Metal oxides are extremely common in our planet. They form the Earth’s crust and, on the surface, they participate in a multitude of processes that affect our every day life. These substituted oxides are intrinsically defective, with multiple oxidation states of the metals, oxide-ion vacancies, and generally a large concentration of defect sites. I will discuss bulk and surface properties, and we will discuss special examples of applications in fuel cells, sensors and catalysis.

As a starting point, DFT calculations showing the structure of Sm doped ceria (SDC), namely what is the arrangement of dopants and vacancies in the bulk and on the surface of these materials will be presented. This provides a baseline for the understanding of defective oxides. Then, the more complex perovskite structure of substituted SmFeO₃ will be introduced. This family of perovskites shows a great range of properties with multiple potential applications. These materials show highly tuneable properties, particularly in regards to conductivity and reactivity. As an example, we can switch the material from p- to n- type conductivity (and back) by small changes in dopant concentration. Surface characteristics are key to the reactivity of the perovskites and surface properties are often different from the bulk material. Two of the applications of these tunable material include their use in sensor devices for the detection of reducing gases (like hydrogen, methane and carbon monoxide) and as carbon resistant anodes for low-temperature solid oxide fuel cells. Their surface properties also make these defective oxides into excellent catalysts and catalyst supports for multiple reactions. An oxidation example for small molecules will be discussed.

email: jgiorgi @ uottawa . ca