Research

1726 KiB

Open AccessArticle

Preparation and Characterization of Nanocomposite Polymer Membranes Containing Functionalized SnO₂ Additives

by Roberto Scipioni, Delia Gazzoli, Francesca Teocoli, Oriele Palumbo, Annalisa Paolone, Neluta Ibris, Sergio Brutti and Maria Assunta Navarra

Membranes 2014, 4(1), 123-142; https://doi.org/10.3390/membranes4010123 - 05 Mar 2014

Cited by 67 | Viewed by 9552

Abstract

In the research of new nanocomposite proton-conducting membranes, SnO₂ ceramic powders with surface functionalization have been synthesized and adopted as additives in Nafion-based polymer systems. Different synthetic routes have been explored to obtain suitable, nanometer-sized sulphated tin oxide particles. Structural and morphological [...] Read more.

In the research of new nanocomposite proton-conducting membranes, SnO₂ ceramic powders with surface functionalization have been synthesized and adopted as additives in Nafion-based polymer systems. Different synthetic routes have been explored to obtain suitable, nanometer-sized sulphated tin oxide particles. Structural and morphological characteristics, as well as surface and bulk properties of the obtained oxide powders, have been determined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) and Raman spectroscopies, N₂ adsorption, and thermal gravimetric analysis (TGA). In addition, dynamic mechanical analysis (DMA), atomic force microscopy (AFM), thermal investigations, water uptake (WU) measurements, and ionic exchange capacity (IEC) tests have been used as characterization tools for the nanocomposite membranes. The nature of the tin oxide precursor, as well as the synthesis procedure, were found to play an important role in determining the morphology and the particle size distribution of the ceramic powder, this affecting the effective functionalization of the oxides. The incorporation of such particles, having sulphate groups on their surface, altered some peculiar properties of the resulting composite membrane, such as water content, thermo-mechanical, and morphological characteristics. Full article

(This article belongs to the Special Issue Advancements in Membranes for Electrochemical Energy Applications)

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1192 KiB

Open AccessArticle

Friedel–Crafts Crosslinked Highly Sulfonated Polyether Ether Ketone (SPEEK) Membranes for a Vanadium/Air Redox Flow Battery

by Géraldine Merle, Filipoi Carmen Ioana, Dan Eugen Demco, Michel Saakes and Seyed Schwan Hosseiny

Membranes 2014, 4(1), 1-19; https://doi.org/10.3390/membranes4010001 - 30 Dec 2013

Cited by 13 | Viewed by 9342

Abstract

Highly conductive and low vanadium permeable crosslinked sulfonated poly(ether ether ketone) (cSPEEK) membranes were prepared by electrophilic aromatic substitution for a Vanadium/Air Redox Flow Battery (Vanadium/Air-RFB) application. Membranes were synthesized from ethanol solution and crosslinked under different temperatures with 1,4-benzenedimethanol and ZnCl_² [...] Read more.

Highly conductive and low vanadium permeable crosslinked sulfonated poly(ether ether ketone) (cSPEEK) membranes were prepared by electrophilic aromatic substitution for a Vanadium/Air Redox Flow Battery (Vanadium/Air-RFB) application. Membranes were synthesized from ethanol solution and crosslinked under different temperatures with 1,4-benzenedimethanol and ZnCl_² via the Friedel–Crafts crosslinking route. The crosslinking mechanism under different temperatures indicated two crosslinking pathways: (a) crosslinking on the sulfonic acid groups; and (b) crosslinking on the backbone. It was observed that membranes crosslinked at a temperature of 150 °C lead to low proton conductive membranes, whereas an increase in crosslinking temperature and time would lead to high proton conductive membranes. High temperature crosslinking also resulted in an increase in anisotropy and water diffusion. Furthermore, the membranes were investigated for a Vanadium/Air Redox Flow Battery application. Membranes crosslinked at 200 °C for 30 min with a molar ratio between 2:1 (mol repeat unit:mol benzenedimethanol) showed a proton conductivity of 27.9 mS/cm and a 100 times lower VO²⁺crossover compared to Nafion. Full article

(This article belongs to the Special Issue Advancements in Membranes for Electrochemical Energy Applications)

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2033 KiB

Open AccessArticle

Insights on the Study of Nafion Nanoscale Morphology by Transmission Electron Microscopy

by Sergey Yakovlev, Nitash P. Balsara and Kenneth H. Downing

Membranes 2013, 3(4), 424-439; https://doi.org/10.3390/membranes3040424 - 16 Dec 2013

Cited by 29 | Viewed by 8202

Abstract

Nafion is one of the most common materials used for polyelectrolyte membranes and is the standard to which novel materials are compared. In spite of great interest in Nafion’s nanostructure, it is still a subject of controversy. While multiple research efforts have addressed [...] Read more.

Nafion is one of the most common materials used for polyelectrolyte membranes and is the standard to which novel materials are compared. In spite of great interest in Nafion’s nanostructure, it is still a subject of controversy. While multiple research efforts have addressed Nafion’s morphology with Transmission Electron Microscopy, the results of these efforts have often been inconsistent and cannot satisfactorily describe the membrane structure. One of the reasons for differences in the reported results is the lack of sufficient control over the damage caused by electron beam irradiation. In this work, we describe some aspects of damage in the material that have a strong influence on the results. We show that irradiation causes mass loss and phase separation in the material and that the morphologies that have been observed are, in many cases, artifacts caused by damage. We study the effect of the sample temperature on damage and show that, while working at low temperature does not prevent damage and mass loss, it slows formation of damage-induced artifacts to the point where informative low-dose images of almost undamaged material may be collected. We find that charging of the sample has a substantial effect on the damage, and the importance of charge neutralization under irradiation is also seen by the large reduction of beam induced movement with the use of an objective aperture or a conductive support film. To help interpret the low-dose images, we can apply slightly higher exposures to etch away the hydrophobic phase with the electron beam and reveal the network formed by the hydrophilic phase. Energy loss spectroscopy shows evidence that fluorine removal governs the beam damage process. Full article

(This article belongs to the Special Issue Advancements in Membranes for Electrochemical Energy Applications)

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775 KiB

Open AccessArticle

Al₂O₃ Disk Supported Si₃N₄ Hydrogen Purification Membrane for Low Temperature Polymer Electrolyte Membrane Fuel Cells

by Xiaoteng Liu, Paul A. Christensen, Stephen M. Kelly, Vincent Rocher and Keith Scott

Membranes 2013, 3(4), 406-414; https://doi.org/10.3390/membranes3040406 - 05 Dec 2013

Cited by 5 | Viewed by 6382

Abstract

Reformate gas, a commonly employed fuel for polymer electrolyte membrane fuel cells (PEMFCs), contains carbon monoxide, which poisons Pt-containing anodes in such devices. A novel, low-cost mesoporous Si₃N₄ selective gas separation material was tested as a hydrogen clean-up membrane to [...] Read more.

Reformate gas, a commonly employed fuel for polymer electrolyte membrane fuel cells (PEMFCs), contains carbon monoxide, which poisons Pt-containing anodes in such devices. A novel, low-cost mesoporous Si₃N₄ selective gas separation material was tested as a hydrogen clean-up membrane to remove CO from simulated feed gas to single-cell PEMFC, employing Nafion as the polymer electrolyte membrane. Polarization and power density measurements and gas chromatography showed a clear effect of separating the CO from the gas mixture; the performance and durability of the fuel cell was thereby significantly improved. Full article

(This article belongs to the Special Issue Advancements in Membranes for Electrochemical Energy Applications)

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1087 KiB

Open AccessArticle

Testing the Chemical/Structural Stability of Proton Conducting Perovskite Ceramic Membranes by in Situ/ex Situ Autoclave Raman Microscopy

by Aneta Slodczyk, Oumaya Zaafrani, Matthew D. Sharp, John A. Kilner, Bogdan Dabrowski, Olivier Lacroix and Philippe Colomban

Membranes 2013, 3(4), 311-330; https://doi.org/10.3390/membranes3040311 - 25 Oct 2013

Cited by 30 | Viewed by 7991

Abstract

Ceramics, which exhibit high proton conductivity at moderate temperatures, are studied as electrolyte membranes or electrode components of fuel cells, electrolysers or CO₂ converters. In severe operating conditions (high gas pressure/high temperature), the chemical activity towards potentially reactive atmospheres (water, CO₂ [...] Read more.

Ceramics, which exhibit high proton conductivity at moderate temperatures, are studied as electrolyte membranes or electrode components of fuel cells, electrolysers or CO₂ converters. In severe operating conditions (high gas pressure/high temperature), the chemical activity towards potentially reactive atmospheres (water, CO₂, etc.) is enhanced. This can lead to mechanical, chemical, and structural instability of the membranes and premature efficiency loss. Since the lifetime duration of a device determines its economical interest, stability/aging tests are essential. Consequently, we have developed autoclaves equipped with a sapphire window, allowing in situ Raman study in the 25–620 °C temperature region under 1–50 bar of water vapor/gas pressure, both with and without the application of an electric field. Taking examples of four widely investigated perovskites (BaZr_0.9Yb_0.1O_3−δ, SrZr_0.9Yb_0.1O_3−δ, BaZr_0.25In_0.75O_3−δ, BaCe_0.5Zr_0.3Y_0.16Zn_0.04O_3−δ), we demonstrate the high potential of our unique set-up to discriminate between good/stable and instable electrolytes as well as the ability to detect and monitor in situ: (i) the sample surface reaction with surrounding atmospheres and the formation of crystalline or amorphous secondary phases (carbonates, hydroxides, hydrates, etc.); and (ii) the structural modifications as a function of operating conditions. The results of these studies allow us to compare quantitatively the chemical stability versus water (corrosion rate from ~150 µm/day to less than 0.25 µm/day under 200–500 °C/15–80 bar P_H2O) and to go further in comprehension of the aging mechanism of the membrane. Full article

(This article belongs to the Special Issue Advancements in Membranes for Electrochemical Energy Applications)

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889 KiB

Open AccessArticle

Interface Properties between Lithium Metal and a Composite Polymer Electrolyte of PEO₁₈Li(CF₃SO₂)₂N-Tetraethylene Glycol Dimethyl Ether

by Hui Wang, Masaki Matsui, Yasuo Takeda, Osamu Yamamoto, Dongmin Im, Dongjoon Lee and Nobuyuki Imanishi

Membranes 2013, 3(4), 298-310; https://doi.org/10.3390/membranes3040298 - 25 Oct 2013

Cited by 37 | Viewed by 9319

Abstract

The electrochemical properties of a composite solid polymer electrolyte, consisting of poly(ethylene oxide) (PEO)-lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and tetraethylene glycol dimethyl ether (TEGDME) was examined as a protective layer between lithium metal and a water-stable lithium ion-conducting glass ceramic of Li₁_+x [...] Read more.

The electrochemical properties of a composite solid polymer electrolyte, consisting of poly(ethylene oxide) (PEO)-lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and tetraethylene glycol dimethyl ether (TEGDME) was examined as a protective layer between lithium metal and a water-stable lithium ion-conducting glass ceramic of Li₁_+x+y(Ti,Ge)_2−xAl_xP_3−ySi_yO₁₂ (LTAP). The lithium ion conductivity and salt diffusion coefficient of PEO₁₈LiTFSI were dramatically enhanced by the addition of TEGDME. The water-stable lithium electrode with PEO₁₈LiTFSI-2TEGDME, as the protective layer, exhibited a low and stable electrode resistance of 85 Ω·cm² at 60 °C, after 28 days, and low overpotentials of 0.3 V for lithium plating and 0.4 V for lithium stripping at 4.0 mA·cm⁻² and 60 °C. A Li/PEO₁₈LiTFSI-2TEGDME/LTAP/saturated LiCl aqueous solution/Pt, air cell showed excellent cyclability up to 100 cycles at 2.0 mAh·cm⁻². Full article

(This article belongs to the Special Issue Advancements in Membranes for Electrochemical Energy Applications)

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126 KiB

Open AccessArticle

Can Biochemistry Usefully Guide the Search for Better Polymer Electrolytes?

by J. Woods Halley

Membranes 2013, 3(3), 242-248; https://doi.org/10.3390/membranes3030242 - 17 Sep 2013

Viewed by 4808

Abstract

I review some considerations that suggest that the biochemical products of evolution may provide hints concerning the way forward for the development of better electrolytes for lithium polymer batteries. Full article

(This article belongs to the Special Issue Advancements in Membranes for Electrochemical Energy Applications)

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323 KiB

Open AccessArticle

The Effects of Sulfonated Poly(ether ether ketone) Ion Exchange Preparation Conditions on Membrane Properties

by Rebecca S. L. Yee, Kaisong Zhang and Bradley P. Ladewig

Membranes 2013, 3(3), 182-195; https://doi.org/10.3390/membranes3030182 - 13 Aug 2013

Cited by 116 | Viewed by 12150

Abstract

A low cost cation exchange membrane to be used in a specific bioelectrochemical system has been developed using poly(ether ether ketone) (PEEK). This material is presented as an alternative to current commercial ion exchange membranes that have been primarily designed for fuel cell [...] Read more.

A low cost cation exchange membrane to be used in a specific bioelectrochemical system has been developed using poly(ether ether ketone) (PEEK). This material is presented as an alternative to current commercial ion exchange membranes that have been primarily designed for fuel cell applications. To increase the hydrophilicity and ion transport of the PEEK material, charged groups are introduced through sulfonation. The effect of sulfonation and casting conditions on membrane performance has been systematically determined by producing a series of membranes synthesized over an array of reaction and casting conditions. Optimal reaction and casting conditions for producing SPEEK ion exchange membranes with appropriate performance characteristics have been established by this uniquely systematic experimental series. Membrane materials were characterized by ion exchange capacity, water uptake, swelling, potential difference and NMR analysis. Testing this extensive membranes series established that the most appropriate sulfonation conditions were 60 °C for 6 h. For mechanical stability and ease of handling, SPEEK membranes cast from solvent casting concentrations of 15%–25% with a resulting thickness of 30–50 µm were also found to be most suitable from the series of tested casting conditions. Drying conditions did not have any apparent impact on the measured parameters in this study. The conductivity of SPEEK membranes was found to be in the range of 10⁻³ S cm⁻¹, which is suitable for use as a low cost membrane in the intended bioelectrochemical systems. Full article

(This article belongs to the Special Issue Advancements in Membranes for Electrochemical Energy Applications)

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