Characterisation and reactivity of oxygen species at the surface of metal oxides

Abstract

Surface reactive oxygen species play a fundamental role in selective oxidation and combustion reactions catalyzed by metal oxides. Unravelling the nature of these transient species, and understanding the details of both their electronic structure and reactivity has been for decades one of the prime research areas of surface and catalytic chemistry. The longstanding activity of Michel Che in this area has been a source of inspiration for generation of researchers, and constitute his outstanding and enduring scientific legacy. Present review provides a survey of the surface oxygen species on oxide materials, which moving on from the Che’s pioneering works includes noteworthy results obtained during the years by other researchers. In particular, applications of two powerful techniques such as electron paramagnetic resonance (EPR) and photoluminescence (PL) for detailed characterization of paramagnetic (O−, O2−, O3−) and diamagnetic surface oxygen varieties (O2−surf), respectively, are addressed here. Classification and insights into the formation pathways of these species on various oxide surfaces, as well as their involvement in model and real gas/solid and liquid/solid reactions of catalytic and photocatalytic relevance is also considered. Finally, the relationship between the thermodynamic and kinetic Bronsted basicity of low coordinated O2−Lc anions is discussed, on the basis of Che’s fundamental studies and on recent developments.