Preparation and Characterization of Nafion/SPPESK-PES/Nafion Multilayer Composite Membrane

Preparation and Characterization of Nafion/SPPESK-PES/Nafion Multilayer Composite Membrane

Hong Zhu*, Ming Wang, Yong-Sheng Wei

Department of Chemistry, School of Science, Beijing Jiaotong University, Beijing 100044, China

*E-mail: hzhu@bjtu.edu.cn; Tel: 86-10-51684001; Fax: 86-10-82161887

Direct methanol fuel cell (DMFC) is considered to be a candidate for portable electrical source. Membrane electrode assembly (MEA) is heart of DMFC, and membrane is a key material for MEA. So far, Nafion is widely used as proton exchange membrane in DMFC. Nafion has a PTFE polymer chain as a backbone, with a flexible branch pendant to this chain, a perfluorinated polyether with a terminal sulfonic group to provide the cation exchange capacity. Nafion has high proton conductivity and outstanding chemical stability. However, high methanol crossover with Nafion is a major technical obstacle that impedes the commercialization of DMFC. The methanol crossover results not only in a loss of fuel cell but also in a mixed potential at the cathode and leading to a lower cell performance.

To reduce methanol crossover, significant research efforts have focused on hydrocarbon membrane. But hydrocarbon membrane is prone to degrade. In order to extend longevity of hydrocarbon membrane and reduce methanol crossover, we design multilayer composite membrane for DMFC, central layer is hydrocarbon membrane as methanol resistant layer, and both sides prevent central layer from degradation. Sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK)is a novel hydrocarbon polymer. Owing to low methanol crossover and high proton conductivity, we chose it as central layer. Nafion was used as anti-degradation layers because of high chemical stability. Therefore, we prepared Nafion/SPPESK-PES/Nafion multilayer composite membrane.

Nafion/SPPESK-PES/Nafion multilayer composite membrane was prepared by spraying Nafion layer on both sides of SPPESK-PES blend membrane. Scanning electron microscopy (SEM), proton conductivity, methanol permeability and longevity of multilayer composite membranes were examined. SEM showed that composite membrane was apparently composed of three layers as a sandwich structure, the both sides Nafion layer and the SPPESK-PES central layer. The both side layers were with good adhesion to the native SPPESK-PES blend membrane. It was found that compared with the native SPPESK-PES membrane, the multilayer composite membrane had higher proton conductivity and higher methanol permeability. The results also showed that with temperature increasing, proton conductivity and methanol permeability both increased. Fenton experiments indicated that the longevity of multilayer composite membrane was extended in that Nafion layer prevented SPPESK-PES blend membrane from degradation. Nafion/SPPESK-PES/ Nafion multilayer composite membrane has a potential to be considered for direct methanol fuel cell application.

Acknowledgements:

The authors gratefully acknowledge the financial support from the National High Technology Research and Development Program of China (863 Program, No. 2006AA03Z226), The National Science Foundation of China (Key Program No. 20636060), International S&T Cooperation Program of China (No. 2006DFA61240) and the Natural Science Foundation of Beijing (No. 2073031).

References

[1] Y. C. Si, J. C. Lin, H. R. Kunz, et al., J. Electrochem. Soc., 151(3), A463-A469 (2004)

[2] S. L. Chen, A.B. Bocarsly, J. Benziger, J. Power Sources, 152, 27-33 (2005)

[3] R. C. Jiang, H. R. Kunz, J. M. Fenton, J. Electrochem. Soc., 153(8), A1554-A1561 (2006)

Author information:

Hong Zhu,Doctor; Professor; Mailing address: Department of Chemistry, School of Science, Beijing Jiaotong University, Beijing 100044, China; E-mail: hzhu@bjtu.edu.cn; Tel: 86-10-51684001; Fax: 86-10-82161887.

Ming Wang, Master candidate; Mailing address: Department of Chemistry, School of Science, Beijing Jiaotong University, Beijing 100044, China; E-mail: 06122083@bjtu.edu.cn; Tel: 86-10-51684001; Fax: 86-10-82161887.

Yong-Sheng Wei, Doctor candidate; Mailing address: Department of Chemistry, School of Science, Beijing Jiaotong University, Beijing 100044, China; E-mail: 06118340@bjtu.edu.cn; Tel: 86-10-51684001; Fax: 86-10-82161887.

Hong Zhu

Description of Education

BS, 1982-- Henan University, Kaifeng, Henan-- Chemistry

MS, 1991-- China University of Mining and Technology, Xuzhou, Jiangsu--Chemical Engineering

PhD, 1998--China University of Mining and Technology, Xuzhou, Jiangsu--Chemical Engineering