A bi-functional polymeric nano-sieve Nafion composite membrane: Improved performance for direct methanol fuel cell applications

A polyamide macromolecular proton conductor with COOH end-capped is used as a bi-functional polymeric nano-sieve (BFPS) in composite Nafion membranes to simultaneously improve the proton conductivity and suppress the methanol permeation. With 1%-5% incorporation of the BFPS into the composite Nafion membrane, not only the proton conductivity and the methanol-permeation resistivity are improved, but also stronger mechanical strength is obtained, compared to the pure Nafion membrane. We show that the membrane with a 5% BFPS content gives the optimal performance and the composite membrane is well suited for applications in direct methanol fuel cells (DMFCs). The DMFC performance of the membrane is found to be more than 60% better than the performance of a recast pure Nafion membrane.