JP3062540B2 - Bipolar plate for water electrolysis tank and cell using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a bipolar plate for a water electrolyzer for producing hydrogen and oxygen using a polymer electrolyte membrane and a cell using the same.

[0002]

2. Description of the Related Art Conventionally, when hydrogen and oxygen are produced by water electrolysis using a polymer electrolyte membrane, the structure of a filter press type electrolytic cell is as shown in FIG. , Cathode main electrode 2, electrode composite membrane 3 comprising ion exchange membrane 4 and catalyst electrode layers 5, 6, anode feeder 7, cathode feeder 8, double pole plate 9 and fastening bolts for integrating these And a nut. In a commercial-scale electrolytic cell, 80 to 600 ion exchange membranes are integrated. When water is supplied from the water absorption header 10 provided at the lower part of the electrolytic cell to the anode side of the anode main electrode 1 and the multi-electrode plate 9 having a flow path upward, on the surface of the catalyst electrode layers 5 and 6, Oxygen and hydrogen are generated on the cathode side, respectively. The generated oxygen and hydrogen reach the respective electrode plates through the porous power supply bodies 7 and 8, respectively, further reach the upper part of the electrolytic cell through the flow passages provided in the respective electrode plates, and are provided here. It is discharged outside through the respective headers 11 and 12.

[0003] Among these components, the most severe condition is required for the bipolar plate 9. That is, as the material conditions, the same material is required to have not only good conductivity but also an oxidizing atmosphere on the anode side and a reducing atmosphere on the cathode side. Further, as structural conditions, functions such as uniformly transmitting the current to the power supply bodies 6 and 7 and securing a flow path through which the supply water and the generated gas can flow uniformly are required. In order to satisfy such a condition, at present, a pure titanium machined or pressed and the surface of which is plated with platinum or molded with carbon is used.

[0004]

When a multipolar plate is manufactured by machining titanium, which is a conventional technique, there are the following problems. (1) It is difficult to accurately process the surface. This is particularly noticeable for large ones. (2) Since both surfaces must be processed with high precision, the plate thickness becomes thick. (3) Due to the high cost, it is not economically possible to process into a complicated shape. Further, in the case of producing a multi-electrode plate by pressing titanium, there are the following problems. (4) When press working pure titanium, since the bending factor (Bend factor) of titanium is large, the width of the flow path of the bipolar plate becomes large and complicated processing cannot be performed.
The supply of power to the power supply and the supply of water to the electrodes are not uniform.

[0005] Further, when a multi-pole plate is manufactured by molding carbon, there are the following problems. (5) Because carbon is brittle, large ones are difficult to manufacture and handle. (6) The plate thickness is almost the same as that of the machined one. (7) Complicated steps of forming titanium and forming and adhering carbon are required, which is expensive. Further, common problems are: (8) It is difficult to supply uniform water to a plurality of cells due to the pressure gradient of the feed water header and the exhaust gas header during operation. For this reason, the film was sometimes damaged by insufficient water supply. In particular, this is a major problem in an electrolytic cell using a polymer electrolyte membrane, which is characterized by operating at a high current density.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has been made by making the equipment compact, greatly reducing the production cost, and making the fluid flow in the electrolytic cell uniform. Its purpose is to extend the life of the film.

[0007]

According to the present invention, in order to solve the above-mentioned problems, a composite for a water electrolyzer comprising a titanium alloy thin plate superplastically processed to have a shape in which peaks and valleys are repeated at a fine pitch. An electrode plate is provided. Further, according to the present invention, the two bipolar plates made of a titanium alloy thin plate superplastically processed into a shape in which the peaks and the valleys repeat at a fine pitch are combined with the peaks and the valleys of one of the bipolar plates. Are disposed so as to correspond to the valleys and peaks of the other bipolar plate, respectively, and an electrode composite film and a cathode power supply using an anode power supply and a polymer electrolyte membrane are provided between these two bipolar plates. A cell for a water electrolysis tank is provided which has a sandwiched structure and is provided with a porous gasket at a water supply header and an oxygen and hydrogen outlet header of the cell.

The bipolar plate of the present invention can be processed into a complex and precise shape by superplastic processing of a titanium alloy thin plate, and satisfies all the functions required for the bipolar plate. By combining with a porous gasket (especially a ring gasket), it becomes possible to reduce the thickness of a unit cell comprising one set of a bipolar plate, an electrode composite film, and a power supply of an electrolytic cell to 3 to 3.5 mm. . Its thickness is 1/3 or less of the conventional one, and its weight is about 1/30 as compared with the case of machining. The electrode chamber volume is the same as that of a conventional commercial alkaline water electrolyzer (current density 20 A / d).
m ² ) or less and 1/3 or less of a conventional electrolytic cell (current density 100 A / dm ² ) using a polymer electrolyte. Further, by adjusting the porosity or width of a porous gasket (particularly a ring gasket) installed in the water supply header and the outlet header, the amount of water supplied to each cell can be made uniform.

[0009]

Embodiments of the present invention will be described below. Embodiment 1 FIG. 1 shows an exploded structural view of an electrolytic cell in the most typical embodiment. In practice, one electrolytic cell is composed of a bipolar plate 9
600 sheets are provided, and these are tightened with a plurality of (four in this figure) through bolts to form an integral structure. The operation of the water electrolyzer according to the present invention will be described with reference to FIG. 1. First, water supplied from the water supply header 10 at the bottom of the electrolyzer is
It flows upward through a channel provided in the anode-side electrode. This supply water passes through the porous anode feeder 7 and reaches the anode-side catalyst electrode layer (5 in FIG. 5) of the electrode composite membrane 3. The electrolysis reaction occurs by the added electric power, and oxygen is generated. The generated oxygen passes through the anode power supply 7 and rises in the flow path provided in the anode side electrode together with unreacted water, and passes through the porous spacer provided on the outer periphery of the oxygen header portion of the bipolar plate 9. It is discharged to the header 11. On the other hand, hydrogen generated on the surface of the cathode-side catalyst electrode layer (6 in FIG. 5) of the electrode composite membrane 3 and water permeated through the ion-exchange membrane (4 in FIG. 5) pass through the porous cathode feeder 8. As a result, the gas flows upward in the flow path provided in the cathode-side electrode, and is discharged to the hydrogen header 12 through the porous spacer provided on the outer periphery of the hydrogen header portion of the bipolar plate 9. In addition, in FIG. 1, 21 is a flange, 22 is a nozzle plate,
23 indicates an insulating packing, A indicates an O-ring gasket, B indicates a porous gasket, and C indicates a seal gasket.

FIG. 2 is a plan view of a unit cell according to the present invention (an anode power supply 7, an electrode composite film 3, and a cathode power supply 8 sandwiched between two bipolar plates 9, 9). And FIG.
(A), (b) and FIGS. 4 (c), (d) show the A section thereof.
Examples of partial cross-sectional views of a B section, a C section, and a D section are shown, respectively. In this example, the bipolar plate 9 satisfies all the conditions required as a bipolar plate by superplastically processing one plate. In other words, as shown in FIG. 3 (a), in the cross section A at the center of FIG. 2, (1) two sheets of superplastically processed two or more superplastics are formed so that peaks and valleys have a shape repeated at a fine pitch. The pole plates 9 and 9 are arranged so that the peaks and valleys of one bipolar plate correspond to the valleys and peaks of the other bipolar plate, respectively.
9, the anode power feeder 7, the electrode composite film 3 using the polymer electrolyte membrane, and the cathode power feeder 8 are sandwiched to maintain the contact between the power feeders 7, 8 and the elasticity of the cell. (2) The valleys on the anode and cathode sides are flow paths for oxygen and hydrogen, respectively. Double pole plate 9
Can be set as appropriate according to the pitch device scale in the repetitive shape of the peaks and valleys, but about 1-3 mm is appropriate. In the present specification, the “peaks” and “valleys” of the bipolar plate are respectively convex when referred to a layer composed of the anode power supply 7, the composite film 3, and the cathode power supply 8. It is assumed that a portion forming a portion is a peak portion and a portion forming a concave portion is a valley portion. Also, in this figure, the ratio between the peaks and the valleys is equal, but the interval between the peaks and the valleys can be set to a ratio that facilitates mold release in superplastic working. The unevenness provided on the outer peripheral portion is an O-ring groove for sealing. The upper and lower portions in FIG. 2 are required to have a function that allows the fluid to flow freely up, down, left, and right and that supports the composite membrane 3 uniformly. In this example, as shown in FIG. 3B, in the cross section B, the composite membrane 3 is alternately supported by the cubic projections from the left and right, and the other portions function as flow channels.

The lower hole in FIG. 1 is a water absorption hole, and the upper left hole is an oxygen-side discharge hole. These cross sections are shown in FIG.
By processing as shown in the cross section C shown in FIG. 5, water can be supplied to the anode side, and the generated oxygen can be discharged to the oxygen side header. In FIG. 4C,
31 indicates a porous spacer, and 32 indicates a packing. The hole on the upper right side of FIG. 1 is a discharge hole on the hydrogen side. By processing this part as shown in the cross section D shown in FIG. 4D, the generated hydrogen can be discharged to the hydrogen side header. become. It is desirable that the fluid flows uniformly in the electrode portion at the center of the bipolar plate. If there is a drift, in an extreme case, the portion becomes dry, which causes an accident such as damaging the film. In this structure, a more uniform flow can be realized by hydrodynamically designing the shape and distribution of the projections of the upper and lower cubes. Further, by adjusting the porosity of the porous spacers 31 at the entrance and the exit, the amount of water flowing into each cell can be made uniform. When such a structure is adopted, the thickness of a unit cell including one set of the bipolar plate 9, the composite film 3, and the power feeders 7 and 8 is about 3 to 3.5 mm. The above explanation is
It is attached when the electrolytic cell is installed horizontally,
The effect is the same when the electrolytic cell is installed vertically.

Example 2 The shape of the water electrolyzer in Example 1 was square, but this example was round. In the water electrolyzer of Example 1, 10 kg / c
Although only a relatively low operating pressure condition of m ² or less could be adopted, if the shape of the water electrolysis tank was round and the same configuration as in Example 1 was used, it could withstand an operating pressure of about 30 kg / cm ^2. The resulting water electrolysis tank can be manufactured with the same configuration as that of the first embodiment.

Example 3 The water electrolyzer of Example 1 is one in which the entire bipolar plate is integrally formed of a titanium alloy. However, only the electrode portion needs to have conductivity, and the surrounding nozzle portion and The seal portion does not need to be provided, and it is rather preferable that the seal portion has no conductivity. If the multi-pole plate is manufactured by molding the outer periphery of the electrode portion which has been superplastically processed as a core with a fluorine resin or a polyimide resin having heat resistance and chemical resistance, the configuration can be the same as that of the first or second embodiment.

Embodiment 4 The water electrolyzer of Embodiment 3 is one in which only a bipolar plate is integrally formed. However, if the anode and cathode power supply bodies are also integrally formed, the workability of assembly is further improved. .

[0015]

According to the first aspect of the present invention, the repetitive shape of the peaks and valleys is formed by superplastic processing of a titanium alloy thin plate. Are all satisfied. In addition, the unit according to claim 2 uses the bipolar plate as described above and combines it with the porous gasket, so that the size of the electrolytic cell becomes compact and the manufacturing cost of the device becomes low. In addition, since the supply of water to each cell and the extraction of gas can be made uniform, the electrolytic cell can be stably operated at a high current density, and as a result, long-term operation is possible.

[Brief description of the drawings]

FIG. 1 is an exploded structural view of an electrolytic cell in Embodiment 1 of the present invention.

FIG. 2 is a plan view of a unit cell (anode power supply, electrode composite film, and cathode power supply) between two bipolar plates in the first embodiment of the present invention.

3 (a) and 3 (b) are partial cross-sectional views of the unit cell shown in FIG. 2 in A section and B section.

4 (c) and (d) show C of the bipolar plate shown in FIG.
It is a cross section in a cross section and a D cross section.

FIG. 5 is a schematic sectional view showing the structure of a conventional filter press type electrolytic cell when producing hydrogen and oxygen.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anode main electrode 2 Cathode main electrode 3 Electrode composite membrane 4 Ion exchange membrane 5 Anode side catalyst electrode layer 6 Cathode side catalyst electrode layer 7 Anode power feeder 8 Cathode power feeder 9 Double electrode plate 10 Water supply header 11 Oxygen header 12 Hydrogen header 21 Flange 22 Nozzle plate 23 Insulation packing 31 Porous spacer 32 Packing A O-ring gasket B Porous gasket C Seal gasket

──────────────────────────────────────────────────続 き Continued on the front page (74) The above three agents 100074505 Patent Attorney Toshiaki Ikeura (72) Inventor Moritaka Kato 2-8-11 Nishishinbashi, Minato-ku, Tokyo 8th floor of the 7th Toyo Maritime Building Global Environment Foundation Industrial Technology Research Institute CO2 fixation project room (72) Inventor Shoji Maezawa 2-8-11 Nishi-Shimbashi, Minato-ku, Tokyo 7th Oriental Maritime Building 8F CO2 Fixation, etc. Project Room (72) Inventor Hiroaki Mori 2-8-11 Nishi-Shimbashi, Minato-ku, Tokyo 8th floor of the 7th Oriental Maritime Building Research Institute for Global Environmental Innovation Project room such as CO2 fixation (72) Inventor Takenaka Keiyasu 1-8-31 Midorioka, Ikeda-shi, Osaka Inside the Osaka Institute of Industrial Technology (72) Inventor Keisuke Oguro Ike, Osaka Midorioka 1-chome, 8-3-1, Osaka Institute of Industrial Technology, Institute of Industrial Science, Examiner Tomoko Hirono (56) References JP-A-48-75496 (JP, A) JP-A-56-38485 (JP, A) 61-502620 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C25B 1/00-15/08

Claims (2)

(57) [Claims] 1. A bipolar plate for a water electrolysis tank comprising a titanium alloy thin plate superplastically processed into a shape in which peaks and valleys repeat at a fine pitch. 2. A two-pole plate made of a titanium alloy thin plate superplastically processed to have a shape in which peaks and valleys are repeated at a fine pitch. A structure in which an anode power supply and an electrode composite film using a polymer electrolyte membrane and a cathode power supply are sandwiched between these two bipolar plates. A cell for a water electrolysis tank, wherein a porous gasket is provided in a water supply header and oxygen and hydrogen outlet headers of the cell.