(528d) Synthesis of Sulfonium Based Polymers for Hydroxide Exchange Membrane Fuel Cell Applications

Chair:

Winston Ho

Professor

Chemical and Biomolecular Engineering

The Ohio State University

Phone Number: 614-292-9970
Email: ho@chbmeng.ohio-state.edu 

Co-Chair:

Peter Pintauro

Professor of Chemical Engineering and Chair

Department of Chemical and Biomolecular Engineering

Vanderbilt University

Olin Hall 107

VU Station Box

Phone Number: 615-343-3878
Email: peter.pintauro@Vanderbilt.Edu 

Synthesis of Sulfonium Based Polymers for Hydroxide Exchange Membrane Fuel
Cell Applications

Bingzi Zhang, Shuang Gu,
Yushan Yan*

Department of
Chemical and Environmental Engineering

University
of
California,
Riverside

Riverside, CA,
92521, USA

*
yushan.yan@ucr.edu

Polymer electrolyte fuel cells, which convert
chemical energy to electrical energy, are regarded as promising future power
sources. So far, the most advanced polymer electrolyte fuel cells are based on
proton exchange membranes (PEMs), in particular Nafion membranes. However, the high cost caused by the use
of noble metals as catalysts hinders the widespread deployment of fuel cell
technology. To solve this problem, there has been an increasing interest in
developing hydroxide exchange membranes (HEMs) for
fuel cell applications because it enables non-precious metals (e.g., nickel) as
catalysts. In addition, HEM fuel cells also have the potential to offer fuel
flexibility, reduce fuel crossover and prevent carbonate precipitation.

             
The most commonly used HEMs today are
quaternary ammonium based polymers. But currently available ammonium based HEMs were found to have low hydroxide conductivity and
stability. In order to improve the performance, HEMs
with novel functional groups have been explored. Recently, we have synthesized
quaternary phosphonium based polymers and showed that
they have higher hydroxide conductivity and stability than ammonium ones [1,2]. We have also implemented crosslinking
for reducing water uptake and swelling [3]. Like phosphorus, sulfur is another
neighbor of nitrogen in the periodic table and triarylsulfonium
salts were reported to have high alkaline stability, which indicates that the
corresponding form of sulfur°ªtertiary sulfonium
based polymer is potentially a promising candidate for HEMs.

             
In this study, we synthesized triarylsulfonium
based polymers with functional groups either in the backbone or in the side
chains. For the former, it was synthesized by reacting poly(arylenethioethersulfone) (PTES) with arylating
agent, while the latter was synthesized by reacting brominated
triarylsulfonium salt with polysulfone.
The structures of these two polymers are characterized by NMR, infrared
spectroscopy and elemental analysis. The alkaline stability and water uptake of
the membranes were also tested. In addition, hydroxide conductivities were
measured as a preliminary test for the application in alkaline fuel cells.

References

[1] S. Gu,
R. Cai, T. Luo, Z. Chen, M.
Sun, Y. Liu, G. He, Y. Yan, Angewandte Chemie International Edition 2009,
48, 6499.

[2] S. Gu, R. Cai, T. Luo, K. Jensen, C.
Contreras, Y. S. Yan, ChemSusChem, 2010, 3, 555.

[3] S. Gu, R. Cai, Y.
S. Yan, Chem. Commun., 2011, 47,
2856.

Key words: Sulfonium, Hydroxide exchange membrane, Fuel cells