Method for manufacturing an anode gas diffusion layer

Abstract

This technology provides a way to suppress the risk of decreased electrolysis efficiency. [Solution] The method for manufacturing an anode gas diffusion layer according to the present disclosure is a method for manufacturing an anode gas diffusion layer used in a water electrolysis cell 10. In this manufacturing method, a slurry containing titanium powder with a particle size of 25 μm or less is coated onto a setter and dried to form a first layer, and titanium powder with a particle size of 45 μm or less is dry-coated onto the first layer to form a second layer, thereby forming a laminate consisting of the first and second layers, and the laminate is sintered using a vacuum sintering furnace to form an anode gas diffusion layer 12.

Description

Technical Field

[0001] This disclosure relates to an anode gas diffusion layer.

Background Art

[0002] There is a water electrolysis device that electrolyzes water or the like to generate hydrogen gas and oxygen gas. When constructing a water electrolysis device, a current feeder is used. The electrolytic cell disclosed in Patent Document 1 includes an anode chamber, which is a space sandwiched between a solid electrolyte membrane and an electrode plate, and a cathode chamber, which is a space sandwiched between the solid electrolyte membrane and the electrode plate. In the electrolytic cell, the current feeder is disposed in the anode chamber. The current feeder is composed of a first current feeder portion and a second current feeder portion. The first current feeder portion contacts the anode catalyst layer that forms the solid electrolyte membrane. The second current feeder portion contacts the electrode plate. The first current feeder portion and the second current feeder portion are each formed by sintering titanium fibers. The porosity of both the first current feeder portion and the second current feeder portion is 40% or more.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventors of the present application have discovered the following technical problems. Since the porosity of the first current feeder portion is high, the contact area between the first current feeder portion and the anode catalyst layer may not be ensured. As a result, the electrolysis efficiency may decrease.

[0005] This disclosure has been made in view of the above problems, and provides a method for manufacturing an anode gas diffusion layer that can suppress the possibility of a decrease in electrolysis efficiency.

Means for Solving the Problems

[0006] The method for manufacturing the anode gas diffusion layer according to this disclosure is: A method for manufacturing an anode gas diffusion layer used in a water electrolysis cell, A slurry containing titanium powder with a particle size of 25 μm or less is coated onto a setter and dried to form a first layer. A laminate consisting of the first and second layers is formed by dry coating titanium powder having a particle size of 45 μm or less onto the first layer to form a second layer. The laminate is sintered using a vacuum sintering furnace to form an anode gas diffusion layer. [Effects of the Invention]

[0007] According to this disclosure, the risk of a decrease in electrolysis efficiency can be suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing the configuration of a water electrolysis apparatus according to Embodiment 1. [Figure 2] This is a cross-sectional view showing the configuration of the main parts of the water electrolysis apparatus according to Embodiment 1. [Figure 3] This table shows the conditions and results of the examples. [Modes for carrying out the invention]

[0009] The following describes specific embodiments to which the present invention is applied, with reference to the drawings. However, the present invention is not limited to the following embodiments. Also, for clarity of explanation, the following description and drawings have been simplified as appropriate.

[0010] <Embodiment 1> Embodiment 1 will be described with reference to Figures 1 and 2. Figure 1 is a schematic diagram showing the configuration of the water electrolysis apparatus according to Embodiment 1. Figure 2 is a cross-sectional view showing the configuration of the main parts of the water electrolysis apparatus shown in Figure 1. In Figure 1, hatching has been omitted for clarity.

[0011] As shown in Figure 1, the water electrolysis apparatus 100 includes a water electrolysis cell 10 and a power supply 5. The water electrolysis apparatus 100 may also include a water electrolysis stack. The water electrolysis stack consists of a plurality of water electrolysis cells 10 arranged in series or parallel. The power supply 5 is electrically connected to the water electrolysis cells 10. The power supply 5 may be, for example, a battery, a solar cell, a fuel cell, etc. The water electrolysis apparatus 100 may also include other components as appropriate, such as a pure water tank, a hydrogen separation tank, an oxygen separation tank, a dehumidifier, a heat exchanger, etc.

[0012] The water electrolysis cell 10 comprises an anode separator 11, an anode gas diffusion layer 12, an anode catalyst layer 13, a membrane 4, a cathode catalyst layer 23, a cathode gas diffusion layer 22, and a cathode separator 21.

[0013] The anode separator 11, the anode gas diffusion layer 12, the anode catalyst layer 13, the film 4, the cathode catalyst layer 23, the cathode gas diffusion layer 22, and the cathode separator 21 are stacked in this order and are in close contact with each other.

[0014] The anode separator 11 may be a plate-like body formed from, for example, pure titanium or a titanium alloy. The anode separator 11 contains voids. The anode separator 11 is provided with a water supply hole 11a and an oxygen discharge hole 11b. Water is supplied to the anode separator 11 from outside the water electrolysis cell 10 through the water supply hole 11a. Oxygen is discharged through the oxygen discharge hole 11b.

[0015] The anode gas diffusion layer 12 is, for example, a plate-like body made of pure titanium or a titanium alloy. As shown in FIG. 2, the anode gas diffusion layer 12 includes a high-density layer 121 and a low-density layer 122. The density of the high-density layer 121 is higher than that of the low-density layer 122. The porosity of the high-density layer 121 is lower than that of the low-density layer 122. Further, the porosity of the high-density layer 121 is preferably lower than 40%, and more preferably 29.0% or less. The low-density layer 122 and the high-density layer 121 are fixed. The low-density layer 122 and the high-density layer 121 are laminated. The low-density layer 122 contacts the anode separator 11 shown in FIG. 1. The high-density layer 121 contacts the anode catalyst layer 13 shown in FIG. 1.

[0016] As shown in FIG. 1, the anode catalyst layer 13 is preferably a plate-like body or a film formed using a material containing iridium. The anode catalyst layer 13 is preferably a porous layer.

[0017] Similar to the anode catalyst layer 13, the cathode catalyst layer 23 is preferably a plate-like body or a film formed using a material containing iridium. The cathode catalyst layer 23 is preferably a porous layer or a porous plating layer. The anode catalyst layer 13 and the cathode catalyst layer 23 may be formed on both sides of the membrane 4 using a chemical method such as electroless plating.

[0018] The membrane 4 is preferably a solid electrolyte membrane. The solid electrolyte membrane is, for example, a membrane made of a solid polymer electrolyte. Specifically, the solid polymer electrolyte is preferably a cation exchange membrane, and more specifically, a fluororesin-based sulfonic acid cation exchange membrane.

[0019] The cathode separator 21 is, for example, a plate-like body formed using pure titanium or a titanium alloy. The cathode separator 21 has a hydrogen extraction hole 21a. Hydrogen is extracted through the hydrogen extraction hole 21a.

[0020] Here, the water electrolysis treatment by the water electrolysis device 100 will be described.

[0021] Water is supplied to the anode separator 11 from an external tank or similar structure of the water electrolysis device 100 through the water supply port 11a. Pure water is preferable for this purpose.

[0022] Furthermore, water is supplied to the anode separator 11, and the power supply 5 supplies current to the water electrolysis cell 10 of the water electrolysis device 100. As a result, water is decomposed in the anode catalyst layer 13, etc., and oxygen gas is generated. Consequently, oxygen is discharged to the outside of the water electrolysis device 100 from the oxygen discharge port 11b. Hydrogen can also be extracted from the hydrogen extraction port 21a.

[0023] Based on the above, the water electrolysis device 100 can generate hydrogen by performing water electrolysis.

[0024] <Manufacturing method> Next, the method for manufacturing the anode gas diffusion layer 12 described above will be explained.

[0025] A first layer is formed by coating a slurry containing titanium powder with a particle size of 25 μm or less onto a setter and drying it (step ST1). The particle size of the titanium powder may be, for example, 20 μm or less. The particle size of the titanium powder may be adjusted using a sieve. The particle size or particle size distribution of the titanium powder may be measured using a laser diffraction particle size distribution analyzer. A slurry can be formed by adding and mixing water, a dispersant, a binder, a plasticizer, and a viscosity modifier to the titanium powder. The resin content of the slurry may be, for example, 4.0 wt% to 5.0 wt%. The coating thickness may be, for example, 0.01 mm to 0.15 mm. The setter described above may be a sintering setter. The sintering setter may be formed using, for example, ceramics suitable for the sintering process. Applying a BN (boron nitride) lubricant to the setter beforehand can suppress adhesion between the setter and the anode gas diffusion layer 12. The slurry described above can be applied to the setter using a coating machine and an applicator. The high-density layer 121 of the anode gas diffusion layer 12 originates from this first layer. Furthermore, the first layer can be dried using a drying oven.

[0026] Next, a titanium powder with a particle size of 45 μm or less is dry-coated onto the first layer to form a second layer, thereby forming a laminate consisting of the first and second layers (step ST2). Since the particle size of the titanium powder used in this step is 45 μm or less, the specific surface area and adhesion of the titanium powder are suppressed, ensuring the fluidity of the titanium powder. Therefore, dry coating can be easily performed. The coating thickness, i.e., the thickness of the second layer, is preferably, for example, 0.15 mm or more and 0.25 mm or less. The titanium powder with a particle size of 45 μm or less, as described above, is dry-coated onto the first layer using a coating machine and an applicator.

[0027] In step ST2, even when the titanium powder comes into contact with the dried first layer, not much moisture moves from the titanium powder to the dried first layer. Therefore, the fluidity of the titanium powder can be ensured, and the titanium powder can be easily dry-coated. In addition, the occurrence of uneven coating can be suppressed. The low-density layer 122 of the anode gas diffusion layer 12 originates from this second layer.

[0028] Finally, the laminate is sintered using a vacuum sintering furnace to form the anode gas diffusion layer 12 (step ST3). The laminate may be degreased before sintering. The sintering temperature is preferably, for example, 895 degrees Celsius or more and 1000 degrees Celsius or less. The thickness of the high-density layer 121 of the anode gas diffusion layer 12 is preferably, for example, 0.01 mm or more and 0.10 mm or less. The thickness of the low-density layer 122 is preferably, for example, 0.15 mm or more and 0.25 mm or less.

[0029] From the above, the anode gas diffusion layer 12 can be manufactured. By stacking the anode gas diffusion layer 12 with the other components of the water electrolysis cell 10, a water electrolysis cell 10 or a water electrolysis stack can be formed. Furthermore, by combining the water electrolysis cell 10 or water electrolysis stack with the power supply 5, a water electrolysis apparatus 100 can be manufactured.

[0030] As described above, the anode gas diffusion layer 12 has a high-density layer 121 with low porosity. Because the high-density layer 121 has few voids, it is hardly locally compressed even when it comes into contact with the anode catalyst layer 13. A sufficient contact area between the high-density layer 121 and the anode catalyst layer 13 can be secured. As a result, the risk of a decrease in electrolysis efficiency can be suppressed. In addition, the smoothness of the high-density layer 121 is improved, and the durability of the film 4 can be improved.

[0031] <Examples> Next, an example will be described with reference to Figure 3. Figure 3 is a table showing the conditions and results of the example.

[0032] Examples 1 and 2 of the anode gas diffusion layer 12 were manufactured using the method for manufacturing the anode gas diffusion layer according to the embodiment described above, under the conditions shown in Figure 3.

[0033] In step ST1 of the manufacturing methods according to Examples 1 and 2, a silicon nitride sintering setter and BN lubricant were used. The coating speed in step ST1 was 5 mm / sec. The slurry components used in Example 1 were 76.93 wt% of pulverized titanium powder with a particle size of 20 μm or less, 13.08 wt% of water, 4.06 wt% of dispersant, 3.50 wt% of binder, 1.54 wt% of plasticizer, and 0.90 wt% of viscosity modifier. The slurry components used in Example 2 were 79.24 wt% of spherical titanium powder with a particle size of 25 μm or less, 10.46 wt% of water, 4.18 wt% of dispersant, 3.61 wt% of binder, 1.58 wt% of plasticizer, and 0.93 wt% of viscosity modifier.

[0034] Furthermore, after step ST1 of the manufacturing method according to Examples 1 and 2, the first layer described above was dried. The drying conditions were a drying temperature of 50°C and a drying time of 30 minutes.

[0035] Furthermore, in step ST3 of the manufacturing method according to Examples 1 and 2, the laminate described above was degreased by heating and holding it in an Ar atmosphere at 250 degrees Celsius for 60 minutes. In addition, this degreased laminate was subjected to a vacuum, specifically a vacuum of 10 degrees Celsius.―3 The material was sintered by heating and holding it at a predetermined heating and holding temperature for 3 hours in a Pa atmosphere.

[0036] The thickness and density of the high-density and low-density layers of the anode gas diffusion layers in Examples 1 and 2 were measured. The density could be measured using the Archimedes method. The porosity was calculated from these measured densities. For example, the density of pure titanium constituting the anode gas diffusion layers in Examples 1 and 2 was 4.51 g / cm³. 3 The density of the titanium alloy is obtained as the true density, that is, the density at 0% porosity. The porosity may be calculated using this obtained density and the density measured above. The measured thickness and density and the calculated porosity are shown in Figure 3.

[0037] The porosity of the high-density layers in Examples 1 and 2 was low at 29.0%. Furthermore, the porosity of the high-density layers in Examples 1 and 2 was lower than that of the first and second power supply sections of the electrolytic cell disclosed in Patent Document 1, which had a porosity of 40% or more. On the other hand, the porosity of the low-density layers in Examples 1 and 2 was high at 46.8% and 51.2%, respectively.

[0038] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. Furthermore, the present invention may be implemented by combining the above embodiments or examples thereof as appropriate. [Explanation of Symbols]

[0039] 100 Water electrolysis equipment 10 Water electrolysis cell 11 Anode separator 11a Water supply hole 11b Oxygen vent 12 Anode gas diffusion layer 121 High density layer 122 Low density layer 13 Anode catalyst layer 21 Cathode Separator 22 Cathode gas diffusion layer 23 Cathode catalyst layer 4. Membrane 5 Power Supply

Claims

[Claim 1] A method for manufacturing an anode gas diffusion layer used in a water electrolysis cell, A slurry containing titanium powder with a particle size of 25 μm or less is coated onto a setter and dried to form a first layer. A laminate consisting of the first and second layers is formed by dry coating titanium powder having a particle size of 45 μm or less onto the first layer to form a second layer. Using a vacuum sintering furnace, the laminate is sintered to form an anode gas diffusion layer. A method for manufacturing an anode gas diffusion layer.

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