Precious Metal Core-shell Structure Nanoparticle Catalysts Photochemical Synthesis And Its Methanol Anodic Oxidation Catalytic Properties

In recent years, bimetallic nanoparticles for precious metals are of great interest due to their unique structure, properties of optical, electrical, catalytic and application in the fields of energy, environment, biomedical, and so on.Fuel cell is one of the most important energy power in the 21st century. Direct methanol fuel cell (DMFC) and proton exchange membrane fuel cell (PEMFC), et al are types priority development. Catalysts for direct methanol fuel cell become a research hotspot because of there is a large amount of Pt and catalyst poisoning problems easily and so on.And electrocatalysts of DMFC and PEMFC is the main application research directions of bimetallic nanoparticles for precious metals.From the current situation, Pt-based catalysts are low temperature fuel cells are still the subject field. As the scarcity of Pt, Pt-based catalysts will be more expensive, low-Pt supported catalyst technology has almost reached the limit of low load. On the other hand, non-platinum catalyst is still at the exploratory stage, the preparation process, stability and catalytic properties such as to achieve practical application; there is still a long way to go. Anode electrocatalysts of DMFC catalysts will be depends on the precious metals in a long period of time. based on Pt-base catalysts in the original theory, the new development of new low-cost, high-performance fuel cell electrocatalysts is necessary.This thesis was designed to dissimilar metals relatively cheap (relatively speaking Pt) for nuclear, Pt nanoparticles for the composite shell. Pt utilization while improving the synergy of two precious metals, precious metal composite nanoparticles to double the electrical activity greatly increased.The master's thesis, photochemical reduction in the PEG-acetone system, respectively, sodium citrate-acetone-ethanol system synthesized Au core@ Pt shell and Pd@Pt core-shell composite nanoparticles, and the synthesis of nano-particle size, morphology, and structure for a more detailed characterization. According to experimental results and the fine structure of the composite nanoparticles were characterized, discussed the growth mechanism of composite particles.The synthesis of the above Pd shell@ Pt core shell composite nanoparticles as catalytic materials, composite nanoparticles loaded in the XC-72 carbon black carrier, the preparation of Pd-core@ Pt Shell/C catalyst. After cyclic voltammetry (CV) and time-current (IT) testing shows that the two types of catalysts for methanol oxidation have high catalytic activity and good stability. The composite catalysts of high activity was a brief discussion on the mechanism that has been checked Pt metal shell is prepared to promote the role of the main reasons for high activity catalyst.The main conclusions are as follows:1. (1) Sodium citrate-acetone-ethanol system to photochemical reduction while reducing or continuous reduction of Au (Ⅲ), Pt (Ⅳ) ion can be synthesized relatively uniform particles with good monodispersity of the Au @ Pt core Shell Nanoparticles average size of 5.1 nm～10.2 run. in the PEG-acetone system, the photochemical reduction of Pd (Ⅱ), Pt (Ⅳ) ions or mixture of Pt (Ⅳ) in the presence of Pd seed growth technique can be synthesized uniform size monodisperse Pd@ Pt core-shell composite nanoparticles. By changing the Pd (Ⅱ) or Pd (0) on the Pt (Ⅳ) ion molar ratio of composite particles can regulate the size and thickness of Pt shell access to the particle diameter in the range of 4.1 to 2.9 and 5.3～7.1 nm.2. Experiments on the synthesis of the Au@ Pt core shell and Pd core@ Pt shell composite nanoparticles, morphology, dispersion and other characterization, which confirmed its core-shell composite structure.by UV-Vis absorption spectroscopy, TEM/HR-TEM, XPS synthesized were characterized composite nano-particle formation mechanism of simple research.3. Electrochemical analysis shows that:from the synthesis of Pd@ Pt nanoparticles prepared by double metal catalysts for methanol oxidation has a high activity; Pd Pt shell has a role in promoting reconciliation, so as to enhance the Pd@ Pt core shell composite Nanoparticles of the electrical activity of methanol oxidation; Pd@ Pt core shell nanoparticles are more sensitive to temperature, with increasing temperature catalytic activity than pure Pt catalyst for more deadly accuracy; small size and continuous, complete Pt Pd shell may facilitate nuclear@ Pt shell nanoparticles of the high catalytic activity.