1-(3-Aminopropyl)imidazole functionalized poly(vinyl chloride) for high temperature proton exchange membrane fuel cell applications

New high temperature proton exchange membranes are fabricated based on low cost polyvinylchloride (PVC) and 1-(3-aminopropyl)imidazole (APIm) by a facile method (i.e. solution casting method). Due to the presence of chemically active chloride sites in the backbone, PVC reacts with the amino and imidazole groups in APIm directly via the nucleophilic reaction. The fabricated membranes possess good thermal stability, high hydrophilicity and mechanical strength as well as superior phosphoric acid (PA) doping capability due to the acid-base and hydrogen bond interactions between the APIm groups and PA molecules. Incorporating pendant APIm groups into PVC endows membranes with significantly higher acid doping levels than membranes functionalized by mono- and bis-amino or imidazole containing compounds. As a result, the PVC-19%APIm/2.4PA membrane displays an outstanding proton conductivity of 0.26 S cm-1 at 180 °C under anhydrous conditions, which is comparable to the conductivity of Nafion-type membranes (> 0.1 S cm-1 at 80 °C). The polarization curve and durability test demonstrate the technical feasibility of the PVC-x%APIm/PA membrane for the high temperature proton exchange membrane fuel cell.