JP3705541B2 - Fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell with improved power generation efficiency.
[0002]
[Prior art]
FIG. 6 is a cross-sectional view showing a configuration of a unit cell in a fuel cell using a conventional solid polymer electrolyte membrane. In this fuel cell, the solid polymer electrolyte membrane 101 is sandwiched between porous electrodes so that the catalyst layers are in close contact with both surfaces thereof. Among these, the electrode on the side supplied with fuel is the fuel electrode 102, and the electrode on the side supplied with oxidant (air) is the oxidant electrode 103. A fuel gas channel 105 and an oxidant gas channel 106 are formed between the electrodes 102 and 103 and a pair of gas-impermeable plates 104 arranged on both sides thereof. Since the output voltage of the unit cell configured as described above is as low as 1 V or less, a fuel cell stack is formed by stacking a plurality of unit cells in order to obtain a desired output voltage.
[0003]
The fuel electrode 102 and the oxidant electrode 103 have a structure in which a catalyst layer containing a catalytically active substance is supported by a porous electrode substrate having conductivity. Hydrogen as fuel that is supplied to the fuel electrode 102 through the electrode base material from the fuel gas flow path 105 including a plurality of parallel grooves, and oxidant that is supplied to the oxidant electrode 103 from the oxidant gas passage 106 In each catalyst layer, an oxygen / catalyst / reactive gas three-phase interface is formed in each catalyst layer, and a reaction as shown by the following reaction formulas (1) and (2) proceeds.
[0004]
Fuel electrode: H ₂ → 2H ⁺ + 2e ^- ... (1)
Oxidant electrode: 2H ⁺ + 2e ^- + (1/2) O ₂ → H ₂ O (2)
That is, an electrochemical reaction that decomposes hydrogen molecules into hydrogen ions and electrons is performed on the fuel electrode 102 side as shown in the above formula (1), and hydrogen ions are shown on the oxidant electrode 103 side as shown in the above formula (2). Electrochemical reaction to produce water from electrons and oxygen is performed. Hydrogen ions generated by the reaction of the above formula (1) on the fuel electrode 102 side permeate the solid polymer electrolyte membrane 101 in a hydrated state with water molecules, and the reaction of the above formula (2) on the oxidant electrode 103 side. To be served.
[0005]
In order to perform these reactions continuously, it is necessary to continuously supply the reactants to the fuel electrode 102 and the oxidant electrode 103 and to quickly remove the product from the vicinity of the electrodes. Specifically, in the oxidizer electrode 103, it is necessary to continuously supply oxygen and remove water which is a generated material. If moisture is not removed quickly, water stays in the vicinity of the electrode and the oxidizer electrode 103 The gas permeability at the electrode 103 is lowered, and the electrode reaction is lowered. In order to prevent such moisture retention at the oxidizer electrode, various devices have been tried for the electrode.
[0006]
For example, in JP-A-7-326361, by forming electrodes facing each other with an electrolyte membrane interposed therebetween using an electrode base material having conductivity and gas permeability and a water-absorbing material having water absorption, There has been proposed a method in which moisture generated in the electrode or on the electrode surface by the reaction of the above (formula 2) is actively absorbed to remove the moisture from the electrode. According to this structure, a large amount of water can be absorbed as compared with the case where the electrode base material alone is used, and therefore, the removal efficiency of excess water in the electrode is improved.
[0007]
[Problems to be solved by the invention]
However, in the method proposed in the above-mentioned Japanese Patent Application Laid-Open No. 7-326361, the electrode is caused by a cause such as exceeding the limit of the water absorption capacity of the water absorbent material or increasing the amount of water generated due to a sudden increase in load. If the surface gets wet with moisture, the ability to remove excess moisture will be saturated. In that case, the diffusion of gas in the electrode is inhibited, concentration polarization occurs, and the battery performance decreases.
[0008]
Furthermore, this structure is obtained by dispersing and holding water-absorbing fine particles such as a crosslinked polyacrylate having a volume ratio of about 20% in porous carbon which is an electrode base material of a cathode (oxidant electrode). Since the mixing ratio of the water-absorbing fine particles and the conductivity of the electrode are in a trade-off relationship, increasing the water-absorbing fine particle mixing ratio in order to increase the water-absorbing ability will lower the electrode conductivity and increase the internal resistance. Will cause energy loss.
[0009]
The present invention has been made to solve such problems of the prior art, and efficiently removes excess moisture in the electrode without reducing the conductivity of the electrode, and stably supplies gas to the electrode. An object of the present invention is to provide a fuel cell that can be used.
[0010]
The fuel cell of the present invention includes a positive electrode on one surface of a solid electrolyte membrane and a negative electrode on the other surface, a fuel gas channel facing the positive electrode, and an oxidant gas flow facing the negative electrode. In the fuel cell having a path, at least one of the fuel gas flow path and the oxidant gas flow path is provided with at least one vibration means, The vibration means includes: a piezoelectric element that generates a displacement according to an applied drive voltage; and a diaphragm that is a base substrate of the piezoelectric element and that receives the displacement of the piezoelectric element and applies vibration to the solid electrolyte membrane. The diaphragm and the piezoelectric element are laminated on the positive electrode or the negative electrode in parallel with the electrode surface. And the above object can be achieved.
[0014]
The piezoelectric element may be made of a PZT film.
[0015]
It is preferable that at least one of the piezoelectric element and the diaphragm has a function of transmitting at least one of gas and moisture.
[0016]
At least one of the piezoelectric element and the diaphragm may have a plurality of through holes.
[0017]
It is preferable that at least one of the piezoelectric element and the diaphragm has a water-repellent coating on the surface.
[0018]
The water repellent film may be made of a silicone resin.
[0019]
The water repellent coating film may be composed of a polymer film having a crosslinked structure.
[0020]
The operation of the present invention will be described below. In the following description, the electrode indicates a fuel electrode or an oxidant electrode, the gas indicates a fuel gas or an oxidant gas, and the moisture indicates a liquid mainly composed of water and a spray body.
[0021]
The present invention In this case, since the vibration means provided in the gas flow path of the fuel cell vibrates during the operation of the fuel cell, the battery in which the solid electrolyte membrane is sandwiched between the fuel electrode (negative electrode) and the oxidant electrode (positive electrode). The reaction layer can be vibrated or vented into the gas flow path. Due to the vibration of the vibrating means, moisture generated on the oxidant electrode side of the battery reaction layer is scattered and removed from the surface of the oxidant electrode. Since the generated moisture is quickly removed from the electrode surface, the diffusion of the gas into the oxidizer electrode is not hindered by the moisture. Further, the gas supply to the fuel electrode or the oxidant gas electrode is not interrupted by the ventilation of the gas flow path by the vibration means, and the diffusion of the gas into the electrode is promoted. As a result, concentration polarization due to gas shortage inside the electrode is reduced, and the power generation efficiency of the fuel cell is increased. This vibration means may be disposed in close contact with the fuel electrode which is one side wall of the fuel gas flow channel or the oxidant electrode which is one side wall of the oxidant fuel gas flow channel, or the fuel electrode or oxidant electrode. You may arrange | position only predetermined distance from.
[0022]
Also, In the present invention, the piezoelectric element is formed on the diaphragm, and the diaphragm is disposed so that the deformation of the piezoelectric element is transmitted to the solid electrolyte membrane through the diaphragm. Since the solid electrolyte membrane is in close contact with the fuel electrode and the oxidant electrode to form a battery reaction layer, the vibration generated in the diaphragm vibrates the entire battery reaction layer. Since the piezoelectric element is deformed according to the drive voltage signal applied from the drive circuit, the drive circuit generates a drive voltage signal that can obtain an appropriate vibration from the diaphragm and applies the drive voltage signal to the piezoelectric element. In this configuration, vibration generated in the diaphragm is transmitted to the entire battery reaction layer, and water on the surface of the oxidant electrode is scattered. In particular, even when the fuel cell is operating at a high current density and the amount of water generated is large, the oxidant electrode itself that generates water vibrates and scatters water, thereby exhibiting a high water removal capability. it can. In addition, since a piezoelectric element can be used to drive the vibration means, the plate can be formed thin, so that the volume of the fuel cell itself is hardly increased by providing the vibration means. Furthermore, since the vibration can be directly applied to the solid electrolyte membrane via the diaphragm, a complicated mechanism for transmitting the vibration is unnecessary, and an increase in the number of components can be suppressed.
[0023]
further, In the present invention, the diaphragm is disposed in parallel with the electrode on the side close thereto, and transmits the vibration to the electrode and the solid electrolyte membrane. Since the piezoelectric element is formed on the diaphragm, the diaphragm and the piezoelectric element are stacked on the electrode. In this configuration, the displacement generated in the piezoelectric element can be effectively transmitted to the electrode to vibrate the solid electrolyte membrane and the electrode. In addition, since the diaphragm and the piezoelectric element are arranged in the gas flow path, it is necessary to make the gas flow path wide in order to ensure the same gas flow path as in the case without the diaphragm and the piezoelectric element. By laminating the diaphragm and the piezoelectric element, the expansion width of the gas flow path can be minimized and an increase in the thickness of the fuel cell can be suppressed.
[0024]
In addition, The diaphragm and the piezoelectric element are disposed in the gas flow path apart from the electrode, and the diaphragm ventilates the fuel electrode or the oxidant electrode by the displacement of the piezoelectric element. Configuration may be . The diaphragm is disposed at a position where the wind can easily reach the fuel electrode or the oxidant electrode. In this configuration, since the electrodes are ventilated by the diaphragm driven by the piezoelectric element, gas supply to the electrode surface can be performed without interruption. Therefore, even when the fuel cell is in an operating state with a high current density, an increase in concentration polarization due to gas shortage inside the electrode can be prevented. Further, the ventilation to the oxidant electrode promotes the scattering or vaporization of water generated in the oxidant electrode, so that the vibration means not only supplies gas to the electrode but also functions to remove water. Since both the gas supply to the oxidizer electrode and the moisture removal can be achieved by the vibration means, an increase in the number of parts can be suppressed. Furthermore, CO as a by-product gas on the fuel electrode side ₂ In the case of a direct methanol type fuel cell in which gas is generated, the fuel gas is supplied by the ventilation to the fuel electrode by the vibration means and the CO 2 is supplied. ₂ Since gas can be removed, shortage of fuel gas in the fuel electrode can be prevented.
[0025]
Claim 2 In the present invention described in 1), the piezoelectric element is made of a PZT (lead zirconate titanate) film. Since the PZT film is a piezoelectric ceramic film, and PZT having ferroelectricity is polarized in the stacking direction in the film, piezoelectric strain is generated according to the applied voltage. The diaphragm can be vibrated by this piezoelectric strain. This PZT film can be produced at a relatively low firing temperature by a sol-gel method or the like. In addition, PZT exhibits satisfactory characteristics as a piezoelectric material in a wide temperature range of −200 ° C. to 200 ° C., so that it can be used in a fuel cell, for example, in a polymer electrolyte fuel cell operating at room temperature to 100 ° C. or less. Suitable as a piezoelectric material.
[0026]
Claim 3 In at least one of the piezoelectric element and the diaphragm according to the present invention described above, there is a function of transmitting at least one of gas and moisture. Therefore, the gas inflow from the gas flow path to the electrode is not hindered, and moisture generated on the oxidizer electrode side can pass through the diaphragm and the piezoelectric element and be discharged out of the system. Therefore, the inside of the electrode is always kept in a state suitable for the cell reaction, and the power generation efficiency of the fuel cell is improved.
[0027]
Claim 4 Since at least one of the piezoelectric element and the diaphragm is provided with a plurality of through holes, at least one of gas or moisture gas and moisture can freely pass through the inside of the through hole. Can pass through. Examples of the method of providing the through hole include a method of punching a metal plate with a press machine and then forming a piezoelectric element thereon, a method of punching after forming a piezoelectric element on the metal plate, and the like. In the latter method, the piezoelectric ceramic film formed by firing is excessively stressed by punching, which may damage the piezoelectric element and cause a problem in manufacturing yield. Therefore, the former method is more preferable. Furthermore, after processing a plurality of parallel slits in a metal plate, a method of producing a piezoelectric element on a so-called expanded metal that is stretched to form a large number of through holes is used. Can be produced.
[0028]
Claim 5 In the present invention described above, since at least one of the piezoelectric element and the diaphragm has a water-repellent coating on the surface, the diaphragm and the piezoelectric element hardly retain moisture. In this case, the generated water can easily take a form from a diffusion state to a solidified state, and the water can be easily removed. The water repellency referred to here refers to those having a receding contact angle of 70 ° or more. Examples of such water-repellent coatings include fluorine resins (for example, perfluorobutylethylene resin and copolymers thereof, trifluoroethyl methacrylate resins and copolymers thereof, vinylidene fluoride resins and copolymers thereof), silicone resins, and the like. (For example, methyl hydrogen silicone resin and copolymer thereof, dimethyl silicone resin and copolymer thereof, phenylmethyl silicone resin and copolymer thereof, and the like) can be mentioned as representative examples. In particular, Claim 6 In the present invention, the water-repellent film is made of a silicone resin, so that the film formation is relatively easy, and it is excellent not only in water repellency but also in weather resistance, and the surfaces of the diaphragm and the piezoelectric element are Not easily deteriorated by heat. further, Claim 7 In the present invention described in the above, by using a polymer film obtained by cross-linking these resins as a water-repellent film, heat resistance is improved and deterioration due to light or heat hardly occurs. Can be achieved.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0030]
(Embodiment 1)
FIG. 1 is a schematic diagram showing a basic cell structure of a polymer electrolyte fuel cell according to an embodiment of the present invention. The fuel battery cell includes a solid polymer electrolyte membrane 1 that is a membrane electrolyte, a battery reaction layer 19 composed of a fuel electrode 2 and an oxidizer electrode that are in close contact with the membrane surface of the solid polymer electrolyte membrane, The gas impermeable plate 4 for partitioning the cell, the piezoelectric element 8 fixed on the thin plate-like diaphragm 7, and a drive circuit 9 for driving the piezoelectric element 8 are configured.
[0031]
The edge of the diaphragm 7 is fixed to the casing of the fuel cell by a fixing member 18, and the portion serves as a fulcrum of vibration of the diaphragm 7. Further, the fixing member 18 is installed without being fixed to the battery reaction layer 19 side so as not to disturb the vibration of the battery reaction layer 19. Further, by integrally forming the fixing member 18 and the diaphragm 7, the number of parts and the manufacturing process can be reduced.
[0032]
In this fuel cell, a fuel gas flow path 5 is provided between the fuel electrode 2 and the gas impermeable plate 4, and an oxidant gas flow path 6 is provided between the oxidant electrode 3 and the gas impermeable plate 4. Yes.
[0033]
The solid polymer electrolyte membrane 1 is a cation exchange membrane having a sulfone group as an ion exchange group for hydrogen ions. For example, a cation exchange membrane made of a fluorine-based polymer resin such as a perfluorocarbon sulfonic acid polymer resin can be used. Since the electrochemical reaction in the fuel cell occurs at the interface between the electrode and the electrolyte, the electrochemical characteristics of the polymer electrolyte membrane 1 greatly affect the current-voltage characteristics of the fuel cell. In particular, since the resistance in the stacking direction is reduced by making the film thin, current-voltage characteristics can be improved. In the case of the above-described resin, it is produced so that the film thickness is about 50 μm to 200 μm. Ionic conductivity is 5 × 10 at 25 ° C. ^-2 ~ 1x10 ^-1 (Ω · cm) ^-1 Therefore, the resistance per unit area of the film thickness is about 0.05 to 0.4Ω.
[0034]
The fuel electrode 2 and the oxidant electrode 3 are each made of graphite having a porous structure with good gas diffusibility so that the electrode reaction of both electrodes does not become gas diffusion controlled. A catalytic reaction layer is formed on the reaction layer surface side of each electrode, that is, the surface in contact with the solid polymer electrolyte membrane 1, and 10-30 wt% platinum is supported as a catalyst in the catalyst reaction layer in the electrode. . Since the electrode reaction requires a sufficient three-phase interface of electrolyte / catalyst / reactive gas, the catalyst reaction layer of the electrode is formed in close contact with the solid polymer electrolyte membrane 1. For example, the solid polymer electrolyte membrane 1 is sandwiched between two electrode sheets of a fuel electrode 2 and an oxidant electrode 3, and 40 to 400 kg / cm ² The electrode sheet and the solid polymer electrolyte membrane 1 are joined and integrated by hot pressing at about 100 to 200 ° C. under moderate pressure.
[0035]
The piezoelectric element 8 is laminated on a metal plate (vibrating plate 7) having a high elastic modulus. As such a metal plate, for example, a stainless plate having a thickness of 10 to 50 μm can be used. The diaphragm 7 as a base substrate of the piezoelectric element 8 is disposed in contact with the oxidant electrode 3 and transmits the displacement of the piezoelectric element 8 to the oxidant electrode 3 side. If the diaphragm 7 and the piezoelectric element 8 prevent gas conduction from the oxidant gas flow path 6 to the oxidant electrode 3 or moisture conduction from the oxidant electrode 3 to the oxidant gas flow path 6, Since the battery reaction does not proceed smoothly, the diaphragm 7 is provided with a through hole. This through hole is, for example, a circular hole having a diameter of 1 mm or more, and a punching metal in which circular holes are punched at intervals of 2 to 3 mm can be used as the diaphragm 7.
[0036]
The piezoelectric element 8 is made of a PZT film having a thickness of about 10 to 50 μm. After applying a sol obtained by hydrolyzing an alkoxide or acetate of titanium, zirconium or lead with an acid onto a base substrate by spin coating or dip coating, 300 Obtained by firing at ~ 600 ° C. Thereafter, an aluminum upper electrode having a thickness of several μm is formed on the PZT film by sputtering or vacuum deposition. The diaphragm 7 also functions as a lower electrode of the piezoelectric element 8, and the piezoelectric element 8 vibrates by applying a drive voltage signal from the drive circuit 9 between the diaphragm 7 and the aluminum upper electrode of the piezoelectric element 8. To do.
[0037]
In this embodiment, Nafion (trade name Nafion 117 manufactured by DuPont, USA), which is a perfluorocarbon sulfonic acid polymer resin, is used as the solid polymer electrolyte membrane 1 constituting the direct methanol fuel cell.
[0038]
The fuel electrode 2 and the oxidizer electrode 3 are each 3.6 mg / cm in graphite. ² Platinum ruthenium alloy, and 1.1 mg / cm ² Of platinum is supported as a catalyst. These two electrode sheets are cut into 50 mm × 50 mm squares, 5% Nafion solution (a solution in which Nafion resin is dissolved in a mixed solvent of alcohol and water) is applied and bonded to the solid polymer electrolyte membrane 1, 200 kg / cm ² Joining with a hot press at 100 ° C.
[0039]
Furthermore, the piezoelectric element 8 is produced to a thickness of 20 μm on a punching metal stainless steel plate (thickness 10 μm) obtained by punching circular holes having a diameter of 1 mm at intervals of 3 mm. In this embodiment, after lead acetate is dissolved in acetic acid, zirconium tetrabutoxide and titanium tetraisopropoxide are further dissolved, water and a small amount of diethylene glycol are added, and the mixture is stirred and hydrolyzed to obtain PZT. Thereafter, 10 wt% of polyethylene glycol monomethyl ether is added to PZT, and a sol obtained by stirring is applied by dip coating, and then heated at 400 ° C. to produce a PZT film. Further, an aluminum film having a thickness of 1 μm is formed on the PZT film by sputtering, and used as the upper electrode of the piezoelectric element 8.
[0040]
The drive circuit 9 for the piezoelectric element 8 has the following configuration. Since the fuel cell single cell outputs a voltage of 0.4 to 0.9 V with the fuel electrode 2 as the negative electrode and the oxidant electrode 3 as the positive electrode, this output voltage is input to the control unit power supply circuit 10 and this control unit power supply A constant power supply voltage (Vcc = 3.3 V) is supplied from the circuit 10 to the waveform output unit 11 and the piezoelectric element driving unit 12. Similarly, the fuel cell output voltage between the fuel electrode 2 and the oxidant electrode 3 is also input to the drive power supply circuit 13, and the drive power supply circuit 13 supplies the piezoelectric element drive voltage 12 to the piezoelectric element drive voltage (Vp). ~ 20V). The waveform output unit 11 generates a rectangular voltage waveform for driving the piezoelectric element, and the piezoelectric element driving unit 12 drives the piezoelectric element 8 by applying a voltage having a peak value Vp to the piezoelectric element 8 according to the input driving voltage waveform. .
[0041]
FIG. 2 shows a detailed configuration of the waveform output unit 11 and the piezoelectric element driving unit 12. In the waveform output unit 11, a driving voltage signal Vc for charging the piezoelectric element 8 and a driving voltage signal Vd for discharging the piezoelectric element 8 are generated by the driving IC 14, and the transistor Tr <b> 1 in the piezoelectric element driving unit 12 is generated. And Tr3. In addition, Vn in a figure is the negative electrode of a fuel cell, ie, the electric potential by the side of a fuel electrode.
[0042]
Next, the operation of the piezoelectric element driving unit 12 will be described. At the time of charging the piezoelectric element, when the drive voltage signal Vc becomes a high level (time t = t1), Tr1 is turned on, whereby Tr2 is turned on. As a result, the voltage Vp supplied from the drive power supply circuit 13 is applied to the piezoelectric element 8 via the Tr2 and the reactor L, and the piezoelectric element 8 is charged and starts to be displaced (expanded). Thereafter, when the drive voltage signal Vd becomes high level (time t = t2), Tr3 is turned on, the electric charge of the piezoelectric element 8 is discharged through the reactors L and Tr3, and the displacement of the piezoelectric element 8 returns to the initial state. .
[0043]
FIG. 3 shows the drive voltage signals Vc and Vd and the voltage Vpiezo applied to the piezoelectric element 8. The piezoelectric element 8 can be vibrated by repeating such charge and discharge according to the drive voltage signal from the drive IC 14.
[0044]
In the operation state of the fuel cell, the piezoelectric element 8 constantly vibrates, and the vibration of the piezoelectric element 8 is transmitted to the oxidant electrode 7 side by the diaphragm 7. Due to this vibration, the moisture on the surface of the oxidant electrode 7 passes through the diaphragm 7 and the through hole of the piezoelectric element 8 and is scattered in the form of a mist toward the oxidant gas flow path 6 side.
[0045]
In the present embodiment, the diaphragm 7 and the piezoelectric element 8 are disposed on the oxidizer electrode 7 side, but may be disposed on the fuel electrode 2 side. That is, even when the diaphragm 7 is disposed in the fuel gas flow path 5 so as to be in contact with the fuel electrode 2, the diaphragm 7 vibrates the fuel electrode 2 and vibrates the solid polymer electrolyte membrane 1 and the oxidizer electrode 3. Therefore, moisture on the surface of the oxidant electrode 3 can be scattered by the vibration. Furthermore, by providing the diaphragm 7 and the piezoelectric element 8 with a through hole, gas supply to the fuel electrode 2 is not hindered in the fuel gas flow path 5.
[0046]
(Embodiment 2)
FIG. 4 is a schematic view showing a cell structure of the polymer electrolyte fuel cell of the present embodiment. The difference from the first embodiment is that a laminated piezoelectric element 15 is formed on the diaphragm 7. The laminated piezoelectric element 15 is obtained by laminating five layers of piezoelectric elements composed of a 10 μm PZT film and 1 μm aluminum electrodes 16 and 17.
[0047]
The aluminum electrode 16 is at the same potential as the diaphragm 7, and the driving voltage signal from the drive circuit 9 is applied between the diaphragm 7 and the aluminum electrode 17 to drive the laminated piezoelectric element 15, as in the first embodiment. To do.
[0048]
In this embodiment, by using a laminated piezoelectric element, a total displacement of 5 times is obtained by lamination compared to the case of a single layer. Therefore, the displacement amount of each piezoelectric element layer is 5 minutes in the case of the first embodiment. 1 is acceptable. Since the displacement of the piezoelectric element is proportional to the electric field strength applied to the element, the voltage applied to the aluminum electrode can be suppressed to about one fifth, so that the piezoelectric element driving voltage supplied by the driving power supply circuit 13 is provided. The voltage Vp can be lowered.
[0049]
(Embodiment 3)
FIG. 5 is a schematic diagram showing a cell structure of the polymer electrolyte fuel cell of the present embodiment. The difference from the first embodiment is that two diaphragms 7 and two piezoelectric elements 8 are used, and an edge on one side thereof is fixed by a fixing member 18 so as not to contact the oxidant electrode 3.
[0050]
In the present embodiment, since the diaphragm 7 and the piezoelectric element 8 are not in contact with the oxidant electrode 3, the oxidant gas conductivity to the oxidant electrode 3 is improved as compared with the first and second embodiments. Further, since the diaphragm 7 and the piezoelectric element 8 are fixed on one side by the fixing member 18, the diaphragm 7 and the piezoelectric element 8 operate as a fan and the ventilation to the oxidant electrode 3 can be efficiently performed by the vibration. Therefore, it is possible to exert two functions, that is, gas supply to the electrode and the scattering of water on the electrode surface or the promotion of vaporization. Furthermore, since the battery reaction layer composed of the solid polymer electrolyte membrane 1, the fuel electrode 2 and the oxidant electrode 3 is not vibrated, the mechanical strength required for the battery reaction layer in the first and second embodiments is high. In this embodiment, it becomes unnecessary, and there is no risk of distortion or deterioration due to vibration.
[0051]
In the present embodiment, the number of the diaphragms 7 and the piezoelectric elements 8 may be further increased and each may be fixed by the fixing member 18. In addition, the number of components can be further reduced by integrally forming the diaphragm 7 and the fixing member 18. Furthermore, in this embodiment, in order to improve the ventilation effect by the operation as a fan, it is good also as a structure which does not provide a through-hole in the diaphragm 7 and the piezoelectric element 8. FIG.
[0052]
(Embodiment 4)
In the present embodiment, an example in which a water repellent coating is formed on at least one surface of the diaphragm and the piezoelectric element 8 will be described. The difference from the first to third embodiments is that, after the diaphragm 7 and the piezoelectric element 8 are produced integrally, a water-repellent film made of silicone resin is applied to them.
[0053]
The silicone resin has characteristics such as high heat resistance and chemical inactivity, but in this embodiment, the water-repellent coating is formed using an alcoholic silicone resin emulsion having particularly high heat resistance (application point 275 ° C.). Make it. First, phenylmethylsilicone resin (made by Toray Dow Corning Silicone Co., Ltd., trade name SH510, phenylation degree 25 mol%) is added to and mixed with a tetrahydrofuran solution of polycarbonate resin (solid content: 10 wt%) to obtain a coating composition. adjust. The obtained coating agent composition is applied to a plate in which the diaphragm 7 and the piezoelectric element 8 are integrated, and then air-dried at room temperature for 1 hour. Next, this is heated at 150 ° C. for 1 hour to obtain a silicone resin film having a thickness of 0.5 μm.
[0054]
In this embodiment, the water repellent effect of the silicone resin film tends to cause water on the diaphragm 7 and the piezoelectric element 8 to be in the form of water droplets, so that the effect of removing moisture by vibration of the diaphragm 7 is improved. In addition, since the silicone resin has high heat resistance, even when the temperature in the cell of the solid polymer fuel cell rises to around 100 ° C., the water-repellent coating hardly deteriorates. Furthermore, since phenylmethyl silicone resin has high insulation, there is no fear of short circuit between the electrode and the diaphragm 7 or the electrode and the piezoelectric element 8 in the fuel battery cell, so that safety is improved.
[0055]
【The invention's effect】
As described above in detail, according to the present invention, the electrode of the fuel cell and the solid electrolyte membrane are vibrated by the vibration means constituted by the piezoelectric element and the diaphragm, etc., and the moisture on the electrode surface is efficiently removed. Can do. Further, by providing a through hole through which gas and moisture can pass through the piezoelectric element and the diaphragm, moisture can be efficiently removed from the electrode without hindering gas supply to the electrode. Further, by causing the diaphragm to operate like a fan and generating wind, it is possible to promote the scattering or vaporization of moisture on the electrode surface along with the supply of gas to the electrode. Furthermore, water can be efficiently removed from the electrodes by providing a water-repellent coating on the piezoelectric element or the diaphragm. According to the present invention, it is possible to improve the power generation efficiency of the fuel cell by suppressing concentration polarization caused by insufficient gas diffusion into the electrode due to moisture adhering to the electrode surface.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a cell structure of a polymer electrolyte fuel cell according to Embodiment 1. FIG.
2 is a circuit diagram showing a configuration of a drive circuit that drives the piezoelectric element of FIG. 1; FIG.
3 is a waveform diagram showing voltages at various parts in the drive circuit of FIG. 2. FIG.
4 is a schematic view showing a cell structure of a polymer electrolyte fuel cell according to Embodiment 2. FIG.
5 is a schematic view showing a cell structure of a polymer electrolyte fuel cell according to Embodiment 3. FIG.
FIG. 6 is a schematic diagram showing a cell structure of a conventional polymer electrolyte fuel cell.
[Explanation of symbols]
1,101 Solid polymer electrolyte membrane
2,102 Fuel electrode
3, 103 Oxidant electrode
4,104 Gas impermeable substrate
5, 105 Fuel gas flow path
6, 106 Oxidant gas flow path
7 Diaphragm
8 Piezoelectric elements
9 Drive circuit
10 Control unit power supply circuit
11 Waveform output section
12 Piezoelectric drive unit
13 Driving power circuit
14 Driving IC
15 Multilayer piezoelectric element
16, 17 Aluminum electrode
18 Fixing member
19 Battery reaction layer

Claims (7)

A fuel cell having a positive electrode on one surface of the solid electrolyte membrane and a negative electrode on the other surface, a fuel gas channel facing the positive electrode, and an oxidant gas channel facing the negative electrode In
At least one of the fuel gas flow path and the oxidant gas flow path is provided with at least one vibration means;
The vibration means includes: a piezoelectric element that generates a displacement according to an applied drive voltage; and a vibration plate that is a base substrate of the piezoelectric element and that vibrates the solid electrolyte film in response to the displacement of the piezoelectric element. Become
The fuel cell, wherein the diaphragm and the piezoelectric element are stacked on the positive electrode or the negative electrode in parallel with the electrode surface . The fuel cell according to claim 1 , wherein the piezoelectric element is made of a PZT film. The fuel cell according to claim 1, wherein at least one of the piezoelectric element and the diaphragm has a function of transmitting at least one of gas and moisture. The fuel cell according to any one of claims 1 to 3 , wherein at least one of the piezoelectric element and the diaphragm has a plurality of through holes. The fuel cell according to any one of claims 1 to 4 , wherein at least one of the piezoelectric element and the diaphragm has a water-repellent coating on the surface. The fuel cell according to claim 5 , wherein the water-repellent coating is made of a silicone resin. The fuel cell according to claim 6 , wherein the water-repellent coating is made of a polymer film having a crosslinked structure.

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