Metal Oxides as Catalyst Promoters for Methanol Oxidation
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Metal Oxides as Catalyst Promoters for Methanol Oxidation Praveen Kolla1, Kimberly Kerce2, Hao Fong2 and Alevtina Smirnova2 1 Material Engineering Science Program and 2Department of Chemistry, South Dakota School of Mines and Technology, Rapid City, SD 57701, U.S.A. ABSTRACT The Transition metal oxides such as TiO2 and CeO2 as catalyst and co-catalyst materials were studied for methanol oxidation. The metal oxide nanoparticles were impregnated into carbon aerogel and Pt-Ru/C (Tanaka) by modified sol-gel Pechini method and heat-treated at different temperatures. Crystal structure, particle size and composition of the catalyst particles were studied using XRD, TEM and EDS techniques. The electrochemical activity and stability of these catalyst materials were studied in acidic medium and the results were compared to their corresponding specific and active surface areas. The aerogel supported metal oxides were stable and proved for better methanol oxidation, while a significant synergetic effect in electrooxidation is observed when the metal oxides were impregnated into the structure of Pt-Ru/C catalyst. The methanol-oxidation was further improved after heat treatment due to its improved structural and surface properties. INTRODUCTION Direct Methanol Fuel Cells (DMFC) is a PEMFC system, which uses renewable methanol as fuel. The high specific-energy density of methanol fuel will greatly simplifies the storage complications associated with hydrogen/air systems and mobility problems with rechargeable battery based portable electronic devices [1]. However, slower anode kinetics, COpoisoning, chemical instability of catalyst in acidic environment and methanol crossover to cathode side are some of the challenges to DMFC commercial viability. At this point, cost reduction through exploration of noble and non-noble metal based anode catalysts, development of more stable and conductive carbon supports, and alloying approach are the current R&D strategies [2]. Some metal oxides are known to show electrochemical catalytic activity because of metal ability to switch between different valences. These metal oxides are also known to exhibit metallike conductivity when partially filled d- and f-bands are available [3]. While Pt-Ru based materials are well known as anode catalysts for methanol oxidation, recent efforts have been focus to promote these catalysts with non-noble metal oxides for better stability and for enhanced oxidation of methanol and CO [4-7]. Advancements in the nanomaterials lead to the development of more stable and highsurface area hybrid-carbon fuel cell supports. Carbon aerogels supports are commercially feasible materials for its scalability of its fabrication and simple catalyst impregnation methods [8]. However, the efficient utilization of catalyst is possible through optimization of these materials in terms catalyst dispersion, electrochemical surface area and pore size distribution for different impregnation methods [2]. In this regard, carbon aerogel supported transition metal oxide catalysts and metal ox
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