Surface Research Of The Model System Based On Two-dimensional Iron-based Catalyst

Deteriorating ecological environment calls for the exploration of clean energy alternatives and effective energy storage approaches which is essential for the global energy,environment,materials and chemistry.Catalytic reactions transform raw materials into value-added chemical fuels and functional materials make sustainable development possible,which are important tools to promote chemical production and energy storage applications.Therefore,highly reactive and durable catalysts are prerequisite to facilitate these chemical reactions.Catalysts composed of iron nanostructures are highly reactive,durable catalysts for a series of chemical reactions.And iron as precursor,with the advantages of large reserves,low cost and excellent chemical stability.However,there are still many key scientific problems to be solved in the controllable preparation,structure and characterization.Therefore,it is highly desirable to explore the two-dimensional iron-based model catalysts and the reaction mechanisms that are involved.In this thesis,we mainly focus on iron-based two-dimensional material catalysts that are produced by molecular beam epitaxy（MBE）and characterized by scanning tunneling microscopy（STM）and X-ray photoelectron spectroscopy（XPS）analysis,combined with density functional theory（DFT）calculation.The main research contents are as follows:（1）Controllable preparation of large scale and high quality mono-and bi-layer Fe O films.Using STM,we reveal an atomic-scale understanding on the growth mechanism and structural properties of large scale ultra-thin Fe O on Au（111）.And we identified a different growth mode that the monolayer Fe O embedded into the Au（111）surface at the initial stage.The bilayer Fe O exhibits a Moirésuperlattice with an ellipsoidal shape due to the strong interlayer Fe-Fe bonding and inequivalent charge distribution.（2）The oxidation of CO on Fe O/Au（111）at room temperature.Benefit from the strong oxide-metal interactions（SOMIs）,we studied the reversible oxidation and reduction of Fe O（111）grown on Au（111）by O₂ and CO,respectively.CO oxidation occurs on the surface dislocation structure of Fe O/Au（111）after O₂activation at room temperature.DFT calculation and XPS analysis allow us to reveal the excellent reactivity and stability of iron-based nanomaterials as inverse catalysts.（3）Preparation of Fe-N-C catalyst and the mechanism for oxygen activation.Based on on-surface reaction,using melamine as the precursor,we synthesize large scale two-dimensional covalent coordination organic frameworks on Au（111）containing the Fe-N_x-C_y motif.Furthermore,combined with in situ STM and XPS analysis,we reveal the mechanism of oxygen adsorption and decomposition,which promotes the research in oxygen reduction reaction.