Nafion/IL Intermediate Temperature Proton Exchange Membranes Improved by Mesoporous Hollow Silica Spheres

A novel polyelectrolyte composite membrane was designed and prepared for intermediate temperature proton exchange membrane fuel cells (PEMFCs). It was composed of perfluorosulfonic acid resin (Nafion((R))), protic ionic liquid (IL,[dema][TfO]) and mesoporous hollow silica spheres (MHSi). The morphologies of MHSi and Nafion-based composite membranes were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effect of MHSi on proton conductivity of the composite membranes versus relative humidity (RH) and temperature (100-140 degrees C) were investigated. The results indicated, that the Nafion/IL/MHSi composite membranes exhibited excellent proton conductivity even under 30% RH or high temperature (above 100 degrees C). A high proton conductivity (5.41 mS cm(-1)) of the composite membrane at 30 degrees C and 30% RH can be observed from the test result, which was five times higher than that of the pristine Nafion. The N-IL-12S composite membrane showed an outstanding proton conductivity, as far as 14.7 mS cm(-1) under 140 degrees C and low RH, which was almost two orders higher than that of the pristine Nafion membrane. Moreover, the unique hollow and mesoporous structure of MHSi improved IL retention rate of the membrane evidently. Together with high thermal stability of the composite membrane confirmed by thermogravimetric analysis (TGA), the Nafion/IL composite membrane improved by MHSi is a potential candidate in intermediate temperature PEMFC.