A comparative study of carbon-supported Pt-Mo and Pt-Ru catalysts for the anodic oxidation of methanol O. Ugalde Reyes a , P. Roquero a , R. Hernández Maya a , A.L. Ocampo Flores a , and E. Sosa Hernández b a Facultad de Química, Universidad Nacional Autónoma de México. Avenida Universidad 3000, CP 04510 México D.F. b Instituto Mexicano del Petróleo. Eje Central Lázaro Cárdenas 152. CP 07730 México D.F. Different carbon–supported Pt-Mo and Pt-Ru materials were synthesized and a systematic study was carried out in order to evaluate their catalytic activity towards methanol oxidation. Direct current methods were applied in sulfuric acid and methanol – containing electrolytes, in order to evaluate the electrochemical response of the studied electrodes. Pt-Mo catalysts reveal similar performances and, in some cases, higher than Pt-Ru materials. For both catalysts series, it was found that low loadings of the promoting metal (Ru or Mo) improve the methanol oxidation activity. Characterizations by means of transmission electron microscopy and X-Ray Diffraction allowed to measure mean particle sizes below 10 nm for all phases. The Pt-Ru catalysts consist of metallic Pt and metallic ruthenium, while in the The Pt- Mo materials platinum is present in its metallic state and MoO 3 is the predominant molybdenum species. Introduction In several works it has been found that platinum – molybdenum catalysts can be used with good results in direct methanol fuel cell systems (1). Today, ruthenium is the most used element in the formulation of promoting phases in bimetallic catalysts for this purpose (2). In a direct methanol fuel cell (DMFC) the oxidation of methanol to CO 2 must take place at the anode and O 2 reduction at the cathode. The fuel is usually a liquid phase containing methanol and water, since the water molecule must provide the oxygen atom necessary for the complete methanol oxidation. The poor performance of most anodic catalysts is still a problem to overcome in order to achieve the commercial use of DMFCs (3). The platinum, which is the main active phase in these catalysts, is poisoned by formaldehyde, formic acid and, mainly, CO. These adsorbed species are produced as reaction intermediates. The transfer of the six electrons in this reaction, involving the formation of several intermediate species which adsorb strongly on the Pt surface in a wide range of potentials, results in a poor activity of platinum towards methanol electro- oxidation (4-6). Because of this, bimetallic catalysts have been proposed and tested as a means of decreasing the poisoning in the main active phase. In these materials a second active phase is sought to dissociate water and facilitate the complete oxidation of the adsorbed carbon species. Ru, Mo, W and Sn are among the most studied metals for this purpose (7-9). ECS Transactions, 36 (1) 21-28 (2011) 10.1149/1.3660595 ©The Electrochemical Society 21 Downloaded 16 Dec 2011 to 201.124.152.44. Redistribution subject to ECS license or copyright; see http://www.ecsdl.org/terms_use.jsp