Phosphoric acid doped fuel cell membranes by radiation grafting of 4-Vinylpyridine/Comonomers mixtures onto poly(ethylene-co-tetrafluoroethylene) films

Proton exchange membrane fuel cell (PEMFC) is one of the most promising green technologies for providing clean and efficient energy and operating above 100 °C is highly desired to enhance the electrodes kinetics and increase tolerance to carbon monoxide impurities from reformed hydrogen. However, th...

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Main Author:	Sithambaranathan, Paveswari
Format:	Thesis
Language:	English
Published:	2018
Subjects:	TP Chemical technology
Online Access:	http://eprints.utm.my/id/eprint/79482/1/PaveswariSithambaranathanPFChE2018.pdf
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spelling	my-utm-ep.794822018-10-31T12:41:38Z Phosphoric acid doped fuel cell membranes by radiation grafting of 4-Vinylpyridine/Comonomers mixtures onto poly(ethylene-co-tetrafluoroethylene) films 2018 Sithambaranathan, Paveswari TP Chemical technology Proton exchange membrane fuel cell (PEMFC) is one of the most promising green technologies for providing clean and efficient energy and operating above 100 °C is highly desired to enhance the electrodes kinetics and increase tolerance to carbon monoxide impurities from reformed hydrogen. However, the commercially available membranes for fuel cell such as Nafion® are expensive and have limited operational temperature (< 80 °C). This work aims to develop alternative phosphoric acid (PA) doped membranes using basic radiation grafted precursor films for PEMFC operating at temperatures 120 °C. Particularly, the main objective of this study was to develop three PA doped membranes by radiation induced grafting of mixture of 4-vinylpyridine (4-VP) with glycidyl methacrylate (GMA), 1-vinylimidazole (1-VIm) or triallyl cyanurate (TAC) onto poly(ethylene-co-tetrafluoroethylene) (ETFE) films followed by doping with PA. A membrane obtained by grafting of 4-VP alone onto ETFE film and acid doping was used as a reference. The degree of grafting (DG) was controlled by optimization of the reaction parameters such as absorbed dose, composition of monomer mixture, temperature and reaction time whereas the acid doping level (DL) was manipulated by variation of PA concentration, reaction temperature and time. The properties of the PA doped membranes denoted as ETFE-g-P(4-VP)/PA, ETFE-g-P(4-VP/GMA)/PA, ETFE-g-P(4-VP/1-VIm)/PA, ETFE-g-P(4-VP/TAC)/PA together with the corresponding grafted and pristine ETFE films were evaluated in correlation with type and concentration of second monomer added to 4-VP (comonomer) using Fourier transform infrared, field emission scanning electron microscope, thermal gravimetric analysis and x-ray diffraction. The membranes were also subjected to elemental as well as mechanical analysis and their proton conductivity together with fuel cell test were investigated at 120 °C. The DG was found to be strongly dependent upon grafting parameters. The obtained membranes attained high DL which reached 97 %, 115 %, 119 % and 113 % for membranes grafted with 4-VP, 4-VP/GMA, 4-VP/1-VIm and 4-VP/TAC, respectively. All the membranes displayed well-defined structures, good thermal stability, reasonable mechanical strength and high proton conductivity in the range of 33-44 mS/cm (at 120 °C and 0 % RH). The mechanical properties of ETFE-g-P(4-VP/TAC)/PA membrane was significantly improved by introducing TAC as a comonomer during grafting, which crosslinked the PA doped grafted chains compared to the other two membranes. ETFE-g-P(4-VP/1-VIm)/PA membrane showed the best fuel cell performance (226 mW/cm2) at 120 °C and 20 % RH conditions compared to the other two membranes and this is due to the increase of number of protonated pyridine and imidazole rings that could host more PA. The sequence of the membranes’ performance in PEMFC represented by power density was ETFE-g-P(4-VP/TAC)/PA (84 mW/cm2) > ETFE-g-P(4-VP/GMA)/PA (76 mW/cm2) > ETFE-g-P(4-VP/1-VIm)/PA (70 mW/cm2) > ETFE-g-P(4-VP)/PA (53 mW/cm2) under dry conditions. Thus, it can be concluded that grafting of comonomers is an effective method to enhance the conductivity of PA doped membranes in way making them more suitable for fuel cell operation above 100 °C. 2018 Thesis http://eprints.utm.my/id/eprint/79482/ http://eprints.utm.my/id/eprint/79482/1/PaveswariSithambaranathanPFChE2018.pdf application/pdf en public phd doctoral Universiti Teknologi Malaysia, Faculty of Chemical & Energy Engineering Faculty of Chemical & Energy Engineering
institution	Universiti Teknologi Malaysia
collection	UTM Institutional Repository
language	English
topic	TP Chemical technology
spellingShingle	TP Chemical technology Sithambaranathan, Paveswari Phosphoric acid doped fuel cell membranes by radiation grafting of 4-Vinylpyridine/Comonomers mixtures onto poly(ethylene-co-tetrafluoroethylene) films
description	Proton exchange membrane fuel cell (PEMFC) is one of the most promising green technologies for providing clean and efficient energy and operating above 100 °C is highly desired to enhance the electrodes kinetics and increase tolerance to carbon monoxide impurities from reformed hydrogen. However, the commercially available membranes for fuel cell such as Nafion® are expensive and have limited operational temperature (< 80 °C). This work aims to develop alternative phosphoric acid (PA) doped membranes using basic radiation grafted precursor films for PEMFC operating at temperatures 120 °C. Particularly, the main objective of this study was to develop three PA doped membranes by radiation induced grafting of mixture of 4-vinylpyridine (4-VP) with glycidyl methacrylate (GMA), 1-vinylimidazole (1-VIm) or triallyl cyanurate (TAC) onto poly(ethylene-co-tetrafluoroethylene) (ETFE) films followed by doping with PA. A membrane obtained by grafting of 4-VP alone onto ETFE film and acid doping was used as a reference. The degree of grafting (DG) was controlled by optimization of the reaction parameters such as absorbed dose, composition of monomer mixture, temperature and reaction time whereas the acid doping level (DL) was manipulated by variation of PA concentration, reaction temperature and time. The properties of the PA doped membranes denoted as ETFE-g-P(4-VP)/PA, ETFE-g-P(4-VP/GMA)/PA, ETFE-g-P(4-VP/1-VIm)/PA, ETFE-g-P(4-VP/TAC)/PA together with the corresponding grafted and pristine ETFE films were evaluated in correlation with type and concentration of second monomer added to 4-VP (comonomer) using Fourier transform infrared, field emission scanning electron microscope, thermal gravimetric analysis and x-ray diffraction. The membranes were also subjected to elemental as well as mechanical analysis and their proton conductivity together with fuel cell test were investigated at 120 °C. The DG was found to be strongly dependent upon grafting parameters. The obtained membranes attained high DL which reached 97 %, 115 %, 119 % and 113 % for membranes grafted with 4-VP, 4-VP/GMA, 4-VP/1-VIm and 4-VP/TAC, respectively. All the membranes displayed well-defined structures, good thermal stability, reasonable mechanical strength and high proton conductivity in the range of 33-44 mS/cm (at 120 °C and 0 % RH). The mechanical properties of ETFE-g-P(4-VP/TAC)/PA membrane was significantly improved by introducing TAC as a comonomer during grafting, which crosslinked the PA doped grafted chains compared to the other two membranes. ETFE-g-P(4-VP/1-VIm)/PA membrane showed the best fuel cell performance (226 mW/cm2) at 120 °C and 20 % RH conditions compared to the other two membranes and this is due to the increase of number of protonated pyridine and imidazole rings that could host more PA. The sequence of the membranes’ performance in PEMFC represented by power density was ETFE-g-P(4-VP/TAC)/PA (84 mW/cm2) > ETFE-g-P(4-VP/GMA)/PA (76 mW/cm2) > ETFE-g-P(4-VP/1-VIm)/PA (70 mW/cm2) > ETFE-g-P(4-VP)/PA (53 mW/cm2) under dry conditions. Thus, it can be concluded that grafting of comonomers is an effective method to enhance the conductivity of PA doped membranes in way making them more suitable for fuel cell operation above 100 °C.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Sithambaranathan, Paveswari
author_facet	Sithambaranathan, Paveswari
author_sort	Sithambaranathan, Paveswari
title	Phosphoric acid doped fuel cell membranes by radiation grafting of 4-Vinylpyridine/Comonomers mixtures onto poly(ethylene-co-tetrafluoroethylene) films
title_short	Phosphoric acid doped fuel cell membranes by radiation grafting of 4-Vinylpyridine/Comonomers mixtures onto poly(ethylene-co-tetrafluoroethylene) films
title_full	Phosphoric acid doped fuel cell membranes by radiation grafting of 4-Vinylpyridine/Comonomers mixtures onto poly(ethylene-co-tetrafluoroethylene) films
title_fullStr	Phosphoric acid doped fuel cell membranes by radiation grafting of 4-Vinylpyridine/Comonomers mixtures onto poly(ethylene-co-tetrafluoroethylene) films
title_full_unstemmed	Phosphoric acid doped fuel cell membranes by radiation grafting of 4-Vinylpyridine/Comonomers mixtures onto poly(ethylene-co-tetrafluoroethylene) films
title_sort	phosphoric acid doped fuel cell membranes by radiation grafting of 4-vinylpyridine/comonomers mixtures onto poly(ethylene-co-tetrafluoroethylene) films
granting_institution	Universiti Teknologi Malaysia, Faculty of Chemical & Energy Engineering
granting_department	Faculty of Chemical & Energy Engineering
publishDate	2018
url	http://eprints.utm.my/id/eprint/79482/1/PaveswariSithambaranathanPFChE2018.pdf
_version_	1747818237034233856

Phosphoric acid doped fuel cell membranes by radiation grafting of 4-Vinylpyridine/Comonomers mixtures onto poly(ethylene-co-tetrafluoroethylene) films

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