Electron transfer in electrochemical environment[HBNI Th25]

Abstract

Though the traditional views of electron transport theories in electrochemical environment is to consider a transfer between two reservoirs or between DBA complexes wherein the donor and acceptor states are in discrete energies, the author presents his results in this thesis for the electron transfer rate from a redox to a reservoir. This problem demands attention since while the reservoir normally has a continum of states while the redox which has single energy level but is dependent on the fluctuation of the solvent that is the polorisation mode of the solvent. Hence the total electron transfer rate is determined by the competition between the resonance tunneling of the electron and the solvation of the redox. Electron transfer through a chemically modified electrode is studied in the present thesis. The adsorbate is randomly distributed on the electrode surface and its coverage factor is allowed to vary from zero to one, this covering all regimes from lone adsorbate to monolayers. A modified Newns-Anderson Hamiltonian is employed to model the system, and the current is calculated with the linear response regime. The randomness in the adsorbate distribution is handled using CPA. The DOS is analysed for different regimes of strong and week coupling as well as lone and monolayer coverage regimes. The current-potential profiles are similarly plotted for various limiting regimes. The Marcus inverted regime is recovered in the low coverage case and also a direct heterogeneous electron transfer in the high coverage regime, when the coupling is strong. A saddle point behaviour is observed in the low coverage regime with weak coupling.