Preface ......................................................... v
Corresponding Authors ......................................... xix
I Fundamentals ............................................... 01
1 Fundamentals ............................................... 03
1.1 Conventions in Electrochemistry ...................... 03
1.1.1 Potential conventions ........................ 03
1.1.2 Current conventions .......................... 06
1.2 Terminology .......................................... 06
1.3 Fundamental Equations ................................ 08
1.3.1 Nernst equation .............................. 09
1.3.2 Equilibrium constant ......................... 09
1.3.3 Mass-transfer limited current ................ 10
1.3.4 Cottrell equation ............................ 10
1.3.5 Faraday's law ................................ 11
1.4 Factors Affecting Reaction Rate and Current .......... 11
1.4.1 Current, current density, and rate ........... 11
1.4.2 Reversibility ................................ 13
1.4.3 Kinetics ..................................... 14
1.5 Equations Governing Modes of Mass Transfer ........... 17
1.5.1 Nernst-Planck equation ....................... 17
1.5.2 Fick's laws of diffusion ..................... 17
1.6 Electrochemical Cells ................................ 20
1.7 Cell Resistance; Capacitance; Uncompensated
Resistance ........................................... 22
1.8 Overview of Electrochemical Experiments .............. 25
1.9 Electrochemistry Literature; Textbooks; Specialized
Books ................................................ 25
1.9.1 Electrochemical journals ..................... 26
1.9.2 Specialized texts ............................ 26
1.9.3 Review series ................................ 28
References ................................................. 28
II Laboratory Practical ........................................ 31
2 Practical Electrochemical Cells ............................ 33
2.1 Materials ............................................ 33
2.2 General Cell Designs ................................. 33
2.2.1 Two-electrode cells .......................... 34
2.2.2 Three-electrode cells ........................ 35
2.3 Electrochemical Cells for Specific Applications ...... 35
2.3.1 Flow-through cells ........................... 35
2.3.2 Thin-layer cells (TLCs) ...................... 41
2.3.3 Spectroelectrochemical cells ................. 43
2.3.4 Electrochemical cells for molten salts ....... 47
2.3.5 Attachment to a vacuum line .................. 49
2.4 Establishing and Maintaining an Inert Atmosphere ..... 50
References ................................................. 55
3 Solvents and Supporting Electrolytes ....................... 57
3.1 Introduction ......................................... 57
3.2 Electrolyte Conductivity ............................. 58
3.3 Cells, Electrodes and Electrolytes ................... 60
3.4 Cell Time Constants .................................. 62
3.5 Solvents ............................................. 62
3.5.1 Protic solvents .............................. 63
3.5.2 Nitriles ..................................... 65
3.5.3 Halogenated organics ......................... 65
3.5.4 Amides ....................................... 65
3.5.5 Sulfoxides and sulfones ...................... 65
3.5.6 Ethers, carbonates, lactone .................. 66
3.6 Salts ................................................ 66
3.7 "Exotic" Electrolytes ................................ 67
3.8 Purification Procedures for some Commonly Used
Solvents in Electrochemistry ......................... 68
3.8.1 Acetonitrile ................................. 69
3.8.2 Butyronitrile ................................ 69
3.8.3 Benzonitrile ................................. 69
3.8.4 Propylene carbonate .......................... 70
3.8.5 Dichloromethane .............................. 70
3.8.6 Dimethylformamide ............................ 70
3.9 Purification Procedures for some Commonly Used
Salts in Electrochemistry ............................ 70
3.9.1 Tetraethylammonium tetrafluoroborate ......... 70
3.9.2 Tetraethylammonium tetraphenylborate ......... 70
3.9.3 Tetraethylammonium hexafluorophosphate ....... 71
3.9.4 Tetrabutylammonium tetrafluoroborate ......... 71
3.9.5 Tetrabutylammonium hexafluorophosphate ....... 71
3.9.6 Lithium perchlorate .......................... 71
References ................................................. 71
4 Reference Electrodes ....................................... 73
4.1 Introduction ......................................... 73
4.1.1 Selecting a reference electrode .............. 73
4.1.2 Converting between aqueous potential
scales ....................................... 74
4.2 Basic Components of a Reference Electrode ............ 74
4.2.1 Body material ................................ 74
4.2.2 Top seal ..................................... 74
4.2.3 Junction (4) ................................. 77
4.2.4 Active component of RE ....................... 79
4.3 Electrode Details and Fabrication .................... 80
4.3.1 Hydrogen electrodes .......................... 80
4.3.2 Mercury electrodes (24) ...................... 86
4.3.3 Silver electrodes ............................ 92
4.3.4 Quasi-reference electrodes (QRE) ............. 94
4.4 Junctions ............................................ 95
4.4.1 Filling solutions ............................ 95
4.4.2 Salt bridges ................................. 96
4.4.3 Double-junction reference electrodes ......... 97
4.4.4 Reference electrode impedance ................ 97
4.5 Reference Electrodes: Nonaqueous Solvents ............ 98
4.6 Reference Electrode Calibration ..................... 100
4.6.1 Versus a second reference electrode ......... 100
4.6.2 Using a well-defined redox couple ........... 100
4.7 Maintenance ......................................... 102
4.7.1 Storage ..................................... 103
4.7.2 Cleaning junctions .......................... 103
4.7.3 Replacing filling solutions ................. 103
4.7.4 Regenerating the reference electrode ........ 103
4.8 Troubleshooting ..................................... 104
4.8.1 Special notes ............................... 104
References ................................................ 108
5 Solid Electrode Materials: Pretreatment and Activation .... 1ll
5.1 Introduction ........................................ 1ll
5.2 Carbon Electrodes ................................... 114
5.2.1 Highly oriented pyrolytic graphite .......... 115
5.2.2 Glassy carbon ............................... 121
5.2.3 Pyrolyzed photoresist films (PPF) ........... 126
5.2.4 Carbon fibers ............................... 128
5.2.5 Carbon nanotubes ............................ 133
5.2.6 Diamond films ............................... 135
5.2.7 Tetrahedral amorphous carbon (Ta-C) films ... 140
5.3 Metal Electrodes .................................... 143
5.3.1 Polycrystalline platinum and gold ........... 144
5.3.2 Single-crystal platinum and gold ............ 146
5.4 Semiconductor Electrodes ............................ 147
5.4.1 Indium tin oxide (ITO) ...................... 147
5.5 Conclusions ......................................... 149
Acknowledgments ........................................... 149
References ................................................ 150
6 Ultramicroelectrodes ...................................... 155
6.1 Behavior Of Ultramicroelectrodes ................... 155
6.1.1 Electrode response times .................... 156
6.1.2 Factors that influence the electrode
response time ............................... 159
6.1.3 Origins of non-ideal responses .............. 160
6.1.4 Fundamentals of faradaic electrochemistry ... 164
6.1.5 Origins of non-ideal faradaic responses ..... 168
References ................................................ 171
6.2 Microelectrode Applications ......................... 171
6.2.1 Electroanalysis at the micro- and nano-
length scale ................................ 172
6.2.2 Spatially heterogeneous systems:
biological structures ....................... 175
6.2.3 Low conductivity media ...................... 177
6.2.4 Ultrafast electrochemical techniques ........ 180
6.2.5 AC electrokinetics .......................... 184
References ................................................ 186
6.3 UME Fabrication/Characterization Basics ............. 189
6.3.1 Platinum and gold inlaid disks ≥ 5 μm
diameter .................................... 189
References .......................................... 197
6.3.2 Platinum and gold inlaid ≥ 5 μm
diameter .................................... 197
References .......................................... 199
6.3.3 Laser-pulled ultramicroelectrodes ........... 199
References .......................................... 211
6.3.4 Platinum conical ultramicroelectrodes ....... 211
References .......................................... 216
6.3.5 Flame-etched carbon nanofibers .............. 217
References .......................................... 221
6.3.6 Electrochemically etched carbon fiber
electrodes .................................. 221
References .......................................... 226
6.3.7 Gold spherical microelectrodes .............. 226
References .......................................... 235
6.3.8 Hg microhemispherical electrodes ............ 235
References .......................................... 243
6.3.9 Clarke oxygen microelectrode ................ 243
References .......................................... 248
6.3.10 Nitric oxide microsensors ................... 249
References .......................................... 253
6.3.11 Glass nanopore electrodes ................... 254
References .......................................... 260
7 Potentiometric Ion-Selective Electrodes ................... 261
7.1 Introduction ........................................ 261
7.2 Classification and Mechanism ........................ 263
7.2.1 Phase boundary potential .................... 263
7.2.2 Ion-exchanger-based ISEs .................... 264
7.2.3 Neutral-ionophore-based ISEs ................ 266
7.2.4 Charged-ionophore-based ISEs ................ 270
7.3 Equilibrium Potentiometric Responses ................ 273
7.3.1 The Nikolsky-Eisenman equation and phase
boundary potential model .................... 273
7.3.2 Effect of ionic sites on selectivity ........ 276
7.3.3 Apparently "non-Nernstian" equilibrium
responses ................................... 279
7.4 Non-Equilibrium Potentiometric Responses ............ 282
7.4.1 Mixed ion-transfer potentials ............... 282
7.4.2 Elimination of non-equilibrium effects in
separate solutions .......................... 284
7.4.3 Effects of transmembrane ion flux on
detection limit ............................. 287
7.4.4 Non-equilibrium responses for polyion
detection ................................... 290
7.5 Conclusions ......................................... 291
References ................................................ 292
8 Chemically Modified Electrodes ............................ 295
8.1 Introduction ........................................ 295
8.2 Substrate Materials and Preparation ................. 296
8.3 Modified Electrode Types ............................ 296
8.3.1 Langmuir-Blodgett ........................... 297
8.3.2 Self-assembly ............................... 300
8.3.3 Covalent attachment ......................... 305
8.3.4 Clay modified electrodes .................... 308
8.3.5 Zeolite modified electrodes ................. 311
8.3.6 Sol-gel modified electrodes ................. 314
8.3.7 Polymer modified electrodes ................. 317
8.3.8 DNA modified electrodes ..................... 322
8.4 Conclusions and Prospects ........................... 322
References ................................................ 323
9 Semiconductor Electrodes .................................. 329
9.1 Introduction ........................................ 329
9.2 Semiconductor Basics ................................ 330
9.2.1 Band theory of solids ....................... 330
9.2.2 Size quantization in semiconductors ......... 336
9.3 Energetics of a Semiconductor ....................... 340
9.3.1 Semiconductor-electrolyte interface (SEI) ... 343
9.4 Semiconductor Electrodes ............................ 346
9.4.1 Electron transfer at semiconductor-
electrolyte interface ....................... 346
9.4.2 Illuminated semiconductor electrodes ........ 349
9.4.3 Cyclic voltammetry (CV) at semiconductor
electrodes .................................. 351
9.4.4 Fermi-level pinning in semiconductor
electrodes .................................. 355
9.4.5 Characterization of the SEI by scanning
electrochemical microscopy (SECM) ........... 358
9.5 Types of Semiconductor Electrodes ................... 367
9.5.1 Single crystal and epitaxial film
electrodes .................................. 367
9.5.2 Polycrystalline electrodes .................. 369
9.6 Nanostructured Semiconductor Electrodes (NSSE) ...... 374
9.6.1 Epitaxial methods for the preparation of
NSSE ........................................ 375
9.6.2 Preparation of particulate films ............ 375
9.6.3 Electrochemistry on nanostructured
semiconductors .............................. 377
9.6.4 Electrochemistry on suspended
semiconductor nanoparticles ................. 378
9.7 Semiconductor Electrode Applications ................ 381
9.7.1 Solar cells ................................. 381
9.7.2 Sensors ..................................... 384
Acknowledgments ........................................... 385
References ................................................ 385
10 Microelectrode Arrays ..................................... 391
10.1 Introduction ........................................ 391
10.2 Classification of Microelectrode Arrays ............. 392
10.2.1 Microelectrode designs ...................... 392
10.2.2 Microelectrode array behavior ............... 394
10.3 Theory: Diffusion at Microelectrode Arrays .......... 396
10.3.1 Arrays of electrodes operating at
identical potentials ........................ 396
10.3.2 Arrays of electrodes operating in
generator/collector mode .................... 400
10.4 Fabrication of Microelectrode Arrays ................ 403
10.4.1 Mechanical methods .......................... 404
10.4.2 Template approaches ......................... 407
10.4.3 Lithographic techniques ..................... 411
10.4.4 Etching techniques .......................... 416
10.5 Electrochemical Characterisation of Microelectrode
Arrays .............................................. 418
10.5.1 Chronoamperometry and cyclic voltammetry .... 419
10.5.2 Scanning electrochemical microscopy ......... 422
10.5.3 Optical microscopy .......................... 422
10.6 Conclusion and Prospects ............................ 422
References ................................................ 423
Techniques ................................................ 429
11 Classical Experiments ..................................... 431
11.1 Introduction ........................................ 431
11.2 Selected Experimental Techniques .................... 432
11.2.1 Potential steps ............................. 432
11.2.2 Potential sweeps ............................ 438
11.2.3 Combinations of sweeps and steps ............ 445
11.2.4 Microelectrodes ............................. 447
11.2.5 Rotating disc electrodes .................... 451
11.2.6 Small amplitude perturbations and
impedance methods ........................... 454
11.3 Simulations ......................................... 458
11.3.1 Electrochemical simulations—a few
questions ................................... 458
11.3.2 Basic principles of an electrochemical
simulation .................................. 460
11.4 Troubleshooting Electrochemical Experiments:
A Checklist ......................................... 464
11.4.1 Checking the results ........................ 464
11.4.2 No current response ......................... 464
11.4.3 Potential shift ............................. 465
11.4.4 Currents lower than expected ................ 466
11.4.5 Slanted voltammogram ........................ 466
11.4.6 Noisy current ............................... 466
11.4.7 Other common problems ....................... 466
References ................................................ 467
12 Scanning Electrochemical Microscopy ....................... 471
12.1 Introduction and Principles ......................... 471
12.2 Instrumentation ..................................... 473
12.2.1 Basic SECM apparatus ........................ 473
12.2.2 Combining SECM with other techniques ........ 475
12.3 Methods and Operational Modes ....................... 479
12.3.1 Amperometric methods ........................ 479
12.3.2 Potentiometric method ....................... 489
12.3.3 Imaging ..................................... 497
12.4 Applications ........................................ 501
12.4.1 Heterogeneous kinetics ...................... 501
12.4.2 Homogeneous chemical reactions .............. 506
12.4.3 Catalytic activity .......................... 510
12.4.4 Surface reactivity .......................... 514
12.4.5 Patterning .................................. 519
12.4.6 Biological applications ..................... 524
References ................................................ 535
13 Electrogenerated Chemiluminescence ........................ 541
13.1 Concepts and History ................................ 541
13.2 Types of Luminescence ............................... 541
13.3 Fundamental Reactions ............................... 542
13.3.1 Ion annihilation ECL ........................ 542
13.3.2 Coreactant ECL (123) ........................ 546
13.4 Experimental Setup .................................. 554
13.4.1 Electrochemical media ....................... 554
13.4.2 Cell design and electrodes .................. 556
13.4.3 Light detection and ECL instrumentation ..... 560
13.5 Types of Experiments ................................ 568
13.5.1 Ion annihilation ECL: Ru(bpy)32+ and
derivatives ................................. 568
13.5.2 Coreactant ECL of Ru(bpy)32+/TPrA system
in aqueous solutions ........................ 570
13.6 Applications ........................................ 572
13.6.1 Applications of Ru(bpy)32+ ECL:
determination of oxalate and organic
acids ....................................... 573
13.6.2 Applications of Ru(bpy)32+ ECL:
determination of amines ..................... 574
13.6.3 Applications of Ru(bpy)32+ ECL:
determination of amino acids ................ 575
13.6.4 Applications of Ru(bpy)32+ ECL:
determination of pharmaceuticals ............ 576
13.6.5 Applications of Ru(bpy)32+ ECL:
determination of Ru(bpy)32+ ................. 577
13.6.6 Applications of Ru(bpy)32+ ECL in
capillary electrophoresis (CE) and micro-
total analysis (μTAS) ....................... 577
13.6.7 Application of Ru(bpy)32+ ECL:
determination of clinical analytes .......... 578
13.6.8 Applications of Ru(bpy)32+ ECL: analytes
associated with food, water, and
biological agents ........................... 580
Acknowledgments ........................................... 582
References ................................................ 582
14 Spectroelectrochemistry ................................... 591
14.1 Introduction ........................................ 591
14.2 Light Transmission and Reflection at an Electrode
Surface ............................................. 592
14.3 Electronic Spectroscopy ............................. 593
14.3.1 Transmittance spectroscopy and optically
transparent cell materials .................. 594
14.3.2 Thin layer spectroelectrochemistry .......... 595
14.3.3 Spectroelectrochemistry: semi-infinite
linear diffusion ............................ 601
14.3.4 Long optical pathway thin layer cells
(LOPTLC) .................................... 603
14.3.5 Reflectance spectroscopy .................... 605
14.4 Luminiscence Spectroelectrochemistry ................ 612
14.4.1 Steady-state luminescence
spectroelectrochemistry ..................... 612
14.4.2 Time-resolved luminescence
spectroelectrochemistry ..................... 615
14.5 Vibrational Spectroelectrochemistry ................. 616
14.5.1 IR spectroelectrochemistry .................. 618
14.5.2 Raman spectroelectrochemistry ............... 623
14.6 Outlook ............................................. 632
References ................................................ 633
Applications .............................................. 637
15 Determination of Electrode Kinetics ....................... 639
15.1 Introduction to Kinetic Measurements ................ 639
15.2 Heterogeneous Electron Transfer: Transient
Methods ............................................. 641
15.2.1 Linear sweep and cyclic voltamrnetry ........ 641
15.2.2 Sampled-current voltammetry ................. 644
15.2.3 Ac voltammetry .............................. 645
15.3 Heterogeneous Electron Transfer: Steady-State
Methods ............................................. 646
15.3.1 Steady-state voltammetry .................... 646
15.3.2 Scanning electrochemical microscopy
(SECM) ...................................... 648
15.4 Processes with Coupled Homogeneous Reactions ........ 651
15.4.1 Linear sweep and cyclic voltammetry ......... 651
15.4.2 Scanning electrochemical microscopy
(SECM) ...................................... 655
15.4.3 Simulations and curve fitting ............... 656
References .......................................... 660
16 Metal Deposition .......................................... 661
16.1 Electrodeposition of Nanostructures and
Microstructures on Highly Oriented Pyrolytic
Graphite (HOPG) ..................................... 661
16.1.1 Introduction and perspective ................ 661
16.1.2 HOPG: seeing electrodeposited metal nano-
and microparticles .......................... 663
16.1.3 Brownian Dynamics simulations:
understanding particle size distribution
broadening .................................. 664
16.1.4 "Slow-growth" electrodeposition:
dimensionally uniform metal nano- and
microparticles .............................. 667
16.1.5 Electrodeposition of metal nanowires ........ 673
References .......................................... 676
16.2 Template Deposition of Metals ....................... 678
16.2.1 Introduction ................................ 678
16.2.2 Templating membranes ........................ 678
16.2.3 Template deposition of metals ............... 686
16.2.4 Morphological and optical properties ........ 695
16.2.5 Electrochemistry with template
nanomaterials: nanoelectrode ensembles ...... 697
16.2.6 Conclusions and prospects ................... 704
References .......................................... 706
16.3 Single Particle Deposition on Nanometer
Electrodes .......................................... 709
16.3.1 Introduction ................................ 709
16.3.2 Electrode selection ......................... 710
16.3.3 Electrodeposition of particles:
electrokinetic vs. diffusion control ........ 711
16.3.4 Nucleation exclusion zones: modeling
particle growth ............................. 715
16.3.5 Examples of systems ......................... 717
References .......................................... 717
17 Electrochemistry in Small Places and at Novel
Interfaces ................................................ 719
17.1 Electrochemistry in and at Single Biological
Cells ............................................... 719
17.1.1 Electrochemistry at the cell membrane-
solution interface .......................... 719
17.1.2 Electrochemistry at lipid bilayer
membranes ................................... 726
17.1.3 Electrochemistry in small drops and
vials ....................................... 737
17.1.4 Intracellular electrochemistry .............. 742
17.1.5 Conclusions ................................. 744
References .......................................... 746
17.2 Single Molecule Electrochemistry .................... 749
17.2.1 Introduction ................................ 749
17.2.2 Special topics .............................. 749
17.2.3 Conclusions ................................. 783
References ................................................ 783
17.3 Electrochemistry at Liquid/Liquid Interfaces ........ 785
17.3.1 Introduction ................................ 785
17.3.2 Fundamentals ................................ 786
17.3.3 Charge transfer reactions at liquid/
liquid interfaces ........................... 793
17.3.4 Methodologies and techniques ................ 799
17.3.5 Applications ................................ 802
17.3.6 Prospects ................................... 806
Acknowledgments ........................................... 806
References ................................................ 806
Data ...................................................... 811
18 Electrode Potentials ...................................... 813
18.1 Overview ............................................ 813
18.2 Estimated Potential Ranges: Aqueous and Non-
aqueous Solutions ................................... 813
18.3 Standard Electrode Potentials: Aqueous
Solutions ........................................... 813
18.4 Formal Electrode Potentials: Aprotic Solvents ....... 813
18.5 Formal Electrode Potentials: Common Organic
Mediators ........................................... 820
18.6 Electrode Potentials: Inorganic One-Electron
Complexes ........................................... 820
18.7 Formal Electrode Potentials: Biological Redox
Species ............................................. 821
18.8 Formal Electrode Potentials: Common Vitamins,
Drags, Neurochemicals ............................... 821
18.9 Abbreviations ....................................... 822
18.10 Chemical Structures ................................. 825
References ................................................ 827
19 Diffusion Coefficients .................................... 829
19.1 Introduction ........................................ 829
19.2 Fundamental Equations ............................... 829
19.3 General Considerations .............................. 830
19.3.1 Selection of a technique .................... 830
19.3.2 Electrode ................................... 833
19.3.3 Electrochemical system ...................... 835
19.3.4 Instrumentation ............................. 835
19.4 Electrochemical Methods ............................. 836
19.4.1 Potential step techniques
(chronoamperometry) ......................... 836
19.4.2 Rotating disk electrode techniques .......... 840
19.4.3 Potential sweep techniques .................. 842
19.4.4 Current step techniques
(chronopotentiometry) ....................... 843
19.4.5 Scanning electrochemical microscopy
(SECM) techniques ........................... 844
19.5 Tables of Diffusion Coefficients .................... 844
References ................................................ 847
20 Liquid Junction Potentials ................................ 849
20.1 Types of Liquid Junctions ........................... 849
20.1.1 Interfacial potentials without
electrolyte transport ....................... 849
20.1.2 Interfacial potentials with electrolyte
transport ................................... 850
20.2 Transference Numbers and Conductivity ............... 854
20.2.1 Experimental methods of determining
transference number ......................... 854
20.2.2 Sample calculations of ionic
transference numbers ........................ 860
20.2.3 Experimental methods of determining
electrolytic conductivity ................... 863
20.2.4 Sample calculations relating to
electrolytic conductivity ................... 864
20.2.5 Tabulation of parameters related to
electrolyte conductance ..................... 866
20.3 Minimization of Liquid Junction Potentials .......... 867
20.3.1 Balancing ionic mobilities .................. 867
20.3.2 The salt bridge ............................. 870
20.4 Junctions of Immiscible Liquids ..................... 870
20.4.1 The non-polarisable liquid/liquid
interface ................................... 870
20.4.2 The polarisable liquid/liquid
interface ................................... 872
20.5 Non-Classical Electrolytes: Polymer-Based
Electrolytes and Ionic Liquids ...................... 874
References ................................................ 876
Subject Index ................................................. 879
Colour Section to be found at the end of the book
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