Anion Exchange Membranes AEMs

Stability and performance of AEM prepared using poly(4-vinyl pyridine-costyrene), quaternized with 1-bromooctane, and deposited on fibrous woven paper was unsatisfactory [189]. Sanchez and coauthors [190] discussed problems related to the use of certain AEMs. They pointed out that the so-called Hoffman degradation that involves attack of a hydroxyl on a-hydrogen in p-position to a quaternary ammonium attached to an aliphatic chain may cause its removal, followed by release of a tertiary amine and formation of a double bond at the end of a broken chain. Attachment of DABCO on short leash prevented chain break due to Hoffman degradation, but release of DABCO and generation of a double bond attached to the chain could take place. Perhaps thermal cross-linking by DABCO of poly(vinyl benzyl chloride) may solve this problem. Sulfonated polymers prepared by polymerization or copolymerization of phosphazene, siloxans, styrene, vinylidene fluoride, and various monomers with aromatic backbones, and possibly with aliphatic spacers, have been used. Various imides as well as PPS, PEK, PEEK, PSU, PEEKK, and PPSU can also be used [190,191]. 

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Solid alkaline membrane fuel cell (SAMFC) working at moderate temperatures (20-80 °C) for which an anion-exchange membrane (AEM) is the electrolyte, electrically conducting by, for example, hydroxyl ions (OH ). 

FIGURE 21.35 Operation of BPM ED using a two-compartment configuration coupling, (a) Cation-exchange membrane (CEM) and (b) anion-exchange membrane (AEM). (Erom Bazinet L., Crit. Rev. Food Sci. Nutr., 45, 307, 2005.)... 

Kunugi cl al. studied Cu coated SPEs prepared from a CEM (Nafion 117) and an anion exchange membrane (AEM) Selemion AMV, attempting to reduce CO2 from combustion flue gas. ° The SPE from Nafion 117 formed C2H4 as the product with the maximum partial current 2 mA cnf at -1.8 V vs. SCE. Both types of SPE retained stable activity in CO2 reduction for 5 hr. 

Amendola et al. [38, 39] constructed Model 2 type cells with an air cathode and an anode made of highly dispersed Au/Pt particles supported on high-surface area carbon silk. An anion exchange membrane (AEM) was used as the electrolyte. The number of electrons utilized per molecule of BH4 oxidized (about 6.9 out of a possible 8) shows efficient utilization of the BH4 oxidation. Specific energy >180Whkg and power densities >20mWcm at room temperature and >60mWcm at 70 °C have been reported. 

IX membranes are either cation-exchange membranes (CEM) or anion-exchange membranes (AEM). CEM are usually made from polystyrene copolymerised with divi-nylbenezene and suphonated to attach ion-exchange groups [16, 17, 26]. AEM... 

Inasmuch as the use of epichlorohydrin concept, Agel et al. [13] developed a new and cheap type of anion exchange membranes (AEM) by preparing the polyepichlorohydrin (PECH) graft quaternary amines (DABCO, TEA) for use in alkaline cells. It s a quasi-gas impervious polymer membrane. The ionic conductivity was much improved to 10 S cm due to the low crystallinity and the anion exchange between Cf and OH ions on the polymer side chains. For the first time, the alkaline SPE employed in alkaline fuel cell, the test results exhibited good performance and could tolerate at high temperature up to 120°C. 

In this chapter a new type of solid electrolyte membrane for low-temperature fuel cell application, the anion exchange membrane (AEM), is reviewed. The properties, advantages, and challenges of the anion exchange membranes are discussed. 

Fig. 2 Schematic picture of transport of OH through an anion exchange membrane (AEM)...

Another approach is to consider Anion Exchange Membranes (AEMs) which may allow the use of non-noble metal catalysts relatively active in alkaline medium for methanol oxidation... 

In configurations (c) and (d), an anion exchange membrane (AEM) is used as an alternative, e.g., as an OH ion conductor. The ion migration, the EOF, and the succession of reactions change their directions compared with a CEM as an ion conductor. However, the discussed effects of configurations (a) and (b) remain valid if the inversion is considered. These inverted directions may influence the performance of the cell significantly. 

The disruptive approach of applying alkaline anion-exchange membranes (AEMs) in alkaline membrane fuel cells (AMFCs) potentially meets several of the challenges facing other approaches to low temperature fuel cells, including the otherwise high catalyst and fuel costs. Thus, the move to alkaline conditions at the electrodes opens the potential use of a range of low cost non-precious-metal catalysts, as opposed to... 

An Overview of Alkaline Anion-Exchange Membranes (AEMs)... 

The separator is an important component in a MFC, which physically separates the anode and cathode. A variety of separators have been explored for MFCs, including a salt bridge, cation exchange membrane (CEM), anion exchange membrane (AEM), bipolar membrane (BPM), microfiltration (MF) membrane, ultrafiltration (UF) membrane, and porous fabrics and porous materials. 

State-of-the-art DMFCs have not been considered for use in vehicles, except small vehicles, because of the lower efficiency and power density. In addition, a carbon-free fuel would be preferable for use in FC-powered vehicles. Alternative fuels, oxidation catalysts, reaction medium, electrolyte membranes, and electrode preparation have been evaluated to obtain optimal DLFCs. L-Ascorbic acid (AA), widely known as vitamin C, has been proposed as a novel fuel that does not require the use of an anode catalyst metal. DLFCs that use ethanol and D-glucose as renewable biofuels have been studied and developed using an anion exchange membrane (AEM). Hydrazine fuel cells were reconsidered for use in transportation based on the application of recent PEMFC technology. A novel anode catalyst for NaBILj oxidation is also described. 

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