from first principles PP-I-1

OP-V-1Controlled Synthesis of Pt 3 Sn/C Electrocatalysts with Exclusive Sn-PtInteraction Designed for Use in Direct Methanol Fuel CellsBorbáth I., Gubán D., Pászti Z., Sajó I., Tompos A.Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences,Hungarian Academy of Sciences, Budapest, PO.B. 17, H-1525 Hungaryborbath.irina@ttk.mta.huHigh resistance to CO is one of the criteria for the preparation of efficient alcoholelectrooxidation catalysts. Pt-Sn bulk alloys are among the most studied bimetallic systemsfor fuel cell application [1]. Exclusive formation of supported Sn-Pt alloy phases withdifferent Sn/Pt ratios can be achieved by using Controlled Surface Reactions (CSRs) betweenhydrogen adsorbed on Pt sites and tetraethyltin [2]. The presence of Sn decreases not only thetotal number of exposed Pt atoms but also the number of extended Pt ensembles, required onthe early stages of the methanol oxidation for methanol adsorption-dehydrogenation reaction.The possibility to find such Pt ensembles decreases with the increasing Sn/Pt ratio. In goodaccordance with this, in our recent study, it was demonstrated [3] that the performance ofPt 3 Sn (fcc) phase is superior to that of the PtSn (hcp) phase for both CO and methanolelectrooxidation reactions. Nevertheless, the promotional effect of Sn for the electrooxidationof CO ad is to provide the necessary OH ad species at less positive potentials than on Pt.Efforts were made to adjust synthesis parameters in order to prepare carbon supported Pt 3 Sn(fcc) alloy phase exclusively. As demonstrated by X-ray diffraction, the amount of the Pt 3 Snphase can be controlled by tuning the conditions of CSRs. Results of XPS after in situtreatment in H 2 at 350 o C showed that the modification of Pt/C catalyst with Sn(C 2 H 5 ) 4 leadsto exclusive formation of Sn-Pt alloy phase without tin introduction onto the carbon support.Thus, the bimetallic catalysts prepared displayed an outstanding performance in both the COand methanol electrooxidation reactions. Upon addition of tin, the onset potential of COoxidation was shifted by 500 mV to more negative potentials, which indicate significantimprovement in CO-resistance of tin-modified sample in comparison to the Pt/C catalyst.References:[1] S. García-Rodríguez, F. Somodi, I. Borbáth, J.L. Margitfalvi, M.A. Peña, J.L.G. Fierro, S. Rojas,Appl. Catal. B: Environmental 91 (2009) 83-91.[2] J.L. Margitfalvi, I. Borbáth, M. Hegedűs, A. Tompos, Appl. Catal. A: General 229 (2002) 35-49.[3] T. Herranz, S. García, M.V. Martínez-Huerta, M.A. Peña, J.L.G. Fierro, F. Somodi, I. Borbáth,K. Majrik, A. Tompos, S. Rojas, Int. J. Hydrogen Energy 37 (2012) 7109-7118.83