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Durch das Aufkommen der Materialwissenschaften und damit der Nanotechnologie wird die Elektrochemie immer wichtiger und gleichzeitig immer interdisziplinärer. Hier ist das neue Lehrbuch der modernen Elektrochemie!Diese Einführung ist die englische Fassung des neu aufgelegten Klassikers von Carl H. Hamann und Wolfgang Vielstich. Mit Andrew Hamnett hat sie ein renommierter Experte und Lehrer für den englischsprachigen Markt überarbeitet. Sie ist um ein Drittel kompakter und behandelt etwa neunzig Prozent des Stoffs, der in der deutschen Auflage behandelt wird. Didaktisch genauso ausgefeilt,…mehr
Durch das Aufkommen der Materialwissenschaften und damit der Nanotechnologie wird die Elektrochemie immer wichtiger und gleichzeitig immer interdisziplinärer. Hier ist das neue Lehrbuch der modernen Elektrochemie!Diese Einführung ist die englische Fassung des neu aufgelegten Klassikers von Carl H. Hamann und Wolfgang Vielstich. Mit Andrew Hamnett hat sie ein renommierter Experte und Lehrer für den englischsprachigen Markt überarbeitet. Sie ist um ein Drittel kompakter und behandelt etwa neunzig Prozent des Stoffs, der in der deutschen Auflage behandelt wird. Didaktisch genauso ausgefeilt, entspricht die Präsentation des Lehrstoffs dem Niveau der deutschen Ausgabe.Gleich ob Sie Vorlesungen über Elektrochemie halten oder sich als Student auf Ihre Prüfung vorbereiten ... mit diesem Buch sind Sie auf jeden Fall richtig beraten!
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Produktdetails
- Produktdetails
- Verlag: Wiley-VCH
- Artikelnr. des Verlages: 1131069 000
- 2nd, rev. and upd. ed.
- Seitenzahl: 532
- Erscheinungstermin: 23. Februar 2007
- Englisch
- Abmessung: 250mm x 175mm x 34mm
- Gewicht: 1138g
- ISBN-13: 9783527310692
- ISBN-10: 352731069X
- Artikelnr.: 20847755
- Herstellerkennzeichnung
- Wiley-VCH GmbH
- Boschstr. 12
- 69469 Weinheim
- wiley.buha@zeitfracht.de
- www.wiley-vch.de
- +49 (06201) 606-0 (AB ab 18.00 Uhr)
- Verlag: Wiley-VCH
- Artikelnr. des Verlages: 1131069 000
- 2nd, rev. and upd. ed.
- Seitenzahl: 532
- Erscheinungstermin: 23. Februar 2007
- Englisch
- Abmessung: 250mm x 175mm x 34mm
- Gewicht: 1138g
- ISBN-13: 9783527310692
- ISBN-10: 352731069X
- Artikelnr.: 20847755
- Herstellerkennzeichnung
- Wiley-VCH GmbH
- Boschstr. 12
- 69469 Weinheim
- wiley.buha@zeitfracht.de
- www.wiley-vch.de
- +49 (06201) 606-0 (AB ab 18.00 Uhr)
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 D.Phil. (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 The Measurement of Stationary Current-Potential Curves 251
5.1.1 The Potentiostat 252
5.1.2 Determination of Kinetic Data by Potential Step Methods 253
5.1.3 Measurements with Controlled Mass Transport 255
5.1.4 Stationary Measurement of Very Rapid Reactions with Turbulent Flow
257
5.2 Quasi-Stationary Methods 260
5.2.1 Cyclic Voltammetry: Studies of Electrode Films and Electrode
Processes - Electrochemical Spectroscopy 260
5.2.2 AC Measurements 278
5.3 Electrochemical Methods for the Study of Electrode Films 291
5.3.1 Measurement of Charge Passed 292
5.3.2 Capacitance Measurements 294
5.4 Spectroelectrochemical and other Non-classical Methods 295
5.4.1 Introduction 295
5.4.2 Infra-Red Spectroelectrochemistry 297
5.4.3 Electron-spin Resonance 305
5.4.4 Electrochemical Mass Spectroscopy 309
5.4.5 Additional Methods of Importance 319
5.4.6 Scanning Microscope Techniques 321
5.5 Preparation of Nanostructures, Combination of STM and UHV-Transfer 326
5.5.1 Use of an STM-tip in SECM Experiments for the Preparation of Definite
Nanostructure 326
5.5.2 Combination of STM and UHV Transfer 326
5.6 Optical Methods 328
5.6.1 Ellipsometry 329
5.6.2 XAS, SXS and XANES 334
6 Electrocatalysis and Reaction Mechanisms 339
6.1 On Electrocatalysis 339
6.2 The Hydrogen Electrode 341
6.2.1 Influence of Adsorbed Intermediates on i-V Curves 342
6.2.2 Influence of the pH-value of the Solution and the Catalyst Surface
344
6.2.3 Hydrogen Oxidation at Platinum and Chemisorbed Oxygen 345
6.3 The Oxygen Electrode 346
6.3.1 Investigation of the Oxygen Reduction Reaction with Rotating
Ring-Disc Electrode 347
6.4 Methanol Oxidation 348
6.4.1 Parallel Pathways of Methanol Oxidation in Acid Electrolyte 350
6.4.2 Methanol Adsorption 350
6.4.3 Reaction Products and Adsorbed Intermediates of Methanol Oxidation
352
6.4.4 Effects of Surface Structure and Adsorbed Anions 354
6.4.5 On the Mechanism of Methanol Oxidation 355
6.4.6 Catalyst Promoters for Methanol Oxidation 356
6.5 Carbon Monoxide Oxidation at Platinum Surfaces 358
6.5.1 Identification of Surface Structures for CO Adsorbed on Pt(111) 358
6.5.2 Oxidation of CO in the Presence of Dissolved CO 359
6.5.3 The Oxidation of Carbon Monoxide: Langmuir-Hinshelwood Mechanism 361
6.5.4 CO Oxidation at Higher Overpotentials, Influence of Mass Transfer and
Oxygen Coverage 363
6.6 Conversion of Chemical Energy of Ethanol into Electricity 364
6.7 Reaction Mechanisms in Electro-organic Chemistry 366
6.7.1 General Issues 366
6.7.2 Classification of Electrode Processes 367
6.7.3 Oxidation Processes: Potentials, Intermediates and End Products 369
6.7.4 Reduction Processes: Potentials, Intermediates and Products 371
6.7.5 Further Electroorganic Reactions and the Influence of the Electrode
Surface 372
6.7.6 Electrochemical Polymerisation 373
6.8 Oscillations in Electrochemical Systems 375
7 Solid and Molten-salt Ionic Conductors as Electrolytes 381
7.1 Ionically Conducting Solids 381
7.1.1 Origins of Ionic Conductivity in Solids 381
7.1.2 Current/Voltage Measurements on Solid Electrodes 385
7.2 Solid Polymer Electrolytes (SPE's) 386
7.2.1 Current/Voltage Measurements with SPE's 388
7.2.2 Other Polymeric Membranes 388
7.3 Ionically-conducting Melts 392
7.3.1 Conductivity 392
7.3.2 Current-Voltage Studies 393
7.3.3 Further Applications of High-temperature Melts 394
7.3.4 Room Temperature Melts 395
8 Industrial Electrochemical Processes 397
8.1 Introduction and Fundamentals 397
8.1.1 Special Features of Electrochemical Processes 397
8.1.2 Classical Cell Designs and the Space-Time Yield 399
8.1.3 Morphology of Electrocatalysts 401
8.1.4 The Activation Overpotential 403
8.2 The Electrochemical Preparation of Chlorine and NaOH 404
8.2.1 Electrode Reactions during the Electrolysis of Aqueous NaCl 404
8.2.2 The Diaphragm Cell 405
8.2.3 The Amalgam Cell 406
8.2.4 The Membrane Process 408
8.2.5 Membrane Processes using an Oxygen Cathode 410
8.3 The Electrochemical Extraction and Purification of Metals 414
8.3.1 Extraction from Aqueous Solution 414
8.3.2 Metal Purification in Aqueous Solution 415
8.3.3 Molten Salt Electrolysis 417
8.4 Special Preparation Methods for Inorganic Chemicals 418
8.4.1 Hypochlorite, Chlorate and Perchlorate 418
8.4.2 Hydrogen Peroxide and Peroxodisulphate 419
8.4.3 Classical Water Electrolysis 420
8.4.4 Modern Water Electrolysis and Hydrogen Technology 420
8.5 Electro-organic Synthesis 422
8.5.1 An Overview of Processes and Specific Features 422
8.5.2 Adiponitrile - The Monsanto Process 424
8.6 Modern Cell Designs 425
8.7 Future Possibilities for Electrocatalysis 428
8.7.1 Electrochemical Modification of Catalytic Activity in Heterogeneous
Chemical Reactions - The NEMCA Effect 429
8.8 Component Separation Methods 431
8.8.1 Treatment of Waste Water 431
8.8.2 Electrodialysis 433
8.8.3 Electrophoresis 434
8.8.4 Electrochemical Separation Procedures in the Nuclear Industry 435
9 Galvanic Cells 439
9.1 Basics 440
9.2 Properties, Components and Characteristics of Batteries 441
9.2.1 Function and Construction of Lead-Acid Batteries 441
9.2.2 Function and Construction of Leclanché Cells 442
9.2.3 Electrolyte and Self-discharge 444
9.2.4 Open-circuit Voltage, Specific Capacity and Energy Density 444
9.2.5 Current-Voltage Characteristics, Power Density and
Power-density/Energy-density Diagrams 446
9.2.6. Battery Discharge Characteristics 447
9.2.7 Charge Characteristics, Current and Energy Yield and Cycle Number 448
9.2.8 Cost of Electrical Energy and of Installed Battery Power 449
9.3 Secondary Systems 450
9.3.1 Conventional Secondary Batteries 450
9.3.2 New Developments 452
9.3.3 Summary of Data for Secondary Battery Systems 461
9.4 Primary Systems other than Leclanché Batteries 464
9.4.1 Alkaline-Manganese Cells 464
9.4.2 The Zinc-Mercury Oxide Battery 465
9.4.3 Lithium Primary Batteries 466
9.4.4 Electrode and Battery Characteristics for Primary Systems 466
9.5 Fuel Cells 468
9.5.1 Fuel Cells with Gaseous Fuels 469
9.5.2 Modern Developments 472
9.5.3 Fuel Cells with Liquid Fuels 481
9.6 Primary and Secondary Air Batteries 483
9.6.1. Metal-Air Primary Batteries 484
9.6.2. Metal-Air Secondary Systems 485
9.7 Efficiency of Batteries and Fuel Cells 486
9.8 Super-capacitors 487
10 Analytical Applications 491
10.1 Titration Processes using Electrochemical Indicators 491
10.2 Electro-analytical Methods 494
10.2.1 Polarography and Voltammetry 494
10.2.2 Further Methods - Coulometry, Electrogravimetry and
Chronopotentiometry 502
10.3 Electrochemical Sensors 505
10.3.1 Conductivity and pH Measurement 505
10.3.2 Redox Electrodes 506
10.3.3 Ion-sensitive Electrodes 506
10.3.4 Sensors for the Analysis of Gases 510
Subject Index 521
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 The Measurement of Stationary Current-Potential Curves 251
5.1.1 The Potentiostat 252
5.1.2 Determination of Kinetic Data by Potential Step Methods 253
5.1.3 Measurements with Controlled Mass Transport 255
5.1.4 Stationary Measurement of Very Rapid Reactions with Turbulent Flow
257
5.2 Quasi-Stationary Methods 260
5.2.1 Cyclic Voltammetry: Studies of Electrode Films and Electrode
Processes - Electrochemical Spectroscopy 260
5.2.2 AC Measurements 278
5.3 Electrochemical Methods for the Study of Electrode Films 291
5.3.1 Measurement of Charge Passed 292
5.3.2 Capacitance Measurements 294
5.4 Spectroelectrochemical and other Non-classical Methods 295
5.4.1 Introduction 295
5.4.2 Infra-Red Spectroelectrochemistry 297
5.4.3 Electron-spin Resonance 305
5.4.4 Electrochemical Mass Spectroscopy 309
5.4.5 Additional Methods of Importance 319
5.4.6 Scanning Microscope Techniques 321
5.5 Preparation of Nanostructures, Combination of STM and UHV-Transfer 326
5.5.1 Use of an STM-tip in SECM Experiments for the Preparation of Definite
Nanostructure 326
5.5.2 Combination of STM and UHV Transfer 326
5.6 Optical Methods 328
5.6.1 Ellipsometry 329
5.6.2 XAS, SXS and XANES 334
6 Electrocatalysis and Reaction Mechanisms 339
6.1 On Electrocatalysis 339
6.2 The Hydrogen Electrode 341
6.2.1 Influence of Adsorbed Intermediates on i-V Curves 342
6.2.2 Influence of the pH-value of the Solution and the Catalyst Surface
344
6.2.3 Hydrogen Oxidation at Platinum and Chemisorbed Oxygen 345
6.3 The Oxygen Electrode 346
6.3.1 Investigation of the Oxygen Reduction Reaction with Rotating
Ring-Disc Electrode 347
6.4 Methanol Oxidation 348
6.4.1 Parallel Pathways of Methanol Oxidation in Acid Electrolyte 350
6.4.2 Methanol Adsorption 350
6.4.3 Reaction Products and Adsorbed Intermediates of Methanol Oxidation
352
6.4.4 Effects of Surface Structure and Adsorbed Anions 354
6.4.5 On the Mechanism of Methanol Oxidation 355
6.4.6 Catalyst Promoters for Methanol Oxidation 356
6.5 Carbon Monoxide Oxidation at Platinum Surfaces 358
6.5.1 Identification of Surface Structures for CO Adsorbed on Pt(111) 358
6.5.2 Oxidation of CO in the Presence of Dissolved CO 359
6.5.3 The Oxidation of Carbon Monoxide: Langmuir-Hinshelwood Mechanism 361
6.5.4 CO Oxidation at Higher Overpotentials, Influence of Mass Transfer and
Oxygen Coverage 363
6.6 Conversion of Chemical Energy of Ethanol into Electricity 364
6.7 Reaction Mechanisms in Electro-organic Chemistry 366
6.7.1 General Issues 366
6.7.2 Classification of Electrode Processes 367
6.7.3 Oxidation Processes: Potentials, Intermediates and End Products 369
6.7.4 Reduction Processes: Potentials, Intermediates and Products 371
6.7.5 Further Electroorganic Reactions and the Influence of the Electrode
Surface 372
6.7.6 Electrochemical Polymerisation 373
6.8 Oscillations in Electrochemical Systems 375
7 Solid and Molten-salt Ionic Conductors as Electrolytes 381
7.1 Ionically Conducting Solids 381
7.1.1 Origins of Ionic Conductivity in Solids 381
7.1.2 Current/Voltage Measurements on Solid Electrodes 385
7.2 Solid Polymer Electrolytes (SPE's) 386
7.2.1 Current/Voltage Measurements with SPE's 388
7.2.2 Other Polymeric Membranes 388
7.3 Ionically-conducting Melts 392
7.3.1 Conductivity 392
7.3.2 Current-Voltage Studies 393
7.3.3 Further Applications of High-temperature Melts 394
7.3.4 Room Temperature Melts 395
8 Industrial Electrochemical Processes 397
8.1 Introduction and Fundamentals 397
8.1.1 Special Features of Electrochemical Processes 397
8.1.2 Classical Cell Designs and the Space-Time Yield 399
8.1.3 Morphology of Electrocatalysts 401
8.1.4 The Activation Overpotential 403
8.2 The Electrochemical Preparation of Chlorine and NaOH 404
8.2.1 Electrode Reactions during the Electrolysis of Aqueous NaCl 404
8.2.2 The Diaphragm Cell 405
8.2.3 The Amalgam Cell 406
8.2.4 The Membrane Process 408
8.2.5 Membrane Processes using an Oxygen Cathode 410
8.3 The Electrochemical Extraction and Purification of Metals 414
8.3.1 Extraction from Aqueous Solution 414
8.3.2 Metal Purification in Aqueous Solution 415
8.3.3 Molten Salt Electrolysis 417
8.4 Special Preparation Methods for Inorganic Chemicals 418
8.4.1 Hypochlorite, Chlorate and Perchlorate 418
8.4.2 Hydrogen Peroxide and Peroxodisulphate 419
8.4.3 Classical Water Electrolysis 420
8.4.4 Modern Water Electrolysis and Hydrogen Technology 420
8.5 Electro-organic Synthesis 422
8.5.1 An Overview of Processes and Specific Features 422
8.5.2 Adiponitrile - The Monsanto Process 424
8.6 Modern Cell Designs 425
8.7 Future Possibilities for Electrocatalysis 428
8.7.1 Electrochemical Modification of Catalytic Activity in Heterogeneous
Chemical Reactions - The NEMCA Effect 429
8.8 Component Separation Methods 431
8.8.1 Treatment of Waste Water 431
8.8.2 Electrodialysis 433
8.8.3 Electrophoresis 434
8.8.4 Electrochemical Separation Procedures in the Nuclear Industry 435
9 Galvanic Cells 439
9.1 Basics 440
9.2 Properties, Components and Characteristics of Batteries 441
9.2.1 Function and Construction of Lead-Acid Batteries 441
9.2.2 Function and Construction of Leclanché Cells 442
9.2.3 Electrolyte and Self-discharge 444
9.2.4 Open-circuit Voltage, Specific Capacity and Energy Density 444
9.2.5 Current-Voltage Characteristics, Power Density and
Power-density/Energy-density Diagrams 446
9.2.6. Battery Discharge Characteristics 447
9.2.7 Charge Characteristics, Current and Energy Yield and Cycle Number 448
9.2.8 Cost of Electrical Energy and of Installed Battery Power 449
9.3 Secondary Systems 450
9.3.1 Conventional Secondary Batteries 450
9.3.2 New Developments 452
9.3.3 Summary of Data for Secondary Battery Systems 461
9.4 Primary Systems other than Leclanché Batteries 464
9.4.1 Alkaline-Manganese Cells 464
9.4.2 The Zinc-Mercury Oxide Battery 465
9.4.3 Lithium Primary Batteries 466
9.4.4 Electrode and Battery Characteristics for Primary Systems 466
9.5 Fuel Cells 468
9.5.1 Fuel Cells with Gaseous Fuels 469
9.5.2 Modern Developments 472
9.5.3 Fuel Cells with Liquid Fuels 481
9.6 Primary and Secondary Air Batteries 483
9.6.1. Metal-Air Primary Batteries 484
9.6.2. Metal-Air Secondary Systems 485
9.7 Efficiency of Batteries and Fuel Cells 486
9.8 Super-capacitors 487
10 Analytical Applications 491
10.1 Titration Processes using Electrochemical Indicators 491
10.2 Electro-analytical Methods 494
10.2.1 Polarography and Voltammetry 494
10.2.2 Further Methods - Coulometry, Electrogravimetry and
Chronopotentiometry 502
10.3 Electrochemical Sensors 505
10.3.1 Conductivity and pH Measurement 505
10.3.2 Redox Electrodes 506
10.3.3 Ion-sensitive Electrodes 506
10.3.4 Sensors for the Analysis of Gases 510
Subject Index 521
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 The Measurement of Stationary Current-Potential Curves 251
5.1.1 The Potentiostat 252
5.1.2 Determination of Kinetic Data by Potential Step Methods 253
5.1.3 Measurements with Controlled Mass Transport 255
5.1.4 Stationary Measurement of Very Rapid Reactions with Turbulent Flow
257
5.2 Quasi-Stationary Methods 260
5.2.1 Cyclic Voltammetry: Studies of Electrode Films and Electrode
Processes - Electrochemical Spectroscopy 260
5.2.2 AC Measurements 278
5.3 Electrochemical Methods for the Study of Electrode Films 291
5.3.1 Measurement of Charge Passed 292
5.3.2 Capacitance Measurements 294
5.4 Spectroelectrochemical and other Non-classical Methods 295
5.4.1 Introduction 295
5.4.2 Infra-Red Spectroelectrochemistry 297
5.4.3 Electron-spin Resonance 305
5.4.4 Electrochemical Mass Spectroscopy 309
5.4.5 Additional Methods of Importance 319
5.4.6 Scanning Microscope Techniques 321
5.5 Preparation of Nanostructures, Combination of STM and UHV-Transfer 326
5.5.1 Use of an STM-tip in SECM Experiments for the Preparation of Definite
Nanostructure 326
5.5.2 Combination of STM and UHV Transfer 326
5.6 Optical Methods 328
5.6.1 Ellipsometry 329
5.6.2 XAS, SXS and XANES 334
6 Electrocatalysis and Reaction Mechanisms 339
6.1 On Electrocatalysis 339
6.2 The Hydrogen Electrode 341
6.2.1 Influence of Adsorbed Intermediates on i-V Curves 342
6.2.2 Influence of the pH-value of the Solution and the Catalyst Surface
344
6.2.3 Hydrogen Oxidation at Platinum and Chemisorbed Oxygen 345
6.3 The Oxygen Electrode 346
6.3.1 Investigation of the Oxygen Reduction Reaction with Rotating
Ring-Disc Electrode 347
6.4 Methanol Oxidation 348
6.4.1 Parallel Pathways of Methanol Oxidation in Acid Electrolyte 350
6.4.2 Methanol Adsorption 350
6.4.3 Reaction Products and Adsorbed Intermediates of Methanol Oxidation
352
6.4.4 Effects of Surface Structure and Adsorbed Anions 354
6.4.5 On the Mechanism of Methanol Oxidation 355
6.4.6 Catalyst Promoters for Methanol Oxidation 356
6.5 Carbon Monoxide Oxidation at Platinum Surfaces 358
6.5.1 Identification of Surface Structures for CO Adsorbed on Pt(111) 358
6.5.2 Oxidation of CO in the Presence of Dissolved CO 359
6.5.3 The Oxidation of Carbon Monoxide: Langmuir-Hinshelwood Mechanism 361
6.5.4 CO Oxidation at Higher Overpotentials, Influence of Mass Transfer and
Oxygen Coverage 363
6.6 Conversion of Chemical Energy of Ethanol into Electricity 364
6.7 Reaction Mechanisms in Electro-organic Chemistry 366
6.7.1 General Issues 366
6.7.2 Classification of Electrode Processes 367
6.7.3 Oxidation Processes: Potentials, Intermediates and End Products 369
6.7.4 Reduction Processes: Potentials, Intermediates and Products 371
6.7.5 Further Electroorganic Reactions and the Influence of the Electrode
Surface 372
6.7.6 Electrochemical Polymerisation 373
6.8 Oscillations in Electrochemical Systems 375
7 Solid and Molten-salt Ionic Conductors as Electrolytes 381
7.1 Ionically Conducting Solids 381
7.1.1 Origins of Ionic Conductivity in Solids 381
7.1.2 Current/Voltage Measurements on Solid Electrodes 385
7.2 Solid Polymer Electrolytes (SPE's) 386
7.2.1 Current/Voltage Measurements with SPE's 388
7.2.2 Other Polymeric Membranes 388
7.3 Ionically-conducting Melts 392
7.3.1 Conductivity 392
7.3.2 Current-Voltage Studies 393
7.3.3 Further Applications of High-temperature Melts 394
7.3.4 Room Temperature Melts 395
8 Industrial Electrochemical Processes 397
8.1 Introduction and Fundamentals 397
8.1.1 Special Features of Electrochemical Processes 397
8.1.2 Classical Cell Designs and the Space-Time Yield 399
8.1.3 Morphology of Electrocatalysts 401
8.1.4 The Activation Overpotential 403
8.2 The Electrochemical Preparation of Chlorine and NaOH 404
8.2.1 Electrode Reactions during the Electrolysis of Aqueous NaCl 404
8.2.2 The Diaphragm Cell 405
8.2.3 The Amalgam Cell 406
8.2.4 The Membrane Process 408
8.2.5 Membrane Processes using an Oxygen Cathode 410
8.3 The Electrochemical Extraction and Purification of Metals 414
8.3.1 Extraction from Aqueous Solution 414
8.3.2 Metal Purification in Aqueous Solution 415
8.3.3 Molten Salt Electrolysis 417
8.4 Special Preparation Methods for Inorganic Chemicals 418
8.4.1 Hypochlorite, Chlorate and Perchlorate 418
8.4.2 Hydrogen Peroxide and Peroxodisulphate 419
8.4.3 Classical Water Electrolysis 420
8.4.4 Modern Water Electrolysis and Hydrogen Technology 420
8.5 Electro-organic Synthesis 422
8.5.1 An Overview of Processes and Specific Features 422
8.5.2 Adiponitrile - The Monsanto Process 424
8.6 Modern Cell Designs 425
8.7 Future Possibilities for Electrocatalysis 428
8.7.1 Electrochemical Modification of Catalytic Activity in Heterogeneous
Chemical Reactions - The NEMCA Effect 429
8.8 Component Separation Methods 431
8.8.1 Treatment of Waste Water 431
8.8.2 Electrodialysis 433
8.8.3 Electrophoresis 434
8.8.4 Electrochemical Separation Procedures in the Nuclear Industry 435
9 Galvanic Cells 439
9.1 Basics 440
9.2 Properties, Components and Characteristics of Batteries 441
9.2.1 Function and Construction of Lead-Acid Batteries 441
9.2.2 Function and Construction of Leclanché Cells 442
9.2.3 Electrolyte and Self-discharge 444
9.2.4 Open-circuit Voltage, Specific Capacity and Energy Density 444
9.2.5 Current-Voltage Characteristics, Power Density and
Power-density/Energy-density Diagrams 446
9.2.6. Battery Discharge Characteristics 447
9.2.7 Charge Characteristics, Current and Energy Yield and Cycle Number 448
9.2.8 Cost of Electrical Energy and of Installed Battery Power 449
9.3 Secondary Systems 450
9.3.1 Conventional Secondary Batteries 450
9.3.2 New Developments 452
9.3.3 Summary of Data for Secondary Battery Systems 461
9.4 Primary Systems other than Leclanché Batteries 464
9.4.1 Alkaline-Manganese Cells 464
9.4.2 The Zinc-Mercury Oxide Battery 465
9.4.3 Lithium Primary Batteries 466
9.4.4 Electrode and Battery Characteristics for Primary Systems 466
9.5 Fuel Cells 468
9.5.1 Fuel Cells with Gaseous Fuels 469
9.5.2 Modern Developments 472
9.5.3 Fuel Cells with Liquid Fuels 481
9.6 Primary and Secondary Air Batteries 483
9.6.1. Metal-Air Primary Batteries 484
9.6.2. Metal-Air Secondary Systems 485
9.7 Efficiency of Batteries and Fuel Cells 486
9.8 Super-capacitors 487
10 Analytical Applications 491
10.1 Titration Processes using Electrochemical Indicators 491
10.2 Electro-analytical Methods 494
10.2.1 Polarography and Voltammetry 494
10.2.2 Further Methods - Coulometry, Electrogravimetry and
Chronopotentiometry 502
10.3 Electrochemical Sensors 505
10.3.1 Conductivity and pH Measurement 505
10.3.2 Redox Electrodes 506
10.3.3 Ion-sensitive Electrodes 506
10.3.4 Sensors for the Analysis of Gases 510
Subject Index 521
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 The Measurement of Stationary Current-Potential Curves 251
5.1.1 The Potentiostat 252
5.1.2 Determination of Kinetic Data by Potential Step Methods 253
5.1.3 Measurements with Controlled Mass Transport 255
5.1.4 Stationary Measurement of Very Rapid Reactions with Turbulent Flow
257
5.2 Quasi-Stationary Methods 260
5.2.1 Cyclic Voltammetry: Studies of Electrode Films and Electrode
Processes - Electrochemical Spectroscopy 260
5.2.2 AC Measurements 278
5.3 Electrochemical Methods for the Study of Electrode Films 291
5.3.1 Measurement of Charge Passed 292
5.3.2 Capacitance Measurements 294
5.4 Spectroelectrochemical and other Non-classical Methods 295
5.4.1 Introduction 295
5.4.2 Infra-Red Spectroelectrochemistry 297
5.4.3 Electron-spin Resonance 305
5.4.4 Electrochemical Mass Spectroscopy 309
5.4.5 Additional Methods of Importance 319
5.4.6 Scanning Microscope Techniques 321
5.5 Preparation of Nanostructures, Combination of STM and UHV-Transfer 326
5.5.1 Use of an STM-tip in SECM Experiments for the Preparation of Definite
Nanostructure 326
5.5.2 Combination of STM and UHV Transfer 326
5.6 Optical Methods 328
5.6.1 Ellipsometry 329
5.6.2 XAS, SXS and XANES 334
6 Electrocatalysis and Reaction Mechanisms 339
6.1 On Electrocatalysis 339
6.2 The Hydrogen Electrode 341
6.2.1 Influence of Adsorbed Intermediates on i-V Curves 342
6.2.2 Influence of the pH-value of the Solution and the Catalyst Surface
344
6.2.3 Hydrogen Oxidation at Platinum and Chemisorbed Oxygen 345
6.3 The Oxygen Electrode 346
6.3.1 Investigation of the Oxygen Reduction Reaction with Rotating
Ring-Disc Electrode 347
6.4 Methanol Oxidation 348
6.4.1 Parallel Pathways of Methanol Oxidation in Acid Electrolyte 350
6.4.2 Methanol Adsorption 350
6.4.3 Reaction Products and Adsorbed Intermediates of Methanol Oxidation
352
6.4.4 Effects of Surface Structure and Adsorbed Anions 354
6.4.5 On the Mechanism of Methanol Oxidation 355
6.4.6 Catalyst Promoters for Methanol Oxidation 356
6.5 Carbon Monoxide Oxidation at Platinum Surfaces 358
6.5.1 Identification of Surface Structures for CO Adsorbed on Pt(111) 358
6.5.2 Oxidation of CO in the Presence of Dissolved CO 359
6.5.3 The Oxidation of Carbon Monoxide: Langmuir-Hinshelwood Mechanism 361
6.5.4 CO Oxidation at Higher Overpotentials, Influence of Mass Transfer and
Oxygen Coverage 363
6.6 Conversion of Chemical Energy of Ethanol into Electricity 364
6.7 Reaction Mechanisms in Electro-organic Chemistry 366
6.7.1 General Issues 366
6.7.2 Classification of Electrode Processes 367
6.7.3 Oxidation Processes: Potentials, Intermediates and End Products 369
6.7.4 Reduction Processes: Potentials, Intermediates and Products 371
6.7.5 Further Electroorganic Reactions and the Influence of the Electrode
Surface 372
6.7.6 Electrochemical Polymerisation 373
6.8 Oscillations in Electrochemical Systems 375
7 Solid and Molten-salt Ionic Conductors as Electrolytes 381
7.1 Ionically Conducting Solids 381
7.1.1 Origins of Ionic Conductivity in Solids 381
7.1.2 Current/Voltage Measurements on Solid Electrodes 385
7.2 Solid Polymer Electrolytes (SPE's) 386
7.2.1 Current/Voltage Measurements with SPE's 388
7.2.2 Other Polymeric Membranes 388
7.3 Ionically-conducting Melts 392
7.3.1 Conductivity 392
7.3.2 Current-Voltage Studies 393
7.3.3 Further Applications of High-temperature Melts 394
7.3.4 Room Temperature Melts 395
8 Industrial Electrochemical Processes 397
8.1 Introduction and Fundamentals 397
8.1.1 Special Features of Electrochemical Processes 397
8.1.2 Classical Cell Designs and the Space-Time Yield 399
8.1.3 Morphology of Electrocatalysts 401
8.1.4 The Activation Overpotential 403
8.2 The Electrochemical Preparation of Chlorine and NaOH 404
8.2.1 Electrode Reactions during the Electrolysis of Aqueous NaCl 404
8.2.2 The Diaphragm Cell 405
8.2.3 The Amalgam Cell 406
8.2.4 The Membrane Process 408
8.2.5 Membrane Processes using an Oxygen Cathode 410
8.3 The Electrochemical Extraction and Purification of Metals 414
8.3.1 Extraction from Aqueous Solution 414
8.3.2 Metal Purification in Aqueous Solution 415
8.3.3 Molten Salt Electrolysis 417
8.4 Special Preparation Methods for Inorganic Chemicals 418
8.4.1 Hypochlorite, Chlorate and Perchlorate 418
8.4.2 Hydrogen Peroxide and Peroxodisulphate 419
8.4.3 Classical Water Electrolysis 420
8.4.4 Modern Water Electrolysis and Hydrogen Technology 420
8.5 Electro-organic Synthesis 422
8.5.1 An Overview of Processes and Specific Features 422
8.5.2 Adiponitrile - The Monsanto Process 424
8.6 Modern Cell Designs 425
8.7 Future Possibilities for Electrocatalysis 428
8.7.1 Electrochemical Modification of Catalytic Activity in Heterogeneous
Chemical Reactions - The NEMCA Effect 429
8.8 Component Separation Methods 431
8.8.1 Treatment of Waste Water 431
8.8.2 Electrodialysis 433
8.8.3 Electrophoresis 434
8.8.4 Electrochemical Separation Procedures in the Nuclear Industry 435
9 Galvanic Cells 439
9.1 Basics 440
9.2 Properties, Components and Characteristics of Batteries 441
9.2.1 Function and Construction of Lead-Acid Batteries 441
9.2.2 Function and Construction of Leclanché Cells 442
9.2.3 Electrolyte and Self-discharge 444
9.2.4 Open-circuit Voltage, Specific Capacity and Energy Density 444
9.2.5 Current-Voltage Characteristics, Power Density and
Power-density/Energy-density Diagrams 446
9.2.6. Battery Discharge Characteristics 447
9.2.7 Charge Characteristics, Current and Energy Yield and Cycle Number 448
9.2.8 Cost of Electrical Energy and of Installed Battery Power 449
9.3 Secondary Systems 450
9.3.1 Conventional Secondary Batteries 450
9.3.2 New Developments 452
9.3.3 Summary of Data for Secondary Battery Systems 461
9.4 Primary Systems other than Leclanché Batteries 464
9.4.1 Alkaline-Manganese Cells 464
9.4.2 The Zinc-Mercury Oxide Battery 465
9.4.3 Lithium Primary Batteries 466
9.4.4 Electrode and Battery Characteristics for Primary Systems 466
9.5 Fuel Cells 468
9.5.1 Fuel Cells with Gaseous Fuels 469
9.5.2 Modern Developments 472
9.5.3 Fuel Cells with Liquid Fuels 481
9.6 Primary and Secondary Air Batteries 483
9.6.1. Metal-Air Primary Batteries 484
9.6.2. Metal-Air Secondary Systems 485
9.7 Efficiency of Batteries and Fuel Cells 486
9.8 Super-capacitors 487
10 Analytical Applications 491
10.1 Titration Processes using Electrochemical Indicators 491
10.2 Electro-analytical Methods 494
10.2.1 Polarography and Voltammetry 494
10.2.2 Further Methods - Coulometry, Electrogravimetry and
Chronopotentiometry 502
10.3 Electrochemical Sensors 505
10.3.1 Conductivity and pH Measurement 505
10.3.2 Redox Electrodes 506
10.3.3 Ion-sensitive Electrodes 506
10.3.4 Sensors for the Analysis of Gases 510
Subject Index 521