Modified, Nafion-based polymer electrolyte membranes for advanced fuel cells

The large-scale development of polymer electrolyte membrane fuel cells (PMFCs) is partly set back by the limitations imposed by the currently available electrolytes, i.e. mainly perfluorosulphonic membranes of the NafionÔ-type. The research in our laboratory of more versatile proton-exchange membranes with adequate performance at low relative humidity has been directed along two strategies. One consists in the incorporation within conventional Nafion membranes of inorganic acidic materials, e.g. sulfated zirconia, SZrO2, in order to improve water retention, as well as to increase the number of acid sites. In this respect, SZrO2 has been dispersed into Nafion to obtain various types of composite membranes varying by the polymer/SZrO2 ratio and by the particle size. The results show that H2-air FCs using selected SZrO2 -added composite membranes can indeed operate under drastic operation conditions which cells based on conventional Nafion membranes cannot stand. The second strategy currently in progress in our laboratory is based on the use of non-volatile, dipolar solvents to be adopted, in place of water, as swelling media of Nafion membranes. Ionic liquids, (IL) due to their high thermal and electrochemical stability together with their intrinsic high proton conductivity appear as excellent candidates. We will show that protic ILs, specifically developed in our laboratory, are quite promising liquid components for the development of membranes for advanced FC configurations.