Mixed Electrodes and Corrosion 225

4.7.1 Mechanism of Acid Corrosion 226

4.7.2 Oxygen Corrosion 227

4.7.3 Potential-pH Diagrams or Pourbaix Diagrams 227

4.7.4 Corrosion Protection 228

4.8 Current Flows on Semiconductor Electrodes 231

4.8.1 Photoeffects in Semiconductors 233

4.8.2 Photoelectrochemistry 234

4.8.3 Photogalvanic Cells 235

4.8.4 Solar Energy Harvesting 236

4.8.5 Detoxification using Photoelectrochemical Technology 240

4.9 Bioelectrochemistry 241

4.9.1 The Biochemistry of Glucose Oxidase as a Typical Redox Enzyme 242

4.9.2 The Electrochemistry of Selected Biochemical Species 244

5 Methods for the Study of the Electrode/Electrolyte Interface 251

5.1...