Electrode and alkaline water electrolysis device

Abstract

This electrode comprises a support sheet and a metal porous sheet. The support sheet has a first main surface. The metal porous sheet has a second main surface and is disposed on the support sheet such that the second main surface faces the first main surface. In a plan view, the apparent area of the support sheet is greater than the apparent area of the metal porous sheet.

Description

Electrode and Alkaline Water Electrolysis Device

[0001] The present disclosure relates to an electrode and an alkaline water electrolysis device. This application claims priority based on Japanese Patent Application No. 2024-201289, which is a Japanese patent application filed on November 19, 2024. Further, all the descriptions described in the Japanese patent application are incorporated herein by reference.

[0002] Japanese Patent Publication No. 2005-536639 (Patent Document 1) describes an electrode used in an electrolytic solution. The electrode described in Patent Document 1 is formed using a wire mesh. Japanese Patent Publication No. 61-57397 (Patent Document 2) describes an electrode used in an electrolytic solution. The electrode described in Patent Document 2 is formed using a sponge-like metal porous body.

[0003] Japanese Patent Publication No. 2005-536639 Japanese Patent Publication No. 61-57397

[0004] The electrode of the present disclosure includes a support sheet and a metal porous body sheet. The support sheet has a first main surface. The metal porous body sheet has a second main surface and is disposed on the support sheet such that the second main surface faces the first main surface. In a plan view, the apparent area of the support sheet is larger than the apparent area of the metal porous body sheet.

[0005] FIG. 1 is a first plan view of the electrode 100A. FIG. 2 is a second plan view of the electrode 100A. FIG. 3 is a cross-sectional view taken along III-III in FIG. 1. FIG. 4 is a cross-sectional view of the alkaline water electrolysis device 200. FIG. 5 is a plan view of the electrode 100A according to a modified example. FIG. 6 is a first explanatory view for explaining the effect of the electrode 100A. FIG. 7 is a second explanatory view for explaining the effect of the electrode 100A. FIG. 8 is a plan view of the electrode 100B. FIG. 9 is a plan view of the electrode 100B according to Modified Example 1. FIG. 10 is a plan view of the electrode 100B according to Modified Example 2. FIG. 11 is an explanatory view for explaining the effect of the electrode 100B.

[0006] The electrode described in Patent Document 1 is formed of a wire mesh, resulting in a small surface area that contributes to the electrochemical reaction. In the electrode described in Patent Document 2, gas bubbles generated within the electrode have difficulty escaping. Therefore, there is room for improvement in the electrolysis voltage of the electrodes described in Patent Document 1 and Patent Document 2. This disclosure provides an electrode capable of reducing the electrolysis voltage.

[0007] The electrode according to this disclosure makes it possible to reduce the electrolysis voltage. (1) The electrode according to the embodiment comprises a support sheet and a porous metal sheet. The support sheet has a first main surface. The porous metal sheet has a second main surface and is arranged on the support sheet such that the second main surface faces the first main surface. In a plan view, the apparent area of ​​the support sheet is larger than the apparent area of ​​the porous metal sheet. The electrode according to (1) above makes it possible to reduce the electrolysis voltage when performing alkaline water electrolysis.

[0008] (2) In the electrode of (1) above, the support sheet may be expanded metal. (3) In the electrode of (1) or (2) above, the porous metal sheet may have multiple sheets. The multiple sheets may be arranged with intervals along the first direction in a plan view. The electrode of (3) above makes it possible to reduce the electrolysis voltage when performing alkaline water electrolysis.

[0009] (4) In the electrode described in (3) above, the angle between the direction in which the gaps between two adjacent sheets extend and the second direction perpendicular to the first direction may be 45° or less in a plan view.

[0010] (5) In the electrode described in (3) above, the width of the gap between two adjacent sheets in the first direction may be 1 / 15 or less of the width of the support sheet in the first direction.

[0011] (6) In the electrode described in (3) above, the width of the gap between two adjacent sheets in the first direction may be 1 / 30 or less of the width of the support sheet in the first direction.

[0012] (7) In the electrode described in (3) above, the width of the gap between two adjacent sheets in the first direction may be 1 / 75 or less of the width of the support sheet in the first direction.

[0013] (8) In the electrodes of (2) to (7) above, the expanded metal may be made of a metallic material containing nickel.

[0014] (9) In the electrodes described in (1) to (8) above, the porous metal sheet may be made of a metal material containing nickel.

[0015] (10) In the electrodes described in (1) to (9) above, the porous metal sheet may be a foamed metal body.

[0016] (11) In the electrodes described in (1) to (9) above, the porous metal sheet may be a nonwoven fabric.

[0017] (12) The porous metal sheet described in (1) to (9) above may be in the form of a mesh. (13) The alkaline water electrolysis apparatus according to the embodiment comprises the electrodes described in (1) to (12) above. The alkaline water electrolysis apparatus described in (13) above makes it possible to reduce the electrolysis voltage when performing alkaline water electrolysis.

[0018] (14) The alkaline water electrolysis apparatus described in (13) above may further include a diaphragm. The porous metal sheet has a third main surface which is the opposite surface to the second main surface, and the third main surface may be in contact with the diaphragm.

[0019] (15) In the alkaline water electrolysis apparatus described in (13) or (14) above, the porous metal sheet may have a plurality of sheets. The plurality of sheets may be arranged at intervals along the first direction in a plan view. In a plan view, the second direction perpendicular to the first direction may be along the vertical direction.

[0020] The following embodiments of the present disclosure will be described in detail with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions will not be repeated.

[0021] (First Embodiment) The electrode according to the first embodiment will be described below. The electrode according to the first embodiment will be referred to as electrode 100A.

[0022] <Configuration of electrode 100A> The configuration of electrode 100A is described below.

[0023] Figure 1 is a first plan view of electrode 100A. Figure 2 is a second plan view of electrode 100A. Figure 2 shows a plan view of electrode 100A as seen from the opposite side to Figure 1. Figure 3 is a cross-sectional view taken along III-III in Figure 1. As shown in Figures 1 to 3, electrode 100A includes a support sheet 10 and a porous metal sheet 20.

[0024] The support sheet 10 is in the shape of a sheet. The support sheet 10 has a main surface 10a and a main surface 10b. The main surface 10b is the opposite surface of the main surface 10a. The main surfaces 10a and 10b are end faces in the thickness direction of the support sheet 10.

[0025] The support sheet 10 is, for example, expanded metal. That is, the support sheet 10 has a plurality of through holes 10c formed therein. The through holes 10c penetrate the support sheet 10 along the thickness direction of the support sheet 10. The plurality of through holes 10c are arranged in a staggered pattern in a plan view. A plan view refers to the view along the direction normal to the main surface 10a (main surface 10b). The support sheet 10 is not limited to expanded metal. The support sheet 10 can be any sheet-like member with through holes formed therein.

[0026] The support sheet 10 is made of a metallic material. The metallic material constituting the support sheet 10 includes, for example, nickel.

[0027] The porous metal sheet 20 is in sheet form. The porous metal sheet 20 has a main surface 20a and a main surface 20b. The main surface 20b is the opposite surface to the main surface 20a. The main surfaces 20a and 20b are end faces in the thickness direction of the porous metal sheet 20. The porous metal sheet 20 is placed on the support sheet 10 such that the main surface 20a faces the main surface 10b.

[0028] The porous metal sheet 20 is a porous material formed from a metal material. The metal material constituting the porous metal sheet 20 includes, for example, nickel. The porous metal sheet 20 is, for example, a metal foam. The metal foam is formed by forming a metal material on the surface of a foamed resin containing voids by plating or the like, and then removing the foamed resin. Therefore, the metal foam is formed from a metal material and has a hollow framework inside, and voids defined by this framework exist within the metal foam. The porous metal sheet 20 may be a mesh-like member, or it may be a nonwoven fabric formed from metal fibers made of a metal material.

[0029] The apparent area of ​​the support sheet 10 is defined as the area inside the outline of the support sheet 10 in a plan view (shown as a dotted line in Figure 1), and the apparent area of ​​the metal porous sheet 20 is defined as the area inside the outline of the metal porous sheet 20 in a plan view. The apparent area of ​​the metal porous sheet 20 is smaller than the apparent area of ​​the support sheet 10. From another point of view, the metal porous sheet 20 is positioned inside the outline of the support sheet 10 in a plan view.

[0030] Figure 4 is a cross-sectional view of the alkaline water electrolysis apparatus 200. Figure 4 shows one electrolytic cell of the alkaline water electrolysis apparatus 200. The electrolytic cell of the alkaline water electrolysis apparatus 200 has a case 210, a diaphragm 220, electrodes 240 and 250, and a power supply 260. For example, electrodes 100A are used for electrodes 240 and 250. Note that the vertical direction in Figure 4 is, for example, along the vertical direction.

[0031] The diaphragm 220 is made of a material that does not allow oxygen or hydrogen gas to pass through, but does allow water to pass through. The diaphragm 220 is placed inside the case 210. The diaphragm 220 divides the internal space of the case 210 into a first space 211 and a second space 212.

[0032] Electrode 240 is positioned in the first space 211 such that its main surface 20b is in contact with one of the main surfaces of the diaphragm 220. Electrode 250 is positioned in the second space 212 such that its main surface 20b is in contact with the other main surface of the diaphragm 220. The porous metal sheet 20 used as electrodes 240 and 250 has a catalyst supported inside.

[0033] The anode of power supply 260 is electrically connected to electrode 240. The cathode of power supply 260 is electrically connected to electrode 250. Electrodes 240 and 250 function as the anode and negative electrode of the electrolytic cell, respectively.

[0034] Case 210 has an inlet 213a and an outlet 213b, and an inlet 214a and an outlet 214b. The inlet 213a and outlet 213b communicate with a first space 211. The inlet 214a and outlet 214b communicate with a second space 212. The alkaline aqueous solution is supplied into the first space 211 from the inlet 213a, flows through the first space 211, and then flows out from the outlet 213b. The alkaline aqueous solution is supplied into the second space 212 from the inlet 214a, flows through the second space 212, and then flows out from the outlet 214b. The alkaline aqueous solution is, for example, an aqueous potassium hydroxide solution.

[0035] As the alkaline aqueous solution flows through the first space 211 and the second space 212, a voltage is applied from the power supply 260 between electrodes 240 and 250, causing electrolysis of the alkaline aqueous solution. Consequently, oxygen gas is generated from electrode 240 and hydrogen gas is generated from electrode 250. The generated oxygen gas flows out from outlet 213b, and the generated hydrogen gas flows out from outlet 214b.

[0036] <Modified Example> Figure 5 is a plan view of the electrode 100A according to a modified example. As shown in Figure 5, if the width of the porous metal sheet 20 in the first direction DR1 is smaller than the width of the support sheet 10 in the first direction DR1, then the width of the porous metal sheet 20 in the second direction DR2, which is perpendicular to the first direction DR1, does not have to be smaller than the width of the support sheet 10 in the second direction DR2. In other words, the edges of the outline of the porous metal sheet 20 located at both ends in the second direction DR2 may coincide with the edges of the outline of the support sheet 10 located at both ends in the second direction DR2.

[0037] In the structure shown in Figure 5, when electrode 100A is used as electrode 240 or electrode 250, electrode 100A is positioned so that the second direction DR2 is aligned with the vertical direction. The width of the porous metal sheet 20 in the first direction DR1 is, for example, 9 / 10 or more and less than 1 of the width of the support sheet 10 in the first direction DR1.

[0038] <Effects of Electrode 100A> The effects of electrode 100A are explained below.

[0039] In alkaline water electrolysis, the electrolysis voltage tends to decrease as the surface area of ​​electrodes 240 and 250 increases. When only the porous metal sheet 20 is used as electrodes 240 and 250, the surface area of ​​electrodes 240 and 250 increases compared to when only the support sheet 10 is used as electrodes 240 and 250. However, hydrogen gas and oxygen gas bubbles generated within the porous metal sheet 20 are difficult to escape. Since the areas where hydrogen gas and oxygen gas bubbles are attached do not contribute to the electrochemical reaction, if the hydrogen gas and oxygen gas bubbles do not escape from within the porous metal sheet 20, the surface area of ​​the porous metal sheet 20 that contributes to the electrochemical reaction decreases, which becomes a factor that increases the electrolysis voltage.

[0040] FIG. 6 is a first explanatory diagram for explaining the effect of the electrode 100A. FIG. 7 is a second explanatory diagram for explaining the effect of the electrode 100A. As described above, in the electrode 100A, since the apparent area of the metal porous sheet 20 is smaller than the apparent area of the support sheet 10, as shown in FIGS. 6 and 7, on the side of the metal porous sheet 20, when the alkaline aqueous solution flows into the metal porous sheet 20, a path through which hydrogen gas and oxygen gas bubbles (see the arrows in the figure) pushed out can pass is secured.

[0041] Therefore, not only do the hydrogen gas and oxygen gas bubbles pass through the main surface 20a and the through-holes 10c of the support sheet 10 and are discharged outside the electrode 100A (see FIG. 7), but they are also discharged outside the electrode 100A through the above-described path (see FIG. 6). Thus, in the electrode 100A, since the bubbles can easily escape even when the metal porous sheet 20 is used, it is possible to reduce the electrolysis voltage in alkaline water electrolysis.

[0042] (Second Embodiment) The electrode according to the second embodiment will be described. The electrode according to the second embodiment is referred to as the electrode 100B. Here, mainly the differences from the electrode 100A will be described, and redundant explanations will not be repeated.

[0043] <Configuration of Electrode 100B> The configuration of the electrode 100B will be described below.

[0044] FIG. 8 is a plan view of the electrode 100B. As shown in FIG. 8, the electrode 100B has a support sheet 10 and a metal porous sheet 20. In the electrode 100B, the apparent area of the metal porous sheet 20 is smaller than the apparent area of the support sheet 10. In these respects, the configuration of the electrode 100B is common to the configuration of the electrode 100A.

[0045] In the electrode 100B, the metal porous sheet 20 is divided into a plurality of sheets 21. In the example shown in FIG. 8, the number of sheets 21 is two. However, the number of the plurality of sheets 21 may be three, or may be four or more. The plurality of sheets 21 are arranged along the first direction DR1 with a gap between two adjacent ones of the plurality of sheets 21 in a plan view. Therefore, a gap 22 exists between two adjacent ones of the plurality of sheets 21. The gap 22 extends along the second direction DR2 in a plan view.

[0046] Let the width of the support sheet 10 in the first direction DR1 be width W1, and the width of the gap 22 in the first direction DR1 be width W2. The width W2 is, for example, 1 / 15 or less of the width W1. The width W2 may be 1 / 30 or less of the width W1, or may be 1 / 75 or less of the width W1. Also, the width W1 is, for example, 2000 mm or less. The width W1 may be 1500 mm or less, or may be 1000 mm or less. The width W2 is, for example, 100 mm or less. The width W2 may be 50 mm or less, or may be 20 mm or less. The width W2 is, for example, 0.2 mm or more.

[0047] Regarding these points, the configuration of the electrode 100B is different from the configuration of the electrode 100A. Note that the electrode 100B is also used as an electrode (electrode 240, electrode 250) of the alkaline water electrolysis device 200, similar to the electrode 100A. At this time, the electrode 100B (electrode 240, electrode 250) is arranged such that the second direction DR2 is along the vertical direction.

[0048] <Modification Example> FIG. 9 is a plan view of the electrode 100B according to Modification Example 1. As shown in FIG. 9, the extending direction of the gap 22 may be inclined with respect to the second direction DR2. Let the angle formed by the extending direction of the gap 22 and the second direction DR2 be angle θ. Note that the smaller angle among the angles formed by the extending direction of the gap 22 and the second direction DR2 is adopted as the angle θ. The angle θ is, for example, 45° or less. The angle θ may be 10° or less, or may be 5° or less.

[0049] Figure 10 is a plan view of electrode 100B according to modified example 2. As shown in Figure 10, the two sheets 21 are designated as sheet 21A and sheet 21B. The width of sheet 21A and the width of sheet 21B in the second direction DR2 may be equal to the width of support sheet 10 in the second direction DR2. The edges of the outline of sheet 21A located on the opposite side of sheet 21B in the first direction DR1 and the edges of the outline of sheet 21B located on the opposite side of sheet 21A in the first direction DR1 may overlap with the edges of the outlines of support sheets 10 located at both ends in the first direction DR1. From another point of view, the sum of the widths of each of the multiple sheets 21 in the first direction DR1 plus the sum of the widths W2 may be equal to the width W1.

[0050] <Effects of Electrode 100B> The effects of electrode 100B are explained below.

[0051] Figure 11 is an explanatory diagram illustrating the effect of electrode 100B. Because a gap 22 exists in electrode 100B, as shown in Figure 11, there are more pathways for hydrogen gas and oxygen gas bubbles generated within the porous metal sheet 20 to escape compared to electrode 100A. Therefore, bubbles escape even more easily in electrode 100B.

[0052] The larger the width W2, the more pathways there are for air bubbles to escape. On the other hand, as the width W2 increases, the apparent area (surface area) of the porous metal sheet 20 decreases, and the number of areas where electrochemical reactions occur decreases. Therefore, by setting the width W2 to 1 / 15 (1 / 30, 1 / 75) or less of the width W1, it is possible to ensure air bubble escape while also ensuring areas where electrochemical reactions occur.

[0053] (Examples) Examples of the present disclosure are described below.

[0054] <Sample> Samples 1 to 17 were prepared to confirm the effect of the electrode according to this disclosure. Samples 1 and 3 to 17 had a support sheet 10 and a porous metal sheet 20. Sample 2 did not have a porous metal sheet 20. In samples 1 to 17, the width of the support sheet 10 in the first direction DR1 was 1500 mm, and the width of the support sheet 10 in the second direction DR2 was 2000 mm.

[0055] In Sample 1 and Sample 3 through Sample 17, the width of the porous metal sheet 20 in the first direction DR1 was varied. In Sample 6 through Sample 17, the width of the porous metal sheet 20 in the first direction DR1 was calculated including the width of the gap 22 (width W1) in the first direction DR1. In Sample 1 and Sample 3 through Sample 17, the width of the porous metal sheet 20 in the second direction DR2 was set to 2000 mm.

[0056] In samples 1 and 3 through 5, the porous metal sheet 20 had one sheet 21. On the other hand, in samples 6 through 15, the porous metal sheet 20 had two sheets 21, and in samples 16 and 17, the porous metal sheet 20 had three sheets 21. In samples 6 through 17, the width W2 was varied. In samples 13 through 15 and 17, the angle θ was varied. Details of samples 1 through 17 are shown in Table 1.

[0057]

[0058] The electrolytic voltage was measured for samples 1 through 17. The electrolytic voltage of each sample was evaluated as follows: Sample 1's electrolytic voltage (2.5V) was used as the reference voltage; a difference of 60mV or more (2.4 percent or more of the reference voltage) was evaluated as A; a difference of 30mV or more but less than 60mV (1.2 percent or more but less than 2.4 percent of the reference voltage) was evaluated as B; a difference of -20mV or more but less than 30mV (-0.8 percent or more but less than 1.2 percent of the reference voltage) was evaluated as C; and a difference of less than -20mV (less than -0.8 percent of the reference voltage) was evaluated as D. A negative difference from the reference potential indicates a higher electrolytic voltage than Sample 1. The reference voltage for each sample was measured over the apparent area of ​​the support sheet 10 over a 1cm² area. ２ The measurements were taken with a current of 1 ampere per unit. The evaluation results for the electrolytic voltage are shown in Table 2.

[0059]

[0060] The electrolysis voltage of sample 2 was higher than the electrolysis voltage (reference voltage) of sample 1. From this comparison, it was found that the presence of the porous metal sheet 20 in the electrode reduced the electrolysis voltage. Furthermore, the electrolysis voltages of sample 3 and sample 4 were equal to or lower than the electrolysis voltage of sample 1. From this comparison, it was found that reducing the apparent area of ​​the porous metal sheet 20 to less than the apparent area of ​​the support sheet 10 reduced the electrolysis voltage.

[0061] Sample 11 had no structural differences from Sample 1, except for the presence of a gap 22 with a width W2 of 1 mm between the two sheets 21. However, the electrolytic voltage of Sample 11 was significantly lower than that of Sample 1. From this comparison, it was found that placing a gap 22 between two adjacent sheets 21 made it easier for air bubbles to escape, thus lowering the electrolytic voltage. Furthermore, from Sample 6 to Sample 11, the electrolytic voltage increased as the width W2 decreased.

[0062] A comparison between sample 10 and sample 16 revealed that a similar effect occurs even when the number of sheets 21 is three or more. A comparison between sample 10 and samples 13 through 15 revealed that a similar effect occurs even when the extension direction of the gap 22 is inclined with respect to the second direction DR2, as long as the angle θ is not excessively large. This was also confirmed by a comparison between sample 16 and sample 17.

[0063] It should be understood that at least one configuration or feature described in each embodiment and example can be combined with or modified in various ways in other embodiments and examples. Furthermore, the embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments described above, and all modifications within the meaning and scope of the claims are intended to be included.

[0064] 10 Support sheet, 10a Main surface, 10b Main surface, 10c Through hole, 20 Porous metal sheet, 20a Main surface, 20b Main surface, 21, 21A, 21B Sheet, 22 Gap, 100A, 100B Electrode, 200 Alkaline water electrolysis device, 210 Case, 211 First space, 212 Second space, 213a, 214a Inlet, 213b, 214b Outlet, 220 Diaphragm, 240, 250 Electrode, 260 Power supply, DR1 First direction, DR2 Second direction, W1, W2 Width.

Claims

1. An electrode comprising a support sheet and a porous metal sheet, wherein the support sheet has a first main surface, and the porous metal sheet has a second main surface, and is arranged on the support sheet such that the second main surface faces the first main surface, and in a plan view, the apparent area of ​​the support sheet is larger than the apparent area of ​​the porous metal sheet.

2. The electrode according to claim 1, wherein the support sheet is expanded metal.

3. The electrode according to claim 1 or claim 2, wherein the porous metal sheet has a plurality of sheets, and the plurality of sheets are arranged at intervals along a first direction in a plan view.

4. The electrode according to claim 3, wherein, in a plan view, the angle between the direction in which two adjacent gaps among the plurality of sheets extend and the second direction perpendicular to the first direction is 45° or less.

5. The electrode according to claim 3, wherein the width in the first direction of the gap between two adjacent sheets is 1 / 15 or less of the width of the support sheet in the first direction.

6. The electrode according to claim 3, wherein the width in the first direction of the gap between two adjacent sheets is 1 / 30 or less of the width of the support sheet in the first direction.

7. The electrode according to claim 3, wherein the width in the first direction of the gap between two adjacent sheets is 1 / 75 or less of the width of the support sheet in the first direction.

8. The electrode according to any one of claims 2 to 7, wherein the expanded metal is formed of a nickel-containing metallic material.

9. The electrode according to any one of claims 1 to 8, wherein the porous metal sheet is formed of a nickel-containing metal material.

10. The electrode according to any one of claims 1 to 9, wherein the porous metal sheet is a foamed metal body.

11. The electrode according to any one of claims 1 to 9, wherein the porous metal sheet is a nonwoven fabric.

12. The electrode according to any one of claims 1 to 9, wherein the porous metal sheet is in the shape of a mesh.

13. An alkaline water electrolysis apparatus comprising the electrode described in any one of claims 1 to 12.

14. The alkaline water electrolysis apparatus according to claim 13, further comprising a diaphragm, wherein the porous metal sheet has a third main surface which is the opposite surface to the second main surface, and the third main surface is in contact with the diaphragm.

15. The alkaline water electrolysis apparatus according to claim 13 or claim 14, wherein the porous metal sheet has a plurality of sheets, the plurality of sheets are arranged at intervals along a first direction in a plan view, and the second direction perpendicular to the first direction in a plan view is along the vertical direction.

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