JOURNAL OF SUSTENABLE ENERGY, VOL. 1, NO. 1, MARCH, 2010 I.S.S.N. 2067-5538 © 2010 JSE NEW NANOHYBRIDE CATHALYTIC SYSTEMS FOR OXYGEN REDUCTION IN RENEWABLE FUEL CELLS BANU A.*, MARCU M.**, TEODORESCU V.*** *Politehnica University from Bucharest, Splaiul Independentei 313, Bucuresti, a_banu_2000@yahoo.com , **Institute of Physical Chemistry, Splaiul Independentei 202, Bucuresti, m_marcu2000@yahoo.com , ***National Institute of Physics of Materials, Atomiştilor 105bis, 077125 Bucharest-Măgurele Abstract - Electrocatalytic oxygen reduction (ORR) has become the focus of considerable attention due of its slow kinetics and the need for better electrocatalysts for fuel cell cathodes in the recent years. In recent publications some results have been reported on the electrocatalytic activity of carbon supported polypyrrole (Ppy), polyaniline (Pani) and poly(3- methylthiophene) (P3MT), modified with cobalt or nickel salts. For these conductive polymer samples, the oxygen reduction occurred at high negative overpotential, since the polymer needs to be in reduced state before catalytic activity can be observed. In most of the cases the addition of cobalt or nickel in the composite, results in an improvement in electrocatalytic activity and a shift to electropositive values for the ORR potentials. In this work the hybrid materials based on polypyrrole and cobalt-nickel oxide were studied as oxygen reduction catalysts. Polypyrrole was electropolimerized on carbon black and stainless steel supported materials and modified with nickel and nickel- cobalt oxide nanoparticles. TEM and SEM images show porous materials with a particle size 30 to 200 nm and EDAX test confirmed the presence of NiO and CoNiO nanoparticles into composite materials. Key words: renewable fuel cells, Polypyrrole, ORR, nickel cobalt oxide, nanocomposite 1. INTRODUCTION In recent years the development of fuel cells has taken fast advances. These systems use hydrogen and oxygen to produce electricity at high efficiency and with zero emission. Conventional fuel cells catalysts are based on carbon-supported platinum and some of its alloys. In the cathode, the catalyzed reaction is the Oxygen Reduction Reaction (ORR) [1-3]. This reaction is relatively slow, compared to the hydrogen oxidation reaction (HOR) in the anode and contributes up to 80% of the total loss in fuel cell performance [4]. The challenge is to substitute these precious metals for more abundant, cheaper and highly stable materials, diminishing the overpotential for the ORR [5,6].New polymeric electrocatalysts for the ORR have been reported based on conductive polymers [7], conducting polymers doped with heteropolyanions and metallic complex [8,9], and polymers modified with precious metals [10]. In recent publications have been reported on the electrocatalytic activity of carbon supported polypyrrole (Ppy), polyaniline (Pani) and poly (3-methylthiophene) (P3MT), modified with cobalt or nickel salts [11,12]. For these conductive polymer samples, the oxygen reduction occurred at high negative overpotential, since the polymer needs to be in reduced state before catalytic activity can be observed [7]. In most of the cases the addition of cobalt or nickel in the composite, results in an improvement in electrocatalytic activity and a shift for the ORR potentials. The paper, presents the preliminary results concerning the structural and electrochemical behavior of carbon and stainless steel supported polypyrrole modified with nickel-cobalt and nickel oxide for ORR. 2. EXPERIMENTAL Were used two types of materials as a support for electrochemical deposition of Ni and Ni-Co oxides in polypyrrole matrix: a 17%Cr ferritic stainless steel (SS) and carbon (C) sheets. Before electrodeposition, the sample’s surfaces were mechanical prepared by polishing with emery paper, washed and ultrasonically cleaned with ethanol and distilled water for 10 minutes. All used solutions were prepared with bidistilled water and analytical-reagent grade substances (Aldrich Fluka). As a disperse phase were use Aldrich-Fluka NiO and NiCoO nano powders. The electrochemical experiments were performed with a PAR 273A potentiostat in a conventional three- electrode cell, by using a platinum auxiliary electrode (~ 3 cm 2 ) and an Ag/AgCl reference electrode, linked to the main compartment of the cell by means of a Vycor glass junction. The measurements were performed at room temperature (25°C) in normal aerated condition and under argon pressure. Electrochemical deposition of polypyrrole was carried out on electrodes substrate from a 0.2 M oxalic acid aqueous solution containing 0.1 M pyrrole. The Pyrrole/oxide mixing ratio was 30% (weight percents) related to oxidic phase.