Direct chemical deposition of platinum on ionic conductive membranes and evaluation of the electrocatalytic activity M. Weissmann a , C. Coutanceau a, * , P. Brault b , J.-M. Le ´ger a a UMR 6503, CNRS – Universite ´ de Poitiers, Equipe Electrocatalyse, 40 Avenue du Recteur Pineau, 86022 Poitiers Cedex, France b Groupe de Recherche sur l’Energe ´tique des Milieux Ionise ´s, UMR 6606 Universite ´ d’Orle ´ans – CNRS Polytech’Orle ´ ans BP6744, F-45067 Orle ´ans Cedex 2, France Received 28 November 2006; received in revised form 18 December 2006; accepted 3 January 2007 Available online 11 January 2007 Abstract Direct chemical deposition of platinum at different polymer electrolyte membranes for a fuel cell application was studied. The devel- oped method allows depositing platinum on acid and alkaline membranes. The depositions realized under different experimental condi- tions were characterized by RBS (Rutherford backscattering spectroscopy) and TEM (transmission electron microscopy) to determine the depth profile in the membranes and the mean size of platinum particles. The active surface area of the catalysts and the related par- ticle size were characterized by cyclic voltammetry. Results indicated that a part of platinum was deposited inside the membrane. Rough- ness as high as 500 could however be achieved. Oxygen reduction reaction under working conditions close to those of a fuel cell cathode was studied to draw some kinetic data. Ó 2007 Elsevier B.V. All rights reserved. Keywords: Direct deposition; Platinum; Solid polymer electrolyte; Fuel cell; Oxygen reduction 1. Introduction Nafion Ò membranes are commonly used in PEMFC [1– 4]. They allow hot pressing of Nafion Ò containing elec- trodes, optimising the membrane–electrode interfaces [5]. Moreover, it has recently been shown that the presence of Nafion Ò in the catalytic layer of the cathode leads to increase the kinetics of the oxygen reduction reaction [6]. However, they also display several limitations: the cross- over of reagents [7,8], the low working temperature range (lower than 100 °C) and their super acidity (making for example impossible to circumvent platinum to initiate the C–H bond cleavage in the first adsorption steps of alcohol in the case of Direct alcohol fuel cells [9]). Moreover, the three-phase reaction zone is not effective for all platinum nanoparticles [10–12]: a part of platinum is not in contact with the electrolyte, decreasing the catalyst utilization efficiency. The development of new polymer electrolyte mem- branes and/or methods of membrane electrode assemblies (MEAs) fabrication can help to overcome these limita- tions. In that case, direct deposition of catalysts on the membrane surface can represent an alternative method to increase the electrolyte/catalyst interface. Plasma sput- tering [12,13] and chemical platinization of Nafion Ò mem- brane by impregnation-reduction method [14] were already proposed for this purpose. In this work, the plat- inum deposition method derived from that of Takenaka et al. [15] for solid polymer electrolyte water electrolysis applications is considered. This method, which is expected to lead to an increase of the platinum utilization efficiency, was applied to both acid and alkaline mem- branes. After physical and electrochemical characterisa- tions of the depositions, their activity and related kinetic data towards the oxygen reduction reaction were evaluated. 1388-2481/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.elecom.2007.01.008 * Corresponding author. Tel.: +33 5 49 45 48 95; fax: +33 5 49 45 35 80. E-mail address: christophe.coutanceau@univ-poitiers.fr (C. Coutan- ceau). www.elsevier.com/locate/elecom Electrochemistry Communications 9 (2007) 1097–1101