Organic/inorganic hybrid membranes for direct methanol fuel cells
TL;DR: In this article, an organic/inorganic hybrid membrane with silica supported heteropoly acid was applied to reduce methanol cross-over with keeping ionic conductivity high for DMFCs.
About: This article is published in Journal of Membrane Science.The article was published on 2007-02-01. It has received 30 citations till now. The article focuses on the topics: Proton exchange membrane fuel cell & Direct-ethanol fuel cell.
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TL;DR: In this paper, 3A, 4A, 5A, 13X, mordenite, and HZSM-5 were incorporated into chitosan (CS) matrix to fabricate the hybrid membranes for direct methanol fuel cell (DMFC).
115 citations
TL;DR: In this article, the status of research and development of polymer electrolyte membranes (PEMs) for direct methanol fuel cells (DMFCs) is described and a review of membrane properties is carried out on the basis of thermal stability, methanoline crossover and proton conductivity.
113 citations
TL;DR: In this article, a free-standing anion-exchange polyethylene oxide (PEO)-SiO 2 hybrid membrane with high flexibility and good mechanical strength (tensile strength (TS) as high as 20.55 MPa) as well as high temperature tolerance (thermal degradation temperature in air, T d, in the range of 220-240 °C) were prepared through sol-gel reaction of different precursors: charged alkoxysilane-functionalized PEO-1000, N -triethoxysilylpropyl-
91 citations
Cites background from "Organic/inorganic hybrid membranes ..."
...cation-exchange organic–inorganic hybrid materials have been frequently reported, in the hope of replacing the expensive perfluorocarbon cation-exchange materials such as Nafion [9–13]....
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TL;DR: A review of the electrochemical properties of polyoxometalates and their applications in fuel cells is presented in this article, with a focus on fuel cells and a critical assessment of their applications.
87 citations
TL;DR: In this paper, a Zwitterion-functionalized covalent organic framework (Z-COF) with both ammonium groups and sulfonic acid groups was synthesized and blended with Nafion to create composite proton exchange membranes.
60 citations
References
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TL;DR: Devising systems that can conduct protons with little or no water is perhaps the greatest challenge for new membrane materials, and new membranes that have significantly reduced methanol permeability and water transport (through diffusion and electro-osmotic drag) are required for automotive applications.
Abstract: Fuel cells have the potential to become an important energy conversion technology. Research efforts directed toward the widespread commercialization of fuel cells have accelerated in light of ongoing efforts to develop a hydrogen-based energy economy to reduce dependence on foreign oil and decrease pollution. Proton exchange membrane (also termed “polymer electrolyte membrane”) (PEM) fuel cells employing a solid polymer electrolyte to separate the fuel from the oxidant were first deployed in the Gemini space program in the early 1960s using cells that were extremely expensive and had short lifetimes due to the oxidative degradation of their sulfonated polystyrene-divinylbenzene copolymer membranes. These cells were considered too costly and short-lived for real-world applications. The commercialization of Nafion by DuPont in the late 1960s helped to demonstrate the potential interest in terrestrial applications for fuel cells, although its major focus was in chloroalkali processes. PEM fuel cells are being developed for three main applications: automotive, stationary, and portable power. Each of these applications has its unique operating conditions and material requirements. Common themes critical to all high performance proton exchange membranes include (1) high protonic conductivity, (2) low electronic conductivity, (3) low permeability to fuel and oxidant, (4) low water transport through diffusion and electro-osmosis, (5) oxidative and hydrolytic stability, (6) good mechanical properties in both the dry and hydrated states, (7) cost, and (8) capability for fabrication into membrane electrode assemblies (MEAs). Nearly all existing membrane materials for PEM fuel cells rely on absorbed water and its interaction with acid groups to produce protonic conductivity. Due to the large fraction of absorbed water in the membrane, both mechanical properties and water transport become key issues. Devising systems that can conduct protons with little or no water is perhaps the greatest challenge for new membrane materials. Specifically, for automotive applications the U.S. Department of Energy has currently established a guideline of 120 °C and 50% relative humidity as target operating conditions, and a goal of 0.1 S/cm for the protonic conductivity of the membrane. New membranes that have significantly reduced methanol permeability and water transport (through diffusion and electro-osmotic drag) are required for portable power oriented direct methanol fuel cells (DMFCs), where a liquid methanol fuel highly diluted in water is used at generally <90 °C as the source of protons. Unreacted methanol at the anode can diffuse through the membrane and react at the cathode, lowering the voltage efficiency of the cell and reducing the system’s fuel efficiency. The methanol is usually delivered to the anode as a dilute, for example, 1 M (or less), solution (3.2 wt %), and relatively thick Nafion 117 (1100 EW, 7 mil ∼ 178 μm thick) is used to reduce methanol crossover. The dilute methanol feed increases the system’s complexity and reduces the energy density of the fuel, while the thick Nafion membrane increases the resistive losses of the cell, especially when compared to the thinner membranes that are used in hydrogen/air systems. The presence of excessive amounts of water at the cathode through diffusion and electro-osmosis * To whom correspondence should be addressed. E-mail: jmcgrath@vt.edu. † Sandia National Laboratory. ‡ Case Western Reserve University. § Los Alamos National Laboratory. | Virginia Polytechnic Institute and State University. 4587 Chem. Rev. 2004, 104, 4587−4612
2,681 citations
TL;DR: In this paper, the authors present an overview of the synthesis, chemical and electrochemical properties, and polymer electrolyte fuel cell applications of new proton-conducting polymers based on hydrocarbon polymers.
1,476 citations
TL;DR: In this paper, a biphenol-based wholly aromatic poly(arylene ether sulfone)s containing up to two pendant sulfonate groups per repeat unit were prepared by potassium carbonate mediated direct aromatic nucleophilic substitution polycondensation of disodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (SDCDPS), 4, 4′-dimethylactamide (DCDPS).
1,142 citations
TL;DR: By converting the ions generated in an electrochemical half-cell reaction to a fluorescence signal, the most active compositions in a large electrode array have been identified.
Abstract: Combinatorial screening of electrochemical catalysts by current-voltage methods can be unwieldy for large sample sizes. By converting the ions generated in an electrochemical half-cell reaction to a fluorescence signal, the most active compositions in a large electrode array have been identified. A fluorescent acid-base indicator was used to image high concentrations of hydrogen ions, which were generated in the electrooxidation of methanol. A 645-member electrode array containing five elements (platinum, ruthenium, osmium, iridium, and rhodium), 80 binary, 280 ternary, and 280 quaternary combinations was screened to identify the most active regions of phase space. Subsequent “zoom” screens pinpointed several very active compositions, some in ternary and quaternary regions that were bounded by rather inactive binaries. The best catalyst, platinum(44)/ruthenium(41)/osmium(10)/iridium(5) (numbers in parentheses are atomic percent), was significantly more active than platinum(50)/ruthenium(50) in a direct methanol fuel cell operating at 60°C, even though the latter catalyst had about twice the surface area of the former.
904 citations
TL;DR: In this article, a series of sequenced sulfonated naphthalenic polyimides with improved solubility were prepared by polycondensation in m-cresol using aromatic diamines containing phenylether bonds and/or bulky groups.
521 citations