Oxide ion migration

In the preceding section, we explained that the bulk diffusion of oxide ion plays an important role in the enhancement of the catalytic activity of the multicomponent bismuth molybdate systems. Here, another important role of the oxide ion migration in increasing the stability of the catalyst system is introduced. 

Since the classification is essentially based on rates of catalytic reactions relative to rates of diffusion of redox carriers, there are oxidation reactions that are intermediate between the two limiting cases. We note that neither the molecular size nor the polarity of reactant molecules is the principal characteristic determining the type of catalysis. Although oxide ions migrate rapidly in the bulk, bulk type II catalysis is not observed for oxidation catalyzed by Bi-Mo oxides. In this case the rate-limiting step is a surface reaction. 

Another application where the reduction of metallic impurities is possible is in the purification of plating solutions containing negatively charged metal oxides, e.g., chromium plating baths [28]. In this application, negative metal oxide ions migrate away from the cathode where the positive impurities (Cu, Zn, Fe ) are reduced. 

SOFC conditions [33]. Furthermore, Mn is known to accept lower coordination numbers in perovskites [34], especially for Mn " ", and thus it may facilitate oxide ion migration. Similarly, Ga is well known to adopt lower coordination than octahedral in perovskite-related oxides. The possibility of mixed ionic/... 

---