Supported by Natural Science Foundation of China(青年基金)
Principal Investigator: Prof. Yan Yang
Key Words: ceria ;active oxygen species;selective oxidation ;interface confinement ;electronic structure
Abstract: Tailoring the generation of active oxygen species on oxide surfaces, especially under mild conditions, is center to current catalysis research, partially owing to its potential application in the green chemistry of chemical conversion, emission control during cold start, oxygen reduction in fuel cell and lithium-air batteries. Paralleling its great importance is the tremendous difficulties confronting the oxidation catalysis research, in identifying the active sites on a complex oxide surface and understanding their role in O2 activation. Taking ceria, a renowned material for catalytic oxidation, as an example, previous spectroscopic studies have identified a series of active oxygen species on ceria, upon its contact with O2 at room temperature. While surface oxygen vacancies on ceria are generally expected as the sites for O2 activation, where and how these different oxygen species are generated remain unknown. Recent advances in the microscopic studies of ceria surfaces revealed a few types of oxygen vacancies at the ceria surface, which leads to the hypothesis that the series of active oxygen species could be generated by these different oxygen vacancies, respectively.Surface science studies, combing STM, IRAS and EPR, on ceria model surfaces will thus allow the answer to this hypothesis.Certainly,the bulk ceria is not active enough for the generation of most active oxygen species at around room temperature. However, understanding the nature of electron transfer between oxygen vacancies and O2 in generating different oxygen species, one could tune the electronic structure of ceria through nano- and interface- confinement effects, to enhance the electronic interaction with O2. Interfacial confinement is our recently developed strategy, that can drastically enhance the catalytic performance of an oxide.Due to the strong interaction between metal and oxides, oxide nanostructures can exhibit great structural flexibilities when supported on a metal surface. Low-valence active centers can thus be stabilized at the interface and the oxides can exhibit a series of novel structures not seen in the bulk phase. Interface-confined ceria, with the precise control of surface science approach, would thus allow the tailored generation of active oxygen species for selective oxidation at low temperature.
Project No.: 21303195