Preparation Of The Ag Core-C Shell Hierarchical Nanostructures And Catalytic Performances

In the last decade, metal nanometerials have attracted extensive attention due to their potentialutility in catalytic, electrical and sensing fields. The synthesis of small size, high dispersion, andhigh number density of noble metals nanometerials with well-controlled shapes and sizes is ofgreat importance in application and development of nanometer metal materials. However, theyare poor at dispersion stability and tend to aggregate in the medium. Core-shell structures canoffer protection to the metal cores as well as introduce new properties to the hybrid structures.What’s more, core-shell structured with noble metal core possess excellently catalytic and highstability compared to the bulk metal nanoparticle. Especially for the multi-core noble metal coreshell structure, a large number of small size package of noble metal nanoparticles are dispersionin the shell, which can prevent noble metal nanoparticles aggregation andoxidation leading toimprove the catalytic efficiency. So the preparation of nanometer noble metal composite materialof core-shell structure, especially the multi-core composite has been paid more and moreattention. In this paper, multiple core Ag@C nonmaterials were prepared by by a templatemethod and one step method aspect. The structure, size, morphology and catalytic properties ofmultiple core nanomaterials have been studied. The main research contents and achievements inthe paper were listed as follows:1. Hollow multiple-Ag-cores-C-shell nanostructures that composed of stabilized Agnamopaticles and porous carbon shell were fabricated from well-defined Ag@C core-shelltemplates via a simultaneous synthesis and assembly strategy. The multiple-Ag-cores-C-shellnanostructures can be fabricated by a redox reaction between the Ag@C templates and H2O2,and the H2O2serve as a smart etchant to control the dissolving and oxidizing of the initial Agcore to Ag+, which was diffused from the core to the carbon shell and reduced to small Agnanoparticles by active groups in the carbon shell. The dispersion, particle size of Agnanoparticles and the arrangement in carbon of resultant assemblages were explored. Thehierarchical hollow multiple-Ag-cores-C-shell nanostructures exhibited an excellent catalyticactivity and recyclability for the reduction of4-nitrophenol due to the small size, high dispersion,and high number density of the Ag NPs in the porous carbon shell.2. The multiple Ag-NPs@C nanostructures with highly dispersed silver NPs incorporated inthe microporous carbon spheres were prepared through facile one-pot and a green wet chemicalsynthesis route under hydrothermal condition. The entire sphere was about300nm in average diameter and the Ag nanoparticles were controlled5-10nm. In this synthesis, glucose can reduceAg+to Ag nanoparticles and form a microporous carbon shell by carbonization. PEO-PPO-PEOblock copolymer P123was used as the stabilizing agents to combine with silver ions to formAg-P123units and structure-directing agents for self-assembly of carbon precursors. Themultiple Ag-NPs@C nanostructures exhibit an excellent catalytic activity for the reduction of4-nitrophenol, and nealy4-nitrophenol can be completely reduced in fifteen minutes.