Membranes

898 KiB

Open AccessArticle

Investigation of La_1−xSr_xCrO_3−∂ (x ~ 0.1) as Membrane for Hydrogen Production

by Yngve Larring, Camilla Vigen, Florian Ahouanto, Marie-Laure Fontaine, Thijs Peters, Jens B. Smith, Truls Norby and Rune Bredesen

Membranes 2012, 2(3), 665-686; https://doi.org/10.3390/membranes2030665 - 11 Sep 2012

Cited by 24 | Viewed by 8868

Abstract

Various inorganic membranes have demonstrated good capability to separate hydrogen from other gases at elevated temperatures. Hydrogen-permeable, dense, mixed proton-electron conducting ceramic oxides offer superior selectivity and thermal stability, but chemically robust candidates with higher ambipolar protonic and electronic conductivity are needed. In [...] Read more.

Various inorganic membranes have demonstrated good capability to separate hydrogen from other gases at elevated temperatures. Hydrogen-permeable, dense, mixed proton-electron conducting ceramic oxides offer superior selectivity and thermal stability, but chemically robust candidates with higher ambipolar protonic and electronic conductivity are needed. In this work, we present for the first time the results of various investigations of La_1−xSr_xCrO_3−∂ membranes for hydrogen production. We aim in particular to elucidate the material’s complex transport properties, involving co-ionic transport of oxide ions and protons, in addition to electron holes. This opens some new possibilities for efficient heat and mass transfer management in the production of hydrogen. Conductivity measurements as a function of pH₂ at constant pO₂ exhibit changes that reveal a significant hydration and presence of protons. The flux and production of hydrogen have been measured under different chemical gradients. In particular, the effect of water vapor in the feed and permeate gas stream sides was investigated with the aim of quantifying the ratio of hydrogen production by hydrogen flux from feed to permeate and oxygen flux the opposite way (“water splitting”). Deuterium labeling was used to unambiguously prove flux of hydrogen species. Full article

(This article belongs to the Special Issue Membrane Processes and Energy)

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6038 KiB

Open AccessReview

A Review of RedOx Cycling of Solid Oxide Fuel Cells Anode

by Antonin Faes, Aïcha Hessler-Wyser, Amédée Zryd and Jan Van herle

Membranes 2012, 2(3), 585-664; https://doi.org/10.3390/membranes2030585 - 31 Aug 2012

Cited by 186 | Viewed by 15581

Abstract

Solid oxide fuel cells are able to convert fuels, including hydrocarbons, to electricity with an unbeatable efficiency even for small systems. One of the main limitations for long-term utilization is the reduction-oxidation cycling (RedOx cycles) of the nickel-based anodes. This paper will review [...] Read more.

Solid oxide fuel cells are able to convert fuels, including hydrocarbons, to electricity with an unbeatable efficiency even for small systems. One of the main limitations for long-term utilization is the reduction-oxidation cycling (RedOx cycles) of the nickel-based anodes. This paper will review the effects and parameters influencing RedOx cycles of the Ni-ceramic anode. Second, solutions for RedOx instability are reviewed in the patent and open scientific literature. The solutions are described from the point of view of the system, stack design, cell design, new materials and microstructure optimization. Finally, a brief synthesis on RedOx cycling of Ni-based anode supports for standard and optimized microstructures is depicted. Full article

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

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271 KiB

Open AccessReview

Microbial Relevant Fouling in Membrane Bioreactors: Influencing Factors, Characterization, and Fouling Control

by Bing Wu and Anthony G. Fane

Membranes 2012, 2(3), 565-584; https://doi.org/10.3390/membranes2030565 - 15 Aug 2012

Cited by 50 | Viewed by 10468

Abstract

Microorganisms in membrane bioreactors (MBRs) play important roles on degradation of organic/inorganic substances in wastewaters, while microbial deposition/growth and microbial product accumulation on membranes potentially induce membrane fouling. Generally, there is a need to characterize membrane foulants and to determine their relations to [...] Read more.

Microorganisms in membrane bioreactors (MBRs) play important roles on degradation of organic/inorganic substances in wastewaters, while microbial deposition/growth and microbial product accumulation on membranes potentially induce membrane fouling. Generally, there is a need to characterize membrane foulants and to determine their relations to the evolution of membrane fouling in order to identify a suitable fouling control approach in MBRs. This review summarized the factors in MBRs that influence microbial behaviors (community compositions, physical properties, and microbial products). The state-of-the-art techniques to characterize biofoulants in MBRs were reported. The strategies for controlling microbial relevant fouling were discussed and the future studies on membrane fouling mechanisms in MBRs were proposed. Full article

(This article belongs to the Special Issue Membranes in Water Purification)

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310 KiB

Open AccessReview

Polymer Electrolytes for Lithium/Sulfur Batteries

by Yan Zhao, Yongguang Zhang, Denise Gosselink, The Nam Long Doan, Mikhail Sadhu, Ho-Jae Cheang and Pu Chen

Membranes 2012, 2(3), 553-564; https://doi.org/10.3390/membranes2030553 - 9 Aug 2012

Cited by 98 | Viewed by 17369

Abstract

This review evaluates the characteristics and advantages of employing polymer electrolytes in lithium/sulfur (Li/S) batteries. The main highlights of this study constitute detailed information on the advanced developments for solid polymer electrolytes and gel polymer electrolytes, used in the lithium/sulfur battery. This includes [...] Read more.

This review evaluates the characteristics and advantages of employing polymer electrolytes in lithium/sulfur (Li/S) batteries. The main highlights of this study constitute detailed information on the advanced developments for solid polymer electrolytes and gel polymer electrolytes, used in the lithium/sulfur battery. This includes an in-depth analysis conducted on the preparation and electrochemical characteristics of the Li/S batteries based on these polymer electrolytes. Full article

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559 KiB

Open AccessArticle

Plasma Membranes Modified by Plasma Treatment or Deposition as Solid Electrolytes for Potential Application in Solid Alkaline Fuel Cells

by Marc Reinholdt, Alina Ilie, Stéphanie Roualdès, Jérémy Frugier, Mauricio Schieda, Christophe Coutanceau, Serguei Martemianov, Valérie Flaud, Eric Beche and Jean Durand

Membranes 2012, 2(3), 529-552; https://doi.org/10.3390/membranes2030529 - 30 Jul 2012

Cited by 12 | Viewed by 8844

Abstract

In the highly competitive market of fuel cells, solid alkaline fuel cells using liquid fuel (such as cheap, non-toxic and non-valorized glycerol) and not requiring noble metal as catalyst seem quite promising. One of the main hurdles for emergence of such a technology [...] Read more.

In the highly competitive market of fuel cells, solid alkaline fuel cells using liquid fuel (such as cheap, non-toxic and non-valorized glycerol) and not requiring noble metal as catalyst seem quite promising. One of the main hurdles for emergence of such a technology is the development of a hydroxide-conducting membrane characterized by both high conductivity and low fuel permeability. Plasma treatments can enable to positively tune the main fuel cell membrane requirements. In this work, commercial ADP-Morgane^® fluorinated polymer membranes and a new brand of cross-linked poly(aryl-ether) polymer membranes, named AMELI-32^®, both containing quaternary ammonium functionalities, have been modified by argon plasma treatment or triallylamine-based plasma deposit. Under the concomitant etching/cross-linking/oxidation effects inherent to the plasma modification, transport properties (ionic exchange capacity, water uptake, ionic conductivity and fuel retention) of membranes have been improved. Consequently, using plasma modified ADP-Morgane^® membrane as electrolyte in a solid alkaline fuel cell operating with glycerol as fuel has allowed increasing the maximum power density by a factor 3 when compared to the untreated membrane. Full article

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

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1338 KiB

Open AccessReview

Electrochemical Membrane Reactors for Sustainable Chlorine Recycling

by Tanja Vidakovic-Koch, Isai Gonzalez Martinez, Rafael Kuwertz, Ulrich Kunz, Thomas Turek and Kai Sundmacher

Membranes 2012, 2(3), 510-528; https://doi.org/10.3390/membranes2030510 - 30 Jul 2012

Cited by 24 | Viewed by 12513

Abstract

Polymer electrolyte membranes have found broad application in a number of processes, being fuel cells, due to energy concerns, the main focus of the scientific community worldwide. Relatively little attention has been paid to the use of these materials in electrochemical production and [...] Read more.

Polymer electrolyte membranes have found broad application in a number of processes, being fuel cells, due to energy concerns, the main focus of the scientific community worldwide. Relatively little attention has been paid to the use of these materials in electrochemical production and separation processes. In this review, we put emphasis upon the application of Nafion membranes in electrochemical membrane reactors for chlorine recycling. The performance of such electrochemical reactors can be influenced by a number of factors including the properties of the membrane, which play an important role in reactor optimization. This review discusses the role of Nafion as a membrane, as well as its importance in the catalyst layer for the formation of the so-called three-phase boundary. The influence of an equilibrated medium on the Nafion proton conductivity and Cl⁻ crossover, as well as the influence of the catalyst ink dispersion medium on the Nafion/catalyst self-assembly and its importance for the formation of an ionic conducting network in the catalyst layer are summarized. Full article

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

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Schematic presentations of different reactor types used for HCl electrolysis: (a) dimensionally stable electrodes–gas diffusion electrodes (DSE–GDE) and (b) gas diffusion electrodes–gas diffusion electrodes (GDE–GDE) configuration. Full article ">Figure 2
Influence of temperature on equilibrium cell voltage for different HCl electrolysis processes. Full article ">Figure 3
Influence of equilibrated medium on Nafion conductivity in the presence of (a) liquid water and vapor water at different relative humidities (RH) and (b) hydrochloric acid at different concentrations. Based on [<a href="#B14-membranes-02-00510" class="html-bibr">14</a>,<a href="#B15-membranes-02-00510" class="html-bibr">15</a>]. Full article ">Figure 4
Schematic representation of the influence of an equilibrated medium concentration on the polymer electrolyte membrane structure (a) concentrations lower and (b) greater than the Donnan concentration cD. Reprinted with permission from reference [<a href="#B16-membranes-02-00510" class="html-bibr">16</a>]. Full article ">Figure 5
Scanning electron microscopy (SEM) micrograph of a cross-section of the membrane electrode assembly, along with a profile of elemental fluorine across the layers. Reprinted with permission from [<a href="#B33-membranes-02-00510" class="html-bibr">33</a>]. Copyright 2012, The Electrochemical Society. Full article ">Figure 6
Comparison of the information obtained by traditional SEM cross-section analysis and micro-computed tomography. Reprinted with permission from [<a href="#B34-membranes-02-00510" class="html-bibr">34</a>]. Copyright 2012, The Electrochemical Society. Full article ">Figure 7
Influence of Nafion loading on (a) electrochemically active surface area (ESA) in the presence of nitrogen at 25 °C and 20 mV s−1 and (b) fuel cell performance at 65 °C employing GDEs comprising carbon supported platinum catalyst. Reprinted with permission from [<a href="#B37-membranes-02-00510" class="html-bibr">37</a>,<a href="#B38-membranes-02-00510" class="html-bibr">38</a>]. Copyright 2012, Elsevier. Full article ">

1338 KiB

Open AccessArticle

Proton Content and Nature in Perovskite Ceramic Membranes for Medium Temperature Fuel Cells and Electrolysers

by Philippe Colomban, Oumaya Zaafrani and Aneta Slodczyk

Membranes 2012, 2(3), 493-509; https://doi.org/10.3390/membranes2030493 - 25 Jul 2012

Cited by 43 | Viewed by 8323

Abstract

Recent interest in environmentally friendly technology has promoted research on green house gas-free devices such as water steam electrolyzers, fuel cells and CO₂/syngas converters. In such applications, proton conducting perovskite ceramics appear especially promising as electrolyte membranes. Prior to a successful [...] Read more.

Recent interest in environmentally friendly technology has promoted research on green house gas-free devices such as water steam electrolyzers, fuel cells and CO₂/syngas converters. In such applications, proton conducting perovskite ceramics appear especially promising as electrolyte membranes. Prior to a successful industrial application, it is necessary to determine/understand their complex physical and chemical behavior, especially that related to proton incorporation mechanism, content and nature of bulk protonic species. Based on the results of quasi-elastic neutron scattering (QNS), thermogravimetric analysis (TGA), Raman and IR measurements we will show the complexity of the protonation process and the importance of differentiation between the protonic species adsorbed on a membrane surface and the bulk protons. The bulk proton content is very low, with a doping limit (~1–5 × 10⁻³ mole/mole), but sufficient to guarantee proton conduction below 600 °C. The bulk protons posses an ionic, covalent bond free nature and may occupy an interstitial site in the host perovskite structure. Full article

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

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(a) Sketch of protonation process: (1) dissociation of water molecules at the surface of the oxygen-deficient perovskite; (2) filling of oxygen vacancies near the ceramic surface at temperature T1; a few days are required; (3) a diffusion of protons and VO/O2− species through a ceramic is required to obtain homogeneous protonation; (4) stable, quenched state after protonation and cooling at To < T1; (b) Sketch of protonated ceramic: homogeneous distribution of bulk protonic species between a ceramic surface and bulk accompanied by the presence of protonic moieties adsorbed to the surface. Full article ">Figure 2
Surface of SZYb high dense ceramic (99%) (a) before; and (b) after protonation at 200 °C under 15 bar during 96 h; low temperature, low-pressure protonation conditions and the use of carbonate-containing water lead to the appearance of SrCO3 crystals. The Raman spectra characteristic of the ceramic surface before protonation—vibrational signature of perovskite structure, and after—vibrational signature of SrCO3 (<a href="#membranes-02-00493-t002" class="html-table">Table 2</a>) are given; (c) Surface of BZYb sample protonated during 23 days at 200 °C under 15 bar pH2O-important layer of carbonates and hydroxides is well seen [<a href="#B24-membranes-02-00493" class="html-bibr">24</a>]; (d) Comparison of the BZI sample [<a href="#B26-membranes-02-00493" class="html-bibr">26</a>] before protonation—ceramic piece, and after protonation—almost powder. Its low density and the presence of secondary phases lead to crumbling and chemical decomposition. The IR spectra characteristic of the ceramic surface before protonation—vibrational signature of perovskite structure, and after—vibrational signature of BaCO3/Ba(OH)2, nH2O (<a href="#membranes-02-00493-t002" class="html-table">Table 2</a>) are given. Full article ">Figure 3
Schematic summarizing the H bulk content as a function of protonation conditions (temperature, water pressure) and sample parameters (densification, i.e., the active surface area/porosity). Full article ">Figure 4
(a) Elastic neutron spectra measured at RT, 400 °C and 660 °C under high vacuum using time-of-flight spectrometer; (b) thermogravimetric (TG) curves recorded for the ~ 94% dense ceramic and the very high dense (~99%) ceramic (He atmosphere). Samples were preliminarily dried at 300 °C to eliminate traces of water molecules adsorbed on the ceramic surface. Full article ">Figure 5
Raman profilometry method: Spectra with characteristic backgrounds of (a) Ln-modified BaZrO3−δ (protonation at 250 °C under 40 bar during 72 h-protons near surface only); (b) Ln-modified SrZrO3−δ (protonation at 500 °C under 80 bar during 96 h homogeneous distributions of protons) were collected along the ceramic section, from the surface to the centre, just after fracture [<a href="#B23-membranes-02-00493" class="html-bibr">23</a>]; (c) The distributions of the spectroscopic signal measured across the half section (sample thickness = 1 mm) follows Fick’s law. Full article ">Figure 6
Neutronography micrographs characteristic of two Ln-modified SrZrO3−δceramics. Hydrogen-rich regions appear in white. (a) On the ceramic surface (250 °C, 40 bar, 72 h); (b) throughout the ceramic (310 °C, 90 bar, 96 h). Full article ">Figure 7
(a) IR spectra recorded on highly dense (99%) polished, thin (~120 µm) pristine (non-protonated), protonated and deprotonated Ln-modified SrZrO3−δ ceramics; (b) Comparison of IR spectra characteristic of low dense (94%) polished, thin Ln-modified SrZrO3−δ ceramic with a Sr(OH)x(CO3)y, nH2O powder dispersed in CsI matrix (see <a href="#membranes-02-00493-t002" class="html-table">Table 2</a> for band wave numbers and assignments). Full article ">

901 KiB

Open AccessArticle

Anion- or Cation-Exchange Membranes for NaBH₄/H₂O₂Fuel Cells?

by Biljana Šljukić, Ana L. Morais, Diogo M. F. Santos and César A. C. Sequeira

Membranes 2012, 2(3), 478-492; https://doi.org/10.3390/membranes2030478 - 19 Jul 2012

Cited by 27 | Viewed by 13002

Abstract

Direct borohydride fuel cells (DBFC), which operate on sodium borohydride (NaBH₄) as the fuel, and hydrogen peroxide (H₂O₂) as the oxidant, are receiving increasing attention. This is due to their promising use as power sources for space [...] Read more.

Direct borohydride fuel cells (DBFC), which operate on sodium borohydride (NaBH₄) as the fuel, and hydrogen peroxide (H₂O₂) as the oxidant, are receiving increasing attention. This is due to their promising use as power sources for space and underwater applications, where air is not available and gas storage poses obvious problems. One key factor to improve the performance of DBFCs concerns the type of separator used. Both anion- and cation-exchange membranes may be considered as potential separators for DBFC. In the present paper, the effect of the membrane type on the performance of laboratory NaBH₄/H₂O₂ fuel cells using Pt electrodes is studied at room temperature. Two commercial ion-exchange membranes from Membranes International Inc., an anion-exchange membrane (AMI-7001S) and a cation-exchange membrane (CMI-7000S), are tested as ionic separators for the DBFC. The membranes are compared directly by the observation and analysis of the corresponding DBFC’s performance. Cell polarization, power density, stability, and durability tests are used in the membranes’ evaluation. Energy densities and specific capacities are estimated. Most tests conducted, clearly indicate a superior performance of the cation-exchange membranes over the anion-exchange membrane. The two membranes are also compared with several other previously tested commercial membranes. For long term cell operation, these membranes seem to outperform the stability of the benchmark Nafion membranes but further studies are still required to improve their instantaneous power load. Full article

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

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Schematic illustration of the major migrative and diffusive fluxes across (a) anion and (b) cation exchange membranes used in direct borohydride/peroxide fuel cells (DBPFCs). Full article ">Figure 2
SEM micrographs (×1000) of (a) AMI-7001S surface; (b) CMI-7000S surface; (c)AMI-7001S cross section and (d) CMI-7000S cross section. Full article ">Figure 3
Polarization curves for DBPFCs employing the two tested membranes, including (a) cell voltage and power density curves and (b) the corresponding electrodes’ potentials. Full article ">Figure 4
Current density versus time at an imposed cell voltage of 0.6 V for DBPFCs employing AMI-7001S and CMI-7000S membrane separators. Full article ">Figure 5
Performance stability of DBPFCs employing AMI-7001S and CMI-7000S membrane separators recorded at the operating current density of 50 mA·cm−2. Full article ">Figure 6
Durability tests for DBPFCs employing AMI-7001S and CMI-7000S membrane separators, at zero current flow, with (a) the cell voltage decay and (b) the corresponding electrodes’ potentials. Full article ">Figure 7
Full discharge of DBPFCs employing AMI-7001S and CMI-7000S membrane separators recorded at the operating current density of 30 mA·cm−2. Full article ">

806 KiB

Open AccessReview

Molecularly Imprinted Membranes

by Francesco Trotta, Miriam Biasizzo and Fabrizio Caldera

Membranes 2012, 2(3), 440-477; https://doi.org/10.3390/membranes2030440 - 19 Jul 2012

Cited by 40 | Viewed by 10143

Abstract

Although the roots of molecularly imprinted polymers lie in the beginning of 1930s in the past century, they have had an exponential growth only 40–50 years later by the works of Wulff and especially by Mosbach. More recently, it was also proved that [...] Read more.

Although the roots of molecularly imprinted polymers lie in the beginning of 1930s in the past century, they have had an exponential growth only 40–50 years later by the works of Wulff and especially by Mosbach. More recently, it was also proved that molecular imprinted membranes (i.e., polymer thin films) that show recognition properties at molecular level of the template molecule are used in their formation. Different procedures and potential application in separation processes and catalysis are reported. The influences of different parameters on the discrimination abilities are also discussed. Full article

(This article belongs to the Special Issue Responsive Polymer Membranes)

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1080 KiB

Open AccessArticle

Poly(imide)/Organically-Modified Montmorillonite Nanocomposite as a Potential Membrane for Alkaline Fuel Cells

by Liliane C. Battirola, Luiz H. S. Gasparotto, Ubirajara P. Rodrigues-Filho and Germano Tremiliosi-Filho

Membranes 2012, 2(3), 430-439; https://doi.org/10.3390/membranes2030430 - 18 Jul 2012

Cited by 8 | Viewed by 6866

Abstract

In this work we evaluated the potentiality of a poly(imide) (PI)/organically-modified montmorillonite (O-MMT) nanocomposite membrane for the use in alkaline fuel cells. Both X-ray diffraction and scanning electron microscopy revealed a good dispersion of O-MMT into the PI matrix and preservation of the [...] Read more.

In this work we evaluated the potentiality of a poly(imide) (PI)/organically-modified montmorillonite (O-MMT) nanocomposite membrane for the use in alkaline fuel cells. Both X-ray diffraction and scanning electron microscopy revealed a good dispersion of O-MMT into the PI matrix and preservation of the O-MMT layered structure. When compared to the pure PI, the addition of O-MMT improved thermal stability and markedly increased the capability of absorbing electrolyte and ionic conductivity of the composite. The results show that the PI/O-MMT nanocomposite is a promising candidate for alkaline fuel cell applications. Full article

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

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Fourier transform infrared spectroscopy (FTIR) spectra of pure pre-polymer (PAA) and poly(imide) (PI). (A) Full-range spectra and (B) expended low-frequency region. Vertical full and dotted lines in (B) indicate bands that vanished and appeared, respectively, as a consequence of the polymerization process. Full article ">Figure 2
FTIR spectra of pure PI (full line) and PI/organically-modified montmorillonite (O-MMT) (dashed line). Full article ">Figure 3
X-ray diffraction patterns of pure O-MMT, pure PI and PI/O-MMT. Full article ">Figure 4
Scanning electron microscopy (SEM) micrograph of the PI/O-MMT nanocomposite. Full article ">Figure 5
Thermal gravimetric analysis (TGA) (A) and DTGA (B) curves for the materials employed in this work. The identity of the samples is indicated in the figures. Full article ">Figure 6
Aqueous 1.5 mol L−1 KOH uptake by PI and PI/O-MMT nanocomposite. Full article ">Figure 7
Conductivity for pure PI and PI/-O-MMT nanocomposite as a function of temperature. Full article ">

1311 KiB

Open AccessArticle

Effectiveness of Water Desalination by Membrane Distillation Process

by Marek Gryta

Membranes 2012, 2(3), 415-429; https://doi.org/10.3390/membranes2030415 - 17 Jul 2012

Cited by 93 | Viewed by 12366

Abstract

The membrane distillation process constitutes one of the possibilities for a new method for water desalination. Four kinds of polypropylene membranes with different diameters of capillaries and pores, as well as wall thicknesses were used in studied. The morphology of the membrane used [...] Read more.

The membrane distillation process constitutes one of the possibilities for a new method for water desalination. Four kinds of polypropylene membranes with different diameters of capillaries and pores, as well as wall thicknesses were used in studied. The morphology of the membrane used and the operating parameters significantly influenced process efficiency. It was found that the membranes with lower wall thickness and a larger pore size resulted in the higher yields. Increasing both feed flow rate and temperature increases the permeate flux and simultaneously the process efficiency. However, the use of higher flow rates also enhanced heat losses by conduction, which decreases the thermal efficiency. This efficiency also decreases when the salt concentration in the feed was enhanced. The influence of fouling on the process efficiency was considered. Full article

(This article belongs to the Special Issue Energy Efficient Membranes)

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751 KiB

Open AccessReview

A Review of Molecular-Level Mechanism of Membrane Degradation in the Polymer Electrolyte Fuel Cell

by Takayoshi Ishimoto and Michihisa Koyama

Membranes 2012, 2(3), 395-414; https://doi.org/10.3390/membranes2030395 - 10 Jul 2012

Cited by 51 | Viewed by 12656

Abstract

Chemical degradation of perfluorosulfonic acid (PFSA) membrane is one of the most serious problems for stable and long-term operations of the polymer electrolyte fuel cell (PEFC). The chemical degradation is caused by the chemical reaction between the PFSA membrane and chemical species such [...] Read more.

Chemical degradation of perfluorosulfonic acid (PFSA) membrane is one of the most serious problems for stable and long-term operations of the polymer electrolyte fuel cell (PEFC). The chemical degradation is caused by the chemical reaction between the PFSA membrane and chemical species such as free radicals. Although chemical degradation of the PFSA membrane has been studied by various experimental techniques, the mechanism of chemical degradation relies much on speculations from ex-situ observations. Recent activities applying theoretical methods such as density functional theory, in situ experimental observation, and mechanistic study by using simplified model compound systems have led to gradual clarification of the atomistic details of the chemical degradation mechanism. In this review paper, we summarize recent reports on the chemical degradation mechanism of the PFSA membrane from an atomistic point of view. Full article

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

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Structure of Nafion® membrane. Full article ">Figure 2
Plot showing relative fluoride emission rate (FER) from Fenton’s test as a function of concentration of reactive end-groups (taken from in reference [<a href="#B82-membranes-02-00395" class="html-bibr">82</a>]). Full article ">Figure 3
Molecular model of perfluorosulfonic acid (PFSA) polymer with atom labels (taken from reference [<a href="#B137-membranes-02-00395" class="html-bibr">137</a>]). Full article ">Figure 4
Potential energy profile under high humidity condition, CF3(CF2)3O(CF2)2OCF2SO3− + OH. The energy values (kJ/mol) are relative to reactants. Optimized structures of reactants, products, intermediate, and transition state are also shown in the potential energy profile. Important distances are shown in Å. Full article ">Figure 5
Potential energy profile under low humidity condition, CF3(CF2)3O(CF2)2OCF2SO3H +·OH. The energy values (kJ/mol) are relative to reactants. Optimized structures of reactants, products, intermediate, and transition state are also shown in the potential energy profile. Important distances are shown in Å. Full article ">Figure 6
Potential energy profile under high humidity condition, model structure of Nafion side chain +·OH. The energy values (kJ/mol) are relative to reactants. Optimized structures of reactants, products, intermediate, and transition state are also shown in the potential energy profile. Important distances are shown in Å. Full article ">Figure 7
Optimized geometry of Nafion® and their molecular orbitals: (a) highest occupied molecular orbital (HOMO) and (b) lowest unoccupied molecular orbital (LUMO) (taken from reference [<a href="#B146-membranes-02-00395" class="html-bibr">146</a>]). Full article ">Figure 8
Degradation mechanism of Nafion® proposed by Yu et al. (taken from reference [<a href="#B147-membranes-02-00395" class="html-bibr">147</a>]). Full article ">

647 KiB

Open AccessArticle

A Composite Membrane of Caesium Salt of Heteropolyacids/Quaternary Diazabicyclo-Octane Polysulfone with Poly (Tetrafluoroethylene) for Intermediate Temperature Fuel Cells

by Chenxi Xu, Xu Wang, Xu Wu, Yuancheng Cao and Keith Scott

Membranes 2012, 2(3), 384-394; https://doi.org/10.3390/membranes2030384 - 10 Jul 2012

Cited by 6 | Viewed by 7011

Abstract

Inorganic-organic composite electrolyte membranes were fabricated from Cs_XH_3−XPMo₁₂O₄₀ (CsPOMo) and quaternary diazabicyclo-octane polysulfone (QDPSU) using a polytetrafluoroethylene (PTFE) porous matrix for the application of intermediate temperature fuel cells. The CsPOMo/QDPSU/PTFE composite membrane was made proton conducting [...] Read more.

Inorganic-organic composite electrolyte membranes were fabricated from Cs_XH_3−XPMo₁₂O₄₀ (CsPOMo) and quaternary diazabicyclo-octane polysulfone (QDPSU) using a polytetrafluoroethylene (PTFE) porous matrix for the application of intermediate temperature fuel cells. The CsPOMo/QDPSU/PTFE composite membrane was made proton conducting by using a relatively low phosphoric acid loading, which benefits the stability of the membrane conductivity and the mechanical strength. The casting method was used in order to build a thin and robust composite membrane. The resulting composite membrane films were characterised in terms of the elemental composition, membrane structure and morphology by EDX, FTIR and SEM. The proton conductivity of the membrane was 0.04 S cm⁻¹ with a H₃PO₄ loading level of 1.8 PRU (amount of H₃PO₄ per repeat unit of polymer QDPSU). The fuel cell performance with the membrane gave a peak power density of 240 mW cm⁻² at 150 °C and atmospheric pressure. Full article

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

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SEM of (a) CsPOMo/QDPSU/PTFE/H3PO4 composite membrane; and (b) PTFE. Full article ">Figure 2
EDX analysis of CsPOMo/QDPSU/PTFE/H3PO4 composite membrane. (a) Cs; (b) S; (c) F; (d) P; (e) Mo. Full article ">Figure 3
Infrared spectra of CsPOMo-PSU-PTFE-H3PO4 composite membrane. Full article ">Figure 4
Conductivities of CsPOMo/PSU/PTFE composite membrane and polybenzimidazole (PBI) membrane loaded with H3PO4 (PRU 1.8) under relative humidity <1%. The thickness of both membranes is 30μm. Full article ">Figure 5
Polarization and power density curves of a fuel cell operated at 150 °C with (a) H2/O2; and (b) H2/air atmospheric pressure. Pt loading: cathode 0.4 mg cm−2; anode 0.2 mg cm−2; no gas humidity, H3PO4 PRU: 1.8, membrane thickness 28 μm. Gas rate: anode: 40 dm3 min−1; cathode: 70 dm3 min−1. Full article ">Figure 6
Polarization curves of CsPOMo/QDPSU/PTFE and PBI fuel cell operated at 150 °C with H2/O2. Atmospheric pressure, no gas humidity. Full article ">Figure 7
(a) IR corrected polarization curves of CsPOMo/PSU/PTFE; (b) Tafel plots obtained from polarization curves (I is current density). Full article ">

1735 KiB

Open AccessReview

Membranes in Lithium Ion Batteries

by Min Yang and Junbo Hou

Membranes 2012, 2(3), 367-383; https://doi.org/10.3390/membranes2030367 - 4 Jul 2012

Cited by 159 | Viewed by 25318

Abstract

Lithium ion batteries have proven themselves the main choice of power sources for portable electronics. Besides consumer electronics, lithium ion batteries are also growing in popularity for military, electric vehicle, and aerospace applications. The present review attempts to summarize the knowledge about some [...] Read more.

Lithium ion batteries have proven themselves the main choice of power sources for portable electronics. Besides consumer electronics, lithium ion batteries are also growing in popularity for military, electric vehicle, and aerospace applications. The present review attempts to summarize the knowledge about some selected membranes in lithium ion batteries. Based on the type of electrolyte used, literature concerning ceramic-glass and polymer solid ion conductors, microporous filter type separators and polymer gel based membranes is reviewed. Full article

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

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733 KiB

Open AccessArticle

Pure and Modified Co-Poly(amide-12-b-ethylene oxide) Membranes for Gas Separation Studied by Molecular Investigations

by Luana De Lorenzo, Elena Tocci, Annarosa Gugliuzza and Enrico Drioli

Membranes 2012, 2(3), 346-366; https://doi.org/10.3390/membranes2030346 - 28 Jun 2012

Cited by 18 | Viewed by 7612

Abstract

This paper deals with a theoretical investigation of gas transport properties in a pure and modified PEBAX block copolymer membrane with N-ethyl-o/p-toluene sulfonamide (KET) as additive molecules. Molecular dynamics simulations using COMPASS force field, Gusev-Suter Transition State Theory (TST) and Monte Carlo [...] Read more.

This paper deals with a theoretical investigation of gas transport properties in a pure and modified PEBAX block copolymer membrane with N-ethyl-o/p-toluene sulfonamide (KET) as additive molecules. Molecular dynamics simulations using COMPASS force field, Gusev-Suter Transition State Theory (TST) and Monte Carlo methods were used. Bulk models of PEBAX and PEBAX/KET in different copolymer/additive compositions were assembled and analyzed to evaluate gas permeability and morphology to characterize structure-performance relationships. Full article

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Membranes, Volume 2, Issue 3 (September 2012) – 15 articles , Pages 346-686

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