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Development of proton conductive polymer electrolytes composed of sulfonated poly(ether ether ketone) and Brønsted acidic ionic liquid (1-methylimidazolium tetrafluoroborate)

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Abstract

This article relates to the synthesis, characterization and dielectric measurements of solid polymer electrolytes, derived from the ionic interaction of sulfonated poly(ether ether ketone) (sPEEK) and a Brønsted acidic ionic liquid (1-methylimidazolium tetrafluoroborate, [Hmim][BF4]) for electrochemical applications. The efficiency of the interaction was examined by incorporating different amounts of ionic liquid (IL) with the sulfonated polymer matrices having three different degrees of sulfonation (DS). The polymer matrices and composite electrolytes were systematically characterized with 1H NMR, FT-IR, SEM, TGA and DMA. Anhydrous proton conductivity and dielectric measurements were studied in detail with varying temperature and frequencies. The presented analyzes revealed that sPEEK1.0–2 sample (2.50–3.51 × 10–1 Sm−1 at 380–450 K) exhibited maximum proton conductivity and thermomechanical stability under anhydrous environment. Dielectric measurements also provided results confirming proton conductivity measurements. Furthermore, sPEEK1.0–2 composite membrane exhibited higher glass transition temperature and reasonable storage modulus value (Tg = 157 °C; E′ = 0.22 GPa) compared to IL-doped sPEEK membranes presented in the literature. The work herein opens new prospects for the as-synthesized materials to use as a solid polymer electrolyte for electrochemical applications such as high temperature proton exchange membrane fuel cells (HT-PEMFC) in a wide temperature range.

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References

  1. K.S. Ngai, S. Ramesh, K. Ramesh, J.C. Juan, A review of polymer electrolytes: fundamental, approaches and applications. Ionics 22, 1259–1279 (2016). https://doi.org/10.1007/s11581-016-1756-4

    Article  CAS  Google Scholar 

  2. E. Abouzari-Lotf, M. Zakeri, M.M. Nasef, M. Miyake, P. Mozarmnia et al., Highly durable polybenzimidazole composite membranes with phosphonated graphene oxide for high temperature polymer electrolyte membrane fuel cells. J. Power Sources 412, 238–245 (2019). https://doi.org/10.1016/j.jpowsour.2018.11.057

    Article  CAS  Google Scholar 

  3. N.N. Krishnan, S. Lee, R.V. Ghorpade, A. Konovalova, J.H. Jang et al., Polybenzimidazole (PBI-OO) based composite membranes using sulfophenylated TiO2 as both filler and crosslinker, and their use in the HT-PEM fuel cell. J. Membr. Sci. 560, 11–20 (2018). https://doi.org/10.1016/j.memsci.2018.05.006

    Article  CAS  Google Scholar 

  4. H.A. Patel, N. Mansor, S. Gadipelli, D.J.L. Brett, Z. Guo, Superacidity in Nafion/MOF hybrid membranes retains water at low humidity to enhance proton conduction for fuel cells. ACS Appl. Mater. Interfaces. 8(45), 30687–30691 (2016). https://doi.org/10.1021/acsami.6b12240

    Article  CAS  Google Scholar 

  5. Y. He, J. Wang, H. Zhang, T. Zhang, B. Zhang et al., Polydopamine-modified graphene oxide nanocomposite membrane for proton exchange membrane fuel cell under anhydrous conditions. J. Mater. Chem. A 2(25), 9548 (2014). https://doi.org/10.1039/c3ta15301k

    Article  CAS  Google Scholar 

  6. Y. Cai, Z. Yue, X. Teng, S. Xu, Radiation grafting graphene oxide reinforced polybenzimidazole membrane with a sandwich structure for high temperature proton exchange membrane fuel cells in anhydrous atmosphere. Eur. Polym. J. 103, 207–213 (2018). https://doi.org/10.1016/j.eurpolymj.2018.02.020

    Article  CAS  Google Scholar 

  7. M. Du, L. Yang, X. Luo, K. Wang, G. Chang, Novel phosphoric acid (PA)-poly(ether ketone sulfone) with flexible benzotriazole side chains for high-temperature proton exchange membranes. Polym. J. (2019). https://doi.org/10.1038/s41428-018-0118-7

    Article  Google Scholar 

  8. Z. Qi, A. Kaufman, Improvement of water management by a microporous sublayer for PEM fuel cells. J. Power Sources 109(1), 38–46 (2002). https://doi.org/10.1016/S0378-7753(02)00058-7

    Article  CAS  Google Scholar 

  9. G.Q. Lu, F.Q. Liu, C.Y. Wang, Water transport through Nafion 112 membrane in DMFCs. Electrochem. Solid-State Lett. 8(1), A1–A4 (2005). https://doi.org/10.1149/1.1825312

    Article  CAS  Google Scholar 

  10. A. Ferraris, A. Messana, A.G. Airale, L. Sisca, P.H. de Carvalho et al., Nafion® tubing humidification system for polymer electrolyte membrane fuel cells. Energies 12(9), 1773 (2019). https://doi.org/10.3390/en12091773

    Article  CAS  Google Scholar 

  11. K. Oh, O. Kwon, B. Son, D.H. Lee, S. Shanmugam, Nafion-sulfonated silica composite membrane for proton exchange membrane fuel cells under operating low humidity condition. J. Membr. Sci. 583, 103–109 (2019). https://doi.org/10.1016/j.memsci.2019.04.031

    Article  CAS  Google Scholar 

  12. N.H. Jalani, K. Dunn, R. Datta, Synthesis and characterization of Nafion®-MO2 (M = Zr, Si, Ti) nanocomposite membranes for higher temperature PEM fuel cells. Electrochim. Acta 51(3), 553–560 (2005). https://doi.org/10.1016/j.electacta.2005.05.016

    Article  CAS  Google Scholar 

  13. J. Maiti, N. Kakati, S.P. Woo, Y.S. Yoon, Nafion® based hybrid composite membrane containing GO and dihydrogen phosphate functionalized ionic liquid for high temperature polymer electrolyte membrane fuel cell. Compos. Sci. Technol. 155, 189–196 (2018). https://doi.org/10.1016/j.compscitech.2017.11.030

    Article  CAS  Google Scholar 

  14. K. Hooshyari, M. Javanbakht, A. Shabanikia, M. Enhessari, Fabrication BaZrO3/PBI-based nanocomposite as a new proton conducting membrane for high temperature proton exchange membrane fuel cells. J. Power Sources 276, 62–72 (2015). https://doi.org/10.1016/j.jpowsour.2014.11.083

    Article  CAS  Google Scholar 

  15. A.R. Kim, M. Vinothkannan, D.J. Yoo, Sulfonated-fluorinated copolymer blending membranes containing SPEEK for use as the electrolyte in polymer electrolyte fuel cells (PEFC). Int. J. Hydrog. Energy 42(7), 4349–4365 (2017). https://doi.org/10.1016/j.ijhydene.2016.11.161

    Article  CAS  Google Scholar 

  16. B. Singh, N.M.H. Duong, D. Henkensmeier, J.H. Jang, H.J. Kim et al., Influence of different side-groups and cross-links on phosphoric acid doped radel-based polysulfone membranes for high temperature polymer electrolyte fuel cells. Electrochim. Acta 224, 306–313 (2017). https://doi.org/10.1016/j.electacta.2016.12.088

    Article  CAS  Google Scholar 

  17. J. Wang, H. Jiang, Y. Xu, J. Yang, R. He, Quaternized poly(aromatic ether sulfone) with siloxane crosslinking networks as high temperature proton exchange membranes. Appl. Surf. Sci. 452, 473–480 (2018). https://doi.org/10.1016/j.apsusc.2018.05.063

    Article  CAS  Google Scholar 

  18. J.P. Melchior, G. Majer, K.D. Kreuer, Why do proton conducting polybenzimidazole phosphoric acid membranes perform well in high-temperature PEM fuel cells? Phys. Chem. Chem. Phys. 19(1), 601–612 (2017). https://doi.org/10.1039/c6cp05331a

    Article  CAS  Google Scholar 

  19. B. Yue, G. Zeng, Y. Zhang, S. Tao, X. Zhang et al., Improved performance of acid-base composite of phosphonic acid functionalized polysulfone and triazolyl functionalized polysulfone for PEM fuel cells. Solid State Ion. 300, 10–17 (2017). https://doi.org/10.1016/j.ssi.2016.11.011

    Article  CAS  Google Scholar 

  20. G.A. Giffin, S. Galbiati, M. Walter, K. Aniol, C. Ellwein et al., Interplay between structure and properties in acid-base blend PBI-based membranes for HT-PEM fuel cells. J. Membr. Sci. 535, 122–131 (2017). https://doi.org/10.1016/j.memsci.2017.04.019

    Article  CAS  Google Scholar 

  21. F. Mack, K. Aniol, C. Ellwein, J. Kerres, R. Zeis, Novel phosphoric acid-doped PBI-blends as membranes for high-temperature PEM fuel cells. J. Mater. Chem. A 3(20), 10864–10874 (2015). https://doi.org/10.1039/c5ta01337b

    Article  CAS  Google Scholar 

  22. M.J. Earle, K.R. Seddon, Ionic liquids: green solvents for the future. Pure Appl. Chem. 72(7), 1391–1398 (2000). https://doi.org/10.1351/pac200072071391

    Article  CAS  Google Scholar 

  23. L. Deng, L.M. Zhang, Rheological characteristics of chitin/ionic liquid gels and electrochemical properties of regenerated chitin hydrogels. Colloids Surf. A 586, 124220 (2020). https://doi.org/10.1016/j.colsurfa.2019.124220

    Article  CAS  Google Scholar 

  24. S. Denizalti, A.K. Ali, Ç. Ela, M. Ekmekci, S. Erten-Ela, Dye-sensitized solar cells using ionic liquids as redox mediator. Chem. Phys. Lett. 691, 373–378 (2018). https://doi.org/10.1016/j.cplett.2017.11.035

    Article  CAS  Google Scholar 

  25. A. Eftekhari, Supercapacitors utilising ionic liquids. Energy Storage Mater. 9, 47–69 (2017). https://doi.org/10.1016/j.ensm.2017.06.009

    Article  Google Scholar 

  26. M. Safa, A. Chamaani, N. Chawla, B. El-Zahab, Polymeric ionic liquid gel electrolyte for room temperature lithium battery applications. Electrochim. Acta 213, 587–593 (2016). https://doi.org/10.1016/j.electacta.2016.07.118

    Article  CAS  Google Scholar 

  27. N. Wang, S. Liang, L. Zhang, P. Cao, L. Xu, M. Lin, Ionic liquid supported nickel-based metal-organic framework for electrochemical sensing of hydrogen peroxide and electrocatalytic oxidation of methanol. Colloids Surf. A 603, 125199 (2020). https://doi.org/10.1016/j.colsurfa.2020.125199

    Article  CAS  Google Scholar 

  28. M. Doyle, S.K. Choi, G. Proulx, High-temperature proton conducting membranes based on perfluorinated ionomer membrane-ionic liquid composites. J. Electrochem. Soc. 147(1), 24–37 (2000). https://doi.org/10.1149/1.1393153

    Article  Google Scholar 

  29. J.R. Nykaza, R. Benjamin, K.M. Meek, Y.A. Elabd, Polymerized ionic liquid diblock copolymer as an ionomer and anion exchange membrane for alkaline fuel cells. Chem. Eng. Sci. 154, 119–127 (2016). https://doi.org/10.1016/j.ces.2016.05.041

    Article  CAS  Google Scholar 

  30. J. Luo, O. Conrad, I.F.J. Vankelecom, Physicochemical properties of phosphonium-based and ammonium-based protic ionic liquids. J. Mater. Chem. 22(38), 20574–20579 (2012). https://doi.org/10.1039/c2jm34359b

    Article  CAS  Google Scholar 

  31. R. Leones, R.C. Sabadini, J.M.S.S. Esperança, A. Pawlicka, M.M. Silva, Playing with ionic liquids to uncover novel polymer electrolytes. Solid State Ion. 300, 46–52 (2017). https://doi.org/10.1016/j.ssi.2016.11.018

    Article  CAS  Google Scholar 

  32. T. Ueki, M. Watanabe, Macromolecules in ionic liquids: progress, challenges, and opportunities. Macromolecules 41(11), 3739–3749 (2008). https://doi.org/10.1021/ma800171k

    Article  CAS  Google Scholar 

  33. A.S. Shaplov, R. Marcilla, D. Mecerreyes, Recent advances in innovative polymer electrolytes based on poly(ionic liquid)s. Electrochim. Acta 175, 18–34 (2015). https://doi.org/10.1016/j.electacta.2015.03.038

    Article  CAS  Google Scholar 

  34. L. Li, J. Zhang, Y. Wang, Sulfonated poly(ether ether ketone) membranes for direct methanol fuel cell. J. Membr. Sci. 226(1–2), 159–167 (2003). https://doi.org/10.1016/j.memsci.2003.08.018

    Article  CAS  Google Scholar 

  35. A. Iulianelli, A. Basile, Sulfonated PEEK-based polymers in PEMFC and DMFC applications: a review. Int. J. Hydrog. Energy 37(20), 15241–15255 (2012). https://doi.org/10.1016/j.ijhydene.2012.07.063

    Article  CAS  Google Scholar 

  36. Y. Li, M. Zhang, X. Wang, Z. Li, L. Zhao, Anhydrous conducting composite membranes composed of SPEEK/silica/ionic liquids for high-temperature proton exchange. Electrochim. Acta 222, 1308–1315 (2016). https://doi.org/10.1016/j.electacta.2016.11.106

    Article  CAS  Google Scholar 

  37. Q. Che, B. Sun, R. He, Preparation and characterization of new anhydrous, conducting membranes based on composites of ionic liquid trifluoroacetic propylamine and polymers of sulfonated poly (ether ether) ketone or polyvinylidenefluoride. Electrochim. Acta 53(13), 4428–4434 (2008). https://doi.org/10.1016/j.electacta.2008.01.028

    Article  CAS  Google Scholar 

  38. M. Yılmazoğlu, Synthesis and characterization of sulfonated polyether ether ketone (sPEEK) electrolytes for PEM fuel cells: effect of sulfonation degree. El-Cezerî J. Sci. Eng. 7(2), 424–435 (2020). https://doi.org/10.31202/ecjse.649784

    Article  Google Scholar 

  39. M. Yılmazoğlu, F. Bayıroğlu, H. Erdemi, U. Abaci, H.Y. Guney, Dielectric properties of sulfonated poly(ether ether ketone) (SPEEK) electrolytes with 1-ethyl-3-methylimidazolium tetrafluoroborate salt: Ionic liquid-based conduction pathways. Colloids Surf. A 611, 125825 (2021). https://doi.org/10.1016/j.colsurfa.2020.125825

    Article  CAS  Google Scholar 

  40. H. Deligöz, M. Yılmazoğlu, Development of a new highly conductive and thermomechanically stable complex membrane based on sulfonated polyimide/ionic liquid for high temperature anhydrous fuel cells. J. Power Sources 196(7), 3496–3502 (2011). https://doi.org/10.1016/j.jpowsour.2010.12.033

    Article  CAS  Google Scholar 

  41. J.F. Blanco, Q.T. Nguyen, P. Schaetzel, Novel hydrophilic membrane materials: sulfonated polyethersulfone cardo. J. Membr. Sci. 186(2), 267–279 (2001). https://doi.org/10.1016/S0376-7388(01)00331-3

    Article  CAS  Google Scholar 

  42. K.H. Lee, J.Y. Chu, A.R. Kim, D.J. Yoo, Enhanced performance of sulfonated poly (arylene ether ketone) block copolymer bearing pendant sulfonic acid groups for PEMFC operating at 80% relative humidity. ACS Appl. Mater. Interfaces 10(24), 20835–20844 (2018). https://doi.org/10.1021/acsami.8b03790

    Article  CAS  Google Scholar 

  43. T. Roy, S.K. Wanchoo, K. Pal, Novel sulfonated poly (ether ether ketone)/rGONR@TiO2 nanohybrid membrane for proton exchange membrane fuel cells. Solid State Ion. 349, 115296 (2020). https://doi.org/10.1016/j.ssi.2020.115296

    Article  CAS  Google Scholar 

  44. F. Gashoul, M.J. Parnian, S. Rowshanzamir, A new study on improving the physicochemical and electrochemical properties of SPEEK nanocomposite membranes for medium temperature proton exchange membrane fuel cells using different loading of zirconium oxide nanoparticles. Int. J. Hydrog. Energy 42(1), 590–602 (2017). https://doi.org/10.1016/j.ijhydene.2016.11.132

    Article  CAS  Google Scholar 

  45. D.J. Kim, D.H. Choi, C.H. Park, S.Y. Nam, Characterization of the sulfonated PEEK/sulfonated nanoparticles composite membrane for the fuel cell application. Int. J. Hydrog. Energy 41(13), 5793–5802 (2016). https://doi.org/10.1016/j.ijhydene.2016.02.056

    Article  CAS  Google Scholar 

  46. M.A. Deyab, M.T. Zaky, M.I. Nessim, Inhibition of acid corrosion of carbon steel using four imidazolium tetrafluoroborates ionic liquids. J. Mol. Liq. 229, 396–404 (2017). https://doi.org/10.1016/j.molliq.2016.12.092

    Article  CAS  Google Scholar 

  47. W. Feng, Y. Lu, Y. Chen, Y. Lu, T. Yang, Thermal stability of imidazolium-based ionic liquids investigated by TG and FTIR techniques. J. Therm. Anal. Calorim. 125(1), 143–154 (2016). https://doi.org/10.1007/s10973-016-5267-3

    Article  CAS  Google Scholar 

  48. M. Vinothkannan, A.R. Kim, G.G. Kumar, J.M. Yoon, D.J. Yoo, Toward improved mechanical strength, oxidative stability and proton conductivity of an aligned quadratic hybrid (SPEEK/FPAPB/Fe3O4-FGO) membrane for application in high temperature and low humidity fuel cells. RSC Adv. 7, 39034–39048 (2017). https://doi.org/10.1039/C7RA07063B

    Article  CAS  Google Scholar 

  49. S. Yi, F. Zhang, W. Li, C. Huang, H. Zhang et al., Anhydrous elevated-temperature polymer electrolyte membranes based on ionic liquids. J. Membr. Sci. 366(1–2), 349–355 (2011). https://doi.org/10.1016/j.memsci.2010.10.031

    Article  CAS  Google Scholar 

  50. F. Gao, X. Li, X. Zhang, W. Liu, C. Liu, Enhancement on both phosphoric acid retention and proton conduction of polybenzimidazole membranes by plasma treatment. Colloids Surf. A 603, 125197 (2020). https://doi.org/10.1016/j.colsurfa.2020.125197

    Article  CAS  Google Scholar 

  51. P.R. Jothi, S. Dharmalingam, An efficient proton conducting electrolyte membrane for high temperature fuel cell in aqueous-free medium. J. Membr. Sci. 450, 389–396 (2014). https://doi.org/10.1016/j.memsci.2013.09.034

    Article  CAS  Google Scholar 

  52. S.M.J. Zaidi, S.D. Mikhailenko, G.P. Robertson, M.D. Guiver, S. Kaliaguine, Proton conducting composite membranes from polyether ether ketone and heteropolyacids for fuel cell applications. J. Membr. Sci. 173(1), 17–34 (2000). https://doi.org/10.1016/S0376-7388(00)00345-8

    Article  CAS  Google Scholar 

  53. H. Deligöz, M. Yılmazoğlu, S. Yılmaztürk, Y. Şahin, K. Ulutaş, Synthesis and characterization of anhydrous conducting polyimide/ionic liquid complex membranes via a new route for high-temperature fuel cells. Polym. Adv. Technol. 23(8), 1156–1165 (2011). https://doi.org/10.1002/pat.2016

    Article  CAS  Google Scholar 

  54. S.U. Çelik, A. Bozkurt, Proton conduction promoted by 1H–1,2,3-benzotriazole in non-humidified polymer membranes. Electrochim. Acta 56(17), 5961–5965 (2011). https://doi.org/10.1016/j.electacta.2011.04.108

    Article  CAS  Google Scholar 

  55. T. Dippel, K.D. Kreuer, J.C. Lassegues, D. Rodriguez, Proton conductivity in fused phosphoric acid; A 1H/31P PFG-NMR and QNS study. Solid State Ion. 61(1–3), 41–46 (1993). https://doi.org/10.1016/0167-2738(93)90332-W

    Article  CAS  Google Scholar 

  56. R.S. Malik, P. Verma, V. Choudhary, A study of new anhydrous, conducting membranes based on composites of aprotic ionic liquid and cross-linked SPEEK for fuel cell application. Electrochim. Acta 152, 352–359 (2015). https://doi.org/10.1016/j.electacta.2014.11.167

    Article  CAS  Google Scholar 

  57. D. Gupta, V. Choudhary, Studies on novel heat treated sulfonated poly(ether ether ketone) [SPEEK]/diol membranes for fuel cell applications. Int. J. Hydrog. Energy 36(14), 8525–8535 (2011). https://doi.org/10.1016/j.ijhydene.2011.04.044

    Article  CAS  Google Scholar 

  58. B. Tareev, Physics of Dielectric Materials (Mir Publishers, Moscow, 1975).

    Google Scholar 

  59. V.M. Mohan, W. Qiu, J. Shen, W.J. Chen, Electrical properties of poly(vinyl alcohol) (PVA) based on LiFePO4 complex polymer electrolyte films. J. Polym. Res. 17, 143–150 (2010). https://doi.org/10.1007/s10965-009-9300-0

    Article  CAS  Google Scholar 

  60. A.S. Marf, R.M. Ranjdar Abdullah, S.B. Aziz, Structural, morphological, electrical and electrochemical properties of PVA:CS-based proton-conducting polymer blend electrolytes. Membranes 10(71), 1–25 (2020). https://doi.org/10.3390/membranes10040071

    Article  CAS  Google Scholar 

  61. A.L. Saroj, R.K. Singh, Thermal, dielectric and conductivity studies on PVA/Ionic liquid [EMIM][EtSO4] based polymer electrolytes. J. Phys. Chem. Solids 73(2), 162–168 (2012). https://doi.org/10.1016/j.jpcs.2011.11.012

    Article  CAS  Google Scholar 

  62. M. Hema, S. Selvasekerapandian, A. Sakunthala, D. Arunkumar, H. Nithya, Structural, vibrational and electrical characterization of PVA–NH4Br polymer electrolyte system. Phys. B 403, 2740–2747 (2008). https://doi.org/10.1016/j.physb.2008.02.001

    Article  CAS  Google Scholar 

  63. A.R. Kim, M. Vinothkannan, M.H. Song, J.Y. Lee, H.K. Lee, D.J. Yoo, Amine functionalized carbon nanotube (ACNT) filled in sulfonated poly(ether ether ketone) membrane: effects of ACNT in improving polymer electrolyte fuel cell performance under reduced relative humidity. Compos. Part B 188, 107890 (2020)

    Article  CAS  Google Scholar 

  64. X. Zhang, S. Yu, Q. Zhu, L. Zhao, Enhanced anhydrous proton conductivity of SPEEK/IL composite membrane embedded with amino functionalized mesoporous silica. Int. J. Hydrog. Energy 44, 6148–6159 (2019). https://doi.org/10.1016/j.ijhydene.2019.01.050

    Article  CAS  Google Scholar 

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Acknowledgements

The author gratefully acknowledges Yalova University for financial support and thanks Assoc. Prof. Dr. Ufuk ABACI for proton conductivity and dielectric constant tests.

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Yılmazoğlu, M. Development of proton conductive polymer electrolytes composed of sulfonated poly(ether ether ketone) and Brønsted acidic ionic liquid (1-methylimidazolium tetrafluoroborate). J Mater Sci: Mater Electron 32, 15393–15411 (2021). https://doi.org/10.1007/s10854-021-06089-w

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