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Fabrication And Microstructure Control Of PEEK-based Ion Exchange Membranes

Posted on:2017-04-08Degree:MasterType:Thesis
Country:ChinaCandidate:M Y GongFull Text:PDF
GTID:2321330512977467Subject:Chemical processes
Abstract/Summary:PDF Full Text Request
In recent years,fuel cells as alternative energy conversion devices have received much attention and are expected to become a source of low-emission power generation owing to their high energy efficiencies and environmental-benign nature.Ion exchange membrane is the core component of fuel cells,thus strengthening membrane performance is the key issue to improve fuel cells performance.In this study,starting from the design of the membrane materials,we have fabricated SPEEK/g-C3N4 nanocomposite membranes,ImPEEK/ImMIL nanocomposite membrane,ImPEEK/ImMSN nanocomposite membrane,and ImPEEK/TMPD co-quaternized membranes to control the physical and chemical microstructure of the membranes and to improve membrane performance.The g-C3N4 nanosheets were prepared and incorporated into SPEEK matrix to fabricate nanocomposite membranes.Ion transport channels were induced between the g-C3N4 nanosheets and SPEEK matrix.The amino?–NH2?and imino?–NH?groups of g-C3N4 could interact with the acid groups?sulfonate groups?in the polymer matrix to form acid-base pairs,facilitating the dissociation of sulfonate groups and enhancing the Grotthuss-type transfer of protons.The incorporation of g-C3N4 nanosheets also improved the mechanical properties and reduced methanol permeability.An increase in proton conductivity from 0.0606 S cm-1 of the SPEEK control membrane to 0.0786 S cm-1 of the nanocomposite membrane was achieved at the g-C3N4 nanosheets content of 0.5 wt % at 20 oC.CM MIL-101?Cr?materials were synthesized and incorporated into ImPEEK to prepare nanocomposite membranes.The incorporation of ImMIL-101?Cr?involved more ionizable hydrophilic groups,providing a better connectivity of the ionic clusters.The porous structure of the ImMIL-101?Cr?would facilitate building nanochannels to enhance ion transport.Because of the interfacial interactions,the mechanical properties were improved while the methanol permeability were reduced.An increase in hydroxide ion conductivity of 71.4% was achieved at the ImMIL-101?Cr?content of 5.0 wt % at 60 oC.Chloromethylated mesoporous silica nanoparticles?MSNs?were synthesized and incorporated into ImPEEK to form nanocomposite membranes.The incorporation of ImMSNs involved more ionizable hydrophilic groups,while their mesoporous structure would contribute to form more continuous nanochannels and provide more ion transport sites.With the incorporation of ImMSNs,pathways for methanol molecules were prolonged and mobility of the polymer chains were suppressed,therefore methanol permeability was reduced.An increase in hydroxide ion conductivity of 88.7 % was achieved at the ImMSN content of 5.0 wt % at 60 oC.Utilizing N,N,N',N'-Tetramethyl-1,4-phenylenediamine?TMPD?and 1-methylimidazole as co-quaternization reagents,we prepared ImPEEK/TMPD co-quaternized membranes.The addition of TMPD involved more ionizable hydrophilic groups,and the hydrophobic structure of TMPD would induce micro-phase separations to form continuous ion transport channels,resulting in improved hydroxide ion conductivity.An increase in hydroxide ion conductivity of 50.0% was achieved at the ImMIL-101?Cr?content of 5.0 wt % at 60 oC.
Keywords/Search Tags:fuel cell, poly(ether ether ketone), ion exchange membrane, microstructure, ion nanochannel
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