Anion exchange groups

The first key component of a membrane fuel cell is the membrane electrolyte. Its central role lies in the separation of the two electrodes and the transport of ionic species (e.g. hydroxyl ion, OH , in an AEM), between them. In general, quaternary ammonium groups are used as anion-exchange groups in these materials. However, due to their low stability in highly alkaline media [43,44], only a few membranes have been evaluated for use as solid polymer electrolytes in alkaline fuel cells. 

All the membranes considered were based on quaternary ammonium groups as anion-exchange groups. However, these conductive groups may decompose in concentrated alkaline solution following the Hofmaim degradation reaction [43]. 

Hiroyama, N. Umehara, W. Makizawa, H. Honjo, T. Ion chromatography using a charged complex anion-exchange group. Anal. Chim. Acta 2000, 409, 17-26. 

Porous titania Anatas Br0nsted and Lewis acid and basic sites, cationic and anionic exchange groups, point of zero charge at pH 5, pJCa of Bronsted add sites 0.2-0.5... 

An outer layer of latex beads, which carry the actual anion exchange groups,... 

Depending on the ionic charge(s) of the solutes to be separated, anion or cation exchange stationary phases must be used. Common ion exchange support materials include silica, poly(styrene-divinylbenzene), and cellulose. Common anion exchange groups anchored to these supports include 1°, 2°, 3°, and 4"" amines. 

F. D Alelio, of General Electric Co., prepared the first styrene-divinyl benzene polymers (U.S. Patents 2,340,110 and 2,340,111). These allowed various porosities of material to be prepared and provided a backbone for various types of cation and anion exchange groups to be added. (See the reaction on p. 271.)... 

The anion-exchange group is introduced into the polymer by chloromethylation and amination with trimethylamine according to the following reaction scheme ... 

Cation exchange groups Apparent pK Anion exchange groups Apparent pK... 

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