As a key part of membrane electrode assemblies (MEAs), Nafion membranes are the most commonly used membranes in direct methanol fuel cells (DMFCs) due to their good proton conductivity and chemical stability, but high methanol crossover through the membrane from the anode to the cathode results in low fuel utilization efficiency. Additionally, Nafion membrane is very expensive and contributes significantly to the overall cost of DMFCs. To overcome the critical barrier for commercialization of DMFC, several hydrocarbon-based membranes have been developed as alternatives for Nafion thanks to small fuel permeability, low cost and excellent chemical stability. However, Nafion is still used as an ionomer in the catalyst layer to fabricate MEAs with these membranes. The high interfacial resistance and delamination between the membrane and electrode arise from the poor compatibility of hydrocarbon polymeric membrane and Nafion ionomer, which leads to performance loss and poor durability.

To address the issue of incompatibility, the blend polymer (SPEEK/PSf-ABIm) consists of sulfonated poly(ether ether ketone) (SPEEK, an acidic polymer) and 2-amide-benzimidazole-tethered polysulfone (PSf-ABIm, basic polymer) was successfully synthesized attributing to their similar backbones. The N-heterocycle groups inserting into the sulfonic acid group domains of SPEEK can facilitate proton conduction and suppress methanol crossover. The impregnation of SPEEK/PSf-ABIm ionomer into the catalyst layer was conducted by dispersing the ionomer in catalyst ink and the MEAs were fabricated with SPEEK/PSf-ABIm blend membrane. The electrochemical properties of the blend ionomer in the catalyst layer and compatibility were investigated in this work. The preliminary results showed that the blend membrane and ionomer can greatly reduce methanol crossover, but the cell performance was worse than that of MEA with Nafion membrane and Nafion ionomer due to lower proton conductivity and slower electrode kinetics.