Oxidative and reductive dissolution of ionic semiconductors

Semiconductor electrodes of ionic compounds can also dissolve with the oxidation of surface anions or with the reduction of surface cations as shown schematically in Fig. 9-15. 

Equation 9—49 is the anodic transfer of surface cation into aqueous solution (cation dissolution) and Eqn. 9-60 is the anodic oxidation (hole capture) of surface anion producing molecules ofX2, i (e.g. gaseous oxygen molecules irom oxide ions). Electric neutrality requires that the rate of cation dissolution equals the rate of anion oxidation hence, the rate of the oxidative dissolution of semiconductor electrode can be represented by the anodic hole current for the oxidation of surface anions. 

The rate uj, of cation transfer of Eqn. 9-49 is given by Eqn. 9-51 as a function of potential of the compact layer  

The rate of oxidative dissolution, vya (= I m = ( x ) can be observed by measuring the anodic hole current, im,v, of the oxidation of surface anions in Eqn. 9-50 as shown in Eqn. 9-53  

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