Characterization of a composite membrane based on SPAES/sulfonated montmorillonite for DMFC application

Abstract

Sulfonated poly(arylene ether sulfone) (SPAES)/sulfonated montmorillonite (SMMT) hybrid membranes were fabricated to evaluate their potential for use as direct methanol fuel cells (DMFCs). To minimize the loss of proton conductivity while reducing methanol permeability, an ion exchange method was used to prepare the SMMT including a sulfonic acid group. The SPAES/NMMT(-Na+) and SPAES/SMMT(-SO3H) hybrid membranes were prepared using a solution casting and evaporation method, and the NMMT/SMMT content in the composite membranes was controlled at 0.5-2.0 wt% based on the SPAES. The performances of the hybrid membranes for the DMFCs in terms of their mechanical and thermal properties, water uptake, water retention, methanol permeability, and proton conductivity were investigated. The mechanical and thermal properties of the SPAES membranes were improved with introduction of the NMMT and SMMT. Methanol permeability reduction was also obtained when the SMMT content and the sulfonation degree increased. The SPAES/SMMT composite membrane showed increased proton conductivity compared with the non-modified MMT composite membrane under the 100% relative humidity condition. As the modified MMT content increased, the proton conductivity increased and the methanol permeability decreased due to the monovalent ions located between the MMT layers. The ratio of methanol permeability to proton conductivity for the SPEAS/SMMT (2.0 wt%) composite membrane was higher than that of NafionA (R) 1135. This property makes hybrid membranes potential candidates for DMFC applications.