Multivalence Ce and Sn oxide doped materials are of critical importance in many renewable energy applications, especially in a porous form. Of special interest is the understanding of the basic properties of Ce-Sn-O nanoparticles and the effect of doping with different trivalent (Fe3+, Yb3+, Gd3+) elements, as well as developing Ce-Sn-O materials in the form of homogeneous and heterogeneous multilayers with unique properties at high temperature. We discuss various applications of nanosize metal-oxide sensors and energy conservation through improved energy efficiency such as renewable sources and fuel cells. In addition, ceria and ceria-based materials are studied for their electronic, magnetic, optical, and catalytic properties, which are important in applications such as gas sensors, heterogeneous catalysis, solid electrolyte fuel cells (SOFC), and UV-shielding application. Additionally, at the nanoscale, the surface area of metal oxide particles is dramatically increased, which not only increases oxygen exchange but also makes it easy for redox reactions.