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Fuel Cell Electrodes Based on Carbon Nanotube/Metallic Nanoparticles Hybrids Formed on Porous Stainless Steel Pellets

DOI: 10.1155/2013/157098

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Abstract:

The preparation of carbon nanotube/metallic particle hybrids using pressed porous stainless steel pellets as a substrate is described. The catalytic growth of carbon nanotubes was carried out by CVD on a nickel catalyst obtained by impregnation of pellets with a highly dispersive colloidal solution of nickel acetate tetrahydrate in ethanol. Granular polyethylene was used as the carbon source. Metallic particles were deposited by thermal evaporation of Pt and Ag using pellets with grown carbon nanotubes as a base. The use of such composites as fuel cell electrodes is discussed. 1. Introduction Fuel cells are electrochemical sources of current in which the chemical energy of the fuel is directly transformed to the electrical energy through the redox chemical reactions proceeding at catalytic electrodes [1, 2]. The good properties of the catalyst support, such as high surface area, low resistance, and high mechanical strength and chemical stability, are essential for catalytic electrodes. The use of carbon nanotubes (CNTs) as a support for catalytic materials is the promising method to prepare novel high efficient electrodes for fuel cells [3–5]. The surface area of carbon nanotubes varies from 500?m2 per gram for the multiwall nanotubes to 1500?m2 per gram for the single wall nanotubes. Chemical vapor deposition (CVD) is one of the methods by which the carbon nanotubes can be obtained [6–8]. 3d-group metal particles (Fe, Co, and Ni) deposited on different substrates are usually used as catalysts for CNTs growth. Due to their low cost, high strength, and corrosion resistance, stainless steels are considered to be good candidates as substrates used in polymer electrolyte membrane (PEM) fuel cell [9]. Traditionally, a single PEM fuel cell consists of few major components: membrane, catalyst, catalyst support, catalyst layer, gas diffusion layer, and current collector. In this paper, experiments on carbon nanotube growth on porous pellets prepared from stainless steel powders and direct deposition of catalytic metallic particles of Pt and Ag on carbon nanotubes obtained at given substrates are presented. The advantage of this approach implies that after CNTs’ growth on porous pellets followed by carbon nanotubes decoration by catalytic nanoparticles, this hybrid structure represents the fuel cell material in which three functions are combined: catalytic electrode, gas diffusion layer, and current collector. 2. Materials and Methods The pellets were pressed from commercially available stainless steel (russian type X23H18) powders. The pellets obtained were

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