Preparation And Mechanism Of Noble Nanostructures And Their Catalytic Performance Study

Noble metal nanostructures have excellent catalytic properties due to size effect and high specific area. Because their catalytic performance of noble nanostructures is highly dependent on size, morphology, composition, the controllable preparation of noble metal nanoparticles are important. This thesis mainly involves using seeded growth to prepare different shaped platinum nanostructures, gold and silver heterogeneous nanostructures. Moreover, their growth mechanism and catalytic properties were also studied. The research content mainly has the following three parts:(1) Through galvanic reaction between Cu nanoparticles and Pt(Ⅱ), various Pt nanostructures were prepared, such as monodisperse octahedra, concaved nanocubes, mμLti-branched nanoparticles. Systematically, the effect of reaction temperature and the amount of precursor on the growth of Pt nanostructures were studied. Moreover, the catalytic performances of prepared Pt nanostructures were also tested using methanol electrocatalytic oxidization. ResuLt show that concaved Pt nanoparticles have the best catalytic performance due to the presence of high index facets.(2) By using Au decahedra or nanorods as seeds, various Au-Ag heterostructured nanorods were prepared through controlling reaction kinetics, such as Au-Ag nanorods, asymmetrical Ag-Au-Ag nanorods, and symmetrical Ag-Au-Ag nanorods. Moreover, the effect of reaction temperature and amount of ammonia on the growth of nanorods were explored. A reasonable mechanism was figured out. Further, Au-Ag nanorods serve as seeds and other nanostructures (Au-Ag nanords with different lengths or different diameters, nanonails and nanocups) were prepared through secondary seeded growth and selective etching,(3) Au@Ag nanocubes and Au-Ag nanorods were first synthesized through using Au octahedra and decahedra as seeds respectively. Further, nanorods and nanocubes act as templates which are used to prepare hollow nanostructure through galvanic reaction, such as hollow Au-Ag/Au nanorods, rattle-like Au-Ag/Au nanoparticles. Besides, when prepared hollow nanostructures serve as seeds for further growth, we found that galvanic etching can induce self-healing growth. The catalytic performance test (the reduction of p-nitrophenol) shows that hollow Au-Ag/Au nanorods are very active and the conversion rate reachs90%in60s, indicating that their excellent catalytic performance is due to the high specific surface area and the presence of high active sites.