Sub-nanometer distributionsof water inside thin films of polymer electrolytesfor fuel cells analyzed by in-situ neutron reflectometry under high temperature and humidity

Abstract

The polymer electrolytes for fuel cells are membraned on SiO₂ and used as 5-nm thick binders on C-supported Pt catalysts. The three-dimensional structures in those materials are unknown and needed for the further improvement of the power generation and durability of fuel cells. We developed an in situ neutron-reflectometry method employed at high temperature and humidity. The internal structures of the polymer electrolyte thin films on SiO₂, Pt, C were understood to be different under power generation conditions. The water distributions were also very different up to 100 nm on different substrates.