| The support material for catalysts, which is highly desirable to distribute and stabilize the catalyst particles in the catalytic system, has been of great interest in recent years. The supporting material of catalysts could make the catalysts not only obtain optimum utilization also reduce the use of precious metals, and thus will reduce catalyst costs. Highly dispersed precious metals on carbon black (Vulcan XC-72) are used as electrocatalyst for small organic molecular oxidation and oxygen reduction reaction (ORR) in proton exchange membrane fuel cell (PEMFCs). However, carbon support is prone to suffer from physical and chemical degradation, as well as carbon corrosion, under prolonged operation at high temperatures, high water content, low pH, high oxygen concentration, existence of the Pt catalyst and/ or high potential. Hence, to search for novel support containing carbon materials is very important through modern advance in nanoscience and nanotechnology.Some researchers have found modifying the surface of carbon support with semiconducting oxides,is an effective way to promote the electrocatalytic activity and stability of catalysts for small organic molecular oxidation and oxygen reduction reaction. It is known that the nitrogen-doped carbon (CNx) show n-type or metallic behavior and have greater electron mobility. CNx with metal catalysts or without metals on them have shown enhanced catalytic activity. Nitrogen incorporation could efficiently introduce chemically active sites into the carbon for use in catalytic reactions and metal nanoparticle anchoring.To match this requirements, we have focused on the preparation of CNx coated oxide by carbonizing polypyrrole (PPy) coated oxide, and heat-treated PPy was as shell-coating and sources of CNx for supports. The new catalysts are found to exhibit high electrocatalytic activities, good stabilities and durability during recation. The structural and chemical properties of samples were characterized by Fourier-Transform infrared, thermogravimetric analysis, X-ray diffraction (XRD), and transmission electron microscopy (TEM), etc. Additionally, the catalysts were tested in a micro fuel cell system by measuring the performance of ORR and formic acid oxidation, which were made from our lab-made catalysts. It was found that these catalysts showed quite good activity for ORR and formic acid oxidation in polymer fuel cells. The thesis is consists of three parts and the research details are as follows:Partâ… : Nitrogen-doped carbon coated palygorskite as an efficient electrocatalyst support for oxygen reduction reactionAn electrocatalyst support, nitrogen-doped graphitic layer (CNx) coated palygorskite (PLS) (donated as PLS@CNx), is synthesized by carbonizing the polypyrrole (PPy) coated PLS and is explored for the first time as a cathode electrocatalyst support in proton exchange membrane fuel cell. The structural and chemical properties of the PLS@CNx are investigated using Fourier-Transform infrared, thermogravimetric analysis, X-ray diffraction and transmission electron microscopy. The electrocatalytic activity and stability of Pt/PLS@CNx towards oxygen reduction reaction (ORR) are studied by cyclic voltammetry (CV) and steady state polarization measurements. Upon loading 20% Pt metal, the catalysts exhibit superior catalytic performance during ORR, surpassing the conventional Pt/C (Vulcan XC-72) catalysts. High electrocatalytic activity and good stability can be attributed to the nitrogen atom incorporation and SiO2 composition in PLS.Partâ…¡: CNx Modified Fe3O4 as Pt Nanoparticles Support for Oxygen Reduction ReactionFe3O4-CNx, which exhibit the advantages of enhanced catalytic activity and stability were employed as an alternative support material for Pt nanoparticles for oxygen reduction. The activity of Pt/Fe3O4-CNx toward oxygen reduction is comparable to commercial Pt/C. The durability and activity of Pt/Fe3O4-CNx is greatly enhanced than that of commercial Pt/C. The enhanced Pt-carbon interaction from N element and Fe3O4 in the support, these are attributed to the activity and stability of the support for Pt loading. The findings indicate that Fe3O4-CNx is a promising, activity, and durable electrocatalyst support for oxygen reduction in fuel cells.Partâ…¢: CNx modified Fe3O4 as support to immobilize Pd nanoparticles for oxidation of formic acid A new kind of carbon nitride (CNx) modified Fe3O4 (Fe3O4-CNx) has been prepared by the carbonizing of polypyrrole modified Fe3O4 at 800℃. The product is coraline-like morphology after calcination, and the pyrrolic nitrogen in the polypyrrole gradually changed to pyridinic and graphitic nitrogen as annealing temperature increased. Polygon Pd nanoparticles with sizes of 7–11 nm are well dispersed on carbon nitride Fe3O4. Attributed to the nitrogen atom incorporation and Fe3O4, the Pd/Fe3O4-CNx catalysts show the higher activity and better stability towards the anodic oxidation of formic acid than commercial Pd/C or Pt/C catalyst.
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