Seed-mediated Growth Of Core-Shell Metal Nanocrystals As Advanced Catalysts

Metal nanocrystals with a core-shell structure represent a class of unique functional materials,which exhibit huge potentials in the application represented by catalysis.On the one hand,the monometallic nanocrystals suffer from limited tuning of physicalchemical properties,while the core-shell nanocrystals can exhibit diverse properties derived from the synergistic effect of different components.As such,the core-shell nanocrystals are expected to show outstanding activity,selectivity,and durability in the catalytic application.On the other hand,the core-shell nanocrystals can effectively reduce the consumption of precious materials,thereby enhancing the utilization efficiency of the shell atoms.As such,rational design and controllable synthesis of core-shell nanocrystals are of fundamental importance in both academic research and industrial application.To this end.on the basis of rapid development of methodology with regard to controllable synthesis of metal nanomaterials,researchers have successfully fabricated different types of core-shell nanocrystals.In particular,the seed-mediated growth represents a process involving heterogeneous nucleation and epixital growth of the shell materials on the surface of the pre-existing seeds.Owing to the relatively lower energy barriers taken by the heterogeneous nucleation,the shell atoms can undergo oriented growth to generate nanocrystals with a high purity.Accordingly,the dissertation mainly demonstrates the utilization of seed-mediated growth combined with other methods to construct core-shell metallic nanocrystals,such as Pd@CuPd core-shell nanocubes,Pd@CuPd core-shell hypercubes,and Pd@CuAu planar tetrapods.The dissertation contains four chapters,and the main content in each chapter is listed as following:In chapter one,we briefly introduced the synthesis core-shell metallic nanocrystals,together with their application in catalysis.Then we emphasized some critical issues during the seed-mediated growth in this chapter.In chapter two,we mainly demonstrated how to incorporate the oxidative etching in the seed-mediated growth to tune the surface structure of Pd-based nanocrystals.First,we employed Pd nanocubes as seeds,on the surface of which CuPd atoms were uniformly deposited to produce Pd@CuPd core-shell nanocubes.Afterwards,with the help of oxidative etching,the side faces of Pd@CuPd core-shell nanocubes were largely etched to generate Pd@CuPd core-shell hypercubes.We carried out detailed characterizations and investigated the formation process of such Pd@CuPd core-shell nanocrystals.Finally,electrochemical measurements indicate that the as-prepared Pd@CuPd core-shell hypercubes exhibited outstanding electrocatalytic performance in the electrochemical reduction of CO2.In chapter three,we performed the seed-mediated growth of Pd@CuAu core-shell planar tetrapods through the kinetically controlled mode.The size of Pd@CuAu core-shell planar tetrapods can be readily adjusted by simply varying the amount of Pd seeds.Moreover,the catalytic performance of as-obtained Pd@CuAu core-shell planar tetrapods was investigated in the oxidation of OPDA.In chapter four,we summarized the main context in the dissertation and prospected the development in the related field.