DOI 10.1515/ract-2014-2106 | Radiochim. Acta 2014; 102(4): 351–362 E. Shamsaei, M. M. Nasef*, H. Saidi, and A. H. Yahaya Parametric investigations on proton conducting membrane by radiation induced grafting of 4-vinylpyridine onto poly(vinylidene fluoride) and phosphoric acid doping Abstract: Proton conducting membrane composed of grafted basic moiety doped with phosphoric acid (PA) was studied. The membrane denoted as PVDF-g-4-VP/PA was prepared by radiation induced grafting of 4-vinylpyridine (4-VP) onto poly(vinylidene fluoride) (PVDF) films fol- lowed by doping with PA. The effect of grafting conditions on the degree of grafting (%) was investigated. The acid doping conditions (%, time and PA concentration) were also investigated with respect to doping level. The grafted precursors and the acid doped membranes were character- ized by means of Fourier transform infrared (FTIR), X-ray diffractometry (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and field emis- sion scanning electron microscopy (FESEM). The mem- branes showed a thermal stability up to a temperature of ∼ 160 ∘ C, above which they undergo a multi-step degra- dation pattern due to decomposition of the protonated functions, poly(4VP) grafts and PVDF matrix, respectively. The proton conductivities of the membranes were found to increase with the increase in % ( doping level) and the temperature with a maximum proton conductivity of 62 mS cm −1 achieved at 100 ∘ C without any humidifica- tion. The results of the present study show that the pre- pared membrane has a potential to be proposed for oper- ating polymer electrolyte membrane fuel cell above 80 ∘ C. Keywords: Proton conducting membrane, Radiation in- duced grafting, 4-vinylpyridine, PVDF film, Phosphoric acid doping, High temperature PEM fuel cell. || *Corresponding Author: M. M. Nasef, Malaysia Japan International Institute of Technology (MJIIT), International Campus, Universiti Teknologi Malaysia, Jalan Semarak, 54100 Kuala Lumpur, Malaysia, E-mail: mahmoudeithar@cheme.utm.my E. Shamsaei, M. M. Nasef, H. Saidi: Institute of Hydrogen Economy (IHE), International Campus, Universiti Teknologi Malaysia, Jalan Semarak, 54100 Kuala Lumpur, Malaysia A. H. Yahaya: Chemistry Department, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia 1 Introduction Polymer electrolyte membrane fuel cells (PEMFCs) have been recognized as one of the most promising candidates for zero emission energy sources for a variety of mobile and stationary applications. One of the key components hav- ing significant role in terms of proton conduction and pre- vention of bulk mixing of gaseous fuel and oxidant is poly- mer electrolyte membrane (PEM). Currently, Nafion ® (per- fluorinated sulfonic acid membrane) is most widely used PEM owing to its excellent chemical stability and high pro- ton conductivity. However, it has obvious shortcomings when operating at temperatures beyond 80 ∘ C including losing a great deal of its water driven proton conductiv- ity together with high fuel gas crossover in addition to the high cost of its fluorinated material [1]. Operation PEMFC at high temperature is highly sought to enhance the effi- ciency through better electrode kinetics, reduce or elim- inate of humidification system, increase the tolerance to fuel impurities. Recently, immense efforts have been dedicated to de- velop low-cost polymer conducting membrane using ra- diation induced grafting techniques [2–5]. This was en- couraged by simplicity of preparation techniques and the strong potential of the obtained membranes for applica- tion in PEMFC [6–8]. However, very limited research efforts have been exerted on the preparation of PEMs by radiation induced grafting (RIG) for the application in PEMFC oper- ating at high temperature [9–11]. Poly(vinylidene fluoride) (PVDF) is a favourite syn- thetic fluorinated polymer with unique mechanical and physicochemical properties in addition to high resistance to ionizing radiation [12] which has been widely studied for membrane preparation including PEM [13–15]. A review of previous studies on sulfonic acid PEMs based on PVDF films can be found in Ref. [16]. Grafting of heterocyclic monomers containing polar pendants groups like -C=N of 4-VP can impart basic prop- erties to a polymer film. Thus, 4-VP was grafted onto var- Brought to you by | Universiti Teknologi Malaysia Authenticated | 161.139.220.106 Download Date | 6/18/14 2:50 PM