Influence of hydrophilic/hydrophobic protic ionic liquids (PILs) on the poly(vinylidene fluoride) (PVDF-ionic liquid) me
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Influence of hydrophilic/hydrophobic protic ionic liquids (PILs) on the poly(vinylidene fluoride) (PVDFionic liquid) membrane properties Isabel Va´zquez-Ferna´ndez1, Adnane Bouzina1, Mohamed Raghibi1, Laure Timperman1, Janick Bigarre´2, and Me´rie`m Anouti1,* 1 2
Laboratoire PCM2E, Université de Tours, Parc de Grandmont, 37200 Tours, France CEA-DAM Le Ripault, BP16, 37260 Monts, France
Received: 10 June 2020
ABSTRACT
Accepted: 30 August 2020
In this study, we investigate the effect of protic ionic liquids (PILs) on the properties of poly(vinylidene fluoride)/protic ionic liquids (PVDF/PIL) composite membranes made by solvent casting. The morphology, polymer phase, crystallinity, proton conductivities and mechanical properties were determined according to the nature and quantities of PIL added. Independently of the ionic liquids nature among EtPy][HSO4], [Py][HSO4], [(Octyl)3NH][HSO4] and [(Octyl)3NH][H2PO4], we observed the crystallization of PVDF into more stable electroactive phases (b and c). Furthermore, the presence of PIL decreased the elastic modulus and modified the crystallization kinetics, as indicated by the size of the spherulitic microstructures. Proton conductivity results suggest the predominance of the Grotthuss-type conduction mechanism for all PVDF/PIL composites membranes supplied by the amphoteric anions, HSO4- and H2PO4-. Finally, the higher stable conductivities observed for hydrated membranes with [(Octyl)3NH][HSO4] evidenced that the Grotthuss mechanism is favored by amphiphilic cation associated with the stronger hydrogen-bonded network of the [HSO4]- anion.
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
Handling Editor: Maude Jimenez.
Address correspondence to E-mail: [email protected]
https://doi.org/10.1007/s10853-020-05207-z
J Mater Sci
GRAPHIC ABSTRACT
Introduction The concern about the use of fossil fuels and their environmental impact has increased considerably in the last 20 years. Coal, oil and natural gas have powered our homes and businesses for many generations, but stocks are running out and cleaner energy sources are needed. In this context, fuel cells have emerged as sustainable alternatives to generate electricity [1]. Proton exchange membrane fuel cells (PEMFCs) are devices capable of converting the chemical energy of hydrogen into electrical energy [2]. In this technology, the membrane is an essential component that plays the role of electronic insulator, proton conductor and separator between the two electrodes. Membranes must meet certain criteria to be used in PEMFCs: high ionic conductivity, mechanical, thermal and electrochemical stability, chemical resistance and low cost [3]. Since the 1970s, a perfluoro sulfonic acid (PFSA) membrane (called ‘‘Nafion’’) developed by DuPont has been the reference for PEMFCs. However, water control at elevated temperatures and the expensive manufacturing process are currently its main drawbacks [4]. In addition to PFSA, alternative polymeric membrane materials such as partially fluorinate
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