Charge Transfer Reactions in Electrochemical and Chemical Processes

The mechanism of an elementary act is undoubtedly one of the most fundamental problems of chemical and, in particular, electro­ chemical kinetics. Although this problem has fascinated scientists for quite a long time, it was only in the late fifties and early sixties that it began to be actively investigated for charge transfer reactions. Owing to the development of new methods in the analysis of this problem, significant advancements were made in theoretical as well as experimental studies. These investigations showed that the physical mechanism of charge transfer in all processes including heterogeneous electrochemical and homogeneous chemical and bio­ chemical processes is basically the same. Hence, the results ob­ tained in the field of electrochemical kinetics are relevant to the understanding of homogeneous chemical reactions as well. This book endeavors to summarize the results of investigations carried out during the last two decades. It is based on the author's monograph "Electrode Reactions: The Mechanism of an Elementary Act" (Nauka, 1979). As compared to the first version, the book has been considerably revised and enlarged not only to include a large body of data published between 1978 and 1982, but also to analyze in detail the links between electrochemical and homogeneous, in particular enzymatic, kinetics. As a result, a new chapter has been added to the book. The change in the title reflects the fact that the material contained in the book is not restricted to an investigation of purely electrochemical problems.

1. The Phenomenological Theory of an Elementary Act.- 1.1. The Brønsted Relation and the Activation Energy of Electrode Reactions.- 1.2. The Temperature Dependence of the Rate of an Electrode Reaction.- 1.3. The Chemical Potential of an Electron, Absolute Potential Drop, and Solvation Energy in Electrochemical Kinetics.- 1.4. The Brønsted Relation and the Activity Coefficient of an Activated Complex.- 1.5. Barrierless and Activationless Processes.- 1.6. Kinetic Equations for Discharge.- 2. Barrierless Discharge in Cathodic Hydrogen Evolution.- 2.1. The Discharge of Hydronium Ions at a Mercury Cathode.- 2.2.* Hydrogen Evolution in the Presence of Tetraalkylammonium Ions. Discharge of Undissociated Acid Molecules.- 2.3. The Activity Coefficient of an Activated Complex.- 2.4. The Temperature Dependence of the Rate of a Barrierless Discharge.- 2.5.* Evolution of Hydrogen at a Silver Cathode.- 2.6.* Evolution of Hydrogen at Other Cathodes.- 2.7. Some Theoretical Problems.- 3. The Quantum-Mechanical Theory of an Elementary Act.- 3.1. Introduction.- 3.2. An Ion in a Polar Solvent.- 3.3. The Elementary Act of Electron Transfer.- 3.4. Adiabatic and Nonadiabatic Transitions.- 3.5. Quantum and Classical Degrees of Freedom. Proton Transfer.- 4. Experimental Verification of the Theories of an Elementary Act of Proton Donor Discharge.- 4.1. Statement of the Problem.- 4.2. Barrierless Discharge. Preexponential Factor for Barrierless and Ordinary Processes.- 4.3. Kinetic Isotope Effect for Metals with High Hydrogen Overpotentials.- 4.4. Effect of the Nature of the Electrode Metal on the Preexponential Factor and the Kinetic Isotope Effect.- 4.5. Effect of the Potential and the Nature of Proton Donors on the Preexponential Factor and the Kinetic Isotope Effect.- 4.6. Effect of the Nature of the Solvent on the Elementary Act of the Discharge of Proton Donors.- 4.7. Conclusion.- 5. Discharge of Heavy Ions. Quasibarrierless and Quasiactivationless Processes.- 5.1. The Elementary Act of a Process Accompanied by the Motion of Heavy Particles.- 5.2. The Theory of Quasibarrierless and Quasiactivationless Processes.- 5.3. Anodic Evolution of Chlorine at a Graphite Electrode.- 5.4.* The Chlorine Evolution Reaction at Ruthenium Dioxide-Titanium Dioxide Anodes.- 5.5.* The Kinetics of Oxidation of an Azide Ion at a Platinum Anode.- 5.6. On the Possibility of Other Quasibarrierless and Quasiactivationless Electrode Reactions.- 6. Mechanism of an Elementary Act and the Kinetics of the Cathodic Evolution of Hydrogen.- 6.1. Kinetic Isotope Effect and ?1-potential. Localization of a Discharging Ion.- 6.2.* Kinetic Isotope Effect. Discrimination of the ?1-effect and the Action of Other Factors.- 6.3.* Hydrogen Evolution at Certain Liquid Alloys.- 6.4. Mechanism of Amalgam Decomposition.- 6.5. Hydrogen Evolution at Iron, Chromium and Manganese during Their Chemical Self-dissolution and Cathodic Polarization.- 6.6. The Ratio of Ortho- and Para-forms of Hydrogen in an Electrolytic Gas.- 6.7. Cathodic Hydrogen Evolution in Nonaqueous Solvents.- 6.8. Electrode Reactions Involving Atomic Hydrogen Generated Through Interaction with Photoelectrons.- 7. Kinetics of Homogeneous and Enzymatic Reactions Involving Charge Transfer.- 7.1. Kinetic Isotope Effect in Homogeneous Proton Transfer Reactions.- 7.2. Medium Reorganization Energy in Proton Transfer Reactions. Comparison of Homogeneous and Electrode Reactions.- 7.3. Simultaneous Transfer of Two Charges. Coupling of Endoergic and Exoergic Reactions.- 7.4. Proton Transfer in Enzymatic Hydrolysis Reactions. Kinetic Isotope Effect.- 7.5. On the Theory of Enzymatic Charge Transfer Reactions.- References.