Mott oxide electrodes

Bockris et al. [87, 290, 291] have recently reported results of a comprehensive program of surface characterization of a large number of perovskite oxide electrodes in oxygen evolution investigations. Anodic and cathodic oxygen reactions were studied in detail as a function of the solid-state surface properties of these materials. Capacity-potential curves were analysed in terms of the Mott-Schottky treatment and indicated that the potential distribution in the oxide corresponds to a depletion of electrons at the oxide electrode surface in the potential region where oxygen reduction... 

Figure 5. The Mott-Schottky plot for a zinc oxide electrode (conductivity = 0.59 cm" ) in...

A certain relationship, which exists between the bulk and surface properties of semiconducting materials and their electrochemical behavior, enables, in principle, electrochemical measurements to be used to characterize these materials. Since 1960, when Dewald was the first to determine the donor concentration in a zinc oxide electrode using Mott-Schottky plots, differential capacity measurements have frequently been used for this purpose in several materials. If possible sources of errors that were discussed in Section III.3 are taken into account correctly, the capacity method enables one to determine the distribution of the doping impurity concentration over the surface" and, in combination with the layer-by-layer etching method, also into the specimen depth. The impurity concentration profile can be constructed by this method. It has recently been developed in greatest detail as applied to gallium arsenide crystals and multilayer structures. 

Figure 5-49 illustrates the Mott-SchottlQ plot observed for two n-type semiconductor electrodes of zinc oxide in a potential range in which the depletion and... 

Fig. 5-49. Mott-Schottky plot of electrode capacity observed for two n-type semiconductor electrodes of zinc oxide (conductivity 0.59 S cm and 1.79 S cm in 1 M KCl at pH 8.5 solid curve = observed dashed curve = calculated. [From Dewald, I960.]...

Silver halide microcrystals are wide band gap semiconductors which exhibit weak photoconductivity. Early experiments demonstrated that dyes that sensitized silver halide photographic action also sensitized silver halide photoconductivity [6c]. Since the observation of photoconductivity necessitates the movement of free charge within the crystals, dye sensitization processes must inject charge into the silver halide lattice in some way. Initial theories of sensitization were based on the semiconductor view of silver halides, especially as espoused by Gurney and Mott [10]. Current ideas are based on thorough studies of the absorption spectroscopy and luminescence of silver halide emulsions and of adsorbed, sensitizing dyes, and the oxidation-reduction properties of the dyes at silver/silver halide electrodes [11]. 

If the contribution of a depletion layer in the semiconducting oxide to the interfacial potential is not negligible, the Mott-Schottky relationship holds between the interfacial capacitance and the electrode potential [13]. For an n-type oxide... 

Figure 1.19 Evaluation of the capacitance according to the Schottky-Mott equation for grains a and b for oxide layers grown potentiodynamically at different formation potentials U (100 pm electrodes, f= 1030 Hz, dU/dt —20mVs 1)[6].

Figure 11.21 Mott-Schottky plot for polythiophene. Electrolyte 0.1 mol-dm LiBF4/H20, potentials versus saturated calomel electrode (SCE). The polythiophene films were prepared by electrochemical oxidation in acetonitrile.

Figure 32. The Mott-Schottky type plot of capacitance (C vs. E) and potential modulation reflectance (PMR), [(d/ /d )(l/f o)] vs. E for the iron electrode covered by passive oxide formed at 1.55 V vs. RHE. The PMR measurement was done at frequency of 500 Hz by light wavelength for 350 nm. Reprint from D. J. Wheeler, B. D. Cahan, C. T. Chen, and E. Yeager, Optical Study of the Passivation of Iron , in Passivity of Metals, Ed. by R. P. Frankenthal and J. Kruger, The Electrochem. Soc. Inc., Pronceton, 1978, p. 546, Copyright 1978 with permission from The Electrochemical Soc.

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