171 1. INTRODUCTION Mechanical alloying is an interesting high energy process for the preparation of a lot materials and specially amorphous alloys, which can be applied as electrodes in electrochemical energy con- version. Fuel cells, mainly direct methanol fuel cells (DMFCs) and polymer electrolyte membrane fuel cells (PEMFCs), are up to now one of the most attractive areas of research because they represent an important environmentally clean and friendly energy source [1- 5]. Worldwide interest in clean energy generation systems has motivated research on the synthesis, characterization and evalua- tion of novel and stable oxygen reduction electrocatalysts for the direct four-electron transfer process to water formation [6-8]. In electrocatalysis, the oxygen reduction reaction, ORR, is a kineti- cally slow electrochemical reaction and it leads to higher reduction overpotential, due to the fact that the oxygen-oxygen bond (O-O) in the dioxygen molecule requires higher bond dissociation energy than other molecules. One of the targets on the cathode electrode is to reduce the platinum content in the PEM fuel cell, increasing or maintaining the electrocatalytic performance with stability for a long time. Bimetallic and alloy catalysts have been a particularly active area of research because of the established fact that for the cathode reaction, multi-metallic surfaces have superior activity compared to pure platinum. The aim of this work is to investigate the kinetics of the oxygen reduction reaction (ORR) in 0.5M H 2 SO 4 on Ni 59 Nb 40 Pt 0.6 Ru 0.4 (PtRu), Ni 59 Nb 40 Pt 0.6 Sn 0.4 (PtSn) and Ni 59 Nb 40 Pt 0.6 Ru 0.2 Sn 0.2 (PtRuSn) amorphous catalysts synthesized by mechanical milling following a procedure previously reported [3,9-11]. The use of amorphous materials arises primarily because of its corrosion resistance due to there is no grain boundary be- tween the metallic elements. Studies have been reported showing that alloy materials present catalytic activity towards ORR, where amorphous catalysts were tested as carbon paste electrodes [9,10]. In this work ink-type thin-film electrodes were used and the elec- trochemical studies were performed by cyclic voltammetry (CV) and rotating disk electrode (RDE). After the electrochemical analysis were carried out, the study of the prepared amorphous alloys as cathodes electrocatalysts was performed in a membrane- electrode assembly (MEA) of a single polymer electrolyte fuel cell, as a complimentary part of this work. *To whom correspondence should be addressed: Email: rosgonzalez_h@yahoo.com.mx Phone: 57296000, ext. 55392 Amorphous Metallic Alloys for Oxygen Reduction Reaction in a Polymer Electrolyte Membrane Fuel Cell R. Gonzalez-Huerta 1,* , I. Guerra-Martinez 1 , J. Santiago Lopez 1 , A.R. Pierna 2 and O. Solorza-Feria 3 1 Instituto Politécnico Nacional, ESIQIE, Laboratorio de Electroquímica, UPALM, Ed.7, 07830, México D.F. Mexico 2 Chemical Engineering and Environment Department. University of the Basque Country, Plaza de Europa, 20018 San Sebastián. Spain 3 Depto. Quíımica, Centro de Investigación y de Estudios Avanzados del IPN, A. Postal 14-740, 07360 México, D.F. Mexico Received: November 20, 2009, Accepted: February 27, 2010 Abstract: Amorphous alloyed compounds have been used as electrode materials in electrochemical energy conversion devices. An inter- esting and important goal for their applications in polymer electrolyte membrane fuel cells is the optimization of the electrocatalysts load- ing in the membrane electrode assemblies (MEAs). Kinetics of the oxygen reduction reaction (ORR) on Ni 59 Nb 40 Pt 0.6 Ru 0.4 , Ni 59 Nb 40 Pt 0.6 Sn 0.4 and Ni 59 Nb 40 Pt 0.6 Ru 0.2 Sn 0.2 amorphous catalysts synthesized by mechanical milling were investigated in 0.5M H 2 SO 4 at 25°C. The electro- catalytic activity of ink thin-film type electrodes evaluated by cyclic voltammetry (CV) and rotating disk electrode (RDE) showed that the Ni 59 Nb 40 Pt 0.6 Sn 0.4 amorphous electrocatalyst was the most active from the three electrodes for the cathodic reaction. Fuel cell experiments were conducted at various temperatures at 30 psi for H 2 and at 34 psi for O 2 . MEAs fabricated using Nafion ® 115 membrane and amor- phous Ni 59 Nb 40 Pt 0.6 Sn 0.4 dispersed on carbon powder was tested as cathode electrocatalyst (1 mg cm -2 ) in a single polymer electrolyte membrane fuel cell, generating a power density of 156 mW cm -2 at 0.43V and 80°C. Keywords: Amorphous alloy, Electrocatalyst, Oxygen reduction, Fuel Cell. Journal of New Materials for Electrochemical Systems 13, 171-176 (2010) © J. New Mat. Electrochem. Systems