Water electrolysis device

Abstract

The objective is to provide a water electrolysis apparatus with improved transport efficiency between the catalyst layer and the electrode, resulting in superior electrolysis efficiency. [Solution] A water electrolysis apparatus using an ion exchange membrane, characterized in that a catalyst layer is provided on the surface of the ion exchange membrane, a porous power supply is provided on the surface of the catalyst layer, and a fibrous power supply is provided on the surface of the porous power supply.

Description

Technical Field

[0001] The present invention relates to a water electrolysis apparatus using an ion exchange membrane, and particularly relates to a feeder structure used therefor.

Background Art

[0002] In the field of water electrolysis apparatuses that generate hydrogen and oxygen through water splitting, apparatuses using an ion exchange membrane have been studied. In this context, there are PEM (Proton Exchange Membrane) type water electrolysis apparatuses and AEM (Anion Exchange Membrane) type water electrolysis apparatuses, and in both cases, it is necessary to form catalyst layers on the cathode side and the anode side of the ion exchange membrane, respectively. Furthermore, a feeder functioning as a transport layer is provided between these catalyst layers and electrodes. This feeder is used to supply water to the catalyst and remove generated gas bubbles, and conventionally fibrous feeders with high porosity have been used. However, fibrous feeders tend to make point contact with the catalyst layer, which has the technical problem of reducing reaction performance. Furthermore, when increasing the clamping force of the fibrous feeder to improve the contact force, the fibrous body is prone to damage.

[0003] For example, Patent Document 1 discloses a technique in which, in an AEM-type water electrolysis apparatus, the anode is formed as a porous sintered body, so that the electrode also functions as a transport layer. However, sintered bodies have the technical problem of lower porosity than conventional fibrous feeders.

Prior Art Literature

Patent Literature

[0004]

Patent Literature 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] The present invention aims to provide a water electrolysis apparatus with improved transport efficiency between the catalyst layer and the electrode, and excellent electrolysis efficiency. [Means for solving the problem]

[0006] The water electrolysis apparatus according to the present invention is a water electrolysis apparatus using an ion exchange membrane, characterized in that it has a catalyst layer on the surface of the ion exchange membrane, a porous power supply body is arranged on the surface of the catalyst layer, and a fibrous power supply body is arranged on the surface of the porous power supply body.

[0007] A water electrolysis device works by electrolyzing water to bring H to the cathode side. + It moves and becomes hydrogen, and OH on the anode side - As these molecules move, oxygen and water are produced. The present invention is characterized by the structure of the power supply used as the transport layer for these ions.

[0008] In water electrolysis devices using ion exchange membranes, catalysts are coated on both the cathode and anode sides of the ion exchange membrane. Therefore, the functions required of the power supply are to promote the reaction by catalyst and to move the generated bubbles (gas). Therefore, in this invention, by placing a porous power supply body in contact with the surface of the catalyst layer, the contact area is improved and the catalytic reaction is promoted, and the movement of generated bubbles is promoted by utilizing the high porosity of the fibrous power supply body placed in contact with the surface of the porous power supply body.

[0009] In the present invention, the porous power supply body is preferably a sheet material with a large number of holes formed in it, and the porous power supply body may also be made into a sheet using a powdered sintered material.

[0010] Water electrolysis includes PEM (Proton Exchange Membrane) type water electrolysis, which uses a proton exchange membrane, and AEM (Anion Exchange Membrane) type water electrolysis, which uses an anion exchange membrane. In both cases, the cathode and anode sides of the ion exchange membrane are coated with catalysts suitable for each side. In PEM-type systems, pure water is often used, and a Pt-based catalyst is frequently employed on the cathode side, while an iridium-based catalyst such as Ir or IrO2 is often used on the anode side. Furthermore, AEM type catalysts often use low-concentration alkaline water, with a Pt-based catalyst used on the cathode side and a Ni-based catalyst or similar often used on the anode side.

[0011] In either of the above cases, the present invention is characterized by the placement of a porous power supply body with a porous structure between the catalyst layer and the fibrous power supply body. Since corrosion resistance is required for the power supply body, it is preferable that the porous power supply body is a sheet material of titanium or an alloy thereof, and that the fibrous power supply body is formed from titanium or an alloy of titanium fibers.

[0012] Furthermore, the ion exchange membrane may be a PEM, the porous power supply may be a sheet material made of titanium or an alloy thereof with numerous pores formed on the surface and coated with platinum, and the fibrous power supply may be made of titanium or an alloy fiber.

[0013] Furthermore, the ion exchange membrane may be an AEM, the porous power supply body may be a sheet material of nickel or an alloy thereof with numerous holes formed in it, or a sintered nickel material, and the fibrous power supply body may be formed from nickel or an alloy of nickel fibers. [Effects of the Invention]

[0014] In this invention, in a PEM-type or AEM-type water electrolysis apparatus, the power supply is combined with a fibrous power supply on the catalyst side, thereby improving the reactivity with the catalyst and increasing the electrolysis efficiency. Furthermore, because it is a sheet-like porous power supply material, it also has excellent voltage resistance. [Brief explanation of the drawing]

[0015] [Figure 1] An example of the configuration of a water electrolysis apparatus according to the present invention is shown. [Figure 2] (a) shows a partially enlarged photograph of a porous current feeder, and (b) shows a partially enlarged photograph of a fibrous current feeder. [Figure 3] shows a partially enlarged photograph of a porous current feeder made of a powdered sintered material. [Figure 4] shows current-voltage characteristics. MODE FOR CARRYING OUT THE INVENTION

[0016] An example of the configuration of a water electrolysis apparatus according to the present invention will be described below with reference to the drawings. A schematic diagram is shown in Fig. 1. Water (H2O) is supplied between a cathode 11 and an anode 12, and an electrolysis voltage is applied. A catalyst layer 2a is coated on the cathode-side surface of an ion exchange membrane 1, and a catalyst layer 2b is coated on the anode-side surface thereof. In the embodiment shown in Fig. 1, there are provided a porous current feeder 3a and a fibrous current feeder 4a disposed in contact with the cathode-side catalyst layer 2a, and a porous current feeder 3b and a fibrous current feeder 4b disposed in contact with the anode-side catalyst layer 2b, respectively. However, the present invention also includes those in which only one of the cathode side or the anode side has the above structure in accordance with the type of catalyst and the layer structure.

[0017] <Example 1> A Pt catalyst is applied at 0.3 to 1.0 mg / cm 2 on the cathode side of a PEM-type ion exchange membrane, and an Ir catalyst is applied at 0.5 to 1.0 mg / cm 2 on the anode side by coating. A porous carbon layer was disposed in contact with the Pt catalyst layer on the cathode side. Further, the porous current feeder shown in Fig. 2(a) was disposed in contact with the Ir catalyst layer on the anode side. This porous current feeder was obtained by forming a large number of pores having a pore diameter of 0.05 to 0.07 mm by etching in a titanium sheet material having a thickness of 0.03 mm, and further performing Pt plating of 0.2 µm (etched titanium sheet). As the fibrous power supply, a mesh material with a thickness of about 0.2 mm was used, made from titanium fibers with a wire diameter of approximately 20 μm, as shown in Figure 2(b).

[0018] <Example 2> Instead of the etched titanium sheet used in Example 1, a sintered titanium sheet was used, which was obtained by sintering titanium powder into a sheet and grinding both sides to a thickness of approximately 0.2 mm, as shown in Figure 3. Alternatively, the sintered sheet, which has been sintered into a sheet shape, may be used as is. In this embodiment, both sides were ground to secure a large flat area in order to increase the contact area between the catalyst and the porous power supply body, but the flattening may also be done by pressing. This sintered titanium sheet was also plated with 0.3 μm of platinum.

[0019] <Comparative Example 1> Only a fibrous power supply made of titanium fibers was used as the power supply element.

[0020] Using the power supply bodies of Examples 1 and 2 and Comparative Example 1 described above, the unit area is approximately cm². 2 Figure 4 shows the results of evaluating the current-voltage characteristics per unit. In Figure 4, in Comparative Example 1, the voltage rose sharply when the current was increased to 3.0A or higher, making measurement impossible. In contrast, both Examples 1 and 2 showed excellent current-voltage characteristics.

[0021] <Example 3> An AEM was used for the ion exchange membrane, and a Pt catalyst layer and a porous carbon layer were formed on the cathode side of the ion exchange membrane. Furthermore, a Ni-based catalyst layer was formed on the anode side of the ion exchange membrane, and a porous power supply was used in contact with its surface. This supply consisted of a nickel sheet material with numerous pores formed on it, or a sheet-like sintered material made by sintering nickel powder and grinding both sides. A fibrous power supply made of nickel fibers was placed in contact with the surface of the porous power supply material. When this was used for water electrolysis, it exhibited excellent electrolytic properties.

[0022] In Comparative Example 1, a fibrous power supply made of titanium fibers was used, resulting in point contact with the catalyst, as in the conventional method, and thus insufficient electrolytic properties. However, when the properties were evaluated using only a sheet-like porous power supply as the power supply, the electrolytic properties were superior to those of the conventional method. This is likely because the sheet-like porous power supply material has many flat surfaces, which increases the contact area with the catalyst. [Explanation of symbols]

[0023] 1. Ion exchange membrane 2a Catalyst layer 2b Catalyst layer 3a Porous power supply 3b Porous power feeder 4a Fibrous power supply 4b Fibrous power supply 11 Cathode 12 anodes

Claims

1. A water electrolysis apparatus using an ion exchange membrane, An ion exchange membrane has a catalyst layer on its surface, and a porous power supply is placed on the surface of the catalyst layer. A water electrolysis apparatus characterized by having a fibrous power supply arranged on the surface of the porous power supply.

2. The water electrolysis apparatus according to claim 1, characterized in that the porous power supply body has a large number of holes formed in a sheet material.

3. The water electrolysis apparatus according to claim 1, characterized in that the porous power supply body is formed from a powdered sintered material.

4. The water electrolysis apparatus according to claim 1, characterized in that the ion exchange membrane is a PEM (Proton Exchange Membrane) or an AEM (Aion Exchange Membrane).

5. The porous power supply body is formed using a sheet material of titanium or an alloy thereof. The water electrolysis apparatus according to claim 1, characterized in that the fibrous power supply body is formed of titanium or an alloy thereof.

6. The ion exchange membrane is PEM, The water electrolysis apparatus according to claim 1, characterized in that the porous power supply body is formed from a sheet material made of titanium or an alloy thereof and coated with platinum on its surface, and the fibrous power supply body is formed using titanium or an alloy of titanium fibers.

7. The aforementioned ion exchange membrane is an AEM, The porous power supply body is a sheet material of nickel or an alloy thereof with numerous holes formed in it, or a sintered material of nickel or an alloy thereof. The water electrolysis apparatus according to claim 1, characterized in that the fibrous power supply body is formed using nickel or an alloy thereof fibers.

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