Chemistry: electrical current producing apparatus – product – and – With pressure equalizing means for liquid immersion operation
Reexamination Certificate
2002-06-14
2004-11-23
Ryan, Patrick (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
With pressure equalizing means for liquid immersion operation
C429S231800, C429S324000, C429S306000, C429S309000, C429S188000, C429S314000, C429S317000, C429S316000, C423S44500R, C423S44500R
Reexamination Certificate
active
06821665
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a proton conductor, a production method thereof, and an electrochemical device using the proton conductor.
2. Description of the Prior Art
In recent years, as a polymer solid-state electrolyte type fuel cell has been used to power cars, there has been known a fuel cell using a polymer material having a proton (hydrogen ionic) conductivity such as a perfluorosulfonate resin (for example, Nafion® produced by Du Pont).
As a relatively new proton conductor, there has also been known a polymolybdate having large amount of hydrated water such as H
3
Mo
12
PO
40
·29H
2
O or an oxide having a large amount of hydrated water such as Sb
2
O
6
·5.4H
2
O.
The above-described polymer material and hydrated compounds each exhibit, if placed in a wet state, a high proton conductivity at a temperature near ordinary temperature.
For example, the reason why the perfluorosulfonate resin can exhibit a very high proton conductivity even at ordinary temperature is that protons ionized from sulfonate groups of the resin are bonded (hydrogen-bonded) with moisture already entrapped in a polymer matrix in a large amount, to produce protonated water, that is oxonium ions (H
3
O
+
), and the protons in the form of the oxonium ions can smoothly migrate in the polymer matrix.
More recently, there has been also developed a proton conductor having a conduction mechanism quite different than that of each of the above-described proton conductors.
That is to say, it has been found that a composite metal oxide having a perovskite structure, such as, SrCeO
3
doped with Yb, exhibits a proton conductivity without use of moisture as a migration medium. The conduction mechanism of this composite metal oxide has been considered such that protons are conducted while being singly channeled between oxygen ions forming a skeleton of the perovskite structure.
The conductive protons, however, are not originally present in the composite metal oxide but are produced by the following mechanism: namely, when the perovskite structure contacts the steam contained in an environmental atmospheric gas, water molecules at a high temperature react with oxygen deficient portions which have been formed in the perovskite structure by doping Yb or the like, to generate protons.
The above-described various proton conductors, however, have the following problems.
The matrix material such as the above-identified perfluorosulfonate resin must be continuously placed in a sufficiently wet state during use in order to keep a high proton conductivity.
Accordingly, a configuration of a system, such as, a fuel cell using such a matrix material, requires a humidifier and various accessories, thereby giving rise to problems in enlarging the scale of the system and raising the cost of the system.
The system using the matrix material has a further problem that the range of the operational temperature must be limited for preventing the freezing or boiling of the moisture contained in the matrix.
The composite metal oxide having the perovskite structure has a problem that the operational temperature must be kept at a high temperature of 500° C. or more for ensuring an effective proton conductivity.
In this way, the related art proton conductors have the problems that the atmosphere dependence on the performance of each conductor becomes high, and more specifically, moisture or stream must be supplied to the conductor to ensure the performance of the conductor, and further, the operational temperature of the conductor is excessively high or the range of the operational temperature is limited.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a proton conductor which is usable in a wide temperature range including ordinary temperature and has a low atmosphere dependence, that is, it requires no moisture despite whether or not the moisture is a migration medium; to provide a method of producing the proton conductor; and to provide an electrochemical device that employs the proton conductor. To meet this objective, the proton conductor includes a proton conductor material that at least has number of functional groups so as to be capable of transferring hydrogen protons between the functional groups of the proton conductor material. The proton conductor material includes a wide variety of carbonaceous materials, examples of which are described in greater detail below with respect to the various illustrative embodiments of the present invention, such as, the first, second, third and fourth proton conductors, production methods and electrochemical devices thereof.
A second object of the present invention is to provide a proton conductor which exhibits a film formation ability while keeping the above-described performance, to be thereby usable as a thin film having a high strength, a gas permeation preventive or impermeable performance, and a good proton conductivity, to provide a method of producing the proton conductor, and to provide an electrochemical device using the proton conductor.
The present invention provides a first proton conductor mainly containing a fullerene derivative obtained by introducing a number of functional groups so as to be capable of transferring protons between the functional groups of the fullerene derivative. The fullerene derivative includes a fullerene molecule or a plurality of fullerene molecules that each contain the functional groups so as to provide the fullerene derivative with the desirable proton conductivity properties as discussed and will be discussed in greater detail below.
The present invention also provides a first method of producing a proton conductor, including the steps of: producing a fullerene derivative by introducing functional groups so as to be capable of transferring protons as previously discussed; and compacting a powder of the fullerene derivative into a desired shape.
The present invention also provides a first electrochemical device including: a first electrode, a second electrode, and a proton conductor held between the electrodes, wherein the proton conductor mainly contains a fullerene derivative as described above.
According to the first proton conductor of the present invention, since the conductor mainly contains the fullerene derivative having a proton transfer capability, protons are easily transferred or conducted, even in a dry state, and further, the protons can exhibit a high conductivity in a wide temperature range (at least in a range of about 160° C. to −40° C.) that includes ordinary temperatures. While the first proton conductor of the present invention has a sufficient proton conductivity even in a dry state, it can also have a proton conductivity in a wet state. The moisture may come from the outside.
According to the first production method of the present invention, since the production method includes the steps of: producing a fullerene derivative by introducing functional groups as discussed and molding a substance comprising the fullerene derivative, the proton conductor can be efficiently produced having the above-described unique performance without use of any binder resin. The term “molding” means molding in a shape of film, pellet or the like. Therefore, compaction or filtration or other like techniques are preferably available for producing the proton conductor.
According to the first electrochemical device of the present invention, since the proton conductor is held between the first and second electrodes, the first electrochemical device can eliminate the need for a humidifier and the like which are necessary for known fuel cells that require moisture as a migration medium so as to enhance proton conductivity. Therefore, the device construction of the present invention has an advantageously smaller and more simplified construction.
The present invention also provides a second proton conductor that includes a polymer material in addition to the fullerene derivative as previously discussed.
The present invention also provides a second method of pro
Ata Masafumi
Hinokuma Koichiro
Pietzak Björn
Rost Constance Gertrud
Bell Boyd & Lloyd LLC
Martin Angela J.
Ryan Patrick
Sony Corporation
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