Proton conducting electrolyte membranes based on tungsten oxide and sulfonated polyether ether ketone hybrid composites

Composite membranes, prepared by mixing sulfonated polyether ether ketone (SPEEK) and WO₃·2H₂O in dimethylacetamide, were characterized by Thermogravimetry, Electrochemical Impedance Spectroscopy and Water Uptake measurements to evaluate their possible performance as proton exchange membranes (PEM). The body of results indicated the existence of a coordinative interaction between the water molecules of tungsten oxide and the sulfonic acid (-SO₃H) groups of SPEEK. Moreover, EIS data demonstrated that the proton conductivity of the composite membranes is higher than both that of pure SPEEK and pure tungsten oxide, suggesting the presence of ion-rich regions where the proton transfer is favored. The SO₃H - H₂O interaction not only lead to enhancement of the proton conductivity of the membranes but also to improvement of their heat resistance as well as to decrease their water solubility.