Composite of polysilamine and strong acid

Details Composite of polysilamine and strong acid Composite of polysilamine and strong acid

1999-04-29

2001-01-16

Nuzzolillo, Maria (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

With pressure equalizing means for liquid immersion operation

C428S447000, C429S313000, C528S027000

Reexamination Certificate

active

06174615

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a composite of a poly-silamine and a strong acid. The composite of the present invention can be suitably used as the electrolyte membrane of a fuel cell.
BACKGROUND OF THE INVENTION
A cell has an electrolyte and a pair of electrodes separated by the electrolyte. In the case of a fuel cell, a fuel (for example, hydrogen) is supplied to one electrode and an oxidizing agent(for example, oxygen) is supplied to the other electrode. In this way, the chemical energy accompanied by the oxidation of the fuel is converted into electric energy. The electrolyte aims to permeate a hydrogen ion but not a reactant (hydrogen and oxygen). Typically, a fuel cell has a plurality of unit cells, and each unit cell has an electrolyte and a pair of electrodes separated by the electrolyte.
A solid such as a polymer electrolyte membrane and a liquid such as phosphoric acid have been used as the electrolyte of the fuel cell in these days. As the electrolyte of the fuel cell, polymer electrolyte membranes can be suitably employed.
The polymer electrolyte includes, for example, a perfluorosulfonic acid polymer, and the perfluorosulfonic acid polymer typically has such a structure that to a perfluorocarbon backbone (for example, a copolymer of tetra-fluoroethylene and trifluorovinyl), side chains having a sulfonic group (for example, a side chain of a sulfonic group bonded to a perfluoroalkylene group) are bonded. The sulfonic acid group can dissociate a hydrogen ion therein to produce an anion thereby showing proton conductivity. Further, the use of a gel as the electrolyte is proposed.
In addition, as other polymer electrolytes, alkylphosphoric acids of polybenzimidazole are described in Japanese Patent Publication (Kokai) No. Hei 9-110982/1997. It is desirable to produce a polymer electrolyte, which is totally different. On the other hand, polysilamines are reported in the March (1995) issue of Polymer, vol. 44, p. 623.
SUMMARY OF THE INVENTION
Accordingly, one aspect of the present invention provides a composite which comprises:
a polysilamine having a repeating unit represented by the following formula
[—N(R
1
)—A
1
—Si(R
2
)(R
3
)—B—]
n
wherein
R
1
, R
2
and R
3
are the same or different and each is a hydrogen atom or a lower alkyl group;
A
1
is a lower alkylene group which may be substituted by a lower alkyl group, a group represented by the formula —A
2
—N(R
4
)—A
3
— or a group represented by the formula —A
2
—N(R
4
)—A
3
—N(R
5
)—A
4
—, wherein A
2
, A
3
and A
4
are the same or different and each is a lower alkylene group which may be substituted by a lower alkyl group;
R
4
and R
5
are the same or different and each is a hydrogen atom or a lower alkyl group;
B is a lower alkylene group which may be substituted by a lower alkyl group; and
n is an integer of not less than 2, and a strong acid.
In the composite of the present invention, a strong acid is retained in the polysilamine by a chemical bond, and thus, it is easy to handle the composite as is the case with a solid electrolyte membrane while the proton conductivity is maintained as is the case with the strong acid alone.
In the present invention, the polysilamine is preferably crosslinked by means of a crosslinking agent.
Also, in the present invention, the composite preferably contains 0.05 to 2 mol of a strong acid per mol of the amino group and, in addition, preferably has a proton conductivity at 100° C. of not less than 10
−6
S/cm.
Another aspect of the present invention provides an electrolyte membrane formed from the composite in the shape of a membrane.
Still another aspect of the present invention provides a fuel cell having a plurality of unit cells, each unit cell having the aforementioned electrolyte membrane and a pair of electrodes holding the electrolyte therebetween.


REFERENCES:
patent: 4170700 (1979-10-01), Sweet
patent: 4250074 (1981-02-01), Foscante
patent: 4826752 (1989-05-01), Yoshida
patent: 5064722 (1991-11-01), Swofford
patent: 5138013 (1992-08-01), Mason
patent: 5209871 (1993-05-01), Mason
patent: 5225582 (1993-07-01), Mason
patent: 5859722 (1999-01-01), Suga
patent: 5902636 (1999-05-01), Grabbe
patent: 5985477 (1999-11-01), Iwasaki

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