Composite membranes of sulfonated polyether ether ketone and montmorillonite as electrolyte for direct methanol fuel cell

摘要

Composite polymer electrolyte membranes made of sulfonated polyether ether ketone (SPEEK) polymer host and montmorillonite (MMT) ceramic fillers (2-10 wt.%), was prepared by a solution casting method. The characteristic properties of the SPEEK/MMT composite polymer membranes were investigated using thermo gravimetric analysis (TGA), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and the AC impedance method. The SPEEK/MMT composite membrane showed good thermal and mechanical properties and appreciable ionic conductivity in the order of 10~(-3) S/cm. Due to the incorporation of the inorganic filler, there is a decrease in the ion exchange capacity (IEC) when compared to the pristine SPEEK which was 2.20 mequiv/g. Though the ionic conductivity decreased with increasing content of MMT, there is an improvement in the mechanical properties with the introduction of MMT. The tensile strength of virgin SPEEK was 24.6 MPa, whereas the composite with 10% MMT showed 40.1 MPa. The incorporation of MMT into the SPEEK matrix enhanced the resistance to the permeation of methanol. The selectivity ratio of the composite membranes were well ahead of pristine SPEEK indicating its suitability for DMFC. It was revealed that the addition of MMT fillers into the SPEEK matrix could markedly improve the electrochemical properties of the composite membranes; which can be accomplished by a simple blend method. As a result, the SPEEK/MMT composite polymer appears to be a good candidate for the DMFC applications.