Different anode catalyst for high temperature polybenzimidazole-based direct ethanol fuel cells Jose ´ J. Linares 1 , Thairo A. Rocha, Sabrina Zignani, Valdecir A. Paganin, Ernesto R. Gonzalez* Instituto de Quı´mica de Sa ˜o Carlos, Universidade de Sa ˜o Paulo, Av. Trabalhador Sa ˜o-Carlense, 400 CP 780, CEP 13560-970 Sa ˜o Carlos, SP, Brazil article info Article history: Received 28 February 2012 Received in revised form 21 June 2012 Accepted 29 June 2012 Available online 25 July 2012 Keywords: DEFC Bimetallic catalysts PBI Cell performance Product distribution abstract Five different bimetallic catalyst formulations (PtRu/C, PtSn/C, PtW/C, PtRh/C and PtOs/C) were prepared by reduction with sodium borohydride, and physico-chemically charac- terized by X-Ray Diffraction, Transmission Electron Microscopy, Temperature Programmed Reduction and X-Ray Photoelectron Spectroscopy. It was observed that in the case of the PtRu/C and PtRh/C a large fraction of the second metal enters the platinum lattice struc- ture. The remaining metal, and in those catalysts in which no alloy was formed, its deposition was in a mixed metallic (Os) and/or oxide form, as TPR and XPS results dis- played. Crystal sizes were in the range 3e5 nm, except for the case of the PtW/C in which there was a large agglomeration of platinum particles, as the TEM images confirmed. Electrochemical half-cell tests demonstrated the better performance of these bimetallic catalysts in terms of ethanol oxidation, with lower onset potential and larger current densities, particularly in the case of the PtOs/C, PtRu/C and PtRh/C materials, and to a lower extent in the case of the PtSn/C. Actual fuel cell tests at high temperature (150 and 200  C) confirmed the beneficial effects of increasing the temperature in terms of cell performance, with an increase in the performance, particularly in the cases of PtOs/C and PtRu/C. Finally, the product distribution was also assessed, observing a large conversion to CO 2 by oper- ating at high temperatures, particularly for PtRh/C at low current density, and for Pt/C at high current density (up to 35%), although acetaldehyde remained as the main oxidation product for all the catalysts. Copyright ª 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction Direct ethanol fuel cells (DEFCs) are an interesting alternative to traditional H 2 -based Polymer Electrolyte Membrane Fuel Cells (PEMFCs) [1]. This interest stems from the intrinsic advantages of ethanol as fuel: (i) non-toxicity, (ii) natural availability (from biomass), (iii) renewability, (iv) high power density (8 kWh kg 1 ), and (v) small green-house contribution to the atmosphere [2,3]. The much higher volumetric energy density (22.11 MJ m 3 vs. 2.531 MJ m 3 for compressed H 2 at 250 bar) defined an ideal scenario, further supported by other advantages such as the safer and easier handling, trans- portation and storage [4]. However, there are severe limita- tions in the development of the DEFC technology when * Corresponding author. Tel.: þ55 1633739899; fax: þ55 1633739903. E-mail address: Ernesto@iqsc.usp.br (E.R. Gonzalez). 1 Current address: Instituto de Quı ´mica, Universidade de Brası ´lia, Campus Darcy Ribeiro CP 04478, CEP 70910-000, Brazil. Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 38 (2013) 620 e630 0360-3199/$ e see front matter Copyright ª 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijhydene.2012.06.113