The alkaline membrane fuel cells (AMFCs), which use the anion-exchange membranes to display the proton-exchange membranes with OH^- anions instead of H⁺ ions, have aroused new interest due to their faster electrokinetics, lower fuel crossover, reduced CO poisoning, and use of non-precious metal catalysts ^1,2.In the development of AEMFCs, the conductivity of  alkaline anion-exchange membranes (AEMs) is considered to be the most challenge, since the mobility of OH^- is only 1/4 of that of the H⁺ transportation (membranes that conduct H⁺ cations), the membranes that can have high OH^- conductivity are highly desired for making a breakthrough in AEMFCs performances^3,4. However, these polymers were generally of high price and their quaternization is complex process.

In this work, we report a novel alkaline anion-exchange membrane prepared from poly(vinyl alcohol)/Bis(2-chloroethyl)ether-1,3-bis[3-(dimethylamino)propyl]urea copolymer (PUB) composite on the basis of direct chemical cross-linking method⁵ .By incorporation of PUB, the OH^- conductivity of the PVA/PUB membrane was found to be greatly improved and reached high up to 5.56×10^-3S cm^-1 .

The membranes were prepared by a simple solution-casting method, where PVA (99% hydrolyzed, average molecular weight Mw=86,000-89,000; Aldrich) was fully dissolved in water to make a 10% solution at 70^oC. PUB (62% as active ingredients in H₂O; Aldrich) and glutaraldehyde (GA) solution(25% mass) was directly added by addition of a drop of HCl to get a homogeneous appearance at room temperature, and stir for 30 min. The anion conductivity of PVA/PUB/GA composite membrane is studied using AC impedance technique.

Figure 1 composite membrane picture of PVA/PUB. It is obvious that the membrane is standing and flexible. 

Figure 2 shows the ionic conductivity of the membrane (PVA:PUB:GA=1:0.25:0.05 and PVA:PUB:GA=1:0.25:0.1 by mass) as a function of content of GA. The s_OH^- values increased with increasing GA contents and reached 5.56×10^-3 S cm^-1 when polymer composition is PVA:PUB:GA=1:0.5:0.1 by mass.

References

1. J. Zhou, M. Ünlü, I. Anestis-Richard, P.A. Kohl, J. Membrane Science, 350 (2010)286.

2.J. L. Qiao, J. Fu, R. Lin, J. X. Ma, J. S. Liu, “Alkaline solid polymer electrolyte membranes based on structurally modified PVA/PVP with improved alkali stability,”Polymer, Vol. 51, pp. 4850-4859(2010).

3. Jinli Qiao, Jing Zhang, Jiujun Zhang, Journal of Power Sources 237 (2013) 1e4.

4.Y. Wan, B. Peppley, K A.M Creber, V. Tam Bui, J. Power Sources. Soc. 195, 3785 (2010).

5.J. L. Qiao, J. Fu, L. L. Liu, L. Xu, Y. Y. Liu, J. W. Sheng, Int. J. Hydrogen Energy 37, 4580 (2012).