Preparation and characterization of phosphotungstic acid-derived salt/Nafion nanocomposite membranes for proton exchange membrane fuel cells

Nafion/Cs_2.5H_0.5PW₁₂O₄₀ nanocomposite membranes are prepared and characterized as alternate materials for PEMFC operation at high temperature/low humidity. The Cs_2.5H_0.5PW₁₂O₄₀ solid acid particles (hereafter CsPWA) have the high surface area, the high hygroscopic property and the ability to generate proton in the presence of water molecules. The results of prepared membranes at three levels (0, 10 and 15%) indicate that the CsPWA particles have influence on the water content, ion exchange capacity, thermal properties (TGA and DSC), proton conductivity and PEM fuel cell performance. Particles agglomeration and Nafion active sites (sulfonic groups) covering are seen in the nanocomposite membranes. The conductivity of nanocomposite membranes at high temperatures (110 and 120 °C) is higher than plain Nafion and may be related to the additional water within the nanocomposite membrane and/or the additional surface functional site provide by CsPWA. The fuel cell responses show that in the fully hydrated state and at the higher current densities, the prepared MEAs with nanocomposite membranes possess better response compared with the plain Nafion. In partially hydrated cell, at both low and high current densities, the superior performance of the MEA prepared by nanocomposite membranes is observed.