Electron exchange between two electrodes mediated by two electroactive adsorbates (original) (raw)
Related papers
Theory of Electrochemical Electron Transfer
Introduction to Marcus Theory of Electron Transfer Reactions, 2020
INTRODUCTION References CHAPTER 2 ELECTRON TRANSFER REACTIONS: CLASSIFICATION AND EXAMPLES 2.1 Introduction 2.2 Outer and Inner Sphere ET Reactions 2.3 Adiabatic and Nonadiabatic ET Reactions References CHAPTER 3 HISTORICAL BACKGROUND 3.1 Introduction 3.2 Classical Theory of Electron Transfer 3.3 Quantum Me.chanical Treatment of Electron Transfer 3.4 Other Developments References CHAPTER 4 THE ROLE OF SOLVENT DYNAMICS IN ELECTRON TRANSFER 4.
A model for electron-transfer reactions via adsorbed intermedaites
Journal of Electroanalytical Chemistry, 1980
A theory is presented for electron-transfer reactions between a strongly coupled metal electrode/adsorbate system and a simple redox system in solution. A model Hamiltonian is set up in which the adsorbate is described by the Anderson model; the current is then calculated within the transfer Hamiltonian formalism. An important factor in the equation for the current is the adsorbate density of states evaluated at the saddle point of the reaction hypersurface; an explicit expression for this quantity is derived. The relation of this work to experimental results and to other theories of electron-transfer reactions is discussed.
The Journal of Chemical Physics, 1965
It is assumed in this paper that at the electrode-solution interface there is molecular order of the electroactive species resembling solid-state order. Specifically, it is assumed that next to the electrode is a layer of adsorbed neutral solvent molecules which are also ligands coordinated to the ions found in the interface. The mechanism of electron transfer from the electrode to the ion or the reverse from the ion to the electrode is assumed initially to involve a transition from either the electrode or the ion to the solvent molecule. This is followed by a transition of the electron from the solvent molecule to either the ion or the electrode. The two transitions involved in the net transfer of an electron across the interface are considered analogous to the charge-transfer mechanism of spectroscopy. The wavefunctions representing the system at the interface are then of the same form as the charge-transfer wavefunctions given by Mulliken. By considering the radiationless transition probabilities for the electron transitions in the interface system at the electrode, it is found that the usual current expressions result. By imposing the condition of zero net current at equilibrium the Nernst equation results. By further considering the polarization of the electrode under nonequilibrium conditions as a perturbation of the energy levels of the system, it is found that with the proper identification of terms the current expression for the polarized electrode results.
Electron Transfer Reaction Through an Adsorbed Layer
We consider electron transfer from a redox to an electrode through and adsorbed intermediate. The formalism is developed to cover all regimes of coverage factor, from lone adsorbate to monolayer regime. The randomness in the distribution of adsorbates is handled using coherent potential approximation. We give current-overpotential profile for all coverage regimes. We explictly analyse the low and high coverage regimes by supplementing with DOS profile for adsorbate in both weakly coupled and strongly coupled sector. The prominence of bonding and anti-bonding states in the strongly coupled adsorbates at low coverage gives rise to saddle point behaviour in current-overpotential profile. We were able to recover the marcus inverted region at low coverage and the traditional direct electron transfer behaviour at high coverage.
Journal of Electroanalytical Chemistry, 1998
A theory for heterogeneous electron transfer of multiple electrons between a metal electrode and a multilevel redox center in a polar electrolyte is developed within the context of an extended Anderson -Newns model. Analytical expressions describing the adiabatic ground state free energy curves are derived for sequential and simultaneous transfer of electrons. The dependence of the activation and reaction free energies of the process on the key parameters of the system are analyzed. It is shown that sequential and parallel mechanisms result in distinct activation patterns. An external bias is shown to have a significant effect on both the reaction and reorganization free energies, as well as the shape of the free energy curves.
Journal of Electroanalytical Chemistry, 2013
The traditional textbook view of adsorptive features in electrochemistry, viz., involving a bell-shaped wave prior to or after the diffusional wave is certainly right but concerns a very limited series of conditions in which adsorption kinetics are too slow vs. the scan rate. Laviron examined the converse situations in which extremely rapid adsorption kinetics make the voltammetric process follow the classical diffusional behavior though the effective electrochemical reactions proceed via adsorbed species. Thanks to a new simulation approach, implemented in KISSA Ó , the present work examines intermediate situations which could not be investigated since they do not lead to analytical formulations. Besides allowing investigating the transition between the two above limiting behaviors, it is established that during such transitions voltammograms display CE-type behaviors in which the rates of the pseudo-antecedent chemical steps feature those of adsorption. An electroactive adsorbed species is indeed involved in a dynamic steady state between its adsorption and its consumption by electron transfer at the electrode surface so that its current is independent of the potential. This is a general situation presently overlooked in electrochemical theories. For example, the same CE-like behavior is also shown to occur during electropolymerization of redox polymers though it now is hidden under the monomer diffusion-controlled wave.
A model for bond-breaking electron transfer at metal electrodes
Chemical Physics Letters, 2006
A model Hamiltonian is proposed for bond-breaking electrochemical electron transfer to an adsorbed molecule. The theory is applied to a homonuclear molecule, and self-consistent equations are derived for the occupation probabilities of the orbitals and the system energy. Model calculations result in an adiabatic potential energy surface with a minimum for the adsorbed state with the bond intact and a valley for the two dissociated anions.
A unified model for electrochemical electron and ion transfer reactions
Chemical Physics Letters, 1995
Electron and ion transfer reactions on metal electrodes are considered in an extended Anderson model, in which the interactions of the reactant with the metal and with the solvent depend on the separation from the interface. The model allows the construction of effective potential energy surfaces. Explicit calculations are performed for the transfer of an iodide ion and for the electron transfer reaction of the Fe2+/Fe 3+ couple.