Synthesis Of Novel Bimetallic Core-shell Nanostructures And Their Catalytic Properties Reserch

Due to the unique synergetic effects,bimetallic nanomaterials display superior optical,electronic and catalytic properties over monometallic counterparts.They have been widely used in the field of optics,electronics,catalysis and bio-medicine,becoming a new hotspot in the material science.The properties of bimetals are tightly determined by their component,size and morphology.So it has been become an important research subject to use simple methods for the composition,size and morphology control synthesis of bimetal composite materials.And then their wide application prospects should be explored.Aiming at synthesis of noble metal nanomaterials via facile and simple method with low cost,we have prepared a series of core-shell bimetallic nanostructure by one-pot wet-chemical co-reduction methods.The transmission electron microscopy(TEM),high-resolution transmission electron microscopy(HR-TEM),energy dispersive X-ray spectroscopy(EDS),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)were employed to examine their morphology,particle size,components,crystal structures and surface states.Finally,their applications in the catalysis were explored.The results are shown below:1.Uniform good shape core-shell AuPd@Pd nanocrystals(AuPd@Pd NCs)were prepared in aqueous solution via a fast and simple co-reduction method,using allantoin as a structure-directing agent and ascorbic acid as a reducing agent,without any pre-made seed,toxic organic solvent,surfactant,polymer or complicted apparatus.The possible growth mechanism was discussed in details and control experiments demonstrated that the amount of allantoin was critical to the final nanocomposites.Compared with home-made Au NCs and commercial Pd black,the AuPd@Pd NCs possessed larger electrochemically active surface area and showed enhanced electrocatalytic ability and stability towards ethylene glycol oxidation.The improved catalytic performance of AuPd@Pd NCs was ascribed to the synergetic effects between the two metal components and their unique nanostructures.2.A facile and simple co-reduction method was developed for the synthesis of good shape and well-dispersed core-shell Pd@Pt dendritic nanocrystals anchored on reduced graphene oxide(rGO)in aqueous solution.Poly(ethylene oxide)(PEO)was employed as a structure-director as well as the stabilizing agent and ascorbic acid was a reducing agent.No pre-made seed,toxic organic solvent orcomplicted apparatus were involved.The possible growth mechanism was discussed in details and control experiments demonstrated the crucial role of PEO for the final nanocomposites.Compared with commercial Pt/C and Pd/C catalysts,the as-obtained Pd@Pt/rGO displayed superior catalytic activity and long-term stability towards methanol and ethanol oxidation.The improved catalytic activity of Pd@Pt/rGO was mainly the consequence of the synergistic effects between Pd and Pt of the dendritic structures,as well as rGO as a support.3.Core-shell AuPt@Au nanocrystals supported on reduced graphene oxide(rGO)were fabricated by a rapid one-step wet-chemical method,where HAuCl4 and H2PtCl4 were co-reduced by hydrazine hydrate in the presence of melamine.The possible growth mechanism was discussed in details and control experiments evidenced the essential role of melamine in the synthetic process.Owing to the support of rGO and the synergistic effects between Au and Pt,the AuPt@Au/rGO displayed improved catalytic activity for the reduction of p-nitrophenol with NaBH4 in contrast with Au/rGO,Pt/rGO and commercial Pt/C.And the AuPt@Au/rGO has acceptable recyclability,which could be reused for at least 5 times.