Preparation Of Noble Metallic(Au/Ag/Pd)Nanoparticles And Their Electrocatalytic Performance Of Methanol Oxidation

Nobel metal nanomaterials are of great interest due to their unique electrical, optical,magnetic and chemical properties, and they have a great number of application in our actual production and daily life. In recent years, there are numerous reports on the synthesis of noble nanoparticles with different morphologies through various methods. However, the performance of single-component noble metal nanomaterials can not meet our needs.Multi-metallic components will greatly improved the performance of noble metal nanomaterials by the synergistic effect, while still retaining the properties of single component. Therefore, The synthesis of multi-metal nanomaterials has become a research highlights. Noble metal nanoparticles can be synthesized by using many kinds of approaches, among which the photomediated method is a common approach for the synthesis of Ag nanoparticles. After the first reported by Mirkin’s group in 2001, great progress has been made for morphology control and mechanism of photomediated synthesis of Ag nanoparticles. But there are still many problems about the small size,unobservable reaction process and in-situ characterization remains unclear. It is necessary to find a new method to observe the reaction and investigate the mechanism of the morphological transformation.Based on the research background mentioned above, this paper mainly includes the following contents:1.The process of photomediated synthesis of Au@Ag core-shell nanostructures is shown as follow: small Au nanoparticles, AgNO3 and sodium citrate are regard as seeds,precursor salt, and reducing agent, respectively. The reaction measurements are carried out under illumination. We monitored the reaction process by UV-vis and characterized the morphology of product by TEM. Au nanoparticles are used as a marker to study the effect of seed on the morphology of the product in the photomediated reaction since it is easy to distinguish Au and Ag in the TEM image. We have drew brief conclusions based on the analysis of our data and the literature reports: the final morphology of the products are closely related to the structure of the seeds: planar twining seeds eventually generate nanoprisms, while five-fold twinning seeds eventually generate decahedra; the final morphologies of silver nanoparticles are different due to the different stability and growth rate of two kind seeds under various conditions.2.Three kinds of Au@Ag-Pd trimetallic nanostructures with different morphologies are prepared. Their morphologies and components are characterized by TEM, SEM, UV-vis,and XPS. The Au@Ag-Pd trimetallic nanoparticles are prepared through three steps. First,the Au nanodecahedra were prepared as seeds. Then, the seed was used to form Au@Ag core-shell nanorods by using adding ammonia water to adjust the reaction kinetics. Finally,the galvanic replacement reaction was used to synthesize Au@Ag-Pd trimetallic nanostructures and the Au @ Ag core-shell nanorods as sacrificial templates. The morphology of the products was controlled by adjusting the amount of H2PdCl4 in the reaction. By this way, we obtained three kinds of metallic nanostructures with different morphologies.3.The performance of three Au@Ag-Pd trimetallic nansructures on the electrocatalytic oxidation of methanol were investigated by comparing with the traditional commercial Pd black electrode. It was found that the three nanostructures have good catalytic activity on the electrocatalytic oxidation of methanol.