Sulfonated Poly(fluorene ether ketone) (SPFEK)/á-Zirconium Phosphate (ZrP) Nanocomposite Membranes for Fuel Cell Applications

Polymer electrolyte membrane fuel cells (PEMFCs) have attracted significant attention because of their high system efficiency and environmental benefits. However, it has proven difficult to develop PEMFC into a commercial product because of several technical obstacles, including: (1) low proton conductivity at low relative humidity (RH) and high temperatures; (2) high fuel permeation (in direct methanol fuel cells); and (3) poor dimensional stability when operating at temperatures higher than 100°C. A series of sulfonated poly(fluorene ether ketone) (SPFEK)/α-zirconium phosphate (ZrP) nanocomposite membranes were synthesized to address the above issues. The nanocomposite membranes were synthesized by casting SPFEK solution containing pre-exfoliated ZrP nanosheets. Because ZrP is proton conductive, incorporating exfoliated individual ZrP nanosheets into SPFEK resulted in nanocomposite membranes with excellent barrier properties while the proton conductivity can be maintained. The presence of ZrP nanosheets also led to improved oxidative stability and dimension stability. Such composite membranes exhibit superior performance in single cell evaluation, especially at elevated temperatures.