Composite proton conducting membrane by radiation-induced grafting of 1-vinylimidazole onto poly(ethylene-co-tetrafluoroethylene) and phosphoric acid doping

Abstract

Composite membrane containing phosphoric acid (PA) for possible use in a fuel cell was prepared by radiation-induced grafting of 1-vinylimidazole (1-VIm) onto poly(ethylene-co-tetrafluoroethylene) (ETFE) films followed by protonation with PA doping. The preparation procedure involved three steps: (i) irradiation of ETFE films by an electron beam, (ii) grafting of 1-VIm onto the irradiated films under selected conditions and (iii) doping the grafted film with PA. The membrane composition, thermal properties and thermal stability were evaluated using Fourier-transformed infrared spectroscopy, thermogravimetric analysis and differential scanning calorimetry, respectively. The obtained membrane was found to have a degree of grafting of 54% and 6.6 mmol PA per poly-VIm repeating unit with ionic conductivity of 140 mS cm À1 at 120 C and *20% relative humidity. The overall results suggest that the membrane has a promising combination of physicochemical properties appealing for possible application in polymer electrolyte membrane fuel cell above 100 C.

Novel concept of polymer electrolyte membranes for high-temperature fuel cells based on ETFE grafted with neutral acrylic monomers

“…As an example, poly(ethylene-alt-tetrafluoroethylene) (ETFE) was used [8,[52][53][54][55][56][57][58][59]. Generally, the polymer backbone material was irradiated and subsequently grafted with basic monomer(s), since it was anticipated that the affinity to PA scales with basicity.…”

Radiation-grafted materials for energy conversion and energy storage applications

“…The membranes achieved very high proton conductivity with 140 mS/cm at low humidity [186]. This method proved to be simpler and had fewer problems than methods involving synthesis by polymerization reactions for obtaining similar membranes [18,92].…”

An Investigation of Proton Conductivity of Vinyltriazole-Grafted PVDF Proton Exchange Membranes Prepared via Photoinduced Grafting

“…Engineering plastics have become the subject of many studies of developing proton exchange membranes used in fuel cells, which involve polytetrafluoroethylene (PTFE), poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), poly(tetrafluoroethylene-co-perfluoropropylvinylether) (PFA), poly(ethylene-alt-tetrafluoroethylene) (ETFE), poly(ether ether ketone) (PEEK), and poly(vinylidene fluoride) (PVDF) films. In these studies, the base film was modified via 2 Journal of Chemistry grafting using UV-light, -rays, electron beam, X-ray, and gamma radiation techniques [3,9,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Previously, Asano et al reported on the development of proton-conducting membranes generated by the -ray radiation grafting of styrene and its derivatives onto fluorine-containing base films and subsequent sulfonation [12,15,22,27].…”

“…The proton transport occurs between hydrogen bonds of neighboring heterocyclic units through structure diffusion [1,3,6,7,10]. However, studies on grafted films containing readily available Nheterocyclic monomers are very rare [23][24][25]29]. Recently, Schmidt and Schmidt-Naake reported on the preparation of phosphoric acid (PA) doped 4-vinylpyridine (4VP) grafted poly(ethylene-co-tetrafluoroethylene), ETFE-graftpoly(4VP), by using radiation-induced grafting method [23].…”

“…Recently, Schmidt and Schmidt-Naake reported on the preparation of phosphoric acid (PA) doped 4-vinylpyridine (4VP) grafted poly(ethylene-co-tetrafluoroethylene), ETFE-graftpoly(4VP), by using radiation-induced grafting method [23]. Quite recently, Nasef et al and Lepit et al declared that the preparation of phosphoric acid (PA) doped 4-vinylpyridine (4VP) and 1-vinylimidazole (VIm) grafted ETFE and PVDF based electrolyte membranes were prepared via radiationinduced grafting method, respectively [24,25,29]. Therefore, it is remarkable that a graft copolymer consisting of 1-vinyl-1,2,4-triazole (VTri) and a PVDF based matrix is prepared under UV light in one step to achieve an anhydrous PEMs.…”