Construction Of Proton Transfer Pathways Of Nanofibrous Composite Proton Exchange Membranes And Study Of Hydrogen Fuel Cell Properties

Proton exchange membrane fuel cell?PEMFC?is a novel kind of generating device which directly converts chemical energy into electrical energy.Owning to high energy density,high conversion efficiency,low pollution and so forth,having attracted an increasing attention.As the heart of proton exchange membrane fuel cell,PEM,the proton conduction property directly determines the performance of PEMFC.Therefore,enhancing the proton conduction characteristics is crucial to the design of high performance PEM,and the membrane microstructure is the foundation of membrane transfer characteristics.Nanofiber,due to its high surface area and good mechanical properties,is considered to be an ideal proton conductor.It is universally acknowledged that the proton conductivity could be enhanced over ten times when the PEM material fibrosis.Based on the superior proton conductivity of nanofiber,by overlapping into a nanofiber mat and incorporating polymer matrix into the holes of the nanofiber to fabricate the nanofibrous composite membrane.By means of the connection of nanofiber in the horizontal direction of the membrane surface,and the connected microchannels in the vertical direction,nanofibrous composite membrane can form three-dimensional networks.Therefore,creating the long proton conduction channels.On the other hand,nanofiber and the filler material can be controlled independently in the composition and the structure,the microstructure of nanofibrous composite membrane can be controlled easily.Therefore,nanofibrous composite membrane possesses unique advantages and potentials to be high performance PEM.This paper reveals the formation mechanism of composite membrane through the exploration of the physicochemical properties of a novel PEM material,developing a novel materials with special physicochemical structure.Besides,explore the proton transfer mechanism and multi scale cooperation mechanism and study the influence of nanofiber structure on physicochemical environment at the interface of membrane,and the induced effect of acid-base interaction and mechanism of water interface membrane on group arrangement were also established.The specific research contents and the main conclusions are listed as follows:?1?Study on the preparation and conduction properties of polyethylene imine nanofibrous composite membrane to preparation PEI nanofibers with abundant alkaline groups via electrospin technology,and regulate the content of PEI of the nanofiber,then incorporate SPEEK,the acid matrix,into the pores to fabricate NFCMs.The cross-sectional SEM images of NFCM showed PEI nanofibers dispersed homogeneously into the SPEEK matrix.FTIR results showed acid-base pairs were formed in the interface of composite membrane and built delivery pathways for proton,significantly increased the proton conduction of nanofibrous composite membranes.The increase of PEI amount could obviously increase the amount of acid-base pairs,thus NFCMs displayed obviously enhanced proton conductivity.Among which,SP/PVA-PEI40 obtain the highest proton conductivity.For example,the highest proton conductivity under hydrated condition was 0.131 S cm^-1?75 ^oC?,which was equivalent to Nafion membrane,the commercial membrane;the higest proton conductivity under anhydrous conduction was 0.0442 S cm^-1?120^oC?,which was much higher than that of Nafion membrane.?2?Choosing ionic liquid as the soft template to prepare porous nanofibrous composite membrane and enhance the proton conductivity of membranes.To begin with,SPEEK porous nanofiber was prepared based on soft template method.Then,CS matrix was incorporated into the porous nanofibers to prepare porous nanofibrous composite membrane.The abundant pores of the porous nanofiber can be used as an effective"tank",greatly enhanced the water absorption capacity of the membrane.In addition,the enlarged surface area of nanofiber further increased the number of sulfonic group exposed to the nanofiber surface.Compared with NFCM,After pouring CS matrix,PNFCM fromed abundant acid-base pairs in the interface of membranes,coulomb force?electrostatic interaction?effectively promotes the protonation and deprotonation processes,endow the membrane with an excellent proton conduction.And the electrostatic interaction between porous nanofiber and matrix can effectively inhibit the motion of polymer chains,enhance the thermal stability of the membrane.Therefore,forming continuous proton construction pathways in the vertical direction of nanofiber can effectively optimize the microstructure of membrane and enhance the proton conductivity.Choosing[C₈mim][TF₂N]and[C₂mim][TF₂N]as template,among which,CS/SP/C₈-35 showed the optimal proton conduction performance.For example,the highest proton conductivity was 1.03 S cm^-1?95 ^oC?under 100%RH,much higher than that of state-of-the art Nafion membrane.Proton the conductivity under 0%RH was 0.22 S cm^-1?120 ^oC?,being 10 times than that of Nafion.The abundant nanopores of porous nanofiber formed the continuous transfer pathways in the vertical direction of the nanofibers,more conducive to the enhancement of the proton conduction in the vertical direction.