Ionically Conductive Membranes

Later, Du Pont in America developed its own ionically conducting membrane, mainly for large-scale electrolysis of sodium chloride to manufacture chlorine, Nafion , (the US Navy also used it on board submarines to generate oxygen by electrolysis of water), while Dow Chemical, also in America, developed its own even more efficient version in the 1980s, while another version will be described below in connection with fuel cells. Meanwhile, Fenton et al. (1973) discovered the first of a... 

The fluoride electrode is a typical example of an ion selective electrode. Its sensitive element is a crystal of lanthanum trifluoride that allows fluorine atoms to migrate into the network formed by lanthanum atoms (Fig. 18.3). Other electrodes use a mineral membrane obtained as agglomerates of crystalline powders (for measurement of Cl-, Br-, I , Pb++, Ag+ and CN ). Generally, the internal electrolyte can be eliminated (by dry contact). However, it is preferable to insert a polymer layer with a mixed-type conductivity to ensure the passage of electrons from the ionic conductivity membrane to the electronic conductivity electrode (Fig. 18.3). 

Some of the many different types of catalysts which have good catalytic properties for the OCM reaction qualify as membrane materials. Membrane reactors for OCM were designed and tested by Nozaki et al. (1992). Three kinds of reactors were developed the first one consisted of a porous membrane covered with a thin film of catalyst (type I) the second one, a dense ionic-conducting membrane (non porous) with catalytic layer (type II) and the third one was a membrane made of perovskite-type mixed oxides which was active for OCM (type III). Figure 11 presents the diagram for the membrane reactor system and table 13 shows the different materials used for supports and coated catalysts. 

Modified polysaccharide biopolymers have found applications from permselective membranes to ionically conductive membranes for fuel cells. In this review, ionically selective membranes in particular will be explored. Recent studies and advances in using modified polysaccharides for food applications will also be reviewed with specific attention given to their potential uses in the development of active food packaging solutions, which include antimicrobial systems, coatings and bioactive compound delivery systems. 

WhUe permselective membranes used in sensor applications focus mainly on the exclusion of certain charge states and inclusion of other charge states, research into ionically conductive membranes focuses primarily on enhancing the transport of charged ions across a membrane. 

Of gallium, chromium and titanium B-site cations, only galhum perovskites have substantial oxygen-ion conductivity. Therefore, if chromium or titanium are used as part of a single-phase mixed electronic-ionic conducting membrane, they need to be used in conjunction with iron or small amounts of cobalt [26]. GaUium perovskites, while possessing potential for excellent ionic conductivity, do not have sufficient electronic conductivity and need the addition of iron, cobalt or chromium. 

More precisely an ionic conducting membrane, see section 1.3.2.2. 

Panero, S., E. Spila, and B. Scrosati. 1995. On the use of ionically conducting membranes for the fabrication of laminated polymer-based redox capacitors. / Electroanal Chem 396 385. 

The structure of the triple layer is suitable for the construction of muscles working in air, by encapsulation of the triple layer keeping a small amount of electrolyte, or by using an adherent, flexible, and ionic conducting membrane between both films of the conducting polymers [55,91,122—127]. 

J. Jouanneau, R. Mercier, L. Gonon, G. Gebel, Synthesis of sulfonated polybenzimidazoles from functionalized monomers preparation of ionic conducting membranes. Macromolecules 40 (4) (2007) 983-990. 

In the following section, we present a simple method to prepare high ionic conducting membrane separators with lower cost non-woven polypropylene/polyethylene (PP/PE)... 

The basic setup of polymer electrolyte membrane fuel cells (PEMFC) as well as direct methanol fuel cells (DMFC) is in line with the standard fuel cell setup the two electrodes are separated by means of an electrically insulating but ionically conductive membrane (polymer electrolyte). In a PEM fuel cell, the anodic reactant is hydrogen, which is oxidized to form protons on the cathode, oxygen is reduced and forms water with protons that are transported through the proton conductive membrane. The overall reaction is... 

Figure 7-24. Schematic representation of a membrane reactor operating with dense ionic conducting membranes for syngas production (a) tubular reactor using a MIEC membrane (b) Electrochemical cell using a purely ion conducting membrane.

Kumar et al. [36] recently published a report on solid-state lithium-air batteries. The lithium-ion, conductive solid electrolyte membrane is based on glass-ceramic (GC) and polymer-ceramic materials. This solid electrolyte is used as the ionic conductive membrane between the lithium electrode and the air electrode. It also is used in the soHd composite air cathode prepared from high-surface-area carbon. The cell exhibited excellent thermal stabihty in the 30-105 °C temperature range... 

Jouanneau, J., Mercier, R., Gonon, L., Gebel, G., Synthesis of sulfonated polybenzimidazoles from functionahzed monomers Preparation of ionic conducting membranes. Macromolecules 2007, 40, 983-990. 

In 1998 Velazquez-Morales et described the synthesis of oxipro-pylated chitosan grafted and crosslinked with oligoether-based mono- and diisocyanates, as in the case of cellulosic ethers. The ionic conducting membranes were obtained by introducing lithium bis(trifluoromethyl sulfonyl) imide (LiN(Cp3S02)2 - LiTFSI) by diffusion from an acetonitrile solution, yielding values similar to those obtained for the cellulose derivative networks described above. 

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