Synthesis,Electrocatalytic Property And Application Of Novel-type Carbon Materials Supported PtRu Catalyst

Fuel cells are regarded as a novel type of energy conversion devices with low emission even no emission and high power density, which have attracted great interest of scientists. Though fuel cells have been investigated over160years, the anode dynamic constraints and high price are still the challenges for the commercialization. Developing carries with unique structure and Pt-based bimetal nanoparticles aiming to prepare high performance of supported Pt-based catalysts is one of the main ways to solve the problem. Novel carbon materials, such as carbon nanotubes, graphene and so on, provide a wider range choice of carrier materials. For carbon nanotubes, their unique one-dimensional structure, excellent electrical conductivity and special physicochemical properties have attracted increasing interests from the scientific workers. However, due to a lack of defect sites and functional groups, the original carbon nanotubes are not suitable for supporting nanoparticles. Likewise, graphene is a kind of newly carbon materials which has two-dimensional large specific surface area, high young’s modulus and good thermal conductivity properties. During the reduction progress of graphene oxide(GO), the monolayer or few layers reduced graphene sheets occurs irreversible aggregation owing to the Van der Waals force between the adjacent graphenes, resulting in an obvious reduction on its physical and chemical performance, especially lessen its specific surface area. Functionalization is one of common and effective solutions to overcome the drawback of these new carbon carriers. After functionalization, carbon nanotubes and graphene materials are not only increased the number of functional groups and defect sites, but also improved the specific surface area and electrical conductivity. In terms of methanol oxidation reaction, PtRu nanoparticles (PtRu NPs) have always been considered as the best precious metal materials. Especially recent years, seeking a clean, efficient, environmentally and large-scalable synthetic method for preparing nanocatalysts is more and more important as energy and environmental problems have become hot spot problems. In this thesis, we successfully realized the functionalization of multi-walled carbon nanotubes (MWCNTs) and graphene, and then in situ loaded PtRu nanoparticles by microwave irradiation assisted with ethylene glycol (EG) reduction. Main research contents are as follows:1. PtRu/MWCNTs systemFirstly, we prepared the catalysts with PtRu NPs (PtRu/MWCNTs) or Pt NPs (Pt/MWCNTs) supported on the acidified MWCNTs as well as pure phase of PtRu without carrier, and all these three catalysts were characterized by TEM, XRD, EDS and so on. Then, catalytic properties of these samples for methanol catalysis were explored by the cyclic voltammograms,I-t curves and CO-tolerance test. The PtRu/MWCNTs has been optimized by controlling the Pt/Ru ratio in the range of2:1,1.5:1,1:1and1:1.5. At last, the catalyst of PtRu/MWCNTs was tested in the direct methanol fuel cells (DMFCs) and compared with commercial PtRu/C (E-TEK) The out power density of PtRu/MWCNTs was121mW/cm2at80℃, indicating a superior performance.2. PtRu/NGA systemFirst, the graphene aerogel (GA) and nitrogen doped graphene aerogel (NGA) with good physical and chemical properties (porosity, good electrical conductivity and operability, etc) were prepared by a hydrothermal synthesis method. The PtRu/GA and PtRu/NGA catalysts were synthesized by in situ loading PtRu nanoparticles. The samples were characterized by SEM, TEM, XPS, etc. Then, catalytic performance of these samples were investigated by the cyclic voltammograms, chronoamperometry and CO-stripping voltammograms. By controling the nitrogen content of carriers and pH value in the process of synthesis, the catalytic properties of PtRu/NGA have been optimized. Finally, we obtained the free-standing catalytic layer by physical press method. The DMFC was fabricated by using the free-standing materials as anode catalytic layer. The output power density of PtRu/NGA device was93mW/cm2at90℃, which is better than the commercial catalvst device.