The metal oxide-electrolyte interface

The reaction site at oxide electrodes, the oxide-electrolyte interface, differs from the metal-electrolyte interface in several respects and its structure and properties are of the utmost importance for the understanding of reaction kinetics at oxide electrodes. Most of the information available on the properties of the interfacial region in oxides comes from colloid chemistry, i.e. electrokinetic, or zeta, potentials and surface titration curves. Several models developed by Lyklema, Berube and De Bruyn, and Levine and Smith to explain these experimental results have been reviewed elsewhere [7-9], 

The surface of an oxide is amphoteric with surface groups which become protonated in acid solutions and negatively charged in basic solutions 

At oxide semiconductor electrode-electrolyte interfaces, with no contribution from surface states, the electrical potential drop exhibits three components the potential drop across the space-charge region, / sc, across the Helmholtz layer, j)H, and across the diffuse double layer, / d, the latter becoming negligible in concentrated electrolytes 

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 

An important consequence of the pH dependence of the interfacial potential at oxide electrodes is the observation of pseudo-orders for protons and hydroxyl ions in simple redox reactions. This will be discussed in Sect. 5.3. 

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CO-ADSORPTION OF THE LOW MOLECULAR CARBOXYLIC ACIDS AND CADMIUM IONS AT THE METAL OXIDE/ ELECTROLYTE INTERFACE... 

Electrical Double Layer at the Metal Oxide-Electrolyte Interface... 

The partial W reduction is not only obtained at the metal-metal oxide or at the metal oxide-electrolyte interface, but the oxide turns blue immediately throughout the whole layer. This proves the above statement concerning the macromolecular film structure. 

Janusz, W. and Matysek, M., Co-adsorption of the low molecular carboxylic acids and cadmium ions at the metal oxide/electrolyte interface, in Surface Chemistry in Biomedical and Environmental Science, Blitz, J.P. and Gunko, V.M., eds.. Springer, Berlin, 2006, p. 383. 

The anodizing potential causes the reaction M° M" + e to occur at the metal/oxide interface, with the reaction occurring at the greatest rate where electric fields are most concentrated. The high-electric field drives the metal ion to the metal oxide/electrolyte interface. 

Janusz, W., Electrical double layer at the metal oxide-electrolyte interface, in Interfacial Forces and Fields. Theory and Application, Hsu, J.-P.(Ed.), Surfactant Science Series, Vol. 85, Marcel Dekker, New York, 1999, pp. 135-206. 

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