Membranes pour piles à combustible : structure et transport. Apport de la diffusion neutronique

Abstract

Membranes for fuel cells are characterized by a nanophase segregation between hydrophilic and hydrophobic domains. Improvement of the ionomer membranes performances, in particular protonic conductivity optimization, is a crucial issue before fuel cells can develop on an industrial market. This necessarily requires a microscopic knowledge of the polymer structure and properties, notably the protonic transport mechanisms, as a function of its hydration state. We show the interest of neutron scattering techniques in these systems. Small-angle neutron scattering has been recently used to measure the transverse water profiles in membranes during fuel cell operation. Quasielastic neutron scattering allowed to study the dynamical properties of water in the Nafion, which is the actual reference material, and to propose a molecular scenario for the mobility of hydration protons.