CeO₂ is one of the most interesting oxides in the fields of catalysis (e.g., environmental catalysis and catalytic oxidation) because of the rapid formation and elimination of oxygen vacancies. The performance of CeO₂ can be strongly improved under doping. Synthesis of ceria-based solid solutions with controllable concentrations of oxygen vacancies is of great fundamental significance. Since the properties of the ceria-based solid solutions are affected by the dopant size and valence (lower valence ions in ceria could lower the activation energy for oxygen migration, and smaller ions enhance the oxygen storage capacity), introducing cations with smaller size and lower valence as compared to Ce⁴⁺ (e.g., Fe³⁺) into the ceria lattice owns considerable scientific and technological value. It has been observed a series of interesting phenomena in the structure and catalytic applications of CeO₂-Fe₂O₃ solid solution. Moreover, the interface between CeO₂ and Fe₂O₃ particles (e.g., Ce-O-Fe bridges) also reveals special features in catalysis. In this review, the structural features of Ce-Fe mixed oxides, including the solubility of Fe ions in ceria lattice, formation of oxygen vacancies and CeO₂-Fe₂O₃ interaction are discussed, which are related to their activity in catalytical applications (e.g., purification of exhaust gases from vehicles, catalytic oxidation, hydrogen and syngas generation, and Fischer-Tropsch synthesis). Some key issues and possible directions on the Ce-Fe mixed oxides used in catalysis are discussed.

Contents
1 Introduction
2 Structural features of ceria-based solid solution
2.1 Formation of ceria-based solid solution and oxygen vacancies
2.2 Relationship among prepare methods, solubility of Fe in ceria lattice and oxygen vacancies concentration
3 Applications of Ce-Fe mixed oxides in catalysis
3.1 Purification of exhaust gases from vehicles
3.2 Catalytic oxidation
3.3 Hydrogen/syngas generation
3.4 Organic synthesis
3.5 Solid oxide fuel cells
3.6 Fischer-Tropsch synthesis
3.7 Catalytic wet peroxide oxidation
4 Conclusion and outlook