Membranes with Phosphonic Acid Moieties for High Temperature PEMFC

The polymer electrolyte membrane fuel cell (PEMFC) has been studied actively for both portable and stationary applications because it can offer high power density in addition to environmental friendliness. Nafion ® offers mechanical and chemical stabilities as well as high conductivity. However, it cannot be used at high temperatures ( ≥ 90 oC) because proton cannot be transferred due to dehydration of membrane. Therefore, for PEMFC to be operated at high temperatures and low RH, we developed nanocomposite membranes functionalized with phosphonic acid groups which can be conductive even without water. 3-Aminopropyl triethoxysilane (APTES) was used to replace sulfonic acid groups of Nafion ® and then its aminopropyl group was chemically functionalized to phosphonic acid groups. The nanocomposite membrane showed very high conductivity of ~0.02 S/cm at 110 oC and RH < 30 % in addition to much better mechanical properties and performance at high temperatures