催化剂-Shape-ControlledNanocrystalsforCatalyticApplications.pdf

Catal Surv Asia DOI 10.1007/s10563-011-9130-z Shape-Controlled Nanocrystals for Catalytic Applications Hyunjoo Lee • Cheonghee Kim • Sungeun Yang • Joung Woo Han • Jiyeon Kim Springer Science+Business Media, LLC 2011 Abstract The activity, selectivity, and long-term stability 1 Introduction of catalyst nanoparticles can be enhanced by shape mod- ulation. Such shaped catalytic nanocrystals have well- Heterogeneous catalytic reactions occur when reactants are defined surface crystalline structures on which the cleavage adsorbed on a surface and undergo a cleavage or recom- and recombination of chemical bonds can be rationally bination of their chemical bonds. Therefore, the surface controlled. Metal and metal oxide nanocrystals have been structure of catalysts strongly affects their catalytic activ- synthesized in various shapes using wet chemistry tech- ity, selectivity, and long-term stability. The atomic niques such as reducing metal precursors in the presence of arrangement on such a surface differs depending on its the surface-capping agents. The surface-capping agents crystalline structure. For example, a {111} surface has a should be removed prior to the catalytic chemical reaction, hexagonal atomic arrangement, whereas a {100} surface which necessitates clean catalytically active surface. The has a square atomic arrangement for face-centered cubic removal process should be performed very carefully (FCC) metals such as Pt, Au, Ag, Pd, and Rh. For high- because this removal often causes shape deformation. index surfaces, where one of the indices h, k, or l is greater A few examples in which the surface-capping agents than one for an {hkl} surface, there are more steps or kinks