Surface chemistry of inorganic materials for composite membranes in PEM fuel cells operating at elevated temperature and reduced relative humidity

A number of proton conductive inorganics and their surface properties such as zeta potential, surface charge density, stoichiometry of surface complexes, etc., which reflect interfacial behavior of the inorganic particles, have been studied to better understand the performance of the solid oxide materials in composite membranes for proton exchange in fuel cells. The parameters and structure of the electrical double layer (EDL) at inorganic/water interface will be discussed in relation to the ionic conductivity and water retention properties of inorganic/polymer composite membranes. We conclude that the experimentally measured zeta potential and surface charge density along with EDL modeling of the inorganic/water interface can elucidate the experimentally found advantages of the composite membranes in proton exchange membrane (PEM) fuel cells operating at elevated temperature and reduced relative humidity.