Development of Blend Nanofiber Composite Polymer Electrolyte Membranes with Dual Proton Conductive Mechanism and High Stability for Next-Generation Fuel Cells

Blend polymer nanofibers (BNF), consisting of sulfonatedpolyimideand polybenzimidazole blends doped with phytic acid, were fabricatedand composed with Nafion to give BNF composite membranes for polymerelectrolyte fuel cells. The BNF composite membrane possessed highmechanical and chemical stabilities and low gas permeability. In addition,the BNF composite membrane showed higher proton conductivity thanthe commercial Nafion NR211 membrane, not only at low temperaturesbut also at high temperatures above 100 degrees C and low relative humidity(ca. 10% RH). The proton conduction mechanism in the BNF compositemembranes was examined and revealed that proton hopping conductionoccurred besides the vehicle mechanism in the BNF composite membranes.The BNF composite membrane provided improved fuel cell performancescompared to the cell using the conventional Nafion NR211 membraneat high humidity, low humidity, and high temperature/low humidity,suggesting the potential of BNF composite membranes for next-generationfuel cells.