Structural characterization of membranes for methanol direct fuel cells

S.P. FERNANDEZ BORDÍN; G. CASTELLANO; H. ANDRADA; A. CARRERAS; N. BAJALES LUNA; V. GALVÁN JOSA

Córdoba

Simposio; 14 INTERNATIONAL SYMPOSIUM ON RADIATION PHYSICS; 2018

IFEG

Polymeric fuel cells based on protonic exchange membrane are electrochemical devices thatgenerate electric energy from a chemical reaction. These devices have become a promisingtype of fuel cell as a clean energy source.The membrane used as electrolyte is a key component in fuel cells. In the case of directmethanol fuel cells the main purpose of the membrane is to provide enhanced conductivity ata reduced methanol crossover. Both methanol crossover and conductivity increase inhydrophilic membranes with the membrane hydration level. Thus, an enhancement of one ofthese properties will have a significant impact on the other. Methanol has high interactionwith polymer chains and high solubility in water, and its permeation easily occurs through thehydrophilic water channels inside the membrane. A network of widely distributed andinterconnected ionic domains that, under proper hydration, give rise to water channels, isessential to achieve a high proton conduction in these membranes.Knowing the structural membrane behavior under differents moisture conditions is importantto optimize fuel cells operations conditions. Small angle X-ray and neutron scattering(SAXS/SANS) are useful techniques in those systems due to allows characterize the size,shape and interfacial properties of particles in nanostructure materials.In this work, Fumapem F1850 and F1410 (Fumatech®) membrane structure were studied . Wecarried out SANS measurements under different moisture conditions at D11 instrument @ILL(Grenoble, Francia). As starting point SEM and AFM characterizations were performed inorder to elaborate a scattering length density maps. These maps were developed using MonteCarlo simulations taken into account the main components of the membrane (water channels,crystalline phase and amorphous matrix). The free parameters of the model are refinedcomparing experimental I(q) and the calculated by using the Inverse Fourier Transform method.