Polymers

Editorial

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3 pages, 187 KiB

Open AccessEditorial

Ionic Conductive Polymers for Electrochemical Devices

by Riccardo Narducci

Polymers 2022, 14(2), 246; https://doi.org/10.3390/polym14020246 - 7 Jan 2022

Cited by 1 | Viewed by 1465

Abstract

Increasing levels of pollution (especially in large cities), the rising cost of oil, and climate change are pushing the scientific community towards more sustainable solutions for the conversion and storage of energy [...] Full article

(This article belongs to the Special Issue Ionic Conductive Polymers for Electrochemical Devices)

Research

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13 pages, 6035 KiB

Open AccessArticle

Stability of Proton Exchange Membranes in Phosphate Buffer for Enzymatic Fuel Cell Application: Hydration, Conductivity and Mechanical Properties

by Luca Pasquini, Botagoz Zhakisheva, Emanuela Sgreccia, Riccardo Narducci, Maria Luisa Di Vona and Philippe Knauth

Polymers 2021, 13(3), 475; https://doi.org/10.3390/polym13030475 - 2 Feb 2021

Cited by 8 | Viewed by 3121

Abstract

Proton-conducting ionomers are widespread materials for application in electrochemical energy storage devices. However, their properties depend strongly on operating conditions. In bio-fuel cells with a separator membrane, the swelling behavior as well as the conductivity need to be optimized with regard to the [...] Read more.

Proton-conducting ionomers are widespread materials for application in electrochemical energy storage devices. However, their properties depend strongly on operating conditions. In bio-fuel cells with a separator membrane, the swelling behavior as well as the conductivity need to be optimized with regard to the use of buffer solutions for the stability of the enzyme catalyst. This work presents a study of the hydrolytic stability, conductivity and mechanical behavior of different proton exchange membranes based on sulfonated poly(ether ether ketone) (SPEEK) and sulfonated poly(phenyl sulfone) (SPPSU) ionomers in phosphate buffer solution. The results show that the membrane stability can be adapted by changing the casting solvent (DMSO, water or ethanol) and procedures, including a crosslinking heat treatment, or by blending the two ionomers. A comparison with Nafion^TM shows the different behavior of this ionomer versus SPEEK membranes. Full article

(This article belongs to the Special Issue Ionic Conductive Polymers for Electrochemical Devices)

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11 pages, 7331 KiB

Open AccessArticle

How the Morphology of Nafion-Based Membranes Affects Proton Transport

by Ernestino Lufrano, Cataldo Simari, Maria Luisa Di Vona, Isabella Nicotera and Riccardo Narducci

Polymers 2021, 13(3), 359; https://doi.org/10.3390/polym13030359 - 22 Jan 2021

Cited by 20 | Viewed by 5150

Abstract

This work represents a systematic and in-depth study of how Nafion 1100 membrane preparation procedures affect both the morphology of the polymeric film and the proton transport properties of the electrolyte. The membrane preparation procedure has non-negligible consequences on the performance of the [...] Read more.

This work represents a systematic and in-depth study of how Nafion 1100 membrane preparation procedures affect both the morphology of the polymeric film and the proton transport properties of the electrolyte. The membrane preparation procedure has non-negligible consequences on the performance of the proton-exchange membrane fuel cells (PEMFC) that operate within a wide temperature range (up to 120 °C). A comparison between commercial membranes (Nafion 117 and Nafion 212) and Nafion membranes prepared by three different procedures, namely (a) Nafion-recast, (b) Nafion uncrystallized, and (c) Nafion 117-oriented, was conducted. Electrochemical Impedance Spectroscopy (EIS) and Pulsed-field gradient nuclear magnetic resonance (PFG-NMR) investigations indicated that an anisotropic morphology could be achieved when a Nafion 117 membrane was forced to expand between two fixed and nondeformable surfaces. This anisotropy increased from ~20% in the commercial membrane up to 106% in the pressed membrane, where the ionic clusters were averagely oriented (Nafion 117-oriented) parallel to the surface, leading to a strong directionality in proton transport. Among the membranes obtained by solution-cast, which generally exhibited isotropic proton transport behavior, the Nafion uncrystallized membrane showed the lowest water diffusion coefficients and conductivities, highlighting the correlation between low crystallinity and a more branched and tortuous structure of hydrophilic channels. Finally, the dynamic mechanical analysis (DMA) tests demonstrated the poor elastic modulus for both uncrystallized and oriented membranes, which should be avoided in high-temperature fuel cells. Full article

(This article belongs to the Special Issue Ionic Conductive Polymers for Electrochemical Devices)

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16 pages, 5123 KiB

Open AccessArticle

Enhanced Hydroxide Conductivity and Dimensional Stability with Blended Membranes Containing Hyperbranched PAES/Linear PPO as Anion Exchange Membranes

by Sang Hee Kim, Kyu Ha Lee, Ji Young Chu, Ae Rhan Kim and Dong Jin Yoo

Polymers 2020, 12(12), 3011; https://doi.org/10.3390/polym12123011 - 16 Dec 2020

Cited by 30 | Viewed by 3383

Abstract

A series of novel blended anion exchange membranes (AEMs) were prepared with hyperbranched brominated poly(arylene ether sulfone) (Br-HB-PAES) and linear chloromethylated poly(phenylene oxide) (CM-PPO). The as-prepared blended membranes were fabricated with different weight ratios of Br-HB-PAES to CM-PPO, and the quaternization reaction for [...] Read more.

A series of novel blended anion exchange membranes (AEMs) were prepared with hyperbranched brominated poly(arylene ether sulfone) (Br-HB-PAES) and linear chloromethylated poly(phenylene oxide) (CM-PPO). The as-prepared blended membranes were fabricated with different weight ratios of Br-HB-PAES to CM-PPO, and the quaternization reaction for introducing the ionic functional group was performed by triethylamine. The Q-PAES/PPO-XY (quaternized-PAES/PPO-XY) blended membranes promoted the ion channel formation as the strong hydrogen bonds interconnecting the two polymers were maintained, and showed an improved hydroxide conductivity with excellent thermal behavior. In particular, the Q-PAES/PPO-55 membrane showed a very high hydroxide ion conductivity (90.9 mS cm⁻¹) compared to the pristine Q-HB-PAES membrane (32.8 mS cm⁻¹), a result supported by the morphology of the membrane as determined by the AFM analysis. In addition, the rigid hyperbranched structure showed a suppressed swelling ratio of 17.9–24.9% despite an excessive water uptake of 33.2–50.3% at 90 °C, and demonstrated a remarkable alkaline stability under 2.0 M KOH conditions over 1000 h. Full article

(This article belongs to the Special Issue Ionic Conductive Polymers for Electrochemical Devices)

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12 pages, 6385 KiB

Open AccessArticle

Modifying the Catalyst Layer Using Polyvinyl Alcohol for the Performance Improvement of Proton Exchange Membrane Fuel Cells under Low Humidity Operations

by Prathak Jienkulsawad, Yong-Song Chen and Amornchai Arpornwichanop

Polymers 2020, 12(9), 1865; https://doi.org/10.3390/polym12091865 - 19 Aug 2020

Cited by 11 | Viewed by 3501

Abstract

A proton exchange membrane fuel cell (PEMFC) system for the application of unmanned aerial vehicles is equipped without humidifiers and the cathode channels of the stack are open to the environment due to limited weight available for power sources. As a result, the [...] Read more.

A proton exchange membrane fuel cell (PEMFC) system for the application of unmanned aerial vehicles is equipped without humidifiers and the cathode channels of the stack are open to the environment due to limited weight available for power sources. As a result, the PEMFC is operated under low humidity conditions, causing membrane dehydration, low performance, and degradation. To keep the generated water within the fuel cell to humidify the membrane, in this study, polyvinyl alcohol (PVA) is employed in the fabrication of membrane electrode assemblies (MEAs). The effect of PVA content, either sprayed on the gas diffusion layer (GDL) or mixed in the catalyst layer (CL), on the MEA performance is compared under various humidity conditions. The results show that MEA performance is increased with the addition of PVA either on the GDL or in the CL, especially for non-humidified anode conditions. The result suggested that 0.03% PVA in the anode CL and 0.1% PVA on the GDL can improve the MEA performance by approximately 30%, under conditions of a non-humidified anode and a room-temperature-humidified cathode. However, MEAs with PVA in the anode CL show better durability than those with PVA on the GDL according to measurement with electrochemical impedance spectroscopy. Full article

(This article belongs to the Special Issue Ionic Conductive Polymers for Electrochemical Devices)

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12 pages, 2607 KiB

Open AccessArticle

Ionic Liquid-Incorporated Zn-Ion Conducting Polymer Electrolyte Membranes

by Jianghe Liu, Sultan Ahmed, Zeba Khanam, Ting Wang and Shenhua Song

Polymers 2020, 12(8), 1755; https://doi.org/10.3390/polym12081755 - 6 Aug 2020

Cited by 21 | Viewed by 3758

Abstract

In this study, novel ionic liquid-incorporated Zn-ion conducting polymer electrolyte membranes containing polymer matrix poly (vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMITf), along with zinc trifluoromethanesulfonate Zn(Tf)₂, are prepared and investigated. It is ascertained that the optimal membrane ILPE-Zn-4 (the mass [...] Read more.

In this study, novel ionic liquid-incorporated Zn-ion conducting polymer electrolyte membranes containing polymer matrix poly (vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMITf), along with zinc trifluoromethanesulfonate Zn(Tf)₂, are prepared and investigated. It is ascertained that the optimal membrane ILPE-Zn-4 (the mass ratio of EMITf:Zn(Tf)₂:PVDF-HFP is 0.4:0.4:1), with abundant nanopores, exhibits a high amorphousness. At room temperature, the optimized electrolyte membrane offers a good value of ionic conductivity (~1.44 × 10⁻⁴ S cm⁻¹), with a wide electrochemical stability window (~4.14 V). Moreover, the electrolyte membrane can sustain a high thermal decomposition temperature (~305 °C), and thus its mechanical performance is sufficient for practical applications. Accordingly, the ionic liquid-incorporated Zn-ion conducting polymer electrolyte could be a potential candidate for Zn-based energy storage applications. Full article

(This article belongs to the Special Issue Ionic Conductive Polymers for Electrochemical Devices)

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26 pages, 4853 KiB

Open AccessArticle

From Cellulose, Shrimp and Crab Shells to Energy Storage EDLC Cells: The Study of Structural and Electrochemical Properties of Proton Conducting Chitosan-Based Biopolymer Blend Electrolytes

by Shujahadeen B. Aziz, Muhamad. H. Hamsan, Muaffaq M. Nofal, Saro San, Rebar T. Abdulwahid, Salah Raza Saeed, Mohamad A. Brza, Mohd F. Z. Kadir, Sewara J. Mohammed and Shakhawan Al-Zangana

Polymers 2020, 12(7), 1526; https://doi.org/10.3390/polym12071526 - 9 Jul 2020

Cited by 44 | Viewed by 3760

Abstract

In this study, solid polymer blend electrolytes (SPBEs) based on chitosan (CS) and methylcellulose (MC) incorporated with different concentrations of ammonium fluoride (NH₄F) salt were synthesized using a solution cast technique. Both Fourier transformation infrared spectroscopy (FTIR) and X-ray diffraction (XRD) [...] Read more.

In this study, solid polymer blend electrolytes (SPBEs) based on chitosan (CS) and methylcellulose (MC) incorporated with different concentrations of ammonium fluoride (NH₄F) salt were synthesized using a solution cast technique. Both Fourier transformation infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results confirmed a strong interaction and dispersion of the amorphous region within the CS:MC system in the presence of NH₄F. To gain better insights into the electrical properties of the samples, the results of electrochemical impedance spectroscopy (EIS) were analyzed by electrical equivalent circuit (EEC) modeling. The highest conductivity of 2.96 × 10⁻³ S cm⁻¹ was recorded for the sample incorporated with 40 wt.% of NH₄F. Through transference number measurement (TNM) analysis, the fraction of ions was specified. The electrochemical stability of the electrolyte sample was found to be up to 2.3 V via the linear sweep voltammetry (LSV) study. The value of specific capacitance was determined to be around 58.3 F/g. The stability test showed that the electrical double layer capacitor (EDLC) system can be recharged and discharged for up to 100 cycles with an average specific capacitance of 64.1 F/g. The synthesized EDLC cell was found to exhibit high efficiency (90%). In the 1st cycle, the values of internal resistance, energy density and power density of the EDLC cell were determined to be 65 Ω, 9.3 Wh/kg and 1282 W/kg, respectively. Full article

(This article belongs to the Special Issue Ionic Conductive Polymers for Electrochemical Devices)

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18 pages, 3296 KiB

Open AccessArticle

A Deep Insight into Different Acidic Additives as Doping Agents for Enhancing Proton Conductivity on Polybenzimidazole Membranes

by Jorge Escorihuela, Abel García-Bernabé and Vicente Compañ

Polymers 2020, 12(6), 1374; https://doi.org/10.3390/polym12061374 - 18 Jun 2020

Cited by 27 | Viewed by 4881

Abstract

The use of phosphoric acid doped polybenzimidazole (PBI) membranes for fuel cell applications has been extensively studied in the past decades. In this article, we present a systematic study of the physicochemical properties and proton conductivity of PBI membranes doped with the commonly [...] Read more.

The use of phosphoric acid doped polybenzimidazole (PBI) membranes for fuel cell applications has been extensively studied in the past decades. In this article, we present a systematic study of the physicochemical properties and proton conductivity of PBI membranes doped with the commonly used phosphoric acid at different concentrations (0.1, 1, and 14 M), and with other alternative acids such as phytic acid (0.075 M) and phosphotungstic acid (HPW, 0.1 M). The use of these three acids was reflected in the formation of channels in the polymeric network as observed by cross-section SEM images. The acid doping enhanced proton conductivity of PBI membranes and, after doping, these conducting materials maintained their mechanical properties and thermal stability for their application as proton exchange membrane fuel cells, capable of operating at intermediate or high temperatures. Under doping with similar acidic concentrations, membranes with phytic acid displayed a superior conducting behavior when compared to doping with phosphoric acid or phosphotungstic acid. Full article

(This article belongs to the Special Issue Ionic Conductive Polymers for Electrochemical Devices)

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13 pages, 2579 KiB

Open AccessArticle

Crosslinked Sulfonated Polyphenylsulfone-Vinylon (CSPPSU-vinylon) Membranes for PEM Fuel Cells from SPPSU and Polyvinyl Alcohol (PVA)

by Je-Deok Kim, Satoshi Matsushita and Kenji Tamura

Polymers 2020, 12(6), 1354; https://doi.org/10.3390/polym12061354 - 16 Jun 2020

Cited by 14 | Viewed by 3131

Abstract

A crosslinked sulfonated polyphenylsulfone (CSPPSU) polymer and polyvinyl alcohol (PVA) were thermally crosslinked; then, a CSPPSU-vinylon membrane was synthesized using a formalization reaction. Its use as an electrolyte membrane for fuel cells was investigated. PVA was synthesized from polyvinyl acetate (PVAc), using a [...] Read more.

A crosslinked sulfonated polyphenylsulfone (CSPPSU) polymer and polyvinyl alcohol (PVA) were thermally crosslinked; then, a CSPPSU-vinylon membrane was synthesized using a formalization reaction. Its use as an electrolyte membrane for fuel cells was investigated. PVA was synthesized from polyvinyl acetate (PVAc), using a saponification reaction. The CSPPSU-vinylon membrane was synthesized by the addition of PVA (5 wt%, 10 wt%, 20 wt%), and its chemical, mechanical, conductivity, and fuel cell properties were studied. The conductivity of the CSPPSU-10vinylon membrane is higher than that of the CSPPSU membrane, and a conductivity of 66 mS/cm was obtained at 120 °C and 90% RH (relative humidity). From a fuel cell evaluation at 80 °C, the CSPPSU-10vinylon membrane has a higher current density than CSPPSU and Nafion212 membranes, in both high (100% RH) and low humidification (60% RH). By using a CSPPSU-vinylon membrane instead of a CSPPSU membrane, the conductivity and fuel cell performance improved. Full article

(This article belongs to the Special Issue Ionic Conductive Polymers for Electrochemical Devices)

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12 pages, 2870 KiB

Open AccessArticle

Electrospun Anion-Conducting Ionomer Fibers—Effect of Humidity on Final Properties

by Manar Halabi, Meirav Mann-Lahav, Vadim Beilin, Gennady E. Shter, Oren Elishav, Gideon S. Grader and Dario R. Dekel

Polymers 2020, 12(5), 1020; https://doi.org/10.3390/polym12051020 - 1 May 2020

Cited by 14 | Viewed by 3648

Abstract

Anion-conducting ionomer-based nanofibers mats are prepared by electrospinning (ES) technique. Depending on the relative humidity (RH) during the ES process (RH_ES), ionomer nanofibers with different morphologies are obtained. The effect of relative humidity on the ionomer nanofibers morphology, ionic conductivity, and [...] Read more.

Anion-conducting ionomer-based nanofibers mats are prepared by electrospinning (ES) technique. Depending on the relative humidity (RH) during the ES process (RH_ES), ionomer nanofibers with different morphologies are obtained. The effect of relative humidity on the ionomer nanofibers morphology, ionic conductivity, and water uptake (WU) is studied. A branching effect in the ES fibers found to occur mostly at RH_ES < 30% is discussed. The anion conductivity and WU of the ionomer electrospun mats prepared at the lowest RH_ES are found to be higher than in those prepared at higher RH_ES. This effect can be ascribed to the large diameter of the ionomer fibers, which have a higher WU. Understanding the effect of RH during the ES process on ionomer-based fibers’ properties is critical for the preparation of electrospun fiber mats for specific applications, such as electrochemical devices. Full article

(This article belongs to the Special Issue Ionic Conductive Polymers for Electrochemical Devices)

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Review

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27 pages, 3686 KiB

Open AccessReview

Recent Progress in the Development of Aromatic Polymer-Based Proton Exchange Membranes for Fuel Cell Applications

by Raja Rafidah R. S., Rashmi W., Khalid M., Wong W. Y. and Priyanka J.

Polymers 2020, 12(5), 1061; https://doi.org/10.3390/polym12051061 - 6 May 2020

Cited by 65 | Viewed by 6351

Abstract

Proton exchange membranes (PEMs) play a pivotal role in fuel cells; conducting protons from the anode to the cathode within the cell’s membrane electrode assembles (MEA) separates the reactant fuels and prevents electrons from passing through. High proton conductivity is the most important [...] Read more.

Proton exchange membranes (PEMs) play a pivotal role in fuel cells; conducting protons from the anode to the cathode within the cell’s membrane electrode assembles (MEA) separates the reactant fuels and prevents electrons from passing through. High proton conductivity is the most important characteristic of the PEM, as this contributes to the performance and efficiency of the fuel cell. However, it is also important to take into account the membrane’s durability to ensure that it canmaintain itsperformance under the actual fuel cell’s operating conditions and serve a long lifetime. The current state-of-the-art Nafion membranes are limited due to their high cost, loss of conductivity at elevated temperatures due to dehydration, and fuel crossover. Alternatives to Nafion have become a well-researched topic in recent years. Aromatic-based membranes where the polymer chains are linked together by aromatic rings, alongside varying numbers of ether, ketone, or sulfone functionalities, imide, or benzimidazoles in their structures, are one of the alternatives that show great potential as PEMs due totheir electrochemical, mechanical, and thermal strengths. Membranes based on these polymers, such as poly(aryl ether ketones) (PAEKs) and polyimides (PIs), however, lack a sufficient level of proton conductivity and durability to be practical for use in fuel cells. Therefore, membrane modifications are necessary to overcome their drawbacks. This paper reviews the challenges associated with different types of aromatic-based PEMs, plus the recent approaches that have been adopted to enhance their properties and performance. Full article

(This article belongs to the Special Issue Ionic Conductive Polymers for Electrochemical Devices)

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