Polymers

Research

16 pages, 5751 KiB

Open AccessArticle

Ameliorated Performance of Sulfonated Poly(Arylene Ether Sulfone) Block Copolymers with Increased Hydrophilic Oligomer Ratio in Proton-Exchange Membrane Fuel Cells Operating at 80% Relative Humidity

by Ae Rhan Kim, Mohanraj Vinothkannan, Kyu Ha Lee, Ji Young Chu, Sumg Kwan Ryu, Hwan Gyu Kim, Jae-Young Lee, Hong-Ki Lee and Dong Jin Yoo

Polymers 2020, 12(9), 1871; https://doi.org/10.3390/polym12091871 - 20 Aug 2020

Cited by 28 | Viewed by 3211

Abstract

We designed and synthesized a series of sulfonated poly(arylene ether sulfone) (SPES) with different hydrophilic or hydrophobic oligomer ratios using poly-condensation strategy. Afterward, we fabricated the corresponding membranes via a solution-casting approach. We verified the SPES membrane chemical structure using nuclear magnetic resonance [...] Read more.

We designed and synthesized a series of sulfonated poly(arylene ether sulfone) (SPES) with different hydrophilic or hydrophobic oligomer ratios using poly-condensation strategy. Afterward, we fabricated the corresponding membranes via a solution-casting approach. We verified the SPES membrane chemical structure using nuclear magnetic resonance (¹H NMR) and confirmed the resulting oligomer ratio. Field-emission scanning electron microscope (FE-SEM) and atomic force microscope (AFM) results revealed that we effectively attained phase separation of the SPES membrane along with an increased hydrophilic oligomer ratio. Thermal stability, glass transition temperature (T_g) and membrane elongation increased with the ratio of hydrophilic oligomers. SPES membranes with higher hydrophilic oligomer ratios exhibited superior water uptake, ion-exchange capacity, contact angle and water sorption, while retaining reasonable swelling degree. The proton conductivity results showed that SPES containing higher amounts of hydrophilic oligomers provided a 74.7 mS cm⁻¹ proton conductivity at 90 °C, which is better than other SPES membranes, but slightly lower than that of Nafion-117 membrane. When integrating SPES membranes with proton-exchange membrane fuel cells (PEMFCs) at 60 °C and 80% relative humidity (RH), the PEMFC power density exhibited a similar increment-pattern like proton conductivity pattern. Full article

(This article belongs to the Special Issue Polymer Based Catalysts and Membranes and Their Composites for Energy Storage and Conversion Applications)

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15 pages, 4848 KiB

Open AccessArticle

Anion Exchange Membranes Obtained from Poly(arylene ether sulfone) Block Copolymers Comprising Hydrophilic and Hydrophobic Segments

by Jun Ha Kim, Mohanraj Vinothkannan, Ae Rhan Kim and Dong Jin Yoo

Polymers 2020, 12(2), 325; https://doi.org/10.3390/polym12020325 - 04 Feb 2020

Cited by 11 | Viewed by 3333

Abstract

The anion exchange membrane may have different physical and chemical properties, electrochemical performance and mechanical stability depending upon the monomer structure, hydrophilicity and hydrophobic repeating unit, surface form and degree of substitution of functional groups. In current work, poly(arylene ether sulfone) (PAES) block [...] Read more.

The anion exchange membrane may have different physical and chemical properties, electrochemical performance and mechanical stability depending upon the monomer structure, hydrophilicity and hydrophobic repeating unit, surface form and degree of substitution of functional groups. In current work, poly(arylene ether sulfone) (PAES) block copolymer was created and used as the main chain. After controlling the amount of NBS, the degree of bromination (DB) was changed in Br-PAES. Following that, quaternized PAES (Q-PAES) was synthesized through quaternization. Q-PAES showed a tendency of enhancing water content, expansion rate, ion exchange capacity (IEC) as the degree of substitution of functional groups increased. However, it was confirmed that tensile strength and dimensional properties of membrane reduced while swelling degree was increased. In addition, phase separation of membrane was identified by atomic force microscope (AFM) image, while ionic conductivity is greatly affected by phase separation. The Q-PAES membrane demonstrated a reasonable power output of around 64 mW/cm² while employed as electrolyte in fuel cell operation. Full article

(This article belongs to the Special Issue Polymer Based Catalysts and Membranes and Their Composites for Energy Storage and Conversion Applications)

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13 pages, 3042 KiB

Open AccessArticle

Study of High Performance Sulfonated Polyether Ether Ketone Composite Electrolyte Membranes

by Gwomei Wu, Sheng-Jen Lin, I-Chan Hsu, Juin-Yih Su and Dave W. Chen

Polymers 2019, 11(7), 1177; https://doi.org/10.3390/polym11071177 - 12 Jul 2019

Cited by 20 | Viewed by 5793

Abstract

In this study, high performance composite electrolyte membranes were prepared from polyether ether ketone polymeric material. An initial sulfonation reaction improved the membrane hydrophilicity and its water absorbability and thus enhanced the ionic conductivity in electrochemical cells. Protonic conductivity was improved from 10 [...] Read more.

In this study, high performance composite electrolyte membranes were prepared from polyether ether ketone polymeric material. An initial sulfonation reaction improved the membrane hydrophilicity and its water absorbability and thus enhanced the ionic conductivity in electrochemical cells. Protonic conductivity was improved from 10⁻⁴ to 10⁻² S cm⁻¹ with an increasing sulfonation time from 72 to 175 h. The effects of blending nano SiO₂ into the composite membranes were devoted to improve thermal and mechanical properties, as well as methanol permeability. Methanol permeability was reduced to 3.1 × 10⁻⁷ cm² s⁻¹. Finally, a further improvement in ionic conductivity was carried out by a supercritical carbon dioxide treatment under 20 MPa at 40°C for 30 min with an optimum SiO₂ blend ratio of 10 wt-%. The plasticizing effect by the Lewis acid-base interaction between CO₂ and electron donor species on polymer chains decreased the glass transition and melting temperatures. The results show that sulfonated composite membranes blended with SiO₂ and using a supercritical carbon dioxide treatment exhibit a lower glass transition temperature, higher ionic conductivity, lower methanol permeability, good thermal stability, and strong mechanical properties. Ionic conductivity was improved to 1.55 × 10⁻² S cm⁻¹. The ion exchange capacity and the degree of sulfonation were also investigated. Full article

(This article belongs to the Special Issue Polymer Based Catalysts and Membranes and Their Composites for Energy Storage and Conversion Applications)

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9 pages, 3184 KiB

Open AccessArticle

A Bioinspired Functionalization of Polypropylene Separator for Lithium-Sulfur Battery

by Zhijia Zhang, Xuequan Li, Yawen Yan, Wenyi Zhu, Li-Hua Shao and Junsheng Li

Polymers 2019, 11(4), 728; https://doi.org/10.3390/polym11040728 - 22 Apr 2019

Cited by 14 | Viewed by 4403

Abstract

Lithium-sulfur batteries have received intensive attention, due to their high specific capacity, but the shuttle effect of soluble polysulfide results in a decrease in capacity. In response to this issue, we develop a novel tannic acid and Au nanoparticle functionalized separator. The tannic [...] Read more.

Lithium-sulfur batteries have received intensive attention, due to their high specific capacity, but the shuttle effect of soluble polysulfide results in a decrease in capacity. In response to this issue, we develop a novel tannic acid and Au nanoparticle functionalized separator. The tannic acid and gold nanoparticles were modified onto commercial polypropylene separator through a two-step solution process. Due to a large number of phenolic hydroxyl groups contained in the modified layer and the strong polarity of the gold nanoparticles, the soluble polysulfide generated during battery cycling is well stabilized on the cathode side, slowing down the capacity fade brought by the shuttle effect. In addition, the modification effectively improves the electrolyte affinity of the separator. As a result of these benefits, the novel separator exhibits improved battery performance compared to the pristine polypropylene separator. Full article

(This article belongs to the Special Issue Polymer Based Catalysts and Membranes and Their Composites for Energy Storage and Conversion Applications)

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11 pages, 2200 KiB

Open AccessArticle

Synthesis and Characterization of 3-DOM IrO₂ Electrocatalysts Templated by PMMA for Oxygen Evolution Reaction

by Fei Liu, Xuechu Sun, Xiu Chen, Cuicui Li, Jun Yu and Haolin Tang

Polymers 2019, 11(4), 629; https://doi.org/10.3390/polym11040629 - 04 Apr 2019

Cited by 6 | Viewed by 4483

Abstract

Three-dimensional ordered macroporous (3-DOM) IrO₂ material was prepared using PMMA as a template and ammonia as a chelator. These 3-DOM IrO₂ honeycomb arrays showed a large surface area and ordered macropores (155 nm in diameter) cross-linked by secondary mesopores. Internal structures [...] Read more.

Three-dimensional ordered macroporous (3-DOM) IrO₂ material was prepared using PMMA as a template and ammonia as a chelator. These 3-DOM IrO₂ honeycomb arrays showed a large surface area and ordered macropores (155 nm in diameter) cross-linked by secondary mesopores. Internal structures of 3-DOM IrO₂ material were observed microscopically through these secondary pores. According to the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) spectra, 3-DOM IrO₂ has a rutile crystal structure and is mainly composed of iridium dioxide. In acidic electrolytes, the overpotential of 3-DOM IrO₂ material at 0.5 mV cm⁻² was only 0.22 V. Accelerated durability tests demonstrated excellent durability of 3-DOM IrO₂ as an oxygen evolution reaction (OER) catalyst. Full article

(This article belongs to the Special Issue Polymer Based Catalysts and Membranes and Their Composites for Energy Storage and Conversion Applications)

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15 pages, 1308 KiB

Open AccessArticle

A Comparative Study on Physiochemical, Thermomechanical, and Electrochemical Properties of Sulfonated Poly(Ether Ether Ketone) Block Copolymer Membranes with and without Fe₃O₄ Nanoparticles

by Ae Rhan Kim and Dong Jin Yoo

Polymers 2019, 11(3), 536; https://doi.org/10.3390/polym11030536 - 21 Mar 2019

Cited by 19 | Viewed by 3310

Abstract

The composite structure, good porosity, and electrochemical behavior of proton exchange membranes (PEMs) are important characteristics, which can improve the performance of polymer electrolyte fuel cells (PEFCs). In this study, we designed and synthesized an XY block copolymer via a polycondensation reaction that [...] Read more.

The composite structure, good porosity, and electrochemical behavior of proton exchange membranes (PEMs) are important characteristics, which can improve the performance of polymer electrolyte fuel cells (PEFCs). In this study, we designed and synthesized an XY block copolymer via a polycondensation reaction that contains sulfonated poly(ether ether ketone) (SPEEK) (X) as a hydrophilic unit and a fluorinated oligomer (Y) as a hydrophobic unit. The prepared XY block copolymer is composed of Fe₃O₄ nanoparticles to create composite architecture, which was subsequently treated with a 1 M H₂SO₄ solution at 70 °C for 1 h to eliminate Fe₃O₄ and generate a pores structure in the membrane. The morphological, physiochemical, thermomechanical, and electrochemical properties of bare XY, XY/Fe₃O₄-9 and XY(porous)-9 membranes were measured and compared in detail. Compared with XY/Fe₃O₄-9 composite, the proton conductivity of XY(porous)-9 membrane was remarkably enhanced as a result of the existence of pores as nano-conducting channels. Similarly, the XY(porous)-9 membrane exhibited enhanced water retention and ion exchange capacity among the prepared membranes. However, the PEFC power density of XY(porous)-9 membrane was still lower than that of XY/Fe₃O₄-9 membrane at 60 °C and 60% relative humidity. Also, the durability of XY(porous)-9 membrane is found to be lower compared with pristine XY and XY/Fe₃O₄-9 membranes as a result of the hydrogen crossover through the pores of the membrane. Full article

(This article belongs to the Special Issue Polymer Based Catalysts and Membranes and Their Composites for Energy Storage and Conversion Applications)

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12 pages, 3101 KiB

Open AccessArticle

K_0.5Na_0.5NbO₃-SrTiO₃/PVDF Polymer Composite Film with Low Remnant Polarization and High Discharge Energy Storage Density

by Chuntian Chen, Lei Wang, Xinmei Liu, Wenlong Yang, Jiaqi Lin, Gaoru Chen and Xinrui Yang

Polymers 2019, 11(2), 310; https://doi.org/10.3390/polym11020310 - 12 Feb 2019

Cited by 31 | Viewed by 4784

Abstract

A high recoverable energy storage density polymer composite film has been designed in which the ferroelectric-paraelectric 0.85 (K_0.5Na_0.5NbO₃)-0.15SrTiO₃ (abbreviated as KNN-ST) solid solution particles were introduced into polyvinylidene fluoride (PVDF) polymer as functional fillers. The effects [...] Read more.

A high recoverable energy storage density polymer composite film has been designed in which the ferroelectric-paraelectric 0.85 (K_0.5Na_0.5NbO₃)-0.15SrTiO₃ (abbreviated as KNN-ST) solid solution particles were introduced into polyvinylidene fluoride (PVDF) polymer as functional fillers. The effects of the polarization properties of K_0.5Na_0.5NbO₃ (KNN) and KNN-ST particles on the energy storage performances of KNN-ST/PVDF film were systemically studied. And the introduction of SrTiO₃ (ST) was effective in reducing the remnant polarization of the particles, improving the dielectric properties and recoverable energy storage density of the KNN-ST/PVDF films. Compared to KNN/PVDF films, the dielectric permittivity of composite films was enhanced from 17 to 38 upon the introduction of ST. A recoverable energy storage density of 1.34 J/cm³ was achieved, which is 202.60% larger than that of the KNN/PVDF composite films. The interface between the particles and the polymer matrix was considered to the enhanced dielectric permittivity of the films. And the reduced remnant polarization of the composites was regarded as the improving high recoverable energy storage density. The results demonstrated that combing ferroelectric- paraelectric particles with polymers might be a key method for composites with excellent dielectric permittivity, high energy storage density, and energy efficiency. Full article

(This article belongs to the Special Issue Polymer Based Catalysts and Membranes and Their Composites for Energy Storage and Conversion Applications)

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