Patent Application
20080070076
The present application will be described in further detail below according to an embodiment with reference to the drawings.
The fuel cell system 1 has, for example, a fuel cell 110, a measurement portion 120 measuring the operation condition of the fuel cell 110, and a control portion 130 defining the operation condition of the fuel cell 110 based on the measurement result by the measurement portion 120. The fuel cell system 1 has, for example, an electrolyte supply portion 140 supplying sulfuric acid as a first fluid F1 including an electrolyte in the fuel cell 110. The fuel cell system 1 has, for example, a fuel supply portion 150 supplying methanol as a second fluid F2 including a fuel. By supplying the electrolyte in the form of fluid, the electrolyte film is unnecessary. Accordingly, the electric generation is enabled without the influence of temperature and moisture and the ion conductivity (proton conductivity) can be increased in comparison with the general fuel cell using the electrolyte film. Because risks such as the deterioration of the electrolyte film and the reduction of the proton conductivity caused by the dryness of the electrolyte film are eliminated, problems such as flooding and liquid management in the oxygen electrode can be solved.
The fuel electrode 10 has a configuration that a catalyst layer 11, a diffusion layer 12 and a current collector 13 are stacked in this order from the oxygen electrode 20 side, and is stored in an external member 14. The oxygen electrode 20 has a configuration that a catalyst layer 21, a diffusion layer 22 and a current collector 23 are stacked in this order from the fuel electrode side, and is stored in an external member 24. Air, that is, oxygen is supplied to the oxygen electrode 20 through the external member 24.
The catalyst layers 11 and 21 as catalysts are, for example, composed of simple substance such as palladium (Pd), platinum (Pt), iridium (Ir), rhodium (Rh), ruthenium (Ru) or the like, or an alloy including these. In the catalyst layers 11 and 12, a proton conductor and a binder may be included in addition to the catalysts. As the proton conductor, given is abovementioned perfluoroalkyl sulfonic acid type resin (“Nafion (a registered trademark)” manufactured by E. I. du Pont de Nemours and Company) or other resin having the proton conductivity. The binder is added to maintain the intensity and flexibility of the catalyst layers 11 and 12, and they are, for example, resin such as polytetrafluoroethylene (PTFE) and polyvinylindene fluoride (PVDF).
The diffusion layers 12 and 22 are, for example, composed of carbon cloth, carbon paper or carbon sheet. The diffusion layers 12 and 22 are preferably subjected to water repellent by polytetrafluoroethylene (PTFE) or the like.
The current collectors 13 and 23 are, for example, composed of titanium (Ti) mesh.
The external members 14 and 24 have, for example, thickness of 2.0 mm, and are composed of material such as a titanium (Ti) plate that is generally available in the market. However, the material is not specifically limited to this. The external members 14 and 24 are preferably as thin as possible in thickness.
The electrolyte channel 30 and the fuel channel 40 are, for example, fine channels formed by processing a resin sheet, and are adhered to the fuel electrode 10. A number of the channels are not limited. A width, height and length of each of the channels are not limited, but they are preferably as small as possible.
The electrolyte channel 30 is connected to the electrolyte supply portion 140 (refer to
The measurement portion 120 shown in
The control portion 130 shown in
The operation portion 131 calculates the output of the fuel cell 110 from the measurement results obtained by the measurement portion 120, and sets the electrolyte supply parameter and the fuel supply parameter. Specifically, the operation portion 131 has functions of: averaging anode electric potential, cathode electric potential, output voltage, and output current sampled at a regular time interval from various measurement results inputted in the memory portion 132; calculating the average anode electric potential, the average cathode electric potential, the average output voltage and the average output current; inputting the resultant into the memory portion 132; and comparing the various average values with each other that are stored in the memory portion 132 in order to judge the electrolyte supply parameter and the fuel supply parameter.
The memory portion 132 memorizes the various measurement values transmitted from the measurement portion 120 and the various average values calculated by the operation portion 131.
The communication portion 133 has functions of receiving the measurement results from the measurement portion 120 through the communication line 123, and inputting the resultant into the memory portion 132. The communication portion 133 also has a function of outputting signals to set the electrolyte supply parameter and the fuel supply parameter respectively into the electrolyte supply portion 140 and the fuel supply portion 150 through the communication line 134.
The electrolyte supply portion 140 shown in
The fuel supply portion 150 shown in
The fuel cell system 1 can, for example, be manufactured in the following way.
An alloy including, for example, platinum (Pt) and ruthenium (Ru) as catalysts at a predetermined rate and a dispersion solution of perfluoroalkyl sulfonic acid type resin (“Nafion (a registered trademark)” manufactured by E. I. du Pont de Nemours and Company) are mixed at the predetermined rate in order to form the catalyst layer 11 of the fuel electrode 10. The catalyst layer 11 is bonded by thermal compression to the diffusion layer 12 of the abovementioned material. Further, the current collector 13 of the abovementioned material is bonded by thermal compression using a hot-melt type adhesive or an adhesive resin sheet in order to form the fuel electrode 10.
A carbon supporting platinum (Pt) as a catalyst and the dispersion solution of perfluoroalkyl sulfonic acid type resin (“Nafion (a registered trademark)” manufactured by E. I. du Pont de Nemours and Company) are mixed at the predetermined rate in order to form the catalyst layer 21 of the oxygen electrode 20. The catalyst layer 21 is bonded by thermal compression to the diffusion layer 22 of the abovementioned material. Further, the current collector 23 of the abovementioned material is bonded by thermal compression using the hot-melt type adhesive or the adhesive resin sheet in order to form the oxygen electrode 20.
The adhesive resin sheet is prepared. Channels are formed on this resin sheet in order to make the electrolyte channel 30 and fuel channel 40, and the electrolyte channel 30 and the fuel channel 40 are bonded by thermal compression to both sides of the fuel electrode 10.
The external members 14 and 24 of the abovementioned material are manufactured. The external member 14 is provided with the fuel inlet 14A and the fuel outlet 14B composed of, for example, joints of resin, and the external member 24 is provided with the electrolyte inlet 24A and the electrolyte outlet 24B composed of, for example, joints of resin.
While externally placing the fuel channel 40, the fuel electrode 10 and the oxygen electrode 20 are oppositely disposed with the electrolyte channel 30 in between, and enclosed in the external members 14 and 24. Thereby, the fuel cell 110 shown in
This fuel cell 110 is installed in the system having the measurement portion 120, the control portion 130, the electrolyte supply portion 140 and the fuel supply portion 150 of the abovementioned configuration. The fuel inlet 14A and the fuel outlet 14B, and the fuel supply portion 150 are connected to the fuel supply line 153 composed of, for example, a silicon tube. The electrolyte inlet 24A and the electrolyte outlet 24B, and the electrolyte supply portion 140 are connected to the electrolyte supply line 143 composed of, for example, a silicon tube. Thereby, the fuel cell system 1 shown in
In this fuel cell system 1, the second fluid F2 including the fuel is supplied to the fuel electrode 10 and the resulting reaction produces the proton and the electron. The proton travels to the oxygen electrode 20 through the first fluid F1 including the electrolyte, and produces water in reaction with the electron and the oxygen. The reactions occurring in the fuel electrode 10, the oxygen electrode 20 and the entire fuel cell 110 are expressed by Chemical formula 2. Thereby, a part of chemical energy of methanol as the fuel is converted to electric energy so that the current is extracted from the fuel cell 110 and the external circuit 2 is driven. The carbon dioxide produced in the fuel electrode 10 and the water produced in the oxygen electrode 20 are removed while they flow with the first fluid F1 including the electrolyte.
Fuel electrode 10:CH3OH+H2O→CO2+6e−+6H+ (Chemical formula 2)
Oxygen electrode 20:(3/2)O2+6e−+6H+→3H2O
Entire fuel cell 110:CH3OH+(3/2)O2→CO2+2H2O
During the operation of the fuel cell 110, the measurement portion 120 measures the operation voltage and the operation current of the fuel cell 110. Based on the measurement result, by the control portion 130, the electrolyte supply parameter and the fuel supply parameter mentioned above are controlled as the operation condition of the fuel cell 110. The measurement by the measurement portion 120 and the parameter control by the control portion 130 are frequently repeated so that, following the property change of the fuel cell 110, the supply conditions of the first fluid F1 including the electrolyte and the second fluid F2 including the fuel are optimized.
Here, because the fuel electrode 10 is provided between the electrolyte channel 40 and the fuel channel 30, the fuel electrode 10 functions as the separation film separating the first fluid F1 including the electrolyte and the second fluid F2 including the fuel. Therefore, although the porous separator as in the laminar flow fuel cell of the related art is not provided, the positional relationship between the first fluid F1 and the second fluid F2 with respect to the fuel electrode 10 is maintained; thereby the electric generation is enabled irrespective of the specific position of the fuel cell 110.
The fuel crossover occurs and the over voltage is generated on the oxygen electrode 20 side when the fuel included in the second fluid F2 necessarily passes through fine pores of the fuel electrode 10 in the unreacted state, and further, during the electric generation, the fuel necessarily passes through the first fluid F1 including the electrolyte flowing at a constant current velocity. However, by providing the fuel electrode 10 between the electrolyte channel 40 and the fuel channel 30, almost all the fuels react when passing through the fine pores of the fuel electrode 10. Even if the fuel passes through the fuel electrode 10 in the unreacted state, before permeating the oxygen electrode 20, the fuel is carried out from inside of the fuel cell 110 by the first fluid F1 including the electrolyte. Thus, the crossover of the fuel is remarkably suppressed. Therefore, the amount of the fuel not used for the electric generation is largely reduced so that the property of high energy density as an original advantage of the fuel cell is utilized.
On the other hand, when the fuel cell using the electrolyte film of the related art and the laminar flow fuel cell of the related art use the highly concentrated methanol water solution or pure methanol as the fuel in order to utilize the high energy density as the feature of the fuel cell, the methanol concentration in the fuel electrode is increased too high. As shown in
According to the present embodiment, because the fuel electrode 10 is provided between the electrolyte channel 30 and the fuel channel 40, the fuel electrode 10 functions as the separation film separating the first fluid F1 including the electrolyte and the second fluid F2 including the fuel.
Although the porous separator as in the laminar flow fuel cell of the related art is not provided, the influence of gravity can be eliminated and the high energy density can be obtained while suppressing the crossover. Because of its simple and highly flexible configuration, the fuel cell can be installed in various devices from the mobile device to the large scale device. Especially, when the fuel cell is used in the electrical device having multiple functions and high performance, the property of the high energy density can be appropriately utilized.
The gas-liquid separation film 50 can be composed, for example, of a film unpermeable of alcohol in the liquid state such as polytetrafluoroethylene (PTFE), polyvinylindene fluoride (PVDF), and polypropylene (PP).
This fuel cell 110A and a fuel cell system 1 using the fuel cell 110A can be manufactured in the same way as the first embodiment except that the gas-liquid separation film 50 is provided between the fuel channel 40 and the fuel electrode 10.
In the fuel cell system 1, the current is extracted from the fuel cell 110A and an external circuit 2 is driven in the same way as the first embodiment. Here, the gas-liquid separation film 50 is provided between the fuel channel 40 and the fuel electrode 10 so that the pure methanol in the liquid state as the fuel spontaneously vaporizes when passing through the fuel channel 40. Then, the resultant in the state of a gas G passes through the gas-liquid separation film 50 from the face adjacent to the gas-liquid film 50, and is supplied to the fuel electrode 10. Thus, the fuel is supplied efficiently to the fuel electrode 10 and the reaction is performed stably. Because the fuel in the gas state is supplied to the fuel electrode 10, the electrode reaction activity is enhanced and the crossover hardly occurs. Therefore, the high performance can be also obtained in an external circuit 2 having high lord.
Even if methanol in the gas state passing through the fuel electrode 10 exists, it is removed by a first fluid F1 including the electrolyte before reaching to the oxygen electrode 20 in the same way as the first embodiment.
According to the second embodiment, the gas-liquid separation film 50 is provided between the fuel channel 40 and the fuel electrode 10 so that pure (99.99%) methanol can be used as a second fluid F2 including the fuel and the property of the high energy density as the feature of the fuel cell can be further utilized. Also, the stability of the reaction and the electrolyte reaction activity can be enhanced while suppressing the crossover. Thus, the high performance can also be obtained in an electrical device having the external circuit 2 of high lord. Further, in a fuel supply portion 150, a concentration adjustment portion adjusting the supply concentration of the second fluid F2 including the fuel can be omitted; thereby size reduction is enabled.
Further, a specific example of the present application will be described. In the below example, a fuel cell 110A having a similar configuration to
The fuel cell 110A having a similar configuration to
A carbon supporting platinum (Pt) as a catalyst and a dispersion solution of perfluoroalkyl sulfonic acid type resin (“Nafion (a registered trademark)” manufactured by E. I. du Pont de Nemours and Company) were mixed at the predetermined rate in order to form a catalyst layer 21 of an oxygen electrode 20. The catalyst layer 21 was bonded by thermal compression to the diffusion layer 22 (HT-2500 manufactured by E-TEK Inc.) of the abovementioned material in the same way as the catalyst layer 11 of the fuel electrode 10. Further, the current collector 23 of the abovementioned material was bonded by thermal compression in the same way as the current collector 13 of the fuel electrode 10 in order to form the oxygen electrode 20.
Next, the adhesive resin sheet was prepared. Channels were formed on the resin sheet in order to form an electrolyte channel 30 and a fuel channel 40, and they were bonded by thermal compression to both sides of the fuel electrode 10.
Next, the external members 14 and 24 of the abovementioned material were manufactured. The external member 14 was provided with a fuel inlet 14A and fuel outlet 14B composed of, for example, joints of resin and the external member 24 was provided with an electrolyte inlet 24A and an electrolyte outlet 24B composed of, for example, joints of resin.
While externally placing the fuel channel 40, the fuel electrode 10 and the oxygen electrode 20 were oppositely disposed with the electrolyte channel 30 in between and the fuel electrode 10 and the oxygen electrode 20 were stored in the external members 14 and 24. At this time, a gas-liquid separation film 50 (manufactured by Millipore Corporation) was provided between the fuel channel 40 and fuel electrode 10; thereby the fuel cell 110A was completed as shown in
This fuel cell 110A was installed in a system having a measurement portion 120, a control portion 130, an electrolyte supply portion 140 and a fuel supply portion 150 of the abovementioned configuration; thereby the fuel cell system 1 was configured as shown in
(Evaluation)
The obtained fuel cell system 1 was connected to an electrochemical measurement system (Multistat 1480 manufactured by Solartoron Co., Ltd) and the properties of the fuel cell system 1 were evaluated. The operation of the constant current (20 mA, 50 mA, 100 mA, 150 mA, 200 mA, and 250 mA) mode was executed, and open circuit voltage (OCV) in the initial state of the measurement, the properties of current-voltage (I-V) and current-power (I-P), and the output density when generating electric power with the current density of 150 mA/cm2 were examined. The results are shown in
That means, if the fuel cell 10 was provided between the electrolyte channel 30 and the fuel channel 40, and the gas-liquid separation film 50 was provided between the fuel channel 40 and the fuel electrode 10, OCV higher than that of DMFC in the related art could be obtained without the crossover although 100% sulfuric acid was used as the fluid F1 including the electrolyte.
As understood from
The present application as described herein should not be limited to such description where modifications thereof should be considered. For example, in the embodiments and example, the configurations of the fuel electrode 10, the oxygen electrode 20, the fuel channel 30 and the electrolyte channel 40 are specifically described, but other configuration or the configuration of other material may be described. For example, it is described in the embodiments and example that the fuel channel 30 is formed by processing the resin sheet and forming channels. However, the fuel channel 30 may be composed of a porous sheet or the like.
Also, it is described that the second fluid F2 including the fuel is composed by methanol, but it may be composed of other alcohol such as ethanol and dimethyl ether. The first fluid F1 including the electrolyte can be unlimitedly composed, as long as it is composed of material having proton (H+) conductivity, for example, such as sulfuric acid, phosphoric acid, and ionic liquid.
Further, for example, the material of each component and the thickness, and the operation condition of the fuel cell 110 are not limited as described in the embodiments and the example. Different material and different thickness, and different operation conditions may be used.
In the embodiments and the example, the fuel is supplied from the fuel supply portion 150 to the fuel electrode 10. However, the fuel electrode 10 may be a closed type and the fuel may be optionally supplied.
In the embodiments and the example, air is supplied to the oxygen electrode 20 by the spontaneous ventilation. However, air may be forcedly supplied by using a pump or the like. In this case, oxygen or gas including oxygen may be supplied instead of air.
The present application is not limited to DMFC, but applicable to other types of fuel cell such as a fuel cell using hydrogen (PEFC or an alkaline fuel cell) as fuel.
In the embodiments and the example, the single cell type fuel cell is described, but the present application is also applicable to a stacked type fuel cell with a plurality of fuel cells in a stacked configuration.
In the embodiments and example, the case is explained where the present application is applied to the fuel cell and the fuel cell system, and the electrical device provided therewith. However, besides the fuel cell, the present application is also applicable to other electrochemical device such as a capacitor, a fuel sensor, or a display.
It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2006-252355 | Sep 2006 | JP | national |
