Zeolites and zeotype materials as efficient barriers for methanol cross-over in DMFCs

In this work, the feasibility of zeolites and zeotype materials as novel ion-conducting materials for fuel cell applications has been assessed by physical, chemical and electrochemical characterization and, specially, by the calculus of the transport selectivity (ion conductivity: methanol conductivity ratio). Particularly, methanol diffusion coefficient has been studied for NaA zeolite (LTA) and mordenite (MOR) commercial zeolites and ETS-10 and Sn–Umbite silicates. In order to explain the different performances achieved, water-uptake, thermogravimetric analyses, BET surface and pore volume measurements have been carried out. As a conclusion, ETS-10 sample exhibits the best performance; showing a methanol diffusion coefficient nearly the half the Nafion value. Although NaA, MOR and Sn–Umbite show transport selectivities at 40 °C two orders of magnitude lower than Nafion, the conduction properties above 100 °C make these materials promising to be used for high-temperature PEMFC. Finally, preparation and characterization of ETS-10 films supported on Carbon Toray paper is presented as a first approximation to a feasible electrolyte membrane.