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Preparation of Core-shell Ag@Pt Nanoparticles and Pthallow Nanospheres and Catalytic C1Oxidation of Small Organic Molecules Properties

Author: LinJianYun
Tutor: ZhongQiLing
School: Jiangxi Normal University
Course: Physical and chemical
Keywords: silver sol core-shell structure of nanoparticles platinum hollownanosphere electro-catalytic oxidation
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Type: Master's thesis
Year: 2013
Downloads: 41
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Abstract


C1small molecules （such as CH3OH, HCOOH, HCHO, etc.） can be used as thefuel of liquid fuel cell which have aroused much great interests. Pt material, organicmolecules in electrocatalytic oxidation. However, the resources of Pt materials in acidor alkaline medium still is the best single-component catalysts of C1small organic arescarce, expensive and the catalytic active sites are susceptible poisoned by CO whichwas produced by oxidation of the small organic and, hinder the commercialization offuel cell. Therefore, reduce the use of platinum, improve the utilization efficiency,catalytic activity and stability, extend the service life of the material and find anodecatalytic materials with excellent performance are still important in fuel cell researchs.In order to enhance the catalytic activity and efficiency, people first thought tosynthetic platinum in nanoscale, however nano materials have large surface area,high surface energy that is easy to reunite. That will reduce the catalytic activity of thematerials and effect the stability and service life. Thus the platinum nanoparticles wasload on carbon powers with high surface area prepared as carbon-platinum-carrying toprevent its aggregates inactivation. The stability and service life was improved insome extent, however, the carborn power was easily to be oxidized and is difficult toavoid the load of platinum nanoparticles fall off and lose activities. However, thesurface of hollow metal catalytic material （such as spherical, rod-shaped, etc.） areporous, the materials have large surface area, low density and high utilizationefficiency. The nanoparticles supported by shell with well catalytic activity andstability, exhibit superior catalytic properties than solid nano-particles. In this text,nano-Se ball was use as template, bulk synthesis platinum hollow nanospheres withhigh activity, good stability and were modified on glassy carbon electrode.It should benoted that Se is easily to formed alloys with transition metal Pd, Ru, etc, and it isdifficult to synthesize Pt-Pd, Pt-Ru or multiple transition metal metal nano-empty ballwhich the catalytic performance may superior than the Platinum hollow nanospheres.So this thesis use silver as template to synthetize platinum hollow nanospheres,andstudy the methods to synthesize platinum hollow nanosphere, characte its morphologyand investigate the electrocatalytic oxidation performance to C1small organicmolecules. Create conditions to synthesis of Pt-Pd, Pt-Ru those two-or multi-metal hollow nanospheres.（1）at a temperature that slightly lower than room temperature, the silver sol incertain particle size was synthesized using silver nitrate precursor, ascorbic acid asreductant, PVP as surfactant. Investigate the effects of pH and temperature onsynthesis of silver sol, a suitable system was looked for to synthesis silver template. Itwas found that the silver sol was easier to be synthesis in alkaline environment at18℃. What’s more, the size of the silver particles was different with pH.（2）Ag@Pt and platinum empty ball nano-particles with uniform size and betterdispersion and core-shell structure were synthesized useing silver sol as atemplate,whith provided an experimental basis for the synthesis of Platinum hollownanospheres.（3）The morphology, composition, structure of the Platinum hollow nanosphereswere characterized by SEM, TEM, EDX and XRD. all of the results showed that thesurface of platinum hollow nanospheres were consist of lots of platinum atomicclusters and polycrystalline platinum.（4）Conventional electrochemical methods （cyclic voltammetry and Chronoampe-rometry） were used to study the electro-catalytic oxidation to the C1of Pthollow/GC indifferent supporting electrolytes. We also explored the platinum Hollow nanospheremodified electrode used as a sensor to analytic the concentration of C1.We last studythe relations of the morphology,structure and the catalytic performances of the electro-de, which provides a basis for the preparation of the anode catalysts for fuel cells.

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