LAUSR

Abstract The use of fuel cells is strategic in the global energy system; their inclusion in eco-cars, avoiding CO 2 emission, represents a crucial enhancement for the environment. For this reason, any improvement in their use and optimization is fundamental for our society. Since one of the main components in these cells is their polymeric proton exchange membrane, in this work, the commercial Fumapem F-14100 and F-1850 membranes have been studied, both representing a cheap and effective alternative in direct methanol fuel cell (DMFC) applications. Their characterization will provide a new insight about them, in order to optimize and improve future fuel cell operation conditions. Small angle neutron scattering (SANS) has been used in this work to achieve a nanometric structural characterization of these membranes, which is key for understanding their physicochemical properties. Starting from SANS measurements, empirical fitting models were applied in order to obtain global sample features, which allowed to propose a lamellar water channel structure. Then, 2D scattering length density maps generated by Monte Carlo simulations were optimized to match the experimental SANS intensity profiles by using the inverse Fourier transform method. In addition, the crystalline contribution from the sample ordered domains was also studied by using X-ray diffraction.