Fuel Cell Electrocatalyst Using Polybenzimidazole‐Modified Carbon Nanotubes As Support Materials

Toward the next generation fuel cell systems, the development of a novel electrocatalyst for the polymer electrolyte fuel cell (PEFC) is crucial to overcome the drawbacks of the present electrocatalyst. As a conductive supporting material for the catalyst, carbon nanotubes (CNTs) have emerged as a promising candidate, and many attempts have been carried out to introduce CNT, in place of carbon black. On the other hand, as a polymer electrolyte, polybenzimidazoles (PBIs) have been recognized as a powerful candidate due to the high proton conductivity above 100 °C under non-humid conditions. In 2008, we found that these two materials have a strong physical interaction and form a stable hybrid material, in which the PBIs uniformly wrap the surfaces of the CNTs. Furthermore, PBIs serve as effective binding sites for the formation of platinum (Pt) nanoparticles to fabricate a ternary composite (CNT/PBIs/Pt). In this review article, we summarize the fundamental properties of the CNT/PBIs/Pt and discuss their potential as a new electrocatalyst for the PEFC in comparison with the conventional ones. Furthermore, potential applications of CNT/PBIs including use of the materials for oxygen reduction catalysts and reinforcement of PBI films are summarized.