The Synthesis And Catalytic Performance Of Pd-based Bimetallic Heterostructured Nanocrystals

Bimetallic nanocrystals are expected to produce new physical or chemical properties because the joining of the second metal can change the binding energy and electronic configuration of the two metals.At the same time,the synergistic effect of the two metals can make it obtain the better performance than the corresponding monometallic metal.And it has important application prospects in catalysis and biomedicine.Therefore,the synthesis of bimetallic nanocrystals has been the research focus in recent years.This thesis mainly used seed growth method to synthesize Pd-Ag,Pd-Au,Pd-Pt and Pd-Ru heterostructured nanocrystals by controlling the kinetic parameters of the reaction,to explore their growth methods and evaluate the catalytic performance.The dissertation mainly includes the following three parts:（1）Taking use of Pd nanowires as the seeds,selective epitaxial growth of Ag on Pd nanowires has been achieved to prepare Pd-Ag heterostructure nanocrystals with different coating degrees by optimizing the ratio of the surface diffusion rate and the deposition rate of Ag,through modifying the factors which can influence the reaction kinetics,such as the reactant concentration,the reaction temperature,and the concentration of metal precursors.Subsequently,this idea was extended to the synthesis of Pd-Au heterostructured nanocrystals.The catalytic performance of the above heterostructured nanocrystals were evaluated by the solvent-free aerobic reaction of toluene and o-xylene under the light.The catalytic results show that the Localized Surface Plasmon Resonance effect of Ag and Au significantly improved the photocatalytic performance.（2）Taking Pd nanowires as the seeds and using solvents that can act as reducing agents（such as ethylene glycol,benzyl alcohol,N,N-dimethylformamide）,epitaxial growth of Pt on the Pd nanowire has been realized to prepare Pd-Pt heterostructured nanocrystals with different morphologies and structures by controlling factors that can affect the reaction kinetics,such as the amount of reactants,temperature and time.The hydrogenation reaction of nitrobenzene was used to evaluate their catalytic performance.The catalytic results showed that the Pd-Pt heterostructured nanocrystals with the zigzag structure have the highest catalytic performance.At the same time,the defects and atomic steps at the zigzag structure have played the important roles in improving the catalytic performance.（3）On the basis of the above work,taking Pd nanowires as seeds and utilizing the simplicity of the solvothermal method and the advantages of ethylene glycol being both a solvent and a reducing agent,the effective deposition of Ru on Pd nanowires has been realized to obtain Pd-Ru heterostructured nanocrystals by regulating the amount of Ru³⁺,temperature and time.The electrocatalytic performance of the obtained nanocrystals was evaluated by electrochemical hydrogen evolution reaction（HER）.The catalytic results showed that the sample of Pd-Ru-1.5 has comparable electrocatalytic hydrogen evolution performance with commercial Pt/C.