CHEMICAL KINETICS R.G. COMPTON A. HAMNETT NEW TECHNIQUES FOR THE STUDY OF ELECTRODES AND THEIR REACTIONS EDITED BY

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CHEMICAL KINETICS EDITED BY R.G. COMPTON M.A., D.Phil. (Oxon.) University Lecturer in Physical Chemistry and Fellow, St. John's College, Oxford Co-editor for Vol. 29 A. HAMNETT M.A., D.Phil. (Oxon.) University Lecturer in Inorganic Chemistry and Fellow, St.

1 CHEMICAL KINETICS EDITED BY R.G. COMPTON M.A., D.Phil. (Oxon.) University Lecturer in Physical Chemistry and Fellow, St. John's College, Oxford Co-editor for Vol. 29 A. HAMNETT M.A., D.Phil. (Oxon.) University Lecturer in Inorganic Chemistry and Fellow, St. Catherine 's College, Oxford VOLUME 29 NEW TECHNIQUES FOR THE STUDY OF ELECTRODES AND THEIR REACTIONS ELSEVIER AMSTERDAM-OXFORD-NEW YORK-TOKYO 1989

Contents 'reface x lhapter 1 (P.A. Christensen and A. Hamnett) n-situ infrared studies of the electrode-electrolyte interface 1 1. The theory of IR reflection and transmission 2 1.

2 Contents 'reface x lhapter 1 (P.A. Christensen and A. Hamnett) n-situ infrared studies of the electrode-electrolyte interface 1 1. The theory of IR reflection and transmission Specular external reflection Internal reflection Attenuated total reflectance (ATR) Ion radical intermediates Molecular adsorption Corrosion Electropolymerisation The double layer Transmission IR External reflectance An electron-transfer reaction in the thin-layer Adsorption Electro-oxidation of small organic molecules Adsorbed hydrogen and its effects on double-layer structure Adsorption of ethylene derivatives Fourier-transform techniques Investigations of simple double layers Adsorption Ion radical intermediates Adsorption at non-metal electrodes Polarization-modulation techniques Transient techniques 67 References 74 Chapter 2 (R.E. Hester) Raman spectroscopic studies of species in situ at electrode surfaces Introduction Resonance Raman enhancement of sensitivity Surface-enhanced Raman spectroscopy (SERS) Surface-enhanced resonance Raman spectroscopy (SERRS) Spectroelectrochemical cells Electrode surface activation for SERS Electrode potential dependence of SERS 91

3. Chemical species adsorbed on metal electrodes 3.1 Modified electrodes 4. Non-aqueous Systems 5. Semiconductor electrodes Acknowledgements References Chapter 3 (R.

3 3. Chemical species adsorbed on metal electrodes 3.1 Modified electrodes 4. Non-aqueous Systems 5. Semiconductor electrodes Acknowledgements References Chapter 3 (R. Parsons) The use of ex-situ UHV techniques to study electrode surfaces 1. Introduction 2. Early work 3. Experimental techniques 3.1 Direct transfer Systems 3.2 Transfer using a glove box 3.3 Parallel experiments 3.4 Transfer of an electrode in and out of an electrolyte: immersion and emersion 4. Some examples of the use of ex-situ techniques in electrochemical problems The nature of oxidized platinum electrodes 4.2 The adsorption of hydrogen on platinum 4.3 The deposition of silver on platinum electrodes protected by iodine Conclusion References Chapter 4 (W.J. Albery, C.C. Jones and A.R. Mount) New hydrodynamic methods 1. Introduction 2. Different hydrodynamic Systems 2.1 Rotating disc 2.2 Wall-jet 2.3 Tube electrode 3. Ring-disc electrodes 3.1 The collection efficiency 3.2 Ring-disc Simulation programs 3.3 Ring-disc transients 3.4 Ring-disc ph transients 4. Measurement of diffusion coefficient by rotation speed step 5. Electrochemical ESR 6. Wall-jet Systems 6.1 Packed-bed wall-jet electrodes 6.2 Colloidal deposition 7. Photoelectrochemistry References Chapter 5 (J. Robinson) Microelectrodes 1. Introduction 2. In vivo studies 3. Finite size effects 4. Experimental details 4.1 Electrode design and construction 4.2 Electronic equipment

5. Application of microelectrodes 159 5.1 The study of kinetics by steady-state measurements 159 5.2 Studies in resistive media 163 5.3 Transient studies of electrode kinetics 167 5.

4 5. Application of microelectrodes The study of kinetics by steady-state measurements Studies in resistive media Transient studies of electrode kinetics Nucleation and phase growth Closure 171 ist of Symbols 171 leferences, 172 'hapter 6 (P.R. Unwin and R.G. Compton) 'he use of Channel electrodes in the investigation of interfacial reaction lechanisms Introduction Mass transport as a variable in the study of electrode processes Channel and tubulär electrodes Mass transport to the Channel electrode The Levich equation Numerical methods The Singh and Dutt approximation Voltammetry and related experiments at Channel electrodes Steady-state voltammetry Linear sweep and cyclic voltammetry Alternating current voltammetry Chronopotentiometry Chronoamperometry Anodic Stripping voltammetry (ASV) Pulsed-flow voltammetry (PFV) Electrode kinetics and coupled homogeneous reactions ECE and related mechanisms EC reactions CE reactions EC reactions Design and fabrication of Channel electrode cells and the associated flow System Channel electrode cells Flow Systems Apparatus for studies in turbulent flow regimes Extension of Channel electrode methodology: practical examples The double Channel electrode The double Channel electrode in the investigation of electrode reaction mechanisms The double Channel electrode in the investigation of anodic metal dissolution The study of electrode reaction mechanisms in a turbulent flow regime at a micro-tubular electrode Mass transport to Channel and tubulär electrodes under a turbulent flow regime Current-potential relationship for steady-state electron transfer Electrode kinetics and coupled homogeneous kinetics: the measurement of the rate of fast chemical reactions Channel electrodes in the study of pitting corrosion Theoretical modeis Experimental investigation of pitting corrosion at Channel electrodes Concluding remarks 268

6.4 Channel electrode methodology in the study of the dissolution kinetics of ionic solids 268 6.4.1 Calcium carbonate dissolution and Channel electrodes 268 6.4.2 Dissolution with amperometric

5 6.4 Channel electrode methodology in the study of the dissolution kinetics of ionic solids Calcium carbonate dissolution and Channel electrodes Dissolution with amperometric detection: the relationship between the shielding of the transport-limited detector electrode current and the rate constant for the heterogeneous process on the crystal surface The dissolution of calcite at ph The dissolution of calcite in aqueous polymaleic acid (PMA) Solution at around ph The dissolution of calcite in aqueous maleic acid Solution (3 mm): a morphological study 283 Appendix Appendix Appendix Acknowledgements 290 References 290 Chapter 7 (A.M. Waller and R.G. Compton) In-situ electrochemical ESR Introduction Electron spin resonance: an introductory survey ESR theory Thegfactor Hyperfine coupling The ESR linewidth ESR Instrumentation Electrochemical ESR _, Historical development Ex-situ methods In-situ methods Contemporary in-situ electrochemical ESR The Bard and Goldberg cell The Bond cell for in-situ ESR at low temperatures The Allendoerfer cell The Compton-Coles cell The Albery in-situ cell The coaxial in-situ cell Applications The mechanism of the reduction of dicyanobenzene Triphenylacetic acid Triphenylmethanol ECE/DISP1: the reduction of fluorescein Polymer-coated electrodes Poly(iV-vinylcarbazole) Polypyrrole Molecular motion within polymer-coated electrodes A spin-labelled electrode Spin trapping Concluding remarks 349 Acknowledgements 349 References 349

hapter 8 (L.M. Peter) hotocurrent spectroscopy 353 1. Introduction 353 2. Light absorption and charge carrier generation in solids 354 3. Collection of photogenerated carriers 357 4.

6 hapter 8 (L.M. Peter) hotocurrent spectroscopy Introduction Light absorption and charge carrier generation in solids Collection of photogenerated carriers Photocurrent generation in semiconducting films of finite thickness Demonstration of photosensitivity of anodic films on metals Experimental aspects of photocurrent spectroscopy Derivation of absorption spectra from photocurrent spectra Bi 2 S 3 films The anodic oxide on iron PbO films on lead electrodes Determination of film thickness by photocurrent spectroscopy Ti0 2 films on Ti CorrosionofPbinH 2 S Internal photoemission An example of a p-type surface film: the oxide film on Cu Organometallic films on metal electrodes 381.cknowledgements 382 ^eferences 382 hapter 9 (A. Hamnett, R.L. Lane, P.R. Trevellick and S. Dennison) llectroreflectance at semiconductors Introduction Basic theoretical development Low-field theories Applications of the Franz-Keldysh theory to more heavily doped III/V semiconductors The effect of inhomogeneous electric field The effect of d.c. potential The effect of donor density The effect of thermal broadening The effect of a.c. amplitude The effect of optical cross-section Experimental results Non-aqueous solvents Conclusions 425 Lcknowledgements 425 leferences 425 lhapter 10 (R. Greef) ülipsometry Introduction. What is ellipsometry? Theory. Three important Parameters Phase Complex refractive index and the Fresnel equations Film thickness Instrumentation The ideal three-phase model. Si0 2 on Si Calculations for the three-phase model A "nearly perfect" three-phase System 439

7. Non-uniform and rough films. Aluminium corrosion 44 8. Aluminium in alkaline Solution: non-uniform and rough films 44 9. Thin films. A biological example 44 10. Spectroscopic ellipsometry 44 11.

7 7. Non-uniform and rough films. Aluminium corrosion Aluminium in alkaline Solution: non-uniform and rough films Thin films. A biological example Spectroscopic ellipsometry Profiling of complex layers Geometrie roughness. An exaet Solution Reviews of ellipsometry applications Outlook Appendix 45 Acknowledgements 45 References 45 Chapter 11 (J.A. Harrison) A Computing strategy for the on-line accumulation and processing of electrochemical data 45 Abstract Introduction On-line accumulation of electrochemical data Choice of electrochemical methods and the processing of electrochemical data Current-potential curve for a Single electrode reaction with single electron transfer: description by Standard rate constant Impedance-potential curve for a single electrode reaction with single electron transfer: description by Standard rate constant Current-potential curve for a single electrode reaction with single electron transfer and complexing of the reaetant Impedance-potential curve for a single electrode reaction with single electron transfer and complexing of the reaetant Single electrode reaction with more than one electron transfer Two electrode reactions in parallel Current-potential curve for two electrode reactions in series Impedance-potential curve for two electrode reactions in series Single electrode reaction: comparison of experiment and theory Dissolution and passivation of titanium in aeid Solution Corrosion of stainless steel and its component metals in aeid Solution Double layer capacity curves Oxidation of chloride and bromide ions on ruthenium dioxide/titanium electrodes Reduction of palladium chloro complexes Corrosion of dental amalgams Conclusions 49 List of symbols 49 References 49 Index 49

e - Galvanic Cell 1. Voltage Sources 1.1 Polymer Electrolyte Membrane (PEM) Fuel Cell

e - Galvanic Cell 1. Voltage Sources 1.1 Polymer Electrolyte Membrane (PEM) Fuel Cell Galvanic cells convert different forms of energy (chemical fuel, sunlight, mechanical pressure, etc.) into electrical energy and heat. In this lecture, we are interested in some examples of galvanic cells.