Studies On The Surface And Interface Engineering And The Hydrogenation Activity Of Ruthenium-based Nanocatalyst

Catalytic hydrogenation reaction is widely used in medicine,food,petrochemical and other industries due to the good product yield and green production process,and it also plays an important role in the synthesis of many important fine chemical products and organic intermediates.Catalyst is one of the main influencing factors in the catalytic hydrogenation reaction,and the morphology,size,structure and other characteristics of the catalyst have an important influence on the catalytic performance.With the development of nanotechnology,the atomically controlled synthesis metal nanoparticles in recent years has been realized,but the specific influence mechanism of catalysts with different characteristics on catalytic performance have not yet been entirely explained.Thus,how to rationally design and control the catalysts and better understand the underlying reaction mechanisms are highly desirable.In this thesis,ruthenium-based nanoparticles are mainly synthesized by regulating the specific organic capping ligands or forming bimetallic core-shell structure and used as a catalyst in catalytic hydrogenation reactions.A series of characterization methods are used to systematically study the structure of the metal catalysts and the reaction mechanism of the hydrogenation reaction.The main contents are as follows:?1?Ruthenium nanoparticles were modified with terminal and internal alkynes to control the hydrogenation selectivity of styrene.The ruthenium-alkyne interface was examined by a series of characterization as ¹H NMR,¹³C NMR,TGA,FTIR,XPS,photoluminescence measurements and DFT calculations,and then the reaction mechanism on catalytic hydrogenation of styrene was discussed.The results show that the ruthenium nanoparticles capped with terminal alkyne only showed significant selective hydrogenation of vinyl moiety?>97%?,whereas the terminal alkyne functionalized nanoparticles exhibited apparent catalytic activity toward both the vinly and phenyl groups.The catalysis tests of CO-poisoned Ru nanoparticles further indicate that the CO bridging site on the surface of ruthenium nanoparticles might be responsible for the hydrogenation of phenyl group on the catalytic hydrogenation of styrene.?2?Pd nanocubes with face-centered cubic?fcc?configuration were serving as seeds for the epitaxial deposition of Ru and formed Pd@Ru core-shell nanocubes maintained the fcc configuration.The thickness and shape of ruthenium shell were controlled to adjust the electronic structure of Pd@Ru nanoparticles and the selective hydrogenation kinetics of4-nitrostyrene on Pd@Ru nanoparticles.HAADF-STEM,EDS,XRD and XPS measurements suggested that Ru adatoms follow the crystal packing of fcc configuration through epitaxial deposition due to the similar radius and lowe lattice mismatch?1.8%?between Pd and Ru atoms.The electronic structure and catalytic activity of Pd@Ru core-shell nanoparticles can be well modulated by controlling the thickness of the epitaxially grown ruthenium shell layer.Electrochemical CO stripping experiments show that,with the increase of Ru shell layer,the adsorption energy of CO on Pd@Ru core-shell nanocubes were consistently reduced due to the down-shift of the d-band center,which promotes the high selectivity for hydrogenation of vinyl group of 4-nitrostyrene?100%?.