Pore-filled anion-exchange membranes for electrochemical energy conversion applications

Abstract

Novel pore-filled anion-exchange membranes (PFAEMs) have been developed by a simple method for electrochemical energy conversion applications. The PFAEMs with the different degrees of crosslinking are successfully fabricated by filling cationic polyelectrolytes into a highly porous PTFE substrate (thickness=ca. 80μm) with chemically stable anion-exchangeable sites. The PFAEMs are shown to possess excellent electrochemical properties and stability. Especially the alkaline stability of the PFAEMs is superior to that of the commercial membrane (i.e., AMX, Astom Corp.) owing to the structural stability of ion-exchange sites and the nature of a highly hydrophobic PTFE substrate. The PFAEMs are also tested for the applications to all-vanadium redox flow battery (VRFB) and alkaline direct liquid fuel cells (ADLFCs). The VRFB employing the PFAEM with high crosslinking degree exhibits excellent energy efficiency (>85%) which is much superior to those of the Nafion and commercial anion-exchange membranes (78.7% and 80.1%, respectively). A promising performance in ADLFC is also achieved by employing the PFAEM with high crosslinking degree owing to the low fuel crossover but the further improvement in the ion conductivity is required.