ABSTRACT
In the case of insulating metal oxides, the ionic adsorption reactions taking place at the metal oxide/solution interface do not affect the bulk solid phase. On the other hand, ionic adsorption does influence the position of the electronic levels of semiconducting oxides. This effect, that extends from the surface throughout a region of variable thickness, influences the interfacial electron exchange processes. A general account of the semiconductor/solution electrochemistry can be found in many reference treatises. This chapter summarizes only the most important aspects related to the dissolution behavior of semiconducting oxides. Charge transfer between the conduction band (or valence band) and dissolved reductants (or oxidants) leads to net redox reactions in solution. The role of a semiconducting oxide is that of a catalyst or that of an energy transducer. Transition metal oxides are often capable of accommodating oxidized or reduced metal ions.
