Journal of Power Sources 160 (2006) 334–339 Development of materials for mini DMFC working at room temperature for portable applications C. Coutanceau a,∗ , R.K. Koffi a , J.-M. L´ eger a , K. Marestin b , R. Mercier b , C. Nayoze c , P. Capron c a Laboratoire de Catalyse en Chimie Organique, Equipe Electrocatalyse, UMR CNRS n ◦ 6503, 40 avenue du Recteur Pineau, 86022 Poitiers Cedex, France b Laboratoire des Mat´ eriaux Organiques ` a Propri´ et´ es Sp´ ecifiques, UMR CNRS – Universit´ e de Savoie n ◦ 5041, BP 24, 69390 Vernaison, France c Commissariat ` a l’Energie Atomique, Service de Conversion et de Stockage de l’Energie, Laboratoire des Sources d’Energie Miniature, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France Received 13 June 2005; received in revised form 24 January 2006; accepted 24 January 2006 Available online 10 March 2006 Abstract Methanol permeability measurements and direct methanol fuel cell tests were performed at room temperature with different commercially available or recast Nafion ® membranes and sulfonated polyimide (SPI) membranes. Power densities as high as 20 mW cm -2 could be obtained with Nafion ® 115. However, in order to meet the technological requirements for portable applications, thinner membranes have to be considered. As the MeOH crossover increases greatly (from (7 to 20) × 10 -8 mol s -1 cm -2 ) while Nafion ® membranes thickness decreases, non-perfluorinated polymers having high IEC are promising candidates for DMFC working at room temperature. The development catalysts tolerant to methanol is also relevant for this application. In spite of the low permeability to MeOH of SPI membranes, the obtained electrical performance with E-TEK electrodes based MEAs was lower than that obtained with Nafion ® membranes. No significant increase of performances was neither evidenced by using homemade PtCr(7:3)/C and PtRu(4:1)/C catalysts instead of E-TEK electrodes with recast Nafion ® based MEAs. However, MEAs composed with thin SPI membranes (50 m) and homemade PtCr/C catalysts gave very promising results (18 mW cm -2 ). Based on experimental observations, a speculative explanation of this result is given. © 2006 Elsevier B.V. All rights reserved. Keywords: Crossover; DMFC; Methanol tolerance; Nafion ® membranes; Platinum based catalysts; Sulfonated polyimide membranes 1. Introduction Nowadays, the technology for portable applications (com- puters, mobile phones, etc.) is in constant evolution for the development of smaller and lighter devices with more perform- ing integrated functions. As a consequence, the on board energy density is a key parameter which has to be taken into account. Up to now, lithium based technology is currently used (volumic energy close to 500 Wh L -1 ) [1,2], but mini fuel cells seem to be a very promising alternative as power supply for the next generation systems. ∗ 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. Coutanceau). In spite of its high specific energy (32 Wh g -1 ) [3] and because of storage problems in portable systems, the use of hydrogen as fuel is dismissed [4]. Liquid fuels as alcohols seem better adapted to the targeted technology. Indeed, alco- hols are easy to store and have a relatively good energy density: 6.1 Wh g -1 (4800 Wh L -1 ) and 8.6 Wh g -1 (6800 Wh L -1 ) for methanol and ethanol, respectively [5]. According to the com- plete oxidation reaction of methanol into CO 2 , one molecule of water is required to oxidize one molecule of methanol, as shown in the following equation: CH 3 OH + H 2 O → CO 2 + 6H + + 6e - (1) Nevertheless, several problems have to be overcome. Low power densities are still currently obtained in DMFC [6] because of the difficulty to activate the oxidation reaction of alcohol and 0378-7753/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2006.01.073