Anion-exchange membrane fuel cells (AEMFCs) researches have recently made a noticeable comeback from proton-exchange membrane fuel cells (PEMFCs) dominant era. The alkaline membrane fuel cells can get faster electrokinetics, lower fuel crossover, reduced CO poisoning, and use of non-precious metal catalysts. ^1-3However, the conductivity and stability of AAEMs are still far less than commercial membrane Nafion.⁴

 Chitosan (CS) is a low-cost biopolymer, which has very good mechanical and chemical stability along with good film formation property. ⁵However, since CS is just a weak alkaline conductivity, it cannot be directly used to fuel cell membrane. In this work, we report a novel series of alkaline anion-exchange membranes: Chitosan /Bis(2-chloroethyl)ether-1,3-bis[3-(dimethylamino)propyl]urea copolymer (PUB) membranes. By incorporation of PUB, the OH^- conductivity of the CS/PUB membrane was found to be greatly improved and reached high up to 4.25×10^-3S cm^-1.

The membranes were prepared by a solution-casting method, where 2g chitosan (degree of deacetylation=80.0-95.0，supplied by Sinopharm Chemical Reagent Co.Ltd.China) was dissolved in deionized water with 2 wt.% acetic acid to form 2 wt.% chitosan solution. Then, PUB was mixed with the above chitosan solution at room temperature. At last, 0.5mg GA was mixed with Chitosan/ PUB composite solution to get a homogeneous appearance. Membranes were obtained with a thickness about 50-100µm. The membrane characteristics were measured using OH^-conductivity and water uptake.

Fig. 1 shows the picture of as-prepared Chitosan/ PUB. It is obvious that the membrane is standing and flexible.

Fig. 2 displays the OH^- conductivity and WU of Chitosan:PUB=1:0.25;1:0.5,1:0.75 membranes. The OH^- value is different with increasing PUB contents and reached 4.25×10^-3 S cm^-1 when polymer composition is 1:0.25:0.1 by mass. The more details, including the effect of cross-linking method on its conductivity, will be reported in the meeting.  

References

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

2. Merle, Géraldine, Matthias Wessling, Kitty Nijmeijer, J. Membr.  377, 1 (2011)

3. J. Ma, Nurul A. Choudhury, Yogeshwar Sahai*, Rudolph G. Buchheit, J. Power Sources, 196, 8257 (2011)

4. Y. Liu, X.H. Cao, R. Hua, Y.Q. Wang , Y.T. Liu , C. Pang , Y. Wang, Hydrometallurgy, 104,150 (2010)

5. G. Wang, Y. Weng, D. Chu, D. Xie, R. Chen, J. Membr. 326(2009) 4e8

Fig. 1 Membrane pictures of Chitosan/PUB membrane. Polymer composition:Chitosan/ PUB/GA = 1: 0.5:0.1 by mass.

Fig.2 OH^- conductivity and water uptake of PVA/PUB/GA membranes in different PUB contents in polymer.