Development of materials for mini DMFC working at room temperature for portable applications

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 Nation (R) 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) x 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 mu 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. (c) 2006 Elsevier B.V. All rights reserved.