Physical Electrochemistry

Professor Noam Eliaz is a full professor, Director of the Biomaterials and Corrosion Laboratory, and the founder of the Department of Materials Science and Engineering at TAU. He earned a BSc degree in Materials Engineering, an MBA degree, and a PhD degree (direct track) in Materials Engineering, all cum laude from Ben-Gurion University of the Negev. Prior to joining TAU, he was a Fulbright and Rothschild Fellow at MIT. His research is interdisciplinary and includes electrodeposition of calcium phosphate coatings for implants, electrodeposition of special alloys for high-temperature applications, corrosion, and failure analysis. From 2005 to 2017 he was the Editor-in-Chief of the journal Corrosion Reviews, and currently he is an editorial board member of this journal as well as of Current Topics in Electrochemistry, Corrosion, and Materials Degradation, and Bioceramics Development and Applications. He is an elected member of The Israel Young Academy and was appointed to the Governing Board of The German-Israeli Foundation for Scientific Research and Development (GIF). He has won numerous awards, including NACE International's Herbert H. Uhlig Award (2010), Fellow Award (2012), and Technical Achievement Award (2014), as well as Fellow of The Japanese Society for the Promotion of Science (2005?2007) and the T.P. Hoar Award (2003).Eliezer Gileadi has been a Professor of Chemistry at Tel-Aviv University (TAU) since 1966 (Emeritus since 2000). He obtained his M.Sc. at the Hebrew University in Jerusalem and his Ph.D. at the University of Ottawa, Canada. He has been a visiting professor and a lecturer at many institutes worldwide, including the University of Virginia, The University of Pennsylvania, Case Western Reserve University, The Johns Hopkins University, University of Ottawa, etc. He is a Fellow of the Royal Society of Canada, the Electrochemical Society, the American Association for the Advancement of Science, and the International Society for Electrochemistry. He received from the Electrochemical Society the prestigious Olin-Palladium Award and the Henry B. Linford Award for Distinguished Teaching. He taught this subject for 40 years and consulted to industry.

• Preface xviiSymbols and Abbreviations xix1 Introduction 11.1 General Considerations 11.1.1 The Transition from Electronic to Ionic Conduction 11.1.2 The Resistance of the Interface can be Infinite 21.1.3 Mass-Transport Limitation 21.1.4 The Capacitance at the Metal/Solution Interphase 41.2 Polarizable and Nonpolarizable Interfaces 41.2.1 Phenomenology 41.2.2 The Equivalent Circuit Representation 5Further Reading 72 The Potentials of Phases 92.1 The Driving Force 92.1.1 Definition of the Electrochemical Potential 92.1.2 Separability of the Chemical and the Electrical Terms 102.2 Two Cases of Special Interest 112.2.1 Equilibrium of a Species Between two Phases in Contact 112.2.2 Two Identical Phases not at Equilibrium 122.3 The Meaning of the Standard Hydrogen Electrode (SHE) Scale 13Further Reading 153 Fundamental Measurements in Electrochemistry 173.1 Measurement of Current and Potential 173.1.1 The Cell Voltage is the Sum of Several Potential Differences 173.1.2 Use of a Nonpolarizable Counter Electrode 173.1.3 The Three-Electrode Setup 183.1.4 Residual jRS Potential Drop in aThree-Electrode Cell 183.2 Cell Geometry and the Choice of the Reference Electrode 193.2.1 Types of Reference Electrodes 193.2.2 Use of an Auxiliary Reference Electrode for the Study of Fast Transients 203.2.3 Calculating the Uncompensated Solution Resistance for a few Simple Geometries 213.2.3.1 Planar Configuration 213.2.3.2 Cylindrical Configuration 213.2.3.3 Spherical Symmetry 223.2.4 Positioning the Reference Electrode 223.2.5 Edge Effects 24Further Reading 264 Electrode Kinetics: Some Basic Concepts 274.1 Relating Electrode Kinetics to Chemical Kinetics 274.1.1 The Relation of Current Density to Reaction Rate 274.1.2 The Relation of Potential to Energy of Activation 284.1.3 Mass-Transport Limitation Versus Charge-Transfer Limitation 304.1.4 The Thickness of the Nernst Diffusion Layer 314.2 Methods of Measurement 334.2.1 Potential Control Versus Current Control 334.2.2 The Need to Measure Fast Transients 354.2.3 Polarography and the Dropping Mercury Electrode (DME) 374.3 Rotating Electrodes 404.3.1 The Rotating Disk Electrode (RDE) 404.3.2 The Rotating Cone Electrode (RConeE) 444.3.3 The Rotating Ring Disk Electrode (RRDE) 45Further Reading 475 Single-Step Electrode Reactions 495.1 The Overpotential, 𝜂 495.1.1 Definition and Physical Meaning of Overpotential 495.1.2 Types of Overpotential 515.2 Fundamental Equations of Electrode Kinetics 525.2.1 The Empirical Tafel Equation 525.2.2 The Transition-State Theory 535.2.3 The Equation for a Single-Step Electrode Reaction 545.2.4 Limiting Cases of the General Equation 565.3 The Symmetry Factor, 𝛽, in Electrode Kinetics 595.3.1 The Definition of 𝛽 595.3.2 The Numerical Value of 𝛽 605.4 The Marcus Theory of Charge Transfer 615.4.1 Outer-Sphere Electron Transfer 615.4.2 The Born–Oppenheimer Approximation 625.4.3 The Calculated Energy of Activation 635.4.4 The Value of 𝛽 and its Potential Dependence 645.5 Inner-Sphere Charge Transfer 655.5.1 Metal Deposition 65Further Reading 666 Multistep Electrode Reactions 676.1 Mechanistic Criteria 676.1.1 The Transfer Coefficient, 𝛼, and its Relation to the Symmetry Factor, 𝛽 676.1.2 Steady State and Quasi-Equilibrium 696.1.3 Calculation of the Tafel Slope 716.1.4 Reaction Orders in Electrode Kinetics 746.1.5 The Effect of pH on Reaction Rates 776.1.6 The Enthalpy of Activation 79Further Reading 817 Specific Examples of Multistep Electrode Reactions 837.1 Experimental Considerations 837.1.1 Multiple Processes in Parallel 837.1.2 The Level of Impurity that can be Tolerated 847.2 The Hydrogen Evolution Reaction (HER) 877.2.1 Hydrogen Evolution on Mercury 877.2.2 Hydrogen Evolution on Platinum 897.3 Possible Paths for the Oxygen Evolution Reaction 917.4 The Role and Stability of Adsorbed Intermediates 947.5 Adsorption Energy and Catalytic Activity 95Further Reading 968 The Electrical Double Layer (EDL) 978.1 Models of Structure of the EDL 978.1.1 Phenomenology 978.1.2 The Parallel-Plate Model of Helmholtz 998.1.3 The Diffuse Double Layer Model of Gouy and Chapman 1008.1.4 The Stern Model 1038.1.5 The Role of the Solvent at the Interphase 105Further Reading 1079 Electrocapillary 1099.1 Thermodynamics 1099.1.1 Adsorption and Surface Excess 1099.1.2 The Gibbs Adsorption Isotherm 1119.1.3 The Electrocapillary Equation 1129.2 Methods of Measurement and Some Results 1149.2.1 The Electrocapillary Electrometer 1149.2.2 Some Experimental Results 1199.2.2.1 The Adsorption of Ions 1199.2.2.2 Adsorption of NeutralMolecules 120Further Reading 12210 Intermediates in Electrode Reactions 12310.1 Adsorption Isotherms for Intermediates Formed by Charge Transfer 12310.1.1 General 12310.1.2 The Langmuir Isotherm and its Limitations 12310.1.3 Application of the Langmuir Isotherm for Charge-Transfer Processes 12510.1.4 The Frumkin Adsorption Isotherms 12610.2 The Adsorption Pseudocapacitance Cϕ 12710.2.1 Formal Definition of Cϕ and its Physical Understanding 12710.2.2 The Equivalent-Circuit Representation 12910.2.3 Calculation of Cϕ as a function of 𝜃 and E 130Further Reading 13311 Underpotential Deposition and Single-Crystal Electrochemistry 13511.1 Underpotential Deposition (UPD) 13511.1.1 Definition and Phenomenology 13511.1.2 UPD on Single Crystals 13911.1.3 Underpotential Deposition of Atomic Oxygen and Hydrogen 141Further Reading 14212 Electrosorption 14512.1 Phenomenology 14512.1.1 What is Electrosorption? 14512.1.2 Electrosorption of Neutral Organic Molecules 14712.1.3 The Potential of Zero Charge, Epzc, and its Importance in Electrosorption 14812.1.4 TheWork Function and the Potential of Zero Charge 15112.2 Adsorption Isotherms for Neutral Species 15212.2.1 General Comments 15212.2.2 The Parallel-Plate Model of Frumkin et al. 15312.2.3 The Water Replacement Model of Bockris et al. 155Further Reading 15713 Fast Transients, the Time-Dependent Diffusion Equation,and Microelectrodes 15913.1 The Need for Fast Transients 15913.1.1 General 15913.1.2 Small-Amplitude Transients 16113.1.3 The Sluggish Response of the Electrochemical Interphase 16213.1.4 How can the Slow Response of the Interphase be Overcome? 16213.1.4.1 Galvanostatic Transients 16213.1.4.2 The Double-Pulse GalvanostaticMethod 16313.1.4.3 The Coulostatic (Charge-Injection) Method 16413.2 The Diffusion Equation 16713.2.1 The Boundary Conditions of the Diffusion Equation 16713.2.1.1 Potential Step, Reversible Case (Chrono-Amperometry) 16813.2.1.2 Potential Step, High Overpotential Region (Chrono-Amperometry) 17113.2.1.3 Current Step (Chronopotentiometry) 17213.3 Microelectrodes 17413.3.1 The Unique Features of Microelectrodes 17413.3.2 Enhancement of Diffusion at a Microelectrode 17513.3.3 Reduction of the Solution Resistance 17613.3.4 The Choice between Single Microelectrodes and Large Ensembles 176Further Reading 17814 Linear Potential Sweep and Cyclic Voltammetry 18114.1 Three Types of Linear Potential Sweep 18114.1.1 Very Slow Sweeps 18114.1.2 Studies of Oxidation or Reduction of Species in the Bulk of the Solution 18214.1.3 Studies of Oxidation or Reduction of Species Adsorbed on the Surface 18214.1.4 Double-Layer Charging Currents 18314.1.5 The Form of the Current–Potential Relationship 18514.2 Solution of the Diffusion Equations 18614.2.1 The Reversible Region 18614.2.2 The High-Overpotential Region 18714.3 Uses and Limitations of the Linear Potential Sweep Method 18814.4 Cyclic Voltammetry for Monolayer Adsorption 19014.4.1 Reversible Region 19014.4.2 The High-Overpotential Region 192Further Reading 19315 Electrochemical Impedance Spectroscopy (EIS) 19515.1 Introduction 19515.2 Graphical Representations 20015.3 The Effect of Diffusion Limitation –TheWarburg Impedance 20315.4 Advantages, Disadvantages, and Applications of EIS 206Further Reading 21116 The Electrochemical Quartz Crystal Microbalance (EQCM) 21316.1 Fundamental Properties of the EQCM 21316.1.1 Introduction 21316.1.2 The EQCM 21416.1.3 The Effect of Viscosity 21716.1.4 Immersion in a Liquid 21816.1.5 Scales of Roughness 21816.2 Impedance Analysis of the EQCM 21916.2.1 The Extended Equation for the Frequency Shift 21916.2.2 Other Factors Influencing the Frequency Shift 22016.3 Uses of the EQCM as a Microsensor 22016.3.1 Advantages and Limitations 22016.3.2 Some Applications of the EQCM 222Further Reading 22517 Corrosion 22717.1 The Definition of Corrosion 22717.2 Corrosion Costs 23017.3 Thermodynamics of Corrosion 23217.3.1 Introduction and Important Terms 23217.3.2 Electrode Potentials and the Standard Electromotive Force (EMF) Series 23617.3.3 The Dependence of Free Energy on the Equilibrium Constant and Cell Potential 24117.3.4 The Nernst Equation 24117.3.5 The Potential–pH (Pourbaix) Diagrams 24217.4 Kinetics of Corrosion 25217.4.1 Introduction and Important Terms 25217.4.2 Two Limiting Cases of the Butler–Volmer Equation: Tafel Extrapolation and Polarization Resistance 25517.4.3 Corrosion Rate 25717.4.4 The Mixed-Potential Theory and the Evans Diagrams 25717.4.5 Passivation and its Breakdown 26417.5 Corrosion Measurements 27017.5.1 Non-Electrochemical Tests 27017.5.2 Electrochemical Tests 27217.5.2.1 Open-Circuit Potential (OCP) Measurements 27217.5.2.2 Polarization Tests 27317.5.2.3 Linear Polarization Resistance (LPR) 27717.5.2.4 Zero-Resistance Ammetry (ZRA) 27717.5.2.5 Electrochemical Noise (EN) Measurements 27817.5.2.6 Electrochemical Hydrogen Permeation Tests 27917.5.3 Complementary Surface-Sensitive Analytical Characterization Techniques 28417.6 Forms of Corrosion 28617.6.1 Uniform (General) Corrosion 28617.6.2 Localized Corrosion 28917.6.2.1 Crevice Corrosion 28917.6.2.2 Filiform Corrosion 29117.6.2.3 Pitting Corrosion 29117.6.3 Intergranular Corrosion 29317.6.3.1 Sensitization 29317.6.3.2 Exfoliation 29417.6.4 Dealloying 29517.6.5 Galvanic (Bimetallic) Corrosion 29517.6.6 Environmentally Induced Cracking (EIC)/Environment-Assisted Cracking (EAC) 29717.6.6.1 Hydrogen Embrittlement (HE) 29717.6.6.2 Hydrogen-Induced Blistering 29917.6.6.3 Hydrogen Attack 29917.6.6.4 Stress Corrosion Cracking (SCC) 30017.6.6.5 Corrosion Fatigue (CF) 30317.6.7 Erosion Corrosion 30417.6.8 Microbiological Corrosion (MIC) 30517.7 Corrosion Protection 30817.7.1 Cathodic Protection 30817.7.1.1 Cathodic Protection with Sacrificial Anodes 30817.7.1.2 Impressed-Current Cathodic Protection (ICCP) 31017.7.2 Anodic Protection 31217.7.3 Corrosion Inhibitors 31317.7.4 Coatings 31517.7.5 Other Mitigation Practices 320Further Reading 32118 Electrochemical Deposition 32318.1 Electroplating 32318.1.1 Introduction 32318.1.2 The Fundamental Equations of Electroplating 32418.1.3 Practical Aspects of Metal Deposition 32518.1.4 Hydrogen Evolution as a Side Reaction 32618.1.5 Plating of Noble Metals 32718.1.6 Current Distribution in Electroplating 32818.1.6.1 Uniformity of Current Distribution 32818.1.6.2 The Faradaic Resistance (RF) and the Solution Resistance (RS) 32818.1.6.3 The DimensionlessWagner Number 32918.1.6.4 Kinetically Limited Current Density 33318.1.7 Throwing Power 33418.1.7.1 Macro Throwing Power 33418.1.7.2 Micro Throwing Power 33418.1.8 The Use of Additives 33618.1.9 The Microstructure of Electrodeposits and the Evolution of Intrinsic Stresses 33918.1.10 Pulse Plating 34118.1.11 Plating from Nonaqueous Solutions 34318.1.11.1 Statement of the Problem 34318.1.11.2 Methods of Plating Al 34518.1.12 Electroplating of Alloys 34618.1.12.1 General Observations 34618.1.12.2 Some Specific Examples 34918.1.13 The Mechanism of Charge Transfer in Metal Deposition 35118.1.13.1 Metal Ions Crossing the Interphase Carry the Charge across it 35118.2 Electroless Deposition of Metals 35218.2.1 Some Fundamental Aspects of Electroless Plating of Metals and Alloys 35218.2.2 The Activation Process 35318.2.3 The Reducing Agent 35318.2.4 The Complexing Agent 35418.2.5 The Mechanism of Electroless Deposition 35418.2.6 Advantages and Disadvantages of Electroless Plating Compared to Electroplating 35718.3 Electrophoretic Deposition (EPD) 358Further Reading 36119 Electrochemical Nanotechnology 36319.1 Introduction 36319.2 Nanoparticles and Catalysis 36319.2.1 Surfaces and Interfaces 36419.2.2 The Vapor Pressure of Small Droplets and the Melting Point of Solid NPs 36519.2.3 TheThermodynamic Stability andThermal Mobility of NPs 36819.2.4 Catalysts 36819.2.5 The Effect of Particle Size on Catalytic Activity 36919.2.6 Nanoparticles Compared to Microelectrodes 37019.2.7 The Need for High Surface Area 37119.3 Electrochemical Printing 37219.3.1 Electrochemical Printing Processes 37319.3.2 Nanoelectrochemistry Using Micro- and Nano-Electrodes/Pipettes 379Further Reading 38420 Energy Conversion and Storage 38720.1 Introduction 38720.2 Batteries 38820.2.1 Classes of Batteries 38820.2.2 TheTheoretical Limit of Energy per UnitWeight 39020.2.3 How is the Quality of a Battery Defined? 39120.2.4 Primary Batteries 39220.2.4.1 Why DoWe Need Primary Batteries? 39220.2.4.2 The Leclanché and the Alkaline Batteries 39220.2.4.3 The Li–Thionyl Chloride Battery 39320.2.4.4 The Lithium–Iodine Solid-State Battery 39520.2.5 Secondary Batteries 39620.2.5.1 Self-Discharge and Specific Energy 39620.2.5.2 Battery Stacks Versus Single Cells 39620.2.5.3 Some Common Types of Secondary Batteries 39720.2.5.4 The Li-ion Battery 40220.2.5.5 Metal–Air Batteries 40820.2.6 Batteries-Driven Electric Vehicles 40920.2.7 The Polarity of Batteries 41020.3 Fuel Cells 41220.3.1 The Specific Energy of Fuel Cells 41220.3.2 The Phosphoric Acid Fuel Cell (PAFC) 41220.3.3 The Direct Methanol Fuel Cell (DMFC) 41520.3.4 The Proton Exchange Membrane Fuel Cell (PEMFC) 41820.3.5 The Alkaline Fuel Cell (AFC) 42020.3.6 High-Temperature Fuel Cells 42120.3.6.1 The Solid Oxide Fuel Cell (SOFC) 42120.3.6.2 The Molten Carbonate Fuel Cell (MCFC) 42220.3.7 Porous Gas Diffusion Electrodes 42320.3.8 Fuel-Cell-Driven Vehicles 42620.3.9 Criticism of the Fuel Cells Technology 42720.4 Supercapacitors 42820.4.1 Electrostatic Considerations 42820.4.2 The Energy Stored in a Capacitor 42920.4.3 The Essence of Supercapacitors 43020.4.4 Advantages of Supercapacitors 43220.4.5 Barriers for Supercapacitors 43520.4.6 Applications of Supercapacitors 43520.5 Hydrogen Storage 436Further Reading 443Index 445