Role of protic ionic liquid concentration in proton conducting polymer electrolytes for improved electrical and thermal properties

Abstract

Protic ionic liquids (PILs) in the acidic medium are known to show higher ionic conductivity than neat PIL or PIL in alkaline media. Hence, polymer electrolyte membranes (PEM) containing both PIL and acids are considered ideal for non-humidified intermediate temperature PEM fuel cells. Herein, we report non-aqueous proton conducting PEM made up of diethylmethylammonium trifluoromethanesulfonate; [dema][TfO] and neat phosphoric acid (H 3 PO 4 ) with poly (vinylidene fluoride-cohexafluoropropylene); PVDF-HFP as the host matrix. The presence of PIL significantly modified the structure and microstructure of the electrolyte films with the emergence of micropores in the PIL containing membranes. SEM images suggest leaching of PIL and phosphoric acid above 80 wt% of PIL in the electrolyte membranes. Thermogravimetric studies show that the dehydration in the PEM films due to phosphoric acid condensation at 100°C-200°C region is arrested by the presence of PIL. The maximum ionic conductivity at room temperature is ∼6.3×10 −4 S cm −1 at 40 wt% of [dema][TfO] addition, which is two orders higher than that of the primary electrolyte (PE) containing only phosphoric acid in PVDF-HFP. This high conductivity in PEM films can be correlated to the increase in polar β and γ phases as well as a drop in the total crystallinity fraction in the film. The study using dielectric spectroscopy reveals a strong coupling of ionic conductivity with the structural or segmental relaxation of the PVDF-HFP due to the presence of [dema][TfO] in the PEMs.

Designing Na2Zn2TeO6-Embedded 3D-Nanofibrous Poly(vinylidenefluoride)-co-hexafluoropropylene-Based Nanohybrid Electrolyte via Electrospinning for Durable Sodium-Ion Capacitors

“…The VDF part of PVDF-HFP contributes to the crystalline entity in the polymer, whereas the amorphous part of the polymer owns the HFP chains. The XRD pattern of the PVDF-HFP polymer exhibits the pronounced peaks at 18.2° (100) and 20° (200), which belong to the α (crystalline) and β (amorphous) phase, respectively . It is obvious from the XRD pattern of esHPMs that the characteristic peak at 18.2° becomes less significant, while the peak at 20° remains significant upon the addition of NZTO fillers in the PVDF-HFP polymer.…”

“…(amorphous) phase, respectively. 67 It is obvious from the XRD pattern of esHPMs that the characteristic peak at 18.2°becomes less significant, while the peak at 20°remains significant upon the addition of NZTO fillers in the PVDF-HFP polymer. The diffraction pattern of the samples reveals the conversion of the crystalline structure from the non-polar α phase to the electroactive β phase with successive addition of fillers.…”

Different Approaches for the Preparation of Composite Ionic Liquid-Based Membranes for Proton Exchange Membrane Fuel Cell Applications—Recent Advancements

“…Nair et al [ 59 ] prepared PVDF- co -hexafluoropropylene (HFP)-based membranes with different diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]) content for use in the low- and middle- temperature range. In this case, 40 wt.% of PA acid was added to the PVDF-HFP solution in acetone and different amounts of [dema][TfO] (20, 40, 60, and 80 wt.%) were introduced thereafter.…”

Ionic liquid‐modified materials as polymer electrolyte membrane and electrocatalyst in fuel cell application: An update

“…In addition to the previously discussed polymer/IL membranes, poly(vinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP), [97][98][99][100] polyvinyl alcohol (PVA), 101 sulfonated poly(styrene-isobutylene-styrene), and cellulose have also been paired with IL for fuel cell application. For example, Nair et al 100 PVA is easy to convert into a film form, cross-link capability, degradable and cost-effective material. Thus, Gohil et al 102 immobilized an IL containing a [bmim] cation and a [PF 6 ] anion into a PVA polymer modified with 4,5-imidazoledicrarboxyic acid (IDC).…”