Zinc oxide electrodes

The behavior of zinc and zinc oxide electrode in 5.3 M KOH in the presence of alkaline earth oxides, SnO, Ni(OH)2 and Co(OH)2, was examined using cyclic voltammetry by Renuka et al. [211]. 

The zinc oxide electrode is a particularly simple example of a semiconductor electrode, because its large energy gap (3. 3 ev) makes the minority-carrier contribution to space charge negligible in the dark and because the fast surface state effects are negligible,. This latter fact has been demonstrated by data of the sort shown in Fig. 3 (3). 

Japanese workers have published a paper regarding the study of photoelectro-chemical reactions at a n-type polycrystalline zinc oxide electrode using photoacoustic detection [125], They monitored in situ photoelectrochemical reactions at semiconductor electrodes using photoacoustic techniques. 

Dewald J. F. (1960b), The charge and potential distributions at the zinc oxide electrode . 

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

The capacity measured is assumed to represent only the capacity of the space-charge region in the semiconductor and not to include, for example, the capacity of surface states, adsorption capacity, etc. In certain cases, this condition is satisfied, for example, on a zinc oxide electrode but more frequent is the situation where the contribution of the capacity of surface states is considerable. 

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. 

Potential-dependent optical properties in nanoporous zinc oxide electrodes... 

Figure 22. Photocurrent, optical absorption, trapped fluorescence (S60nm), and excitonic fluorescence of a nanoporous zinc oxide electrode as a function of the applied potential vs. Ag/AgCl, pH 8 bufler.

Figure 24. Cyclovoltamogram of a nanoporous zinc oxide electrode. Film thickness, 1.3/tm scan speed, 10mVs , pH 8 buffer.

Figure 26. Time-resolved photocurrent profiles of a nanoporous zinc oxide electrode after excitation with a 308-nm excimer laser flash at various applied potentials. The experimental setup is shown schematically in the inset of the figure. R, C, reference and counter electrodes pH 8 buffer film thickness, 3...

Electrolytic oxidation of sucrose, maltose and glucose on a lead-(II) oxide-coated titanium mesh electrode has been studlgd in connection with electrochemical treatment of effluents. Hydroxide radicals are the effective oxidant in the stepwise photoanodlc oxidation of D-glucose to carbon dioxide on a polycrystalline zinc oxide electrode in alkaline solution. The electrocatalytic oxidation of D-glucose at a glucose oxidase-immobilized benzoquinone-mixed carbon paste electrode has been studied and the Imj ortance of various concentration parameters on the oxidation examined. A comparative study of the electrocatalytic Influence of underpotential heavy... 

Cells containing calcium zincate electrodes can be manufactured in at least two different ways. Calcium hydroxide can be added to the zinc oxide electrode mixture. In this case, the calcium zincate is formed in situ as the electrode is cycled in the ceU during the electrochemical formation process. Another method is to form calcium zincate in a separate step and then use this material in the electrode fabrication process. Calcium zincate can be prepared, purified and identified by its X-ray diffraction pattern, shown in Fig. 31.6. This process produces electrodes with a more uniform distribution of calcium zincate and overcomes the problem of zinc dissolution that occurs during the first few cycles before the calcium-zincate has fully formed in the in situ method. This serves to increase the overall cycle Ufe and performance of the battery. In either case, an important advantage of the plastic-bonded calcium zincate stmcture is the reduction of the tendency to form zinc dendrites. The zinc active materials are embedded in the three-dimensional stmcture of the PTFE nanofibers. This increases the stability of the electrode. Although it is possible for some zinc dissolution and migration to occur in the cell, dendritic deposits which penetrate the separator are rarely seen. 

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