Activation energy for electron transfer

Each of these free energy relationships employs the intrinsic barrier AGo+ as the disposable parameter. [The intrinsic barrier represents the activation energy for electron transfer when the driving force is zero, i.e., AG = AGo at AG = 0 or the equili-... 

The resemblance between this equation and the Arrhenius equation should automatically alert us to the fact that kei is an activated quantity. Variation of with V ciecirode will allow US (ultimately) to obtain the activation energy for electron transfer. 

Figure 17-2 (cr) Schematic energy profile for election transfer from a metal to H30. leading to liberation of H2- (b) Applying a potential to the metal raises the energy of the electron in the metal and decreases the activation energy for electron transfer. 

It is important to note that the description of electron transfer kinetics is different in the case of semiconductor electrodes. For an n-type semiconductor electrode in the dark, the rate of electron transfer depends not only on the concentration of redox species in the solution but also on the potential dependent density of electrons in the semiconductor. Under depletion conditions, most of the potential drop is located in the solid, so that to a good approximation the activation energy for electron transfer is independent of potential. Electron transfer at semiconductor electrodes is therefore characterised in terms of a second order heterogeneous rate constant with units cm4 s-1. 

Jortner, J., 1976, Temperature dependent activation energy for electron transfer between biological molecules J. Chem. Phys. 64 486034867. 

Step 6 Electrons can be taken up directly by protonated bases (or amino acids) attached immediately to the surface. Additionally a second mechanism is possible, namely, an electron hopping over a distance to bases (or amino acids) inside the dehydrated parts of adsorbed molecules. Because water is squeezed out, especially for the semiconductor network of the 7r-state, the activation energy for electron transfer into the conduction band should be lowered and thus electrons can move inside the double Y helix (or in the globulus ). 

From [67Hir4] for DMOE (310 K), THF (298 K), MTHF (273 K), and tetrahydropyran (280 K). Determination of rate constants and activation energies for electron transfer between ketyls and ketones. Assignment based on Hiickel calculation of spin densities. 

The term electrocatalysis refers to the acceleration of the rate of an electrochemical reaction taking place at a solid electrode. The main role of the catalyst material is to lower the activation energy for electron transfer between energy levels of electroactive species on the electrolyte side and electronic states at the Fermi level in the metal. Although the electrode itself does not undergo any chemical transformation, it participates in the reaction indirectly by acting as a reservoir of electrons. Moreover, the catalyst surface provides active sites for the adsorption of reaction intermediates. 

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