research article polymer electrolyte membrane fuel cell...

Research ArticlePolymer Electrolyte Membrane Fuel Cell Performanceof a Sulfonated Poly(Arylene Ether Benzimidazole)Copolymer Membrane

Hasan Ferdi Gerccedilel CcedilaLla Guumll Tosun and Levent AkyalccedilJn

Department of Chemical Engineering Anadolu University 26555 Eskisehir Turkey

Correspondence should be addressed to Hasan Ferdi Gercel hfgercelanadoluedutr

Received 6 June 2016 Revised 24 October 2016 Accepted 25 October 2016

Academic Editor Gianluca Cicala

Copyright copy 2016 Hasan Ferdi Gercel et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Disodium-331015840-disulfonate-441015840-dichlorodiphenylsulfone (SDCDPS) and 551015840-bis[2-(4-hydroxyphenyl)benzimidazole] (HPBI)monomers were synthesized Binding thesemonomers via nucleophilic aromatic polycondensation reaction a sulfonated poly(ary-lene ether benzimidazole) copolymer was synthesized Structures of monomers and copolymer were confirmed by proton nuclearmagnetic resonance spectroscopy (1HNMR) and Fourier transform infrared (FTIR) spectroscopy analyses Proton exchangemem-brane was prepared by dissolving copolymer in dimethylacetamide (DMAc) and casting onto a glass plate Copolymer membranewas doped with sulfuric acid to ensure proton exchange character Single cell performance of the copolymer membrane was testedin a polymer electrolytemembrane fuel cell test stationThe highest power density of themembrane wasmeasured as 237mWcmminus2at 80∘C Thermogravimetric analysis (TGA) showed that as the degree of disulfonation is increased thermal stability of thecopolymer is increased

1 Introduction

Environmental challenges of fossil fuel use effects of harmfulemissions on human health and dependence of industrialnations on oil that leads to oil crises have induced the devel-opment of fuel cell technologies in past 25 years [1 2] Fuelcells are considered to be the solution of environmentallyfriendly and highly efficient electrical energy production ofthe future Among fuel cell types polymer electrolyte mem-brane fuel cells (PEMFCs) attract most attention due to theirhigh power density high energy transformation efficiencyand wide range of applications in stationary and portabledevices [3 4] Perfluorosulfonic acid based polymer mem-branes such as Nafion are considered as state-of-the-artmembranes and used frequently in PEMFCs owing to theiroutstanding chemical and physical stabilities and high protonconductivity at moderate operating temperatures Howeverstudies on development of alternative polymer electrolytemembranes continue because of the drawbacks of Nafion

membranes like decrease in proton conductivity at tem-peratures above 80∘C due to dehydration humidificationrequirement and high prices [5ndash7]

Studies about polymer based sulfonated proton exchangemembrane materials such as poly(arylene ether sulfone)s [8ndash11] poly(ether ether ketone)s [12ndash14] poly(arylene thioether)[15ndash17] poly(phenylene)s [18ndash20] polyimides [21ndash24] andother types of polymers have largely taken place in the scopeof polymer electrolyte membrane researches so far

Polybenzimidazole (PBI) membranes doped with strongacids predominate over other proton exchange membranesdue to their stable proton conductivity at temperatures higherthan 100∘C However synthesis of high molecular weight PBIpolymer is difficult and cost is quite high Besides dissolutionof PBI in common organic solvents is difficult due to its rigidmolecular structure On the other hand synthesis of poly-(arylene ether sulfone)s is easier and cost is lower Howeverthey have low mechanical stability due to water swelling anddissolution of the poly(arylene ether sulfone) membranes in

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2016 Article ID 6123213 8 pageshttpdxdoiorg10115520166123213

2 Advances in Materials Science and Engineering

water that limits their practical applications [6 7] In thisstudy a sulfonated poly(arylene ether benzimidazole) copol-ymer was synthesized [25ndash30] and a copolymer membranewas prepared by solution casting method The membranewas treated with sulfuric acid to strengthen the protonconductivity character Finally single cell performance of thecopolymer membrane was tested in a PEMFC test station

2 Experimental

21 Materials 441015840-Dichlorodiphenyl sulfone (DCDPS) and4-hydroxybenzoic acid phenyl ester were purchased fromABCR and vacuum dried at 50∘C for 24 h before use Fumingsulfuric acid (65 SO3 extra pure) phenylsulfone and 1-methyl-2-pyrrolidone (+995) were used as received fromMerck Sodium chloride 331015840-diaminobenzidine (DAB) andDMAc were purchased from Sigma Aldrich DAB was vac-uum dried at 50∘C for 24 h before use Sodium hydroxidetoluene and isopropanol were used as received from Riedelde Haen Potassium carbonate (Alfa AESAR) was vacuumdried at 50∘C for 24 h prior to use Sulfuric acid (95ndash97) wasused as received from Fluka

22 Synthesis of Monomers Synthesis of HPBI has beenpreviously reported by several researchers [29 30] DAB(0467mole) 4-hydroxybenzoic acid phenyl ester(0934mole) phenylsulfone (500 g) and toluene (150mL)were added to a jacketed four-necked cylindrical reactorequipped with a Dean-Stark trap a condenser a mechanicalstirrer and a nitrogen inlet-outlet Reaction temperaturewas controlled by oil bath circulator Reactor was isolated toprevent heat loss Dean and Stark trap was filled with tolueneto remove water azeotropically Temperature was raised to150∘C and the solution was allowed to reflux for 6 hoursToluene was removed and the solution was heated to 280∘Cfor 2 hGeneratedwater andphenolwere removed fromDeanand Stark trap and the monomer precipitated For furtherremoval of phenol outlet gas stream was connected to twoserial gas washing bottles and vacuum was applied for 2hours Solution was left to cool and excess ethanol was addedat 150∘C Product was left at room temperature overnightand filtered to separate the phenylsulfone that crystallizedout of solution Synthesized tan monomer was washed withacetone and dried at 120∘C for 24 hours

331015840-Disulfonated-441015840-dichlorodiphenyl sulfone (SDCDPS)monomer [30ndash33] synthesized in a four-necked round bot-tomflask equippedwith a thermometer a condenser amech-anical stirrer and a nitrogen inlet-outlet DCDPS (99mmol)was dissolved in fuming sulfuric acid (65 SO3) Tempera-ture was raised to 110∘C and the mixture was stirred for 6hours to produce a homogeneous solutionThen solutionwascooled to room temperature and sodium chloride was addedThe dark brown color of the solution turned into white andthe productwas neutralized to pH6-7with sodiumhydroxideand excess sodiumchloridewas added to precipitate themon-omer as its sodium form Synthesized SDCDPS was filteredrecrystallized from isopropanol andwatermixture for furtherpurification Resulted white monomer dried at 120∘C for 24hours

23 Disulfonated Poly(Arylene Ether Benzimidazole) (SPAEB)Copolymers Synthesis Einsla has previously reported thesynthesis of disulfonated poly(arylene ether benzimidazole)copolymer [30] SDCPS (7mmol) and equimolar DCDPSand HPBI (14mmol) were introduced into a 250mL four-necked flask equipped with a thermometer mechanicalstirrer a Dean-Stark trap a condenser and a nitrogen inlet-outlet Potassium carbonate (16mmol) and 75mL of NMPwere introduced to the reaction flask As an azeotroping agent40mL of toluene was introduced to the flask and the Dean-Stark trap was filled with toluene Temperature was raised to140∘C for dehydration of the system for 4 hours and Deanand Stark trap was emptied Temperature was raised to 170∘Cand reaction was carried out for 20 hours Generated tolueneduring reaction was removed via Dean and Stark trap Thedark brown viscous solution poured into deionized water andthe precipitated copolymer was filteredThe yellowish-brownfibrous copolymer was dried at 120∘C for 24 h and grounded

24 Postsulfonation of SPAEB Copolymers A postsulfona-tion method was used for further sulfonation of synthe-sized SPAEB copolymers to analyze the effect of degreeof sulfonation to thermal stability and proton conductivityPostsulfonation was carried out by dissolving 5 g of thecopolymer in 100mL fuming sulfuric acid (65) and stirredfor 10 hours at 30∘C Resulting product was denoted asSPAEB oleum (SO365) After the reaction the reactionmixture was poured into a large volume water to precipitatethe product The sulfonated polymer material was recoveredand washed with water until the wash was pH neutral and itwas then dried for 48 h at 100∘C

25 Membrane Preparation and Acid Doping Synthesizedcopolymer (075 g) was dissolved in 3188mL of DMAc(25 wwminus1) in a 250mL two-necked flask equipped witha mechanical stirrer and a condenser The flask was insertedin an ultrasonic water bath Temperature was heated to 80∘Cfor 4 hours After filtration solutionwas cast onto petri dishesand dried Resulting transparent membranes were immersedin boiling 05MH2SO4 for 2 hours and dried to removeabsorbed water The same membrane preparation procedurewas performed for SPAEB oleum (SO365) too

26 Characterization The 1HNMR spectra of themonomersand copolymer were recorded on a 500MHz BrukerAVANCE II NMR spectrometer Grounded monomers andcopolymer were dissolved in deuterated dimethylsulfoxide(DMSO-d6) and chemical shifts were measured againsttetramethylsilane (TMS) as an internal standard We usedthe integral area belonging to the protons adjacent to thesulfonate groups and the integral area of the protons next tothe carbon of the imidazole moiety degrees of disulfonationobtained from 1H NMR

Fourier transform infrared (FTIR) spectra were recordedusing a Perkin Elmer Frontier spectrometer All the sampleswere dried at 105∘C for 24 h prior to analyses

Thermogravimetric curves are largely affected by exper-imental conditions especially by the heating rate So the

Advances in Materials Science and Engineering 3

minus1minus05

10

15

20

25

30

35

40

45

50

5558

T

4000 3500 3000 2500 2000 1500 1000 500

(cmminus1

)

Figure 1 FTIR spectrum of SDCDPS

degradation experiments of samples were carried out at thesame scanning rate 10∘Cmin because it is a medium scan-ning rate among those usually employed for thermal degrada-tions [34 35]Thermogravimetric analysis (TGA)was carriedout in dynamic heating conditions under flowing nitro-gen (100mLminus1) in the temperature range 35ndash600∘C usinga Netzsch STA 449 F3 thermogravimetric analyzer Samplesof about 930 times 10minus3 g for SPAEB and 959 times 10minus3 g forSPAEB oleum (SO365) were used for degradation exper-iments Their masses as a function of temperature weremonitored and the experimental data were used to plotthe percentage of undegraded copolymer as a function oftemperature

A Cannon Ubbelohde dilution viscometer was used tomeasure inherent viscosity of the copolymer in DMAc at aconcentration of 05 g dLminus1 at 30∘C

27 Proton Conductivity Measurements Themembrane sam-ples were prepared as rectangular sheets and placed in aTeflon conductivity cell (Bekktech 112) which is connectedto four Pt electrodes and the distance between the twoinner electrodes was used to measure the potential differencetrough the sample Proton conductivities of the membraneswere measured for planar direction sending hydrogen (rela-tive humidity (RH) = 0) into a Scribner 850 fuel cell testsystem connected to the proton conductivity cell at 80∘C ASolartron 1287 electrochemical interface was used tomeasurevoltage and current values Proton conductivity of a sampleof commercial Nafion 212 membrane was measured at 80∘Cwith 100 RH to see the reliability of the results

28 Single Cell Performance Test The standard fuel cell teststation was described elsewhere [36] Copolymer membranewas sandwiched between the catalyst coated electrodes toproduce the membrane electrode assembly The Pt loadingsof cathode and anode were approximately 05mg cmminus2 SGL-10BCwas used as gas diffusion layer and the active area of thesingle cell was 25 cm2 The current and power densities of thefuel cell were recorded The working temperature of the fuelcell was kept at 80∘C Hydrogen and oxygen were both fed

012345678910

(ppm)

Figure 2 1H NMR spectrum of SDCDPS

to the fuel cell at a rate of 80 sccm without external humi-dification at ambient pressure

3 Results and Discussion

31 Structural Analysis of SDCDPS The FTIR spectrumof SDCDPS is shown in Figure 1 C-H stretching of aro-matic ring is assigned at 3095 cmminus1 The absorption peak at1638 cmminus1 represents the C=C stretching vibrations bandsPeaks at 813ndash824 cmminus1 are attributed to the C-Cl stretchingbands In-plane bending of aliphatic C-H is assigned at1288 cmminus1 Peak observed at 594 cmminus1is due to C-S aromaticring stretching The absorption peaks at 1024 and 1084 cmminus1indicates the S=O stretching vibrations of sulfonic acidgroups This result confirms the sulfonation of DCDPS1HNMR spectrum of SDCDPS is shown in Figure 2 The

existence of the resonance at 834 ppm represents the protonsadjacent to the sulfonate groupsThis result confirms that thesulfonation of DCDPS was achieved

32 Structural Analysis of HPBI In the FTIR spectrum ofHPBI represented in Figure 3 the large peaks observed at2500ndash3200 cmminus1 are assigned to R2NH stretching vibra-tion and Ar-OH vibration bands Peaks at 1593 cmminus1


4000 3500 3000 2500 2000 1500 1000 500

(cmminus1

)

2

4

6

8

10

12

14

16

18

20

2223

T

Figure 3 FTIR spectrum of HPBI

012345678910111213

(ppm)

Figure 4 1H NMR spectrum of HPBI

and 1620 cmminus1 show C=C stretching and C=N stretching-vibration bands (characteristic band of imidazole groups)

Figure 4 shows the 1H NMR spectrum of HPBI Thepeak observed at 133 ppm is assigned to N-H groups Peakat 10 ppm confirms the existence of the protons of Ar-OHgroups This result shows that HPBI monomer synthesis wasperformed successfully

33 Characterization of Copolymer Inherent viscosity of thecopolymerwasmeasured as 092 dL gminus1 inDMAc at a concen-tration of 05 g dLminus1 at 30∘C In FTIR spectrum of sulfona-ted poly(arylene ether benzimidazole) copolymer shown inFigure 5 peaks at 3000ndash3500 cmminus1 are attributed to the N-H vibration bands of amide groups Peaks observed at 1500ndash1600 cmminus1 are due to the aromatic C=C and C=N stretchingbands and they arise from in-plane bending of N-H and con-jugation vibration between benzene and imidazole ringsThepeak at 1149 cmminus1 indicates aromatic sulfone groups Peaksat 1027 cmminus1 and 1243 cmminus1 indicate stretching vibration ofO=S=O sulfonic acid groups

Figure 6 shows the 1H NMR spectrum of sulfonatedpoly(arylene ether benzimidazole) (SPAEB) copolymer Pro-ton resonances at 700 785 and 833 ppmconfirm that sulfonegroups are involved in the structure

Figure 7 shows 1H NMR spectrum of SPAEB oleum(SO365)1H NMR spectra were also used to evaluatethe degrees of disulfonation of SPAEB and SPAEB oleum(SO365) using a literature method [30] and calculated as

Degree of disulfonation 2 times (119867119886119867119887) times 100 (1)

where119867119886 is the peak which is attributed to the protons adja-cent to the sulfonate groups and 119867119887 is the peak assigned toprotons next to the carbon of the imidazole group located atboth the sulfonated and nonsulfonated regions The degreesof disulfonation for SPAEB and SPAEB oleum (SO365)were calculated as 31 and 52 respectively

34 FTIR Analysis and Thermal Behavior of SPAEB Mem-brane FTIR spectrum of SPAEB copolymer membrane isshown in Figure 8 Spectrum shows benzimidazole adsorp-tion bands at 1629 cmminus1 1584 cmminus1 and 1465 cmminus1 Peaks at1025 cmminus1 and 1097 cmminus1 are assigned to stretching of thesulfonate groups

TGA curves of the SPAEB and SPAEB oleum (SO365)copolymer membranes are shown in Figure 9 The firstdecomposition step around 300∘C is attributed to the decom-position of the sulfone groups according to the literature [3738] Second thermal degradation steps occurring in tempera-ture ranges 450ndash500∘C should be due to polymermain chainTGA curves reveal that SPAEB copolymer degrades at about450∘C whereas the postsulfonated SPAEB oleum (SO365)copolymer is thermally stable up to sim475∘C This thermaldegradation behavior can be explained with higher percent-age of double-bond character due to the increasing numberof sulfone groups incorporated in copolymer chain in agree-ment with the literature [39 40] This result also shows thatthe presence of sulfonic groups involving strong intra- andintermolecular hydrogen bonds increases thermal stability asin the literature [41]

35 Proton Conductivity The resistance 119877 (Ω) of the mem-branes was calculated as the slope of voltage versus currentgraphs Voltage versus current graphs plotted for 30 times to


21

242628303234363840424446

48

T

4000 3500 3000 2500 2000 1500 1000 500

(cmminus1

)

Figure 5 FTIR spectrum of sulfonated poly(arylene ether benzimidazole) copolymer

0123456789101112

(ppm)

Figure 6 1H NMR spectrum of SPAEB copolymer

7273747576777879808182838485

(ppm)

Ha

Hb

Figure 7 1H NMR spectrum of SPAEB oleum (SO365)

reach a stable resistance value for each membrane Figure 10shows the voltage versus current graphs of SPAEB oleum(SO365) SPAEB and commercial Nafion 212 membranesThe proton conductivity 120590 (Scm) values were calculatedfrom the equation

120590 = 1119877 times119871(119882 times 119879) (2)

where 119871 (0425 cm) is the distance between the voltagesense electrodes (two inner electrodes) 119879 is the membranethickness which is 00051 cm 00144 cm and 00784 cm forNafion 212 SPAEB oleum (SO365) and SPAEBmembranesrespectively and119882 is the sample width

Proton conductivities of the membranes at 80∘C arecalculated as 0203 Scm (RH = 100) 00059 Scm (RH =0) and 00012 Scm (RH = 0) for Nafion 212 SPAEB andSPAEB oleum (SO365) respectively This result suggeststhat as more sulfonic acid sites are incorporated into themembrane structure the proton conductivity is decreasedPresence of sulfonic acid groups in the membrane structuredecreases proton conductivity interacting with imidazolesites

36 Fuel Cell Performance Test Figure 11 shows the polar-ization and power density curves of SPAEB copolymermembrane Average membrane thickness was measured as00094 cm The highest power density of the membrane wasmeasured as 237mWcmminus2 at 80∘C without humidification

4 Conclusions

SPAEB copolymer was synthesized successfully via nucle-ophilic aromatic polycondensation of the twomonomers syn-thesized (SDCDPS andHPBI) and the commercial monomerDCDPS Structures of monomers and the copolymer wereconfirmed by 1H NMR and FTIR analysis TGA analysesshowed that as the degree of disulfonation is increasedthermal stability of the copolymer is increased due to double-bonds and hydrogen bonds of sulfone groups According toresults of proton conductivity tests as the degree of disul-fonation increases proton conductivity of the membranesdecreases Sulfonic acid groups prevent proton conductionfrom interacting with imidazole groups Single cell perfor-mance test result shows that SPAEB membranes can be usedas a polymer electrolyte membrane

Since cost of PBI synthesis is quite high SPAEB copoly-mer membrane which includes a cheaper component poly-(arylene ether) reduces the cost of the synthesis There canbe further researches to enhance the fuel cell performance ofSPAEB membranes

Competing Interests

The authors declare that they have no competing interests


T

4000 3500 3000 2500 2000 1500 1000 500

(cmminus1

)

5355

60

65

70

75

80

85

90

95

100

105

Figure 8 FTIR spectrum of SPAEB copolymer membrane

20

40

60

80

100

120

Wei

ght (

)

Temperature (∘C)

100 200 300 400 500 600

SPAEB_oleum (SO365)SPAEB

Figure 9 TGA curves of the SPAEB and SPAEB oleum (SO365) copolymers

E(V

olts)

minus00002 minus00001 0 00001 00002

I (Ampscm2)

SPAEB_oleum(SO365)RH = 0

SPAEBRH = 0

Nafion 212RH = 100

minus010

minus005

0

005

010

Figure 10 Voltage versus current graphs of SPAEB oleum (SO365) SPAEB and commercial Nafion 212 membranes


0

01

02

03

04

05

06

07

08

09

1

Volta

ge (V

)

0 20 40 60 80 100 120

Current density (mA cmminus2)

0

5

10

15

20

25

Pow

er d

ensit

y (m

Wcm

minus2)

Polarization curvePower density curve

Figure 11 Polarization and power density curves of SPAEB copoly-mer membrane

Acknowledgments

This research was supported by Anadolu University ScientificResearch Projects Committee (Project no 1206F102)

References

[1] L Carrette K A Friedrich and U Stimming ldquoFuel cells prin-ciples types fuels and applicationsrdquoChemPhysChem vol 1 no4 pp 162ndash193 2000

[2] Y Qi Y Gao S Tian et al ldquoSynthesis and properties of novelbenzimidazole- containing sulfonated polyethersulfones forfuel cell applicationsrdquo Journal of Polymer Science Part A Poly-mer Chemistry vol 47 no 7 pp 1920ndash1929 2009

[3] Y Sakaguchi A Kaji K Kitamura et al ldquoPolymer electrolytemembranes derived from novel fluorine-containing poly(ary-lene ether ketone)s by controlled post-sulfonationrdquo Polymervol 53 no 20 pp 4388ndash4398 2012

[4] Y Sakaguchi K Kitamura and S Takase ldquoIsomeric effect ofsulfonated poly(arylene ether)s comprising dihydroxynaphtha-lene on properties for polymer electrolyte membranesrdquo Journalof Polymer Science Part A Polymer Chemistry vol 50 no 22pp 4749ndash4755 2012

[5] E P Jutemar S Takamuku and P Jannasch ldquoSulfonated poly-(arylene ether sulfone) ionomers containing di- and tetrasul-fonated arylene sulfone segmentsrdquo Polymer Chemistry vol 2no 1 pp 181ndash191 2011

[6] C-H Shen S L-C Hsu E Bulycheva and N BelomoinaldquoHigh temperature proton exchange membranes based onpoly(arylene ether)s with benzimidazole side groups for fuelcellsrdquo Journal of Materials Chemistry vol 22 no 36 pp 19269ndash19275 2012

[7] S-W Chuang S L-C Hsu and C-L Hsu ldquoSynthesis and pro-perties of fluorine-containing polybenzimidazolemontmorill-onite nanocomposite membranes for direct methanol fuel cellapplicationsrdquo Journal of Power Sources vol 168 no 1 pp 172ndash177 2007

[8] P Chen X Chen Z An K Chen and K Okamoto ldquoQuino-xaline-based crosslinkedmembranes of sulfonated poly(arylene

ether sulfone)s for fuel cell applicationsrdquo International Journalof Hydrogen Energy vol 36 no 19 pp 12406ndash12416 2011

[9] X Li Y YuQ Liu andYMeng ldquoSynthesis and characterizationof anion exchange membranes based on poly(arylene ether sul-fone)s containing various cations functioned tetraphenyl meth-ane moietiesrdquo International Journal of Hydrogen Energy vol 38no 25 pp 11067ndash11073 2013

[10] J-Y Park T-H Kim H J Kim J-H Choi and Y T HongldquoCrosslinked sulfonated poly(arylene ether sulfone) membra-nes for fuel cell applicationrdquo International Journal of HydrogenEnergy vol 37 no 3 pp 2603ndash2613 2012

[11] J-H Seol J-H Won K-S Yoon Y T Hong and S-Y LeeldquoSiO2 ceramic nanoporous substrate-reinforced sulfonatedpoly(arylene ether sulfone) composite membranes for protonexchange membrane fuel cellsrdquo International Journal of Hydro-gen Energy vol 37 no 7 pp 6189ndash6198 2012

[12] M Han G ZhangM Li et al ldquoConsiderations of themorphol-ogy in the design of proton exchange membranes cross-linkedsulfonated poly(ether ether ketone)s using a new carboxyl-terminated benzimidazole as the cross-linker for PEMFCsrdquoInternational Journal of Hydrogen Energy vol 36 no 3 pp2197ndash2206 2011

[13] Y Li M Xie X Wang D Chao X Liu and C Wang ldquoNovelbranched sulfonated poly(ether ether ketone)s membranes fordirect methanol fuel cellsrdquo International Journal of HydrogenEnergy vol 38 no 27 pp 12051ndash12059 2013

[14] D W Seo Y D Lim S H Lee et al ldquoPreparation and charac-terization of sulfonated poly(tetra phenyl ether ketone sulfone)sfor proton exchange membrane fuel cellrdquo International Journalof Hydrogen Energy vol 37 no 7 pp 6140ndash6147 2012

[15] L Gui C Zhang S Kang N Tan G Xiao and D Yan ldquoSyn-thesis and properties of hexafluoroisopropylidene-containingsulfonated poly(arylene thioether phosphine oxide)s for pro-ton exchange membranesrdquo International Journal of HydrogenEnergy vol 35 no 6 pp 2436ndash2445 2010

[16] L P Shen G Y Xiao D Y Yan and G M Sun ldquoSulfonatedpoly(arylene thioether ketone ketone sulfone)s for protonexchange membranes with high oxidative stabilityrdquo E-Polymersvol 5 no 1 pp 321ndash330 2005

[17] S J Wang Y Z Meng A R Hlil and A S Hay ldquoSynthesisand characterization of phthalazinone containing poly(aryleneether)s poly(arylene thioether)s and poly(arylene sulfone)s viaa novel NminusC coupling reactionrdquo Macromolecules vol 37 no 1pp 60ndash65 2004

[18] G Bahlakeh and M Nikazar ldquoMolecular dynamics simulationanalysis of hydration effects on microstructure and trans-port dynamics in sulfonated poly(26-dimethyl-14-phenyleneoxide) fuel cell membranesrdquo International Journal of HydrogenEnergy vol 37 no 17 pp 12714ndash12724 2012

[19] T Xu D Wu S-J Seo J-J Woo L Wu and S-H MoonldquoProton exchange compositemembranes from blends of bromi-nated and sulfonated poly(26-dimethyl-14-phenylene oxide)rdquoJournal of Applied Polymer Science vol 124 no 4 pp 3511ndash35192012

[20] X Zhang Z Hu Y Pu et al ldquoPreparation and properties ofnovel sulfonated poly(p-phenylene-co-aryl ether ketone)s forpolymer electrolyte fuel cell applicationsrdquo Journal of PowerSources vol 216 pp 261ndash268 2012

[21] S Adanur and H Zheng ldquoSynthesis and characterization ofsulfonated polyimide based membranes for proton exchangemembrane fuel cellsrdquo Journal of Fuel Cell Science and Technol-ogy vol 10 no 4 Article ID 041001 2013


[22] L Akbarian-Feizi S Mehdipour-Ataei and H Yeganeh ldquoSur-vey of sulfonated polyimide membrane as a good candidate fornafion substitution in fuel cellrdquo International Journal of Hydro-gen Energy vol 35 no 17 pp 9385ndash9397 2010

[23] B-K Chen T-Y Wu C-W Kuo et al ldquo441015840-Oxydianiline(ODA) containing sulfonated polyimideprotic ionic liquidcomposite membranes for anhydrous proton conductionrdquoInternational Journal of Hydrogen Energy vol 38 no 26 pp11321ndash11330 2013

[24] X Liu J Yin Y Kong et al ldquoElectrical andmechanical propertystudy on three-component polyimide nanocomposite filmswith titanium dioxide and montmorilloniterdquo Thin Solid Filmsvol 544 pp 352ndash356 2013

[25] J W Connell J G Smith and P M Hergenrother ldquoPropertiesand potential applications of poly(arylene ether benzimida-zole)srdquo in High-Temperature Properties and Applications ofPolymeric Materials M R Ant J W Connell and H L NMcManus Eds vol 603 of ACS Publications pp 186ndash199American Chemical Society Washington DC USA 1995

[26] Y T Hong C H Lee H S Park et al ldquoImprovement of electro-chemical performances of sulfonated poly(arylene ether sul-fone) via incorporation of sulfonated poly(arylene ether benz-imidazole)rdquo Journal of Power Sources vol 175 no 2 pp 724ndash7312008

[27] F Ng D J Jones J Roziere B Bauer M Schuster and MJeske ldquoNovel sulfonated poly(arylene ether benzimidazole)Cardo proton conducting membranes for PEMFCrdquo Journal ofMembrane Science vol 362 no 1-2 pp 184ndash191 2010

[28] J Yu M Ree T J Shin et al ldquoMiscibility behavior of polyimide(PI)poly(arylene ether benzimidazole) (PAEBI) blends and itseffects on the adhesion of PIPAEBIcopper jointsrdquo Polymervol 41 no 1 pp 169ndash177 2000

[29] P M Hergenrother J G Smith Jr and J W Connell ldquoSynthesisand properties of poly(arylene ether benzimidazole)srdquo Polymervol 34 no 4 pp 856ndash865 1993

[30] B R Einsla High temperature polymers for proton exchangemembrane fuel cells [PhD thesis] Virginia Polytechnic Instituteand State University Blacksburg Va USA 2005

[31] W L Harrison F Wang J B Mecham et al ldquoInfluence ofthe bisphenol structure on the direct synthesis of sulfonatedpoly(arylene ether) copolymers Irdquo Journal of Polymer SciencePart A Polymer Chemistry vol 41 no 14 pp 2264ndash2276 2003

[32] MUeda H Toyota T Ouchi et al ldquoSynthesis and characteriza-tion of aromatic poly(ether sulfone)s containing pendant sod-ium sulfonate groupsrdquo Journal of Polymer Science Part A Poly-mer Chemistry vol 31 no 4 pp 853ndash858 1993

[33] F Wang M Hickner Q Ji et al ldquoSynthesis of highly sulfonatedpoly(arylene ether sulfone) random (statistical) copolymers viadirect polymerizationrdquo Macromolecular Symposia vol 175 no1 pp 387ndash396 2001

[34] I Blanco L Abate F A Bottino G Cicala and A LatterildquoDumbbell-shaped polyhedral oligomeric silsesquioxanespol-ystyrene nanocomposites the influence of the bridge rigidityon the resistance to thermal degradationrdquo Journal of CompositeMaterials vol 49 no 20 pp 2509ndash2517 2015

[35] I Blanco F A Bottino G Cicala A Latteri and A ReccaldquoSynthesis and characterization of differently substituted phenylhepta isobutyl-polyhedral oligomeric silsesquioxanepolysty-rene nanocompositesrdquo Polymer Composites vol 35 no 1 pp151ndash157 2014

[36] S Kaytakoglu and L Akyalcin ldquoOptimization of parametricperformance of a PEMFCrdquo International Journal of HydrogenEnergy vol 32 no 17 pp 4418ndash4423 2007

[37] F Samperi C Puglisi T Ferreri et al ldquoThermal decompositionproducts of copoly(arylene ether sulfone)s characterized bydirect pyrolysis mass spectrometryrdquo Polymer Degradation andStability vol 92 no 7 pp 1304ndash1315 2007

[38] F Samperi S Battiato C Puglisi et al ldquoSynthesis and character-ization of sulfonated copolyethersulfonesrdquo Journal of PolymerScience Part A Polymer Chemistry vol 48 no 14 pp 3010ndash3023 2010

[39] I Blanco G Cicala A Latteri A Mamo and A Recca ldquoTher-mal and thermo-oxidative degradations of poly(26-dimethyl-14-phenylene oxide) (PPO)copoly(aryl ether sulfone) P(ESES-co-EES) block copolymers a kinetic studyrdquo Journal of ThermalAnalysis and Calorimetry vol 112 no 1 pp 375ndash381 2013

[40] I Blanco F A Bottino G Cicala A Latteri and A Recca ldquoAkinetic study of the thermal and thermal oxidative degradationsof new bridged POSSPS nanocompositesrdquo Polymer Degrada-tion and Stability vol 98 no 12 pp 2564ndash2570 2013

[41] L Abate V Asarisi I Blanco G Cicala and G Recca ldquoTheinfluence of sulfonation degree on the thermal behaviour of sul-fonated poly(arylene ethersulfone)srdquo Polymer Degradation andStability vol 95 no 9 pp 1568ndash1574 2010

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Journal ofNanomaterials


water that limits their practical applications [6 7] In thisstudy a sulfonated poly(arylene ether benzimidazole) copol-ymer was synthesized [25ndash30] and a copolymer membranewas prepared by solution casting method The membranewas treated with sulfuric acid to strengthen the protonconductivity character Finally single cell performance of thecopolymer membrane was tested in a PEMFC test station

2 Experimental

21 Materials 441015840-Dichlorodiphenyl sulfone (DCDPS) and4-hydroxybenzoic acid phenyl ester were purchased fromABCR and vacuum dried at 50∘C for 24 h before use Fumingsulfuric acid (65 SO3 extra pure) phenylsulfone and 1-methyl-2-pyrrolidone (+995) were used as received fromMerck Sodium chloride 331015840-diaminobenzidine (DAB) andDMAc were purchased from Sigma Aldrich DAB was vac-uum dried at 50∘C for 24 h before use Sodium hydroxidetoluene and isopropanol were used as received from Riedelde Haen Potassium carbonate (Alfa AESAR) was vacuumdried at 50∘C for 24 h prior to use Sulfuric acid (95ndash97) wasused as received from Fluka

22 Synthesis of Monomers Synthesis of HPBI has beenpreviously reported by several researchers [29 30] DAB(0467mole) 4-hydroxybenzoic acid phenyl ester(0934mole) phenylsulfone (500 g) and toluene (150mL)were added to a jacketed four-necked cylindrical reactorequipped with a Dean-Stark trap a condenser a mechanicalstirrer and a nitrogen inlet-outlet Reaction temperaturewas controlled by oil bath circulator Reactor was isolated toprevent heat loss Dean and Stark trap was filled with tolueneto remove water azeotropically Temperature was raised to150∘C and the solution was allowed to reflux for 6 hoursToluene was removed and the solution was heated to 280∘Cfor 2 hGeneratedwater andphenolwere removed fromDeanand Stark trap and the monomer precipitated For furtherremoval of phenol outlet gas stream was connected to twoserial gas washing bottles and vacuum was applied for 2hours Solution was left to cool and excess ethanol was addedat 150∘C Product was left at room temperature overnightand filtered to separate the phenylsulfone that crystallizedout of solution Synthesized tan monomer was washed withacetone and dried at 120∘C for 24 hours

331015840-Disulfonated-441015840-dichlorodiphenyl sulfone (SDCDPS)monomer [30ndash33] synthesized in a four-necked round bot-tomflask equippedwith a thermometer a condenser amech-anical stirrer and a nitrogen inlet-outlet DCDPS (99mmol)was dissolved in fuming sulfuric acid (65 SO3) Tempera-ture was raised to 110∘C and the mixture was stirred for 6hours to produce a homogeneous solutionThen solutionwascooled to room temperature and sodium chloride was addedThe dark brown color of the solution turned into white andthe productwas neutralized to pH6-7with sodiumhydroxideand excess sodiumchloridewas added to precipitate themon-omer as its sodium form Synthesized SDCDPS was filteredrecrystallized from isopropanol andwatermixture for furtherpurification Resulted white monomer dried at 120∘C for 24hours

23 Disulfonated Poly(Arylene Ether Benzimidazole) (SPAEB)Copolymers Synthesis Einsla has previously reported thesynthesis of disulfonated poly(arylene ether benzimidazole)copolymer [30] SDCPS (7mmol) and equimolar DCDPSand HPBI (14mmol) were introduced into a 250mL four-necked flask equipped with a thermometer mechanicalstirrer a Dean-Stark trap a condenser and a nitrogen inlet-outlet Potassium carbonate (16mmol) and 75mL of NMPwere introduced to the reaction flask As an azeotroping agent40mL of toluene was introduced to the flask and the Dean-Stark trap was filled with toluene Temperature was raised to140∘C for dehydration of the system for 4 hours and Deanand Stark trap was emptied Temperature was raised to 170∘Cand reaction was carried out for 20 hours Generated tolueneduring reaction was removed via Dean and Stark trap Thedark brown viscous solution poured into deionized water andthe precipitated copolymer was filteredThe yellowish-brownfibrous copolymer was dried at 120∘C for 24 h and grounded

24 Postsulfonation of SPAEB Copolymers A postsulfona-tion method was used for further sulfonation of synthe-sized SPAEB copolymers to analyze the effect of degreeof sulfonation to thermal stability and proton conductivityPostsulfonation was carried out by dissolving 5 g of thecopolymer in 100mL fuming sulfuric acid (65) and stirredfor 10 hours at 30∘C Resulting product was denoted asSPAEB oleum (SO365) After the reaction the reactionmixture was poured into a large volume water to precipitatethe product The sulfonated polymer material was recoveredand washed with water until the wash was pH neutral and itwas then dried for 48 h at 100∘C

25 Membrane Preparation and Acid Doping Synthesizedcopolymer (075 g) was dissolved in 3188mL of DMAc(25 wwminus1) in a 250mL two-necked flask equipped witha mechanical stirrer and a condenser The flask was insertedin an ultrasonic water bath Temperature was heated to 80∘Cfor 4 hours After filtration solutionwas cast onto petri dishesand dried Resulting transparent membranes were immersedin boiling 05MH2SO4 for 2 hours and dried to removeabsorbed water The same membrane preparation procedurewas performed for SPAEB oleum (SO365) too

26 Characterization The 1HNMR spectra of themonomersand copolymer were recorded on a 500MHz BrukerAVANCE II NMR spectrometer Grounded monomers andcopolymer were dissolved in deuterated dimethylsulfoxide(DMSO-d6) and chemical shifts were measured againsttetramethylsilane (TMS) as an internal standard We usedthe integral area belonging to the protons adjacent to thesulfonate groups and the integral area of the protons next tothe carbon of the imidazole moiety degrees of disulfonationobtained from 1H NMR

Fourier transform infrared (FTIR) spectra were recordedusing a Perkin Elmer Frontier spectrometer All the sampleswere dried at 105∘C for 24 h prior to analyses

Thermogravimetric curves are largely affected by exper-imental conditions especially by the heating rate So the


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4 Conclusions



Competing Interests



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Acknowledgments


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CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




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7273747576777879808182838485

(ppm)

Ha

Hb



120590 = 1119877 times119871(119882 times 119879) (2)




4 Conclusions



Competing Interests



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Acknowledgments


References



















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




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0123456789101112

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7273747576777879808182838485

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Ha

Hb



120590 = 1119877 times119871(119882 times 119879) (2)




4 Conclusions



Competing Interests



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Acknowledgments


References



















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




21

242628303234363840424446

48

T

4000 3500 3000 2500 2000 1500 1000 500

(cmminus1

)


0123456789101112

(ppm)


7273747576777879808182838485

(ppm)

Ha

Hb



120590 = 1119877 times119871(119882 times 119879) (2)




4 Conclusions



Competing Interests



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Acknowledgments


References



















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




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Acknowledgments


References



















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




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Acknowledgments


References



















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



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