Preparation,Characterization And Catalytic Performance Of Yolk-shell Nanostructures

Special morphology and structure usually make materials to have some excellent properties,such as adsorption and catalytic properties.Yolk-shell nanostructure composite material is a new catalytic material which is discovered in recent years,it has low density,high specific surface area and can be readily modified.The void space can enrich more reactant molecules involved in the react ion,and the shell act as a protective shield to prevent the core from agglomeration,which is conduc tive to improving the catalytic reaction rate and cycle performance.By choosing different components as the core and shell of the yolk-shell nanostructure,the materials have more excel ent performance,thus becoming the hotspot in the field of catalysis.Herein,we report a facile synthesis of Au@ void@PMO yolk-shell nanostructure with Au NPs as the core and PMO as the shell via a layer-by-layer deposition process followed by a selective etching technique,and a series of contrast materials.The morphology,pore structure,physical and chemical properties of the composite materials are characterized by scan electron microscopy?SEM?,transmission electron microscope?TEM?,N₂ adsoprtion/desorption,UV-vis,Infred spectrum?IR?and 29 Si solid nuclear manganetic resonance?NMR?and etc.Au@ void@PMO used as catalysts for reduction of p-nitrophenol,it is found that the role of PVP makes the Au nanoparticles anchored in the porous shell,which reduces the contact time of reagent and catalytic activity.This unique structure greatly improved the catalytic reaction rate and the kinetic rate constant reached 473 min^-1·mg^-1,exhibiting good catalytic activity.At the same time because of the shell prevents Au NPs from escape and agglomeration,Au@ void@PMO can be recycled for four runs,so the material has good structural stability.In the second part of this thesis,we successfully prepare yolk-shell nanostructure Ru/Fe₃O₄@void@PMO-SO₃ H composite material with Fe₃O₄ core and PMO-SO₃ H modified shell through a combination of layer-by-layer parcels and selective etching method,which can catalytic conversion of cellulose to prepare multi sugar alcohol and recovered by magnetic performance.The morphology,pore structure,physical and chemical properties of the composite materials are characterized by TEM,N₂ adsoprtion/desorption,X-ray photoelectron spectrum?XPS?,IR and etc.Ru/Fe₃O₄@void@PMO-SO₃ H used as catalysts for conversion of cellulose to prepare multi sugar alcohol.The results showed when the yolk-shell nanostructure materials with the same containing acid supported Ru nanoparticles with different sizes,the yolk-shell nanostructure material with an average diameter of 2.2 nm of Ru NPs exhibited the maximum isosorbide yield of 60% under the same reaction conditions.When the yolk-shell nanostructures were deposited Ru nanoparticles with an average diameter of 2.2 nm,the increase of the acid content of the carrier would increase the yield of target product isosorbide.Furthermore,these yolk-shell nanostructure materials can be faciley recoved by virtue of the core of magnetic Fe₃O₄ NPs.It is proved that the materials have bifunctional properties.