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 sulfonated polyimide and polybenzimidazole blends doped with phytic acid, were fabricated and composed with Nafion to give BNF composite membranes for polymer electrolyte fuel cells. The BNF composite membrane possessed high mechanical and chemical stabilities and low gas permeability. In addition, the BNF composite membrane showed higher proton conductivity than the commercial Nafion NR211 membrane, not only at low temperatures but also at high temperatures above 100 °C and low relative humidity (ca. 10% RH). The proton conduction mechanism in the BNF composite membranes was examined and revealed that proton hopping conduction occurred besides the vehicle mechanism in the BNF composite membranes. The BNF composite membrane provided improved fuel cell performances compared to the cell using the conventional Nafion NR211 membrane at high humidity, low humidity, and high temperature/low humidity, suggesting the potential of BNF composite membranes for next-generation fuel cells.