Electrospun multifunctional sulfonated carbon nanofibers for design and fabrication of SPEEK composite proton exchange membranes for direct methanol fuel cell application

Microstructural construction of a polymer/inorganic filler interface in organic/inorganic composite proton exchange membranes is a key to design of high performance proton conducting materials. Here, carbon nanofibers (CNFs) prepared through electrospun were successfully sulfonated to improve interfacial compatibility between the sulfonated poly(ether ether ketone) (SPEEK) and the sulfonated CNFs (SCNFs) via hydrogen bonding interaction. In addition, carbon nanofiber mats were successfully sheared into short lengths to facilitate dispersion of the SCNFs in the composite membranes. To demonstrate the effectiveness of the SCNFs on improvement of properties of the composite membranes, key physical quantities, i.e. mechanical strength, proton conductivity and methanol permeation were measured and systematically compared with the results of the neat SPEEK and Nafion 117 membranes. It was found that doping with the SCNFs of various contents could profoundly influence the physical properties of the composite membranes. In particular, mechanical strength, proton conductivity and methanol permeability prevention of the composite membranes were significantly enhanced upon incorporation of the SCNFs as fillers. The study provides useful insight into the investigation of the SCNFs based composite membranes for fuel cell applications.