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12 pages, 5793 KB

Open AccessArticle

Ion-Exchange Strategy Enabling Direct Reformation of Unreliable Perfluorinated Cationic Polymer for Robust Proton Exchange Membrane towards Hydrogen Fuel Cells

by Xuqiu Xie, Wenjing Jia, Changyuan Liu, Yongzhe Li, Anhou Xu and Xundao Liu

Energies 2024, 17(12), 2954; https://doi.org/10.3390/en17122954 - 15 Jun 2024

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Abstract

Perfluorosulfonated anionic ionomers are known for their robust ion conductivity and chemical and mechanical stability. However, the structure and transport property degradation of perfluorinated cationic polymers (PfCPs) are not well understood. Herein, we propose an ion-exchange strategy to identify the structural degradation, ion transport mechanisms, and architectural reformation of PfCPs. Particularly, we demonstrate that the utility of a –SO₂–N⁺ strategy employing the Menshutkin reaction cannot yield reliable PfCPs and anion-exchange membranes, but can yield an unreliable zwitterionic intermediate (cations–anions molar ratio is approximately 7.6%). Moreover, the degradation products were efficiently reformed as proton exchange membranes (PEMs), and the as-reformed PEMs achieved an ion-exchange capacity (IEC) value (0.89 mmol g⁻¹), meanwhile retaining more than 94.7% of their initial capacity. Furthermore, the fuel cell assembled with reformed PEMs displayed a power density of 0.91 Wcm⁻² at 2.32 A cm⁻², which was 90.1% of that of the robust perfluorosulfonic acid PEMs. Our combined findings shed some fresh light on the state of understanding of the structure–property relationship in PfCPs. Full article

(This article belongs to the Section D2: Electrochem: Batteries, Fuel Cells, Capacitors)

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23 pages, 6961 KB

Open AccessArticle

Structural Characterization and Physicochemical Properties of Functionally Porous Proton-Exchange Membrane Based on PVDF-SPA Graft Copolymers

by Maria Ponomar, Valentina Ruleva, Veronika Sarapulova, Natalia Pismenskaya, Victor Nikonenko, Alina Maryasevskaya, Denis Anokhin, Dimitri Ivanov, Jeet Sharma, Vaibhav Kulshrestha and Bruno Améduri

Int. J. Mol. Sci. 2024, 25(1), 598; https://doi.org/10.3390/ijms25010598 - 2 Jan 2024

Cited by 7 | Viewed by 3315

Abstract

Fluorinated proton-exchange membranes (PEMs) based on graft copolymers of dehydrofluorinated polyvinylidene fluoride (D-PVDF), 3-sulfopropyl acrylate (SPA), and 1H, 1H, 2H-perfluoro-1-hexene (PFH) were prepared via free radical copolymerization and characterized for fuel cell application. The membrane morphology and physical properties were studied via small-(SAXS) and wide-angle X-ray scattering (WAXS), SEM, and DSC. It was found that the crystallinity degree is 17% for PEM-RCF (co-polymer with SPA) and 16% for PEM-RCF-2 (copolymer with SPA and PFH). The designed membranes possess crystallite grains of 5–6 nm in diameter. SEM images reveal a structure with open pores on the surface of diameters from 20 to 140 nm. Their transport and electrochemical characterization shows that the lowest membrane area resistance (0.9 Ωcm²) is comparable to perfluorosulfonic acid PEMs (such as Nafion^®) and polyvinylidene fluoride (PVDF) based CJMC cation-exchange membranes (ChemJoy Polymer Materials, China). Key transport and physicochemical properties of new and commercial membranes were compared. The PEM-RCF permeability to NaCl diffusion is rather high, which is due to a relatively low concentration of fixed sulfonate groups. Voltammetry confers that the electrochemical behavior of new PEM correlates to that of commercial cation-exchange membranes, while the ionic conductivity reveals an impact of the extended pores, as in track-etched membranes. Full article

(This article belongs to the Special Issue Ion and Molecule Transport in Membrane Systems 5.0)

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15 pages, 2010 KB

Open AccessArticle

Ex-Situ Evaluation of Commercial Polymer Membranes for Vanadium Redox Flow Batteries (VRFBs)

by Nana Zhao, Harry Riley, Chaojie Song, Zhengming Jiang, Keh-Chyun Tsay, Roberto Neagu and Zhiqing Shi

Polymers 2021, 13(6), 926; https://doi.org/10.3390/polym13060926 - 17 Mar 2021

Cited by 14 | Viewed by 3412

Abstract

Polymer membranes play a vital role in vanadium redox flow batteries (VRFBs), acting as a separator between the two compartments, an electronic insulator for maintaining electrical neutrality of the cell, and an ionic conductor for allowing the transport of ionic charge carriers. It is a major influencer of VRFB performance, but also identified as one of the major factors limiting the large-scale implementation of VRFB technology in energy storage applications due to its cost and durability. In this work, five (5) high-priority characteristics of membranes related to VRFB performance were selected as major considerable factors for membrane screening before in-situ testing. Eight (8) state-of-the-art of commercially available ion exchange membranes (IEMs) were specifically selected, evaluated and compared by a set of ex-situ assessment approaches to determine the possibility of the membranes applied for VRFB. The results recommend perfluorosulfonic acid (PFSA) membranes and hydrocarbon anion exchange membranes (AEMs) as the candidates for further in-situ testing, while one hydrocarbon cation exchange membrane (CEM) is not recommended for VRFB application due to its relatively high VO²⁺ ion crossover and low mechanical stability during/after the chemical stability test. This work could provide VRFB researchers and industry a valuable reference for selecting the polymer membrane materials before VRFB in-situ testing. Full article

(This article belongs to the Special Issue Polymer Membranes for Energy Applications)

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21 pages, 5836 KB

Open AccessArticle

The Development of Electroconvection at the Surface of a Heterogeneous Cation-Exchange Membrane Modified with Perfluorosulfonic Acid Polymer Film Containing Titanium Oxide

by Violetta Gil, Mikhail Porozhnyy, Olesya Rybalkina, Dmitrii Butylskii and Natalia Pismenskaya

Membranes 2020, 10(6), 125; https://doi.org/10.3390/membranes10060125 - 17 Jun 2020

Cited by 12 | Viewed by 3409

Abstract

One way to enhance mass transfer and reduce fouling in wastewater electrodialysis is stimulation of electroconvective mixing of the solution adjoining membranes by modifying their surfaces. Several samples were prepared by casting the perfluorosulfonic acid (PFSA) polymer film doped with TiO₂ nanoparticles onto the surface of the heterogeneous cation-exchange membrane MK-40. It is found that changes in surface characteristics conditioned by such modification lead to an increase in the limiting current density due to the stimulation of electroconvection, which develops according to the mechanism of electroosmosis of the first kind. The greatest increase in the current compared to the pristine membrane can be obtained by modification with the film being 20 μm thick and containing 3 wt% of TiO₂. The sample containing 6 wt% of TiO₂ provides higher mass transfer in overlimiting current modes due to the development of nonequilibrium electroconvection. A 1.5-fold increase in the thickness of the modifying film reduces the positive effect of introducing TiO₂ nanoparticles due to (1) partial shielding of the nanoparticles on the surface of the modified membrane; (2) a decrease in the tangential component of the electric force, which affects the development of electroconvection. Full article

(This article belongs to the Special Issue In-Depth on the Fouling and Antifouling of Ion-Exchange Membranes)

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16 pages, 2126 KB

Open AccessArticle

Perfluorosulfonic Acid Membranes Thermally Treated and Modified by Dopants with Proton-Acceptor Properties for Asparaginate and Potassium Ions Determination in Pharmaceuticals

by Anna Parshina, Tatyana Kolganova, Ekaterina Safronova, Alexander Osipov, Ekaterina Lapshina, Anastasia Yelnikova, Olga Bobreshova and Andrey Yaroslavtsev

Membranes 2019, 9(11), 142; https://doi.org/10.3390/membranes9110142 - 30 Oct 2019

Cited by 11 | Viewed by 3876

Abstract

The influence of incorporation of the dopants with proton-acceptor properties into perfluorosulfonic acid cation exchange membranes (MF-4SC and Nafion), and their treatment conditions on the characteristics of Donnan potential (DP)-sensors (analytical signal is the Donnan potential) in the aqueous solutions containing asparaginate and potassium ions in a wide pH range was investigated. A silica, surface modified by 3-aminopropyl and 3-(2-imidazolin-1-yl)-propyl groups, was used as the dopant. The membranes were subjected to mechanical deformation and thermal treatment at various relative humidities. The relationship between water uptake and diffusion permeability of membranes subjected to modification and treatment and the cross sensitivity of DP-sensors based on them to counter and co-ions was studied. The multisensory systems for the simultaneous determination of asparaginate and potassium ions in a concentration range from 1.0 × 10⁻⁴ to 1.0 × 10⁻² M and pH range from 4 to 8 were developed. An array of cross-sensitive DP-sensors based on MF-4SC membranes containing 3 wt.% SiO₂ modified by 10 mol.% 3-aminopropyl and 3-(2-imidazolin-1-yl)-propyl was used for the potassium asparaginate hemihydrate and magnesium asparaginate pentahydrate determination in Panangin^® (with an error of 2 and 4%, respectively). Full article

(This article belongs to the Special Issue Ion-Exchange Membranes and Processes)

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