ABSTRACT: The global demands of energy are still increasing alongside many civilizational problems, notably the effects on the environment due to the overuse of traditional energy sources based on fossil fuels. New cleaner, renewable sources for sustainable energy systems are a key challenge of the 21st century society.N/

Rangel, C. M.

Teixeira, António P. S.

Teixeira, Fatima

Renewable Energy

English

In this work, new doped Naﬁon membranes for PEMFC are prepared by casting with 1 wt% loading of the prepared indazole- and condensed pyrazolebisphosphonic acids (AzBPs). The new membranes were analysed by ATR-FTIR spectroscopy and their morphology was examined by SEM. Membranes were evaluated for water uptake and ion exchange capacity (IEC), and their hydration number was estimated. The proton conduction properties of the modiﬁed membranes were evaluated by electrochemical impedance spectroscopy (EIS), at different temperatures (30, 40, 50 and 60 ºC) and relative humidity (RH) (40, 60 and 80%). The proton conductivities of all membranes increase with increasing temperature and RH. Also, all new membranes doped with AzBPs exhibited higher proton conductivities than Naﬁon N-115, used as a reference and tested at the same experimental conditions, with values up to 1.5-fold. Results show that the incorporation of AzBPs dopants on Naﬁon membranes enhances the proton conduction throughout the modiﬁed membranes. The best proton conductivity was observed for membranes with AzBP1 as dopant, with a value of 94 mS cm-1. These results indicate that the Naﬁon membranes doped with indazole- and condensed pyrazolebisphosphonic acids are a promising approach for new membranes for PEMFC with improved proton conductivity

Teixeira, Fátima C.

Repositório Científico da Universidade de Évora

New proton conductive membranes of indazole- and condensed pyrazolebisphosphonic acid-Naﬁon membranes for PEMFC

ABSTRACT: In this work, new doped Nafion membranes for PEMFC are prepared by casting with 1 wt% loading of the prepared indazole- and condensed pyrazolebisphosphonic acids (AzBPs). The new membranes were analysed by ATR-FTIR spectroscopy and their morphology was examined by SEM. Membranes were evaluated for water uptake and ion exchange capacity (IEC), and their hydration number was estimated. The proton conduction properties of the modified membranes were evaluated by electrochemical impedance spectroscopy (EIS), at different temperatures (30, 40, 50 and 60 °C) and relative humidity (RH) (40, 60 and 80%). The proton conductivities of all membranes increase with increasing temperature and RH. Also, all new membranes doped with AzBPs exhibited higher proton conductivities than Nafion N-115, used as a reference and tested at the same experimental conditions, with values up to 1.5-fold. Results show that the incorporation of AzBPs dopants on Nafion membranes enhances the proton conduction throughout the modified membranes. The best proton conductivity was observed for membranes with AzBP1 as dopant, with a value of 94 mS cm-1. These results indicate that the Nafion membranes doped with indazole- and condensed pyrazolebisphosphonic acids are a promising approach for new membranes for PEMFC with improved proton conductivity.info:eu-repo/semantics/publishedVersio

Repositório do LNEG

lable at ScienceDirectRenewable Energy 196 (2022) 1187e1196Contents lists avaiRenewable Energyjournal homepage: www.elsevier .com/locate/reneneNew proton conductive membranes of indazole- and condensedpyrazolebisphosphonic acid-Nafion membranes for PEMFCFatima C. Teixeira a, Antonio P.S. Teixeira b, C.M. Rangel a, *a Laboratorio Nacional de Energia e Geologia, I.P., Estrada do Paço do Lumiar, 22, 1649-038, Lisboa, Portugalb Departamento de Ciências Medicas e da Saúde, ESDH & LAQV- REQUIMTE, IIFA, Universidade de Evora, R. Rom~ao Ramalho, 59, 7000-671, Evora, Portugala r t i c l e i n f oArticle history:Received 7 March 2022Received in revised form8 June 2022Accepted 11 July 2022Available online 14 July 2022Keywords:Proton exchange membranesFuel cellsNafionBisphosphonic acidsProton conductivity* Corresponding author.E-mail address: carmen.rangel@lneg.pt (C.M. Ranghttps://doi.org/10.1016/j.renene.2022.07.0540960-1481/© 2022 Elsevier Ltd. All rights reserved.a b s t r a c tIn this work, new doped Nafion membranes for PEMFC are prepared by casting with 1 wt% loading of theprepared indazole- and condensed pyrazolebisphosphonic acids (AzBPs). The new membranes wereanalysed by ATR-FTIR spectroscopy and their morphology was examined by SEM. Membranes wereevaluated for water uptake and ion exchange capacity (IEC), and their hydration number was estimated.The proton conduction properties of the modified membranes were evaluated by electrochemicalimpedance spectroscopy (EIS), at different temperatures (30, 40, 50 and 60 C) and relative humidity(RH) (40, 60 and 80%). The proton conductivities of all membranes increase with increasing temperatureand RH. Also, all new membranes doped with AzBPs exhibited higher proton conductivities than NafionN-115, used as a reference and tested at the same experimental conditions, with values up to 1.5-fold.Results show that the incorporation of AzBPs dopants on Nafion membranes enhances the protonconduction throughout the modified membranes. The best proton conductivity was observed formembranes with AzBP1 as dopant, with a value of 94 mS cm-1. These results indicate that the Nafionmembranes doped with indazole- and condensed pyrazolebisphosphonic acids are a promising approachfor new membranes for PEMFC with improved proton conductivity.© 2022 Elsevier Ltd. All rights reserved.1. IntroductionThe need of energy for the development of the world is stillgrowing along with the rising of many civilizational problems. Thesupply of the global demanding energy has its bases on the overuseof traditional energy sources based on fossil fuels, with consider-able effects on the environment recognized as a key factorregarding climate change [1e3]. The paradigm for the 21st centurysociety is the transition from traditional energy to cleaner andrenewable sources, integrating sustainable energy systems,ensuring that the needed ambitious and well-defined targets andimplementation plans, being established by national governmentsand international institutions, are implemented so that a decar-bonized energy system is achieved by 2050 [4e7].However, renewable energy sources are unstable and low-density sources of production, dependent at all times on the in-tensity of the source that originates them, such as the sun or wind,and therefore remain intermittent production providers, unable toel).meet energy needs in certain periods of higher energy consump-tion. In these periods, it is necessary to compensate the insufficientproduction of renewable energy using stored energy as an alter-native [7]. Energy storage thus attracts a growing interest for amore complete use of intermittent renewable energies, integratingproposals from other vectors, such as hydrogen, in an energy sys-tem that is intended to be more flexible, robust, constant, and moresustainable [3,8,9].In the case of hydrogen, it can be generated by electrolysis ofwater and renewable electricity, so it can be used as a green fuel.Green hydrogen technology can surpass the drawbacks of manyrenewable energy systems, but it still remains dependent fromseveral factors, such as, its production and storage. Hydrogen can beused as a green fuel for fuel cells, which are electrochemical devicesthat can convert its chemical energy to electric energy. The directand efficient conversion of hydrogen, with formation of water,without formation of intermediates, by-products or toxic gases,makes the hydrogen fuel cells technology a promising renewableand clean energy source [10e12].Proton exchange membrane fuel cells (PEMFCs) are consideredthe most promising power sources amongst fuel cells, due to their

New proton conductive membranes of indazole- and condensed pyrazolebisphosphonic acid-Nafion membranes for PEMFC

       HYPOTHESIS XVI  NOVEMBER 8-10, 2021 Online Conferencep. 15New proton conductive membranes of indazole- and condensed pyrazolebisphosphonic acid-Nafion membranes for PEMFCFátima C. Teixeira1, António P. S. Teixeira2 and Carmen M. Rangel11 Laboratório Nacional de Energia e Geologia, I.P., Estrada do Paço do Lumiar, 22, 1649-038 Lisboa, Portugal2 Departamento de Ciências Médicas e da Saúde, ESDH & LAQV- REQUIMTE, IIFA, Universidade de Évora, R. Romão Ramalho, 59, 7000-671 Évora, Portugalcarmen.rangel@lneg.ptThe global demands of energy are still increasing alongside many civilizational problems, notably the effects on the environment due to the overuse of traditional energy sources based on fossil fuels. New cleaner, renewable sources for sustainable energy systems are a key challenge of the 21st century society. There is a societal effort towards the use of renewable energies, but the actual sources remain low density, unstable and intermittent production providers [1]. Fuel cells are among the clean energy conversion technologies, that using hydrogen, can provide electrical energy with high efficiency and low environmental impact. Membranes for proton-exchange membrane fuel cells (PEMFC) still are a key component for this technology [2]. Our previous studies have demonstrated that incorporation of dopants into Nafion results in an enhancement of their proton conductivity [3-5]. Following our long-standing interest on PEMFC membranes, the aim of this work centers on the preparation of new Nafion membranes doped with azaheteroaromatic bisphosphonic acid (AzBPs) derivatives. These AzBPs are expected to act both as a source of protons and proton acceptors, facilitating the intermolecular transmission of protons throughout the membrane. In this study, we report on different AzBPs derivatives (Figure 1(a)), following strategies devised on our previous studies, to afford two indazole-bisphosphononic acid substituted at N-1 with a side chain of one or two methylene groups, and pyrazolo[3,4-b]pyridine- and pyrazolo[3,4-b]quinolinebisphosphononic acid substituted at N-1.New doped Nafion membranes were prepared by casting with 1 wt% loading of the prepared AzBPs. The new membranes were analysed by ATR-FTIR spectroscopy and their morphology was examined by SEM. The new membranes were evaluated for their water uptake capacity, by gravimetry, their ion exchange capacity (IEC), by determining the presence of ionizable groups on the membrane through an acid-base potentiometric titration, and their degree of hydration. The proton conduction properties were evaluated by Electrochemical Impedance Spectroscopy (EIS). The in-plane proton conductivity of the membranes doped with AzBPs were evaluated at different temperatures (30, 40, 50 and 60 ºC) and RH conditions (40, 60 and 80%). The proton conductivity of all membranes increases with the increasing of temperature and RH (Figure 1(b)).        HYPOTHESIS XVI  NOVEMBER 8-10, 2021 Online Conferencep. 16The incorporation of AzBPs dopants on Nafion polymer enhances the proton conductivities since all prepared membranes show higher proton conductivities than Nafion N-115, used as a reference, with values up to 1.42-fold, when tested in the same experimental conditions. In the studied conditions, all new membranes exhibited proton conductivities of the same order of magnitude. The best proton conductivity was observed for membrane doped with AzBP1 as dopant, with a value of 94 mScm-1. These results indicate that the azaheteroaromatic bisphosphonic acid-Nafion doping is a promising approach to obtain new membranes for PEMFC with better proton conductivity. Figure 1: (a) AzBPs used as dopants of Nafion; (b) Proton conductivity of Nafion membranes vs reciprocal temperature at 80% RH.Acknowledgements - -SOE1/P1/E0293 and -EAPA_204/2016, co-financed by the European Regional Development Fund in the framework of the Interreg Sudoe and INTERREG ATLANTIC programmes. References[1] I. Sta ell, D. Scamman, A.V. Abad, P. Balcombe, P.E. Dodds, P. Ekins, N. Shahd, K.R. Ward, -491.[2] -acid Rev., 117, 2017, 987-1104.[3] F.C. Teixeira, A.I. de SSurf. Sci., 487, 2019, 889-897.conductivity of Nafion-New J. Chem., 43, 2019, 15249-15257.[5] F.C. Teixeira, A.I. de Sá, A.P.S. Teixeira, V.M. Ortiz-Martinez, A. Ortiz, I. -bisphosphonic acid composite membranes forHydrogen Energy, 46, 2021, 17562-17571.

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New proton conductive membranes of indazole- and condensed pyrazolebisphosphonic acid-Nafion membranes for PEMFC

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