Electron self-exchange process

In this case arguments similar to concentration polarization of substrate S in the layer apply, as previously given for Eqn. 50. The reaction layer Xq is important when substrate 5 moves readily through the layer and reacts with the mediator species before they can diffuse very far from the inner interface via the electron self-exchange processes, i.e., electron hopping. 

The cross relation has proven valuable to estimate ET rates of interest from data tliat might be more readily available for individual reaction partners. Simple application of tire cross-relation is, of course, limited if tire electronic coupling interactions associated with tire self exchange processes are drastically different from tliose for tire cross reaction. This is a particular concern in protein/protein ET reactions where tire coupling may vary drastically as a function of docking geometry. 

The qualitative elements of Marcus theory are readily demonstrated. For example, the process of transferring an electron between two metal ions, Fe2+ and Fe3 +, may be described schematically by Fig. 33 (Eberson, 1982 Albery and Kreevoy, 1978). The reaction may be separated into three discrete stages. In the first stage the solvation shell of both ions distorts so that the energy of the reacting species before electron transfer will be identical to that after electron transfer. For the self-exchange process this of course means that the solvation shell about Fe2+ and Fe3+ in the transition state must be the same if electron transfer is not to affect the energy of the system. In the second phase, at the transition state, the electron is transferred without... 

Despite the lack of theoretical models for interfacial recombination processes in excitonic solar cells, it is obvious empirically that those cells which function efficiently must have a very slow rate of recombination. In DSSCs, this can be explained simply by the slow electron self-exchange rate of the I /I2 redox couple and the absence of field-driven recombination. However, in the case of solid-state, high-surface-area OPV cells, such as the conducting polymer/C60-derivative cells [36,39], the slow rate of interfacial recombination is an important problem that is not yet understood. 

Initially, all the Fc sites further removed from the electrode surface are still in the unoxidized Fc state. Electrons can, however, hop from these distant Fc sites to the Fc+ sites at the electrode surface (Fig. 13.3C). Electron hopping occurs via a well-known chemical process called electron self-exchange whereby the reduced half of a redox couple (Fc) simply gives its electron to an oxidized counterpart (Fc+). This reaction can be written as... 

The Marcus therory provides an appropriate formalism for calculating the rate constant of an outer-sphere redox reaction from a set of nonkinetic parameters1139"1425. The simplest possible process is a self-exchange reaction, where AG = 0. In an outer-sphere electron self-exchange reaction the electron is transferred within the precursor complex (Eq. 10.4). 

Three processes can control the rate of homogeneous charge transport through a redox-active polymer film, i.e. electron self-exchange between redox-active centers,... 

Figure 1 shows the double-well potential which is often used to represent the electron transfer act in oxidation-reduction. The special case of a self-exchange process was chosen for simplicity. (For a full discussion of the issues being discussed in relation to the potential energy diagram, see Ref. 11. Ref. 13 gives a more compact treatment.) The implications of the diagram may not be immediately obvious, and the... 

Coni(en)3]3+/[Con(en)3]2+ couple, E° = -0.02 V versus the normal hydrogen electrode (NHE) [18]. Such an electron transfer is especially slow. In particular, for the self-exchange process ... 

The oxidized and reduced forms of blue copper proteins can coexist in equilibrium in solution. This allows two identical molecules to exchange one electron, giving the so-called electron self-exchange (ESE) reaction (Marcus and Sutin, 1985). The rates of this process usually depend on the pH, temperature, and ionic strength of the solution. When the two forms... 

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