Preparation Of SPEEK/Phosphonic Acid Modified Fillers Composite Membrane And Intensification Of Proton Conduction Property

For a proton exchange membrane fuel cell, the membrane is a core andperformance-determinant component. Intensification of proton conduction property ofthe membrane is a crucial issue to improve the performance of the fuel cell. In thisstudy, polymeric phosphoric acid submicrospheres (PPASs), polymeric phosphoricacid submicrocapsules (PASCs) and polymeric phosphonic acid nanotubes (PANTs))are designed and synthesized, and then incorporated into the SPEEK matrixs toprepare composite membranes. In order to intensify proton conduction property viaGrotthuss and vehicle mechanisms, this study focuses on three key issues: optimizingproton carriers, enhancing water retention and constructing proton conductionchannels of the membranes.The first part of this study is the preparation of SPEEK/PPASs compositemembrane and intensification of proton conduction property. In this part, PPASs aredesigned and synthesized, and then incorporated into a SPEEK matrix to prepare aseries of membranes. Amphoteric phosphonic acids serve as both proton donors andacceptors, and form dynamical hydrogen-bond networks, promoting proton transfervia Grotthuss mechanism. As a result, it is found that the composite membrane with15wt.%PPASs acquires a proton conductivity of0.0066S/cm in vertical direction,5times higher than that of the control membrane (0.0011S/cm) after90min testing, at40oC and20%RH.The second part is the preparation of SPEEK/PASCs composite membrane andintensification of proton conduction property. Water molecule is medium of protontransfer by vehicle mechanism. Based on the previous work, PASCs are designed andsynthesized, and then incorporated into a SPEEK matrix to prepare compositemembranes. The superior water storage space of the PASCs enhances water uptakeand water retention properties of the membranes, and further boosts protonconductivity of the membranes. As a result, under40oC and20%RH, the compositemembrane filled with15wt.%PASCs (128nm lumen) shows the highest protonconductivity of0.0142S/cm in vertical direction, about twelve times higher than thatof the control membrane (0.0011S/cm) after90min testing, which is positivelycorrelated with the water retention of the membrane. The third part is the preparation of SPEEK/PANTs composite membrane andintensification of proton conduction property. Consecutive proton conductionchannels are the basement of high proton conductivity. Based on the previous parts,PANTs are designed and synthesized, and then incorporated into a SPEEK matrix toprepare composite membranes. The PANTs enrich phosphonic acid groups, whichrendering an enhanced proton conduction property by constructing a consecutivepathway for proton transfer via phosphonic acid groups and the absorbed water. At30oC, the composite membranes filled with7.5wt.%PANT-3#exhibites a high protonconductivity of0.1032S/cm in horizontal direction, which is2times over that of thecontrol membrane.