A high-performance sandwiched-porous polybenzimidazole membrane with enhanced alkaline retention for anion exchange membrane fuel cells

Abstract

Alkaline doped polybenzimidazole (PBI) has been commonly utilized as an anion exchange membrane in anion exchange membrane fuel cells (AEMFCs) over the past decade. However, the progressive release of the doped alkali during fuel cell operation is a challenging issue for this type of membrane. To address this issue, we propose and fabricate a sandwiched-porous PBI (sp-PBI) membrane. The porous structure of the membrane prepared by a pore-forming method renders numerous interconnected macropores and sponge-like walls, which provide enhanced attraction between the doped alkali and the PBI skeleton. Using this approach, both ionic conductivity and alkali retention of the membrane are substantially enhanced. Meanwhile, to evaluate the performance of the membrane in a H₂/O₂ AEMFC, we develop a new nanocomposite, PBI-decorated reduced graphene oxide (rGO) as the supporting material and then deposit electrocatalysts on this nanocomposite. This new catalyst structure not only exhibits a superior electro-catalytic activity toward the oxygen reduction reaction, but also facilitates mass transportation in the catalyst layer. It is demonstrated that the use of this new PBI-based membrane electrode assembly with the membrane and catalyst in the fuel cell can reach a peak power density of 544 mW cm⁻², which is among the highest power densities reported for this type of fuel cell in the existing literature.