Anion Conductive Membrane

Overall, a great deal of attention has been paid to inducing ionic conductivity in chitosan membranes for application in fuel cell membranes. In both cationic and anionic membranes, the fuel cell performance values are approaching that of the industry standard Nation membranes. 

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In an alkaline fuel cell, which contains an anionically conductive membrane, the exchange media is a hydroxyl radical, ("OH). At the anode, hydrogen is oxidized through a redox reaction, (Equation 3.3), producing water and... 

All these materials are acid proton conductors. Anion conducting membranes have recently been developed [1,2], however, they did not find widespread use so far. The reasons for this among others are their lower ionic conductivity, their instability at temperatures above 60 °C and their sensitivity towards atmospheric CO2 causing significant reductions in performance. However, there are indications that CO2 can be removed from certain anion exchange membranes by superimposing a suitable current profile to the fuel cell. 

Firstly, Nafion and other perfluorinated sulfonic acid ionomers will be discussed, along with inorganic- and organic-Nafion based composites. Secondly, we will introduce non-fluorinated single and composite membranes, including membranes for high temperature DAFC. Finally we will discuss anion conducting membranes for alkaline DAFC. 

Zhou J, Unlii M, Anestis-Richard I, Kohl PA (2010) Crosslinked, epoxy-based anion conductive membranes for alkaline membrane fuel cells. J Membr Sci 350 286-292... 

Faraj M, Elia E, Boccia M, Filpi A, Pucci A, Ciardelli F (2011) New anion conducting membranes based on functionalized styrene-butadiene-styrene triblock copolymer for fuel cells applications. J Polym Sci A Polym Chem 49 3437-3447. doi 10.1002/pola.24781... 

Aili D, Hansen MK, Renzaho RF et al (2013) Heterogeneous anion conducting membranes based on linear and crossiinked KOH doped polybenzimidazole for alkaline water electrolysis. J Membr Sci 447 424 32... 

Stoica et al. [140,141] developed and characterized another anion-conducting membrane based on a poly(epichlorohydrin) copolymer using allyl glycidyl ether as cross-linking agent. In order to introduce anionic properties, two cyclic diamines were incorporated DABCO and l-azabicyclo-[2.2.2]-octane (quinuclidine) (Fig. 5.13). To stabilize the membrane, the film was thermally or photochemically cross-linked. High conductivities were obtained without any KOH addition. At 60 °C and 98% relative humidity, the membrane exhibited a hydroxyl conductivity of 1.3 X 10 S/cm and an ion exchange capacity of 1.3 X 10 equiv./g. The performance of this MEA in H2/O2 AFC operation was 100 X 10 W/cm for 270 X 10 A/cm [142]. 

During fuel cell operation, ions would conduct through PEMs, which leads to current flow in the cell system. Thus, the conductivity of PEMs plays an important role in fuel cell performances, and membrane conduction mechanism has drawn much attention in fuel cell researches. There are mainly two kinds of conduction mediums in PEMs according to the fuel cell type proton (H+) and hydroxyl (OH ). As aliphatic membranes were usually used for anion-conduction membrane and proton-conduction mechanism has been discussed already in the preceding chapters, we will focus our attention mainly to hydroxyl conduction mechanism in this chapter, although they have a lot in common. 

Source Z.S. Mai et al.. Anion-conductive membranes with ultralow vanadium permeability and excellent performance in vanadium flow batteries, ChemSusChem 2013, 6, 328-335. Copyright Wiley-VCH Verlag GmbH Co. KGaA. Reprinted with permission. QAPESl-40, QAPESl with thickness of 40 pm QAPESl-60, QAPESl with thickness of 60 pm QAPES2-60, QAPES2 with thickness of 60 pm where the lEC of QAPESl > QAPES2. 

EX. Zhang, H.M. Zhang and C. Qu, Influence of solvent on p>olymer prequater-nization toward anion-conductive membrane fabrication for aU-vanadium flow battery,. Phys. Chem. B116,2012,9016-9022. 

J. Qiao, J. Fu, L. Liu, Y. Liu, J. Sheng, Highly stable hydroxyl anion conducting membranes poly(vinyl alcohol)/poly(acrylamide-co-diallyldimethylammonium chloride) (PVA/PAADDA) for alkaline fuel cells Effect of cross-linking. International Journal of Hydrogen Energy, 37 (2012) 4580—4589. 

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