Potential Dependence of Interfacial Rate Constants

OXIDES AND SENSITIZATION CELLS 1. Potential Dependence of Interfacial Rate Constants 

Since the potential-dependent photocurrent and the potential-dependent PMC signal were measured and P(AU) is a known function, the potential-dependent interfacial rate constant kr can be determined. It turns out that it increases exponentially with the electrode potential applied 

The reason for the exponential increase in the electron transfer rate with increasing electrode potential at the ZnO/electrolyte interface must be further explored. A possible explanation is provided in a recent study on water photoelectrolysis which describes the mechanism of water oxidation to molecular oxygen as one of strong molecular interaction with nonisoenergetic electron transfer subject to irreversible thermodynamics.48 Under such conditions, the rate of electron transfer will depend on the thermodynamic force in the semiconductor/electrolyte interface to 

This discussion has shown how useful PMC measurements are for addressing new questions in semiconductor electrochemistry. 

Preliminary measurements with space-resolved PMC techniques have shown that PMC images can be obtained from nanostructured dye sensitization cells. They showed a chaotic distribution of PMC intensities that indicate that local inhomogeneities in the preparation of the nanostructured layer affect photoinduced electron injection. A comparison of photocurrent maps taken at different electrode potentials with corresponding PMC maps promises new insight into the function of this unconventional solar cell type. 

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