Protic ionic liquid-grafted polybenzimidazole as proton conducting catalyst binder for high-temperature proton exchange membrane fuel cells

Development of suitable catalyst binder with reasonable proton conductivity is of great importance for improving catalytic performance of oxygen reduction reactions of platinum-based catalysts. Herein, we report that polybenzimidazole grafted with protic ionic liquid moieties is an effective catalyst binder for oxygen reduction of Pt/C catalysts. The designed Pt/C catalyst layer using protic ionic liquid grafted polybenzimidazole as catalyst binder exhibits an improved catalytic activity for oxygen reduction compared with the sample using commercial Nafion as catalyst binder as evidenced by the positive shift of half-wave potential by about 20 mV with the very similar limiting current density. The specific activity of Pt/C catalyst using the synthesized material as catalyst binder at 0.9 V under acidic conditions is about two times higher than that of catalyst using Nafion as catalyst binder. The peak current density of thus-assembled fuel cell using protic ionic liquid functionalized polybenzimidazole as catalyst binder is about 1.7 times higher than the cell assembled from pristine polybenzimidazole as catalyst binder at 160 °C under anhydrous conditions.