Preparation and Characterization of Platinum/Ceria-based Catalysts for Methanol Electro-oxidation in Alkaline Medium
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Preparation and Characterization of Platinum/Ceria-based Catalysts for Methanol Electro-oxidation in Alkaline Medium Christian L. Menéndez1 Ana-Rita Mayol2 and Carlos R. Cabrera1,3 1
University of Puerto Rico, Rio Piedras Campus, Chemistry Graduate Program, PO Box 23346, San Juan, PR, 00931-3346, U.S.A. 2 Institute for Functional Nanomaterials, University of Puerto Rico, Rio Piedras Campus, PO Box 23346, San Juan, PR 00931-3346, U.S.A. 3 Center for Advanced Nanoscale Materials, University of Puerto Rico, Rio Piedras Campus, PO Box 23346, San Juan, PR 00931-3346,U.S.A. ABSTRACT Platinum/Cerium oxide-based catalysts for methanol electro oxidation were prepared by the occlusion deposition technique. Composite glassy carbon (GC) electrodes were modified and then tested towards the methanol electro oxidation half reaction in acid and alkaline medium. Cyclic voltammetry and chronoamperometry techniques were used to test the catalytic response of the composite electrodes. AFM studies were carried out in order to have a measurement of the particle size and distribution of the platinum/ceria catalyst on HOPG.
INTRODUCTION The conversion of the chemical energy of alcohols into electricity has been carried out using two basic types of fuel cells: alkaline and acidic. The commercialization of acidic-type fuel cells still remains as a problem due to the large amount of platinum required to obtain good performance. The use of alkaline-type fuel cells is more promising because the catalytic activity to the methanol oxidation reaction is higher[1]. In most of the investigations about fuel cells methanol is used as a fuel. The principal reason of this is because of the big energy density associated with this alcohol (6 kWhKg-1), the low cost of the alcohol and the easy storage and transportation in comparison with other fuels as hydrogen gas. In addition, methanol is the shortest alcohol and its oxidation is more feasible than for other alcohols since methanol does not have C-C bonds [2]. The use of alkaline medium in fuel cells technology has increased due to its higher stability and efficiency, versatility of materials and catalysts for the electrodes and more efficient reactions at the cathode and the anode. The electro oxidation of methanol in alkaline medium has made possible the use of nickel as catalysts [3]. To this day, Pt-Ru is the most efficient and stable catalyst for methanol electro oxidation at low temperature fuel cells. This is the reason why different bimetallic combinations of catalysts with
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non noble elements have been studied and tested in order to enhance the catalytic activity of methanol electro oxidation [4]. Cerium oxide is one of the most used rare earth oxide catalysts due to its good efficiency to oxidize carbon monoxide. Pt-CeO2/CNTs (carbon nanotubes) catalysts have been prepared and compared their efficiency towards the methanol electro oxidation with Pt only supported on CNTs. Results obtained indicate that CeO2 can significantly increase the catalytic activity of Pt for this reaction [5]. We
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