Gerischer theory

Figure 42. Scheme comparing expected potential-independent charge-transfer rates from Marcus-Gerischer theory of interfacia) electron transfer (left) with possible mechanisms for explaining the experimental observation of potential-dependent electron-transfer rates (right) a potential-dependent concentration of surface states, or a charge-transfer rate that depends on the thermodynamic force (electric potential difference) in the interface. 

Gumey-Gerischer theory of charge transfer, 38 84 kinetics, 38 85... 

If the graphical description of the Gerischer theory is used (Figure 25), it follows that cathodic electron transfer will predominantly occur by tunneling in the energy range close to Asq)]. It follows that the rate of cathodic transfer will increase less than exponentially with If becomes equal to or higher than the cathodic... 

It is surprising that Kamat, O Regan and co-workers found a decreased injection yield at potentials near the flat-band condition. In the standard Gerischer model for sensitized planar electrodes, the low photocurrent near the flat band results because the injected carriers rapidly recombine with the oxidized sensitizer owing to the lack of a substantial depletion layer. Gerischer theory would not predict a decreased injection yield near the flat band, but this behavior can clearly be realized at sensitized nanocrystalline semiconductor films. 

Schultze and Vetter (257) investigated the influence of oxide layer thickness and temperature on the OER overpotential. Following the Gurney-Gerischer theory of charge transfer (252, 253) and assuming the following reaction sequence ... 

ETR are important for the formation (indirect), reduction, and modification of oxide films (see Sect. 3.2.4.3). They can be treated on the basis of various theoretical models like the Marcus-Gerischer theory [51, 52, 60] or the perturbation theory of Dogonadze [51]. For semiconducting... 

The details of the overall picture are therefore rather complex. However, the broad outlines of the Balandin-Parsons-Gerischer theory which, after full analysis, gives a good account of the changes in rate-determining steps and at least a macroscopic estimation of rates on individual metals, may be said to be obeyed. However, from a more microscopic viewpoint, complications arise, especially in the case of the transition metals that have medium to high adsorbate coverages. 

Gerischer has demonstrated that the potential of a redox electrolyte in solution represents an electrochemical potential [34,35]. The Fermi level of a semiconductor can also be considered as electrochemical potential. Equilibrium formation demands that the electrochemical potentials equilibrate. The schematic in Fig. 1 shows the respective density of states (DOS) of a series of semiconductors and of a redox solution before contact formation. The solution DOS is given by the Marcus-Gerischer theory [27, 36] and is characterized by Gaussian distributions for the oxidized (unoccupied) and reduced (occupied) component of the redox couple (see Eq. 1). 

Semiconductor-Liquid Junction From Fundamentals to Solar Fuel Generating Structures, Fig. 7 Overview of selected output power characteristics of photoelectrochemical solar cells operating in the photovoltaic mode note that here, also 2-electron transfCT redox couples have been used, for which the Marcus-Gerischer theory does not apply the output power characteristics have been normalized and the respective efficiencies are given at each characteristic the conditions (illumination intensity and source) are as follows n-GaAs 95mWcm (sunlight) [15, 17] p-InP ... 

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