(220g) Highly Durable Aromatic Anion Exchange Membranes for Solid Alkaline Fuel Cells

Authors: 
Yamaguchi, T., Tokyo Institute of Technology
Miyanishi, S., CREST, JST
Kuroki, H., Kanagawa Academy of Science and Technology

Introduction Solid alkaline
fuel cell using anion exchange membrane (AEM)
attracts increasing attention since non-noble metal electrode catalyst and high
density liquid fuel can be used. However, development of chemically durable membrane
is critical for long-term operation. AEM
consisting of only aromatic component and anion exchange group such as polyphenylene AEM
is potential candidate for highly durable membranes, but is suffered from low
solubility due to the rigid linear backbone.

To
overcome this problem, we have synthesized a spirobifluorene-
based aromatic AEM as a highly
soluble and durable AEM and used
this AEM as an ionomer of methanol
fuel cell.

Method
Target
AEM was synthesized by
polymerization of the spirobifluorene and the phenyl
monomers and successive quaternization. Alkaline and
radical stability of this membrane were evaluated by comparing 1H-NMR
spectra before and after soaking into 1M NaOH aq, and fentone solution. Finally,
MEA was fabricated by using this AEM ionomer
and direct Methanol fuel cell performance and durability were investigated at
80 oC.

Results
and Discussion
The synthesized membrane can be dissolved well into chloroform, tetrahydrofran and mixed solvent of THF and 1-propanol but
not dissolved into fuel methanol.

1H-NMR spectra of
this membrane did not change at all even after soaking into 1M NaOH aq. for one week indicating high alkaline stability.
After soaking into fentone solution, the aromatic
region of 1H-NMR did not change indicating high radical stability of
the polymer backbone.

Direct methanol fuel cell using this membrane shows high and durableperformances
at 80 oC. These performances did not
change even after one week operation indicating that highly durable solid alkaline
fuel cell was realized by using the membrane (Fig 1).