| Supported Noble Metal Nanocatalyst can own the unique physicochemical properties of noble metal and the excellent performance of support at the same time, thus yield lots of novel and splendid function such as wide dispersion of active component, Strong-Metal-Support-Interaction, strong chemically and catalytic stable properties and also low cost. Thereby the Supported Noble Metal Nanocatalyst is a promising candidate for applications in Biomedical?Environmental Protection?petrochemicals and new energy. In this paper, one step aerosol method assisted to synthesis two supported noble metal catalyst were studied, and the application in the reduction of 4-NP to 4-AP were discussed. Main lists are included as follows:First of all, Fe3O4 nanoparticle with uniform size (almost 20nm) were prepared by chemical precipitation process, then Magnetic Fe3O4@C-SiO2 core-shell particles with Fe3O4 core and Carbon-Silicon hybrid shell were synthesized by a surfactant-aided aerosol process. Hereafter Magnetic C-C@Fe3O4 hollow microspheres were prepared by using aerosol-based Fe3O4@C-SiO2 core-shell particles as templates. The magnetic double-shelled microspheres efficiently worked as carriers to load Pt nanoparticles, thereby making the catalyst recyclable and reusable. The reduction of 4-nitrophenol 4-NP) by NaBH4 to 4-aminophenol(4-AP) was chosen as the model reaction to evaluate the catalytic capability the C-C@Fe3O4-Pt composite. The reduction of 4-NP into 4-AP was completed within 8 min, and also the stability of the catalyst was investigated by repeating the reduction reaction with the same catalyst five times. After each reaction, the catalyst was recycled by an external magnetic field, followed by washing with deionized water and absolute ethanol several times. The C-C@Fe3O4-Pt catalyst showed high activity after 5 successive reaction cycles, with conversion near 100% within 8min. Clearly, the magnetic C-C microspheres were efficient in working as a carrier to load the Pt nanoparticles, thus making the catalyst recyclable and reusable.To broad the synthesis of supported noble metal nanospheres, Metal nanocrystal@ RF-COOH nanospheres with uniform size were easily obtained by a one-step hydrothermal method, the nanostructures and compositions of encapsulated metal nanocrystals were readily controlled, then the nanospheres were used as ideal templates to carry the pregrown noble metals into the mesoporous silica microspheres by a general aerosol process. Especially, novel unique Au/Pt and Pt yolk-shell nanostructures were obtained in the hollow interiors of the silicon microspheres.4-nitrophenol (4-NP) by NaBH4 to 4-aminophenol (4-AP) was chosen as the model reaction to evaluate the catalytic capability of these catalysts. The catalytic activities of nanocrystals with york-shell structure are about 9-14 times higher than those of the monometallic counterparts on the basis of the same amount of monometals. Moreover, the yolk-shell nanostructure of the Au/Pt alloy and the highly ordered mesporous silica wall preserved after five cycle usage, suggesting superior chemical and catalytic stability for liquid-phase catalytic reaction of the metal nanocrystal-embedded mesoporous silica microspheres.To enrich the extension of liquid-phase reaction catalyzed by supported noble metal nanospheres, RF-COOH nanospheres with uniform size (about 500nm) were easily obtained by a one-step hydrothermal method, then noble metal Pt were reduced and deposited on the surface of the RF-COOH nanospheres. Hydrolytic dehydrogenation of Ammonia Borane(AB) were used to evaluate the catalytic capability of these catalysts. The result shows the way for the rational design of highly active and durable Pt catalysts for hydrogen generation.3.5 mg/mL of AB aqueous solution was hydrolysis thoroughly in the presence of RF-COOH-Pt (6mL), and activation energy was 37.88kJ/mol. More interesting, after 5 successive cycle reaction the catalyst can still remain the excellent catalytic and chemically stable properties. |
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