Alkaline water electrolysis device

Abstract

The present invention provides an alkaline electrolyzed water device comprising: a diaphragm including a first main surface and a second main surface facing the first main surface; a first electrode including a third main surface and a fourth main surface facing the third main surface, the third main surface being provided so as to face the first main surface of the separator; and a first bipolar plate including a fifth main surface, the fifth main surface being provided in contact with the fourth main surface of the first electrode, and the first electrode comprising a first metal porous body having a three-dimensional network structure.

Description

Technical Field

[0001] The present invention relates to an alkaline water electrolysis device. This application claims priority to Japanese patent application No. 2022-138136 filed on August 31, 2022. All the contents described in the Japanese patent application are incorporated herein by reference. Background Art

[0002] In order to achieve carbon neutrality, hydrogen has attracted attention as a next-generation energy source. Hydrogen can be produced by alkaline electrolysis of water. As an alkaline water electrolysis device, a device has been proposed, which has an electrolytic cell, and the electrolytic cell is divided into a cathode chamber and an anode chamber by a diaphragm, a cathode is provided in the cathode chamber, and an anode is provided in the anode chamber (Patent Document 1).

[0003] In Patent Document 1, a so-called zero-gap structure is adopted, in which a porous plate is used in the anode and the cathode, and the cathode and the anode are directly in contact with the diaphragm to reduce the solution resistance between the anode and the cathode. In the zero-gap structure, the alkaline aqueous solution cannot pass through the diaphragm side of the electrode. Therefore, in Patent Document 1, in order to ensure the flow path of the alkaline aqueous solution, a space is provided on the opposite side of the electrode and the diaphragm side.

[0004] In recent years, from the perspective of carbon neutrality and energy conservation, it is required to further reduce the power required for alkaline water electrolysis devices to produce hydrogen. In alkaline water electrolysis devices, the larger the surface area of ​​the electrode, the lower the electrolysis voltage, and the lower the power required to produce hydrogen.

[0005] Patent Document 2 proposes a technique of using a porous metal body having a three-dimensional network structure having a large surface area as an electrode of an alkaline water electrolysis device.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent document 1: International Publication No. 2021 / 200376;

[0009] Patent document 2: International Publication No. 2019 / 163256. Summary of the invention

[0010] The alkaline water electrolysis device of the present invention has:

[0011] A diaphragm comprising a first main surface and a second main surface opposite to the first main surface;

[0012] a first electrode including a third main surface and a fourth main surface opposite to the third main surface, wherein the third main surface is disposed opposite to the first main surface of the diaphragm; and

[0013] A first bipolar plate includes a fifth main surface, wherein the fifth main surface is disposed in contact with the fourth main surface of the first electrode.

[0014] The first electrode is composed of a first porous metal body having a three-dimensional network structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a diagram for explaining a typical configuration example of the alkaline water electrolysis device according to the first embodiment.

[0016] Figure 2 It is a schematic diagram of a device for measuring electrode potential oscillation data.

[0017] Figure 3 This is a diagram showing potential oscillation data obtained by performing constant current electrolysis on the first electrode of Embodiment 1.

[0018] Figure 4 Yes Figure 3 The data obtained by multiplying the potential oscillation data at the flow rate of 1 m / min and the flow rate of 10 m / min by the window function are Fourier transformed, and the results of the above Fourier transform are shown in a graph with the X-axis as frequency (Hz) and the Y-axis as amplitude (mV).

[0019] Figure 5 yes Figure 1 VV line cross-sectional view. DETAILED DESCRIPTION

[0020] [Problems to be Solved by the Invention]

[0021] As an electrode of an alkaline water electrolysis device having the structure of Patent Document 1, if the three-dimensional network structure of Patent Document 2 is applied, the gas generated at the electrode will be retained inside the three-dimensional network structure, and the electrolysis reaction will be hindered due to gas resistance, the electrolysis voltage will rise, and the power required to generate hydrogen will increase. Therefore, an alkaline water electrolysis device is required that can suppress the retention of gas at the electrode even when a metal porous body having a three-dimensional network structure is used for the electrode.

[0022] Therefore, an object of the present invention is to provide an alkaline water electrolysis device which can suppress gas accumulation at the electrodes even when a metal porous body having a three-dimensional network structure is used for the electrodes.

[0023] [Effects of the Invention]

[0024] According to the present invention, it is possible to provide an alkaline water electrolysis device capable of suppressing gas accumulation at the electrodes even when a metal porous body having a three-dimensional network structure is used for the electrodes.

[0025] [Description of Embodiments of the Invention]

[0026] First, embodiments of the present invention are listed for description.

[0027] (1) The alkaline water electrolysis device of the present invention has:

[0028] A diaphragm comprising a first main surface and a second main surface opposite to the first main surface;

[0029] a first electrode including a third main surface and a fourth main surface opposite to the third main surface, wherein the third main surface is disposed opposite to the first main surface of the diaphragm; and

[0030] A first bipolar plate includes a fifth main surface, wherein the fifth main surface is disposed in contact with the fourth main surface of the first electrode.

[0031] The first electrode is composed of a first porous metal body having a three-dimensional network structure.

[0032] According to the present invention, it is possible to provide an alkaline water electrolysis device capable of suppressing gas accumulation at the electrodes even when a metal porous body having a three-dimensional network structure is used for the electrodes.

[0033] (2) In the above (1), it is preferred that the alkaline water electrolysis device has:

[0034] a second electrode including a sixth main surface and a seventh main surface opposite to the sixth main surface, wherein the sixth main surface is disposed opposite to the second main surface of the diaphragm; and

[0035] The second bipolar plate comprises an eighth main surface, wherein the eighth main surface is arranged in contact with the seventh main surface of the second electrode.

[0036] The second electrode is composed of a second metal porous body having a three-dimensional network structure.

[0037] As a result, the reaction sites for generating gas increase and the electrolysis voltage decreases.

[0038] (3) In the above (1) or (2), preferably, in the first spectrum at a flow rate of 1 m / min and the second spectrum at a flow rate of 10 m / min,

[0039] The first spectrum has a maximum peak in a frequency range of 0.2 Hz to 10 Hz.

[0040] In the first spectrum, the frequency at the maximum peak amplitude P1 is F1.

[0041] The ratio P2 / P1 of the amplitude P2 of the second spectrum at the frequency F1 to the amplitude P1 is less than 0.5,

[0042] The first spectrum at the flow rate of 1 m / min and the second spectrum at the flow rate of 10 m / min are as follows: the third main surface is made into a square of 1 cm×1 cm, and constant current electrolysis is performed for 100 seconds at a current of 1.5 A under the conditions of a gas pressure of 0.1 MPa and a flow rate of the potassium hydroxide aqueous solution of 1 m / min or 10 m / min to obtain potential oscillation data every 1 ms, and the data obtained by multiplying the potential oscillation data by a window function are Fourier transformed, and the results of the Fourier transform are shown in a coordinate system with the X-axis as the frequency and the Y-axis as the amplitude.

[0043] Thus, the specific surface area of ​​the first electrode is large, and by increasing the flow rate of the alkaline aqueous solution flowing through the first electrode, the residence time of the gas in the first electrode can be further shortened, and the electrolysis voltage can be further reduced.

[0044] (4) In the above (2), it is preferred that the second electrode has a third spectrum at a flow rate of 1 m / min and a fourth spectrum at a flow rate of 10 m / min,

[0045] The third spectrum has a maximum peak in a frequency range of 0.2 Hz to 10 Hz.

[0046] In the third spectrum, the frequency at the maximum peak amplitude P3 is F3.

[0047] A ratio P4 / P3 of the amplitude P4 of the fourth spectrum at the frequency F3 to the amplitude P3 is less than 0.5,

[0048] The third spectrum at the flow rate of 1 m / min and the fourth spectrum at the flow rate of 10 m / min are as follows: the sixth main surface is made into a square of 1 cm×1 cm, and constant current electrolysis is performed for 100 seconds at a current of 1.5 A under the conditions of a gas pressure of 0.1 MPa and a flow rate of the potassium hydroxide aqueous solution of 1 m / min or 10 m / min to obtain potential oscillation data every 1 ms, and the data obtained by multiplying the potential oscillation data by a window function are Fourier transformed, and the results of the Fourier transform are shown in a coordinate system with the X-axis as the frequency and the Y-axis as the amplitude.

[0049] Thus, the specific surface area of ​​the second electrode is large, and by increasing the flow rate of the alkaline aqueous solution flowing through the second electrode, the residence time of the gas in the second electrode can be further shortened, and the electrolysis voltage can be further reduced.

[0050] [Details of the embodiments of the present invention]

[0051] Below, while referring to the attached Figure 1 The specific example of the alkaline water electrolysis device of the present invention is described. In the drawings of the present invention, the same reference numerals represent the same parts or equivalent parts. In addition, in order to make the drawings clear and concise, the dimensional relationship of length, width, thickness, depth, etc. will be appropriately changed, and it does not necessarily represent the actual dimensional relationship.

[0052] In this specification, expressions in the form of "A to B" refer to the upper and lower limits of a range (i.e., greater than A and less than B). When A has no unit but only B has a unit, the unit of A is the same as that of B.

[0053] In the present specification, when a compound or the like is represented by a chemical formula, unless the atomic ratio is particularly limited, all conventionally known atomic ratios are included and the atomic ratio is not necessarily limited to the stoichiometric range.

[0054] In the present invention, when more than one numerical value is recorded as the lower limit and the upper limit of the numerical range, it is also deemed that a combination of any numerical value recorded in the lower limit and any numerical value recorded in the upper limit is disclosed. For example, when more than a1, more than b1, and more than c1 are recorded as the lower limit and less than a2, less than b2, and less than c2 are recorded as the upper limit, it is deemed that more than a1 and less than a2, more than a1 and less than b2, more than a1 and less than c2, more than b1 and less than a2, more than b1 and less than b2, more than b1 and less than c2, more than c1 and less than a2, more than c1 and less than b2, more than c1 and less than c2 are disclosed.

[0055] [Implementation Method 1]

[0056] use Figure 1 An alkaline water electrolysis device according to an embodiment of the present invention (hereinafter also referred to as "embodiment 1") is described. The alkaline water electrolysis device of embodiment 1 comprises: a diaphragm 13, which includes a first main surface 13a and a second main surface 13b opposite to the first main surface 13a; a first electrode 21, which includes a third main surface 21a and a fourth main surface 21b opposite to the third main surface 21a, and the third main surface is arranged opposite to the first main surface 13a of the diaphragm 13; and a first bipolar plate 4A, which includes a fifth main surface 4a, and the fifth main surface 4a is arranged in contact with the fourth main surface 21b of the first electrode 21, and the first electrode 21 is composed of a first metal porous body having a three-dimensional network structure.

[0057] Figure 1The alkaline water electrolysis device further comprises: a second electrode 22, which comprises a sixth main surface 22a and a seventh main surface 22b opposite to the sixth main surface 22a, the sixth main surface 22a being arranged opposite to the second main surface 13b of the diaphragm; and a second bipolar plate 4B, which comprises an eighth main surface 4b, the eighth main surface 4b being arranged in contact with the seventh main surface 22b of the second electrode 22. The second electrode 22 is composed of a second metal porous body having a three-dimensional network structure.

[0058] exist Figure 1 In the embodiment 1, the first electrode 21 and the second electrode 22 are both composed of a metal porous body having a three-dimensional network structure, but in the embodiment 1, as long as at least the first electrode 21 is composed of a metal porous body having a three-dimensional network structure, the second electrode 22 may not be a metal porous body having a three-dimensional network structure. For example, the second electrode 22 may be a porous plate such as a metal mesh or a punched metal. If the first electrode 21 and the second electrode 22 are both composed of a metal porous body having a three-dimensional network structure, the electrolysis voltage is reduced, and the power required to produce hydrogen and oxygen is reduced, so it is preferred.

[0059] The alkaline water electrolysis device has a gasket 7 for holding a diaphragm 13, and the gasket 7 is sandwiched by a first bipolar plate 4A and a second bipolar plate 4B. The first bipolar plate 4A and the second bipolar plate 4B are connected to a power source 18. A first electrode 21 is provided in a first space surrounded by a first main surface 13a of the diaphragm 13, a fifth main surface 4a of the first bipolar plate 4A, and an inner wall of the gasket 7. A second electrode 22 is provided in a space surrounded by a second main surface 13b of the diaphragm 13, an eighth main surface 4b of the second bipolar plate 4B, and an inner wall of the gasket 7.

[0060] In the following, a case where the first electrode 21 is a cathode and the second electrode 22 is an anode is described, but the first electrode 21 may be an anode and the second electrode 22 may be a cathode.

[0061] The first bipolar plate 4A is provided with: a first alkaline aqueous solution supply channel 2A, which supplies an alkaline aqueous solution into the first space; and a first alkaline aqueous solution recovery channel 2B, which recovers hydrogen and alkaline aqueous solution generated at the first electrode 21. The alkaline aqueous solution supplied from the first alkaline aqueous solution supply channel 2A passes through the interconnecting holes of the metal porous body with a three-dimensional network structure constituting the first electrode 21, passes through the inside of the first electrode 21, reaches the first alkaline aqueous solution recovery channel 2B and is recovered. When the alkaline aqueous solution passes through the first electrode 21, hydrogen is generated inside the first electrode 21. The hydrogen is pushed by the flow of the alkaline aqueous solution, moves to the outside of the first electrode 21, and reaches the first alkaline aqueous solution recovery channel 2B together with the alkaline aqueous solution and is recovered.

[0062] In the first embodiment, the fourth main surface 21b of the first electrode 21 is in contact with the fifth main surface 4a of the first bipolar plate 4A, so almost all of the alkaline aqueous solution supplied from the first alkaline aqueous solution supply flow channel 2A reaches the first alkaline aqueous solution recovery flow channel 2B through the first electrode 21. As a result, the gas (hydrogen gas) generated inside the first electrode 21 can be effectively squeezed out to the downstream side of the liquid flow, that is, the outside of the alkaline aqueous solution recovery flow channel side of the first electrode 21, by the flow of the alkaline aqueous solution passing through the first electrode 21, thereby suppressing the retention of the gas at the first electrode.

[0063] exist Figure 1 In the embodiment, the first alkaline aqueous solution supply channel 2A and the first alkaline aqueous solution recovery channel 2B are provided in the first bipolar plate 4A, but as long as the alkaline aqueous solution can pass through the interior of the first electrode 21, the positions of the first alkaline aqueous solution supply channel 2A and the first alkaline aqueous solution recovery channel 2B are not particularly limited. For example, the first alkaline aqueous solution supply channel 2A and the first alkaline aqueous solution recovery channel 2B may also be provided in the gasket 7.

[0064] The second bipolar plate 4B is provided with: a second alkaline aqueous solution supply channel 3A, which supplies an alkaline aqueous solution into the second space; and a second alkaline aqueous solution recovery channel 3B, which recovers oxygen and alkaline aqueous solution generated at the second electrode 22. The alkaline aqueous solution supplied from the second alkaline aqueous solution supply channel 3A passes through the interconnecting holes of the metal porous body with a three-dimensional network structure constituting the second electrode 22, passes through the inside of the second electrode 22, reaches the second alkaline aqueous solution recovery channel 3B and is recovered. When the alkaline aqueous solution passes through the second electrode 22, oxygen is generated inside the second electrode 22. The oxygen is pushed by the flow of the alkaline aqueous solution, moves to the outside of the second electrode 22, and reaches the second alkaline aqueous solution recovery channel 3B together with the alkaline aqueous solution and is recovered.

[0065] In embodiment 1, the seventh main surface 22b of the second electrode 22 is connected to the eighth main surface 4b of the second bipolar plate 4B, so almost all of the alkaline aqueous solution supplied from the second alkaline aqueous solution supply channel 3A reaches the second alkaline aqueous solution recovery channel 3B through the second electrode 22. As a result, the gas (oxygen) generated inside the second electrode 22 can be effectively squeezed out to the downstream side of the liquid flow, that is, the outside of the alkaline aqueous solution recovery channel side of the second electrode 22 by the liquid flow of the alkaline aqueous solution passing through the second electrode 22, thereby suppressing the retention of gas at the second electrode. The bubbles of oxygen generated at the electrode composed of a porous body are larger than the bubbles of hydrogen formed under the same conditions, and there is a tendency to be easily retained in the electrode. Therefore, it can be inferred that, especially on the anode side where oxygen is generated, it is easy to obtain the gas extrusion effect and gas retention suppression effect brought about by the liquid flow of the alkaline aqueous solution.

[0066] exist Figure 1In the embodiment, the second alkaline aqueous solution supply flow channel 3A and the second alkaline aqueous solution recovery flow channel 3B are provided in the second bipolar plate 4B, but as long as the alkaline aqueous solution can pass through the interior of the second electrode 22, the positions of the second alkaline aqueous solution supply flow channel 3A and the second alkaline aqueous solution recovery flow channel 3B are not particularly limited. For example, the second alkaline aqueous solution supply flow channel 3A and the second alkaline aqueous solution recovery flow channel 3B may also be provided in the gasket 7.

[0067] A known material can be used for the diaphragm 13. The material of the diaphragm 13 is not particularly limited as long as it has wettability, ion permeability, alkali resistance, non-conductivity, non-air permeability, thermal stability, etc. Examples of the material of the diaphragm 13 include fluororesin impregnated with potassium titanate, polyantimonic acid, polysulfone, hydrophilized polyphenylene sulfide, polyvinylidene fluoride, polytetrafluoroethylene, and Zirfon Perl UTP 500 of AGFA.

[0068] The first electrode 21 is composed of a first metal porous body having a three-dimensional network structure. In this embodiment, the "three-dimensional network structure" refers to a structure in which the solid components (such as metal, etc.) constituting the first metal porous body are extended in a three-dimensional network. Since the first metal porous body has such a three-dimensional network structure, it has interconnecting holes. Therefore, the alkaline aqueous solution can pass through the first electrode 21 composed of the first metal porous body through the interconnecting holes.

[0069] The first metal porous body can be composed of the following structure: a skeleton, which is composed of a metal or alloy having a three-dimensional network structure; and a coating layer, which includes a metal disposed on the skeleton. As metals or alloys constituting the skeleton, for example: metal single substances such as nickel (Ni), iron (Fe), titanium (Ti), chromium (Cr) and cobalt (Co); alloys of these metals; and various stainless steels. In particular, nickel having a wide stable potential range in alkali is preferred. As materials for the coating layer, for example: metal single substances such as nickel (Ni), iron (Fe), titanium (Ti), chromium (Cr) and cobalt (Co); alloys of these metals; and various stainless steels.

[0070] Preferably, in the first spectrum of the first electrode 21 at a flow rate of 1 m / min and the second spectrum at a flow rate of 10 m / min, the first spectrum has a maximum peak in a frequency range of 0.2 Hz to 10 Hz, in the first spectrum, the frequency at the amplitude P1 of the maximum peak is F1, and the ratio P2 / P1 of the amplitude P2 of the second spectrum at the frequency F1 to the amplitude P1 is 0.5 or less, and the first spectrum at the flow rate of 1 m / min and the second spectrum at the flow rate of 10 m / min are as follows: the third main surface 21a is made into a 1 cm × 1 cm square, and constant current electrolysis is performed for 100 seconds at a current of 1.5 A under the conditions of a gas pressure of 0.1 MPa and a flow rate of a potassium hydroxide aqueous solution of 1 m / min or 10 m / min, to obtain potential oscillation data every 1 ms, and the data obtained by multiplying the potential oscillation data by a window function is Fourier transformed, and the result of the Fourier transform is shown in a coordinate system with the X-axis as the frequency and the Y-axis as the amplitude. For this structure, use Figure 2 to Figure 4 Provide specific instructions.

[0071] Figure 2 Schematic diagram of the potential oscillation data measuring device. The potential oscillation data measuring device includes: an alkaline electrolytic water tank 40; a pressure vessel 9; and circulation paths 10A, 10B, 10C, and 10D for circulating alkaline water between the alkaline electrolytic water tank 40 and the pressure vessel 9.

[0072] The alkaline electrolytic water tank 40 includes: a diaphragm 13; a cathode 31, which is provided on one main surface of the diaphragm 13; an anode 32, which is provided on the main surface of the diaphragm 13 opposite to the main surface on which the cathode 31 is provided; and a cathode side current collecting member 6A and an anode side current collecting member 6B, which are respectively provided on the main surface side of the cathode 31 and the anode 32 opposite to the diaphragm 13. When obtaining the potential oscillation data described later, the first electrode of the measurement object is used as the anode 32 and the cathode 31. The anode side current collecting member 6B and the cathode side current collecting member 6A are respectively pressed toward the diaphragm 13 side at a pressure of 0.6 MPa, and a zero-pole gap structure is formed in which the diaphragm 13 is respectively in contact with the anode 32 and the cathode 31. In addition, the main surfaces of the anode 32 and the anode side current collecting member 6B are in contact with each other, and the main surfaces of the cathode 31 and the cathode side current collecting member 6A are in contact with each other. The diaphragm 13 is held by a gasket 7.

[0073] A resin flow channel frame 8 is provided around each of the anode side current collecting member 6B and the cathode side current collecting member 6A. The flow channel frame 8 is provided with: an alkaline aqueous solution supply flow channel 2C, which supplies the alkaline aqueous solution stored in the water tank in the pressure vessel 9 to the cathode 31 or the anode 32; and an alkaline aqueous solution recovery flow channel 3C, which recovers the gas (oxygen or hydrogen) and the alkaline aqueous solution generated at the anode 32 or the cathode 31. A through flow channel 7A connecting the diaphragm surface and the flow channel frame 8 is formed in the gasket 7 on the anode 32 side and the alkaline aqueous solution recovery flow channel 3C side, and an internal space 8A connected to the through flow channel is formed in the flow channel frame 8. A reference electrode 5 is inserted into the internal space 8A. The alkaline aqueous solution is filled in the internal space 8A through the diaphragm 13. When obtaining the potential oscillation data described later, the potential between the reference electrode 5 and the anode side current collecting member 6B is measured.

[0074] The material of the current collecting member is not particularly limited as long as it is an alkali-resistant conductive material. For example, nickel can be used. The material of the flow channel frame 8 is not particularly limited as long as it is an alkali-resistant insulating material. For example, polypropylene and polyetheretherketone (PEEK) can be used. The alkaline aqueous solution uses a 30°C potassium hydroxide aqueous solution (concentration 7 mol / L). The reference electrode uses an Ag / AgCl reference electrode (RE-11A manufactured by EC Frontier, the internal solution is saturated KCL).

[0075] A water tank is provided inside the pressure container 9, and an alkaline aqueous solution 30 is stored in the water tank. The alkaline aqueous solution 30 in the water tank is pumped by pumps (not shown) provided in the first circulation path 10A and the second circulation path 10B, respectively, and supplied to the alkaline electrolytic water tank 40 via the first circulation path 10A and the second circulation path 10B. By adjusting the output of the pump, the flow rate of the alkaline aqueous solution supplied to the alkaline electrolytic water tank 40 can be adjusted.

[0076] The alkaline aqueous solution recovered from the alkaline electrolytic water tank 40 is returned to the water tank via the third circulation path 10C and the fourth circulation path 10D. A nitrogen injection port and a valve 33 are provided in the pressure container 9 to adjust the gas pressure in the pressure container 9. When obtaining the potential oscillation data described later, the gas pressure in the pressure container 9 is maintained at 0.1 MPa.

[0077] The first electrode is cut in such a way that the third principal surface 21a becomes a square of 1 cm×1 cm to obtain a measurement sample. Two measurement samples are prepared. When the size of the third principal surface of the first electrode is smaller than the square of 1 cm×1 cm, a plurality of first electrodes are arranged in a continuous manner on the third principal surface to ensure a size of 1 cm×1 cm. The size of the fourth principal surface 21b is also preliminarily unified to the same size as the third principal surface. The thickness of the third principal surface of the measurement sample in the normal direction is not particularly limited and can be set, for example, to 0.3 mm to 2.2 mm. The measurement sample is arranged at Figure 2 At this time, the third main surface is in contact with the separator 13, and the fourth main surface 21b is in contact with the current collecting member.

[0078] While the gas pressure in the pressure vessel 9 is maintained at 0.1 MPa, the flow rate of the potassium hydroxide aqueous solution is maintained at 1 m / min or 10 m / min by a pump, and constant current electrolysis is performed for 100 seconds at a current of 1.5 A to obtain potential oscillation data every 1 ms. The flow rate is calculated by dividing the flow rate by the cross-sectional area of ​​the electrode (width 1 cm × thickness in the normal direction of the third main surface). Here, the cross-sectional area of ​​the electrode refers to the cross-sectional area obtained by cutting the electrode with a plane including the normal direction of the third main surface. The cross-sectional area is equivalent to the cross-sectional area obtained by cutting the electrode with a plane having the liquid flow of the alkaline aqueous solution as the normal line. The flow rate is adjusted by controlling the flow rate. The position for measuring the flow rate is the first circulation path 10A. Figure 3 This is an example of a graph showing potential oscillation data obtained by subjecting the first electrode of Embodiment 1 to constant current electrolysis under the above-mentioned conditions. The first electrode is composed of a metal porous body having a three-dimensional network structure made of nickel, and has an average pore diameter of 0.45 nm.

[0079] exist Figure 3 In the graph, the X-axis represents the time t (unit: second (s)) from the start of constant current electrolysis, and the Y-axis E / Vvs.SSCE represents the potential of the reference electrode SSCE (Ag / AgCl reference electrode). Figure 3 In the graph of FIG. 1 , for reference, except for the flow rate of the potassium hydroxide aqueous solution shown in FIG. 1 , the flow rate of the potassium hydroxide aqueous solution is 1 m / min (in Figure 3 In the case of 1m / min) and the flow rate is 10m / min (in Figure 3 In addition to the data for the case where the flow rate is 2 m / min (in Figure 3 In the case of flow rate 5m / min (in Figure 3 In the case of 5m / min). Figure 3 It was confirmed that the behavior of the potential change greatly differed depending on the flow rate of the potassium hydroxide aqueous solution.

[0080] Next, the data obtained by multiplying the potential oscillation data obtained at the flow velocity of 1 m / min and the flow velocity of 10 m / min by the window function are subjected to Fourier transformation, and the result of the Fourier transformation is shown in a coordinate system with the X axis as the frequency and the Y axis as the amplitude. Thus, the first spectrum at the flow velocity of 1 m / min and the second spectrum at the flow velocity of 10 m / min are obtained. Here, the window function uses the Hanning window represented by the following formula.

[0081]

[0082] In this analysis, n=t, N=100 (for 100 seconds of data) with respect to time t(s).

[0083] Figure 4 Yes Figure 3 The data obtained by multiplying the potential oscillation data at the flow rate of 1 m / min and the flow rate of 10 m / min by the window function are Fourier transformed, and the results of the above Fourier transform are shown in a graph with the X-axis as the frequency (unit: Hz) and the Y-axis as the amplitude (unit: mV). Figure 4 As a reference, except for the first spectrum at a flow rate of 1 m / min (in Figure 4 , represented by 1 m / min) and the second spectrum at a flow rate of 10 m / min (in Figure 4 In addition to the spectrum at a flow rate of 2 m / min (in Figure 4 , represented by 2m / min) and the spectrum at a flow rate of 5m / min (in Figure 4 , represented by 5m / min). Figure 4 It was confirmed that when the flow rate of the potassium hydroxide aqueous solution increased, the amplitude decreased, the peak became broader, and the peak shifted to the high-frequency side.

[0084] If the gas generated at the electrode is retained in the electrode, the electrolysis voltage rises due to the gas resistance. If the gas is separated from the electrode, the gas resistance disappears, so the electrolysis voltage decreases. The longer the gas is retained in the electrode, the greater the increase in the electrolysis voltage becomes, and the greater the decrease in the electrolysis voltage when the gas is separated becomes. In this case, Figure 4 On the other hand, the shorter the gas residence time in the electrode, the smaller the rise in electrolysis voltage becomes, and the smaller the drop in electrolysis voltage when the gas is released becomes. In this case, Figure 4 The amplitude of the spectrum shown becomes smaller. Figure 4 In the spectrum shown, the greater the flow rate of the potassium hydroxide aqueous solution, the smaller the amplitude. This means that the greater the flow rate of the potassium hydroxide aqueous solution, the longer the gas stays in the electrode, and the gas is more quickly released from the electrode in the form of small bubbles.

[0085] The first spectrum preferably has a maximum peak P1 in a frequency range of 0.2 Hz to 10 Hz. The first spectrum has a maximum peak in a frequency range of 0.2 Hz to 10 Hz, which means that the specific surface area of ​​the porous metal body with a three-dimensional network structure constituting the first electrode is large and it is difficult for the gas to escape. In the first spectrum, the frequency range of the maximum peak is preferably 0.2 Hz to 10 Hz, more preferably 0.3 Hz to 8 Hz, and further preferably 0.4 Hz to 6 Hz. The maximum peak P1 is, for example, preferably 0.2 mV to 5 mV, more preferably 0.3 mV to 4 mV, and further preferably 0.4 mV to 3 mV.

[0086] In the first spectrum, the frequency at the amplitude P1 of the maximum peak is F1, and the ratio P2 / P1 of the amplitude P2 of the second spectrum at the frequency F1 relative to the amplitude P1 is preferably 0.5 or less. P2 / P1 being 0.5 or less means that by increasing the flow rate of the potassium hydroxide aqueous solution flowing through the first electrode, the residence time of the gas in the first electrode becomes shorter, and the electrolysis voltage can be reduced. From the viewpoint of being able to reduce the residence time of the gas in the first electrode and reducing the electrolysis voltage, the upper limit of P2 / P1 is preferably 0.5 or less, more preferably 0.4 or less, and further preferably 0.35 or less. The lower limit of P2 / P1 is not particularly limited, for example, it can be set to more than 0.05. P2 / P1 is preferably 0.05 or more and 0.5 or less, more preferably 0.05 or more and 0.4 or less, and further preferably 0.05 or more and 0.35 or less.

[0087] The second electrode 22 is composed of a second metal porous body having a three-dimensional network structure. The second metal porous body can adopt the structure described in the first metal porous body. The first metal porous body and the second metal porous body can be the same or different.

[0088] Preferably, in the third spectrum of the second electrode at a flow rate of 1 m / min and the fourth spectrum at a flow rate of 10 m / min, the third spectrum has a maximum peak in a frequency range of 0.2 Hz to 10 Hz, in the third spectrum, the frequency at the amplitude P3 of the maximum peak is F3, and the ratio P4 / P3 of the amplitude P4 of the fourth spectrum at the frequency F3 to the amplitude P3 is 0.5 or less, and the third spectrum at the flow rate of 1 m / min and the fourth spectrum at the flow rate of 10 m / min are: the sixth main surface is made into a square of 1 cm×1 cm, and constant current electrolysis is performed for 100 seconds at a current of 1.5 A under the conditions of a gas pressure of 0.1 MPa and a flow rate of the potassium hydroxide aqueous solution of 1 m / min or 10 m / min to obtain potential oscillation data every 1 ms, and the data obtained by multiplying the potential oscillation data by a window function are Fourier transformed, and the result of the Fourier transform is shown in a coordinate system with the X-axis as the frequency and the Y-axis as the amplitude. The second electrode has a large specific surface area, and by increasing the flow rate of the potassium hydroxide aqueous solution flowing through the second electrode, the residence time of the gas in the second electrode can be shortened, thereby reducing the electrolysis voltage.

[0089] The third spectrum and the fourth spectrum can be obtained using the same measuring device as the first spectrum and the second spectrum of the first electrode, with the second electrode as the measuring object, and under the same measuring conditions.

[0090] The first porous metal body and the second porous metal body (hereinafter, the first porous metal body and the second porous metal body are also collectively referred to as “porous metal bodies”) can be produced by, for example, the following method.

[0091] First, a resin molded body having a three-dimensional network structure (hereinafter, also referred to as "resin molded body") is prepared. As the resin molded body, polyurethane resin, melamine resin, etc. can be used. Next, a conductive layer is formed on the surface of the resin molded body. For example, a conductive coating containing conductive particles such as carbon and conductive ceramics is applied, or a layer based on conductive metals such as nickel and copper is formed by chemical plating, or a layer based on conductive metals is formed by evaporation or sputtering. Next, the resin molded body with a conductive layer formed on the surface is used as a substrate, and a metal layer is formed on the substrate by electroplating. The electroplating method can be performed by a known method.

[0092] Next, the resin molded body used as a substrate is removed by heat treatment or the like. Thus, a skeleton having a three-dimensional network structure can be obtained. The average pore size of the skeleton is approximately equal to the average pore size of the resin molded body used as a substrate. Therefore, the average pore size of the resin molded body can be appropriately selected according to the average pore size of the skeleton as a manufacturing target. The porosity of the skeleton is determined by the final amount of metal, so the amount of metal attached by plating or the like can be appropriately selected according to the porosity of the skeleton as a manufacturing target. The porosity and average pore size of the resin molded body are defined in the same manner as the porosity and average pore size of the above-mentioned metal porous body.

[0093] Next, a coating layer is formed on the skeleton to obtain a porous metal body. As long as the coating layer can be uniformly formed on the skeleton, the method for forming the coating layer is not particularly limited. For example, the coating layer can be formed by a plating method. As the plating method, an electroplating method is preferred. The electroplating method can be performed by a known method.

[0094] From the viewpoint of the ease of gas separation and the ease of flow of the alkaline aqueous solution, the lower limit of the porosity of the first metal porous body and the second metal porous body is preferably 70% or more, more preferably 80% or more, and more preferably 85% or more. From the viewpoint of strength, the upper limit of the porosity of the first metal porous body and the second metal porous body is preferably 99.5% or less, more preferably 99.2% or less, and more preferably 99% or less. The porosity of the first metal porous body and the second metal porous body is preferably 70% or more and 99.5% or less, more preferably 80% or more and 99.2% or less, and more preferably 85% or more and 99% or less.

[0095] The porosity of the above-mentioned porous metal body is defined by the following formula.

[0096]

[0097] Mp: Mass of the porous metal [g]

[0098] Vp: Volume of the external shape of the metal porous body [cm 3 ]

[0099] dp: Density of the metal constituting the porous metal [g / cm 3 ]

[0100] From the perspective of the ease of flow of the alkaline aqueous solution, the lower limit of the average pore size of the first metal porous body and the second metal porous body is preferably 100 μm or more, more preferably 200 μm or more, and further preferably 300 μm or more. From the perspective of increasing the specific surface area, the upper limit of the average pore size of the first metal porous body and the second metal porous body is preferably 2000 μm or less, more preferably 1500 μm or less, and further preferably 1000 μm or less. The average pore size of the first metal porous body and the second metal porous body is preferably 100 μm or more and 2000 μm or less, more preferably 200 μm or more and 1500 μm or less, and further preferably 300 μm or more and 1000 μm or less.

[0101] The average pore size of the porous metal body refers to the value calculated by the following formula by observing the surface of the porous metal body in at least 10 viewing fields using a microscope or the like and finding the average number (nc) of cells per 1 inch (25.4 mm = 25400 μm).

[0102]

[0103] The area S1 of the third main surface 21a of the first electrode 21 is preferably 25% or more of the area S2 of the region surrounded by the outer edge of the spacer 7. This can increase the amount of hydrogen generation while minimizing the size of the alkaline water electrolysis device.

[0104] use Figure 5 The area S1 and the area S2 in the present invention will be described. Figure 5 It is cut by VV line Figure 1 A cross-sectional view of the side of the first electrode 21 obtained by the alkaline water electrolysis device shown in FIG. In the present invention, area S1 refers to the area of ​​the region surrounded by the outer edge 21A of the third main surface 21a. Since the first electrode 21 is composed of a metal porous body having a three-dimensional network structure, the third main surface 21a has a plurality of openings from a microscopic point of view. Area S1 is equivalent to the area of ​​the region including both the solid portion constituting the metal porous body and the openings defined by the solid portion. In the present invention, area S2 refers to the region surrounded by the outer edge 7B of the gasket 7 in the cross-section obtained by cutting the gasket 7 with a plane parallel to the third main surface 21a of the first electrode 21. Holes for setting the diaphragm 13 and the electrode are provided in the gasket 7. Area S2 is equivalent to the area of ​​the region including both the hole and the main body of the gasket 7 defining the hole.

[0105] The length L1 of the first electrode 21 along the direction of flow of the alkaline aqueous solution is preferably at least 25% of the length L2 of the gasket 7 along the direction of flow of the alkaline aqueous solution. This can increase the amount of hydrogen generated while minimizing the size of the alkaline water electrolysis device.

[0106] like Figure 5 As shown, in the present invention, the length L1 refers to the maximum length along the alkaline aqueous solution flow direction A1 in the third main surface 21a of the first electrode 21. In the present invention, the length L2 refers to the maximum value of the distance between two points where a straight line along the alkaline aqueous solution flow direction A1 is drawn in a cross section obtained by cutting the gasket 7 with a plane parallel to the third main surface 21a of the first electrode 21, and the straight line intersects the outer edge 7B of the gasket 7.

[0107] The above describes the relationship between the sizes of the first electrode 21 and the gasket 7, but the relationship between the sizes of the second electrode 22 and the gasket 7 can also be the same as the relationship between the sizes of the first electrode 21 and the gasket 7. That is, the area S3 of the sixth main surface 22a of the second electrode 22 is preferably 25% or more of the area S2 of the area surrounded by the outer edge of the gasket 7. The length L3 of the second electrode 22 along the direction of flow of the alkaline aqueous solution is preferably 25% or more of the length L2 of the gasket 7 along the direction of flow of the alkaline aqueous solution.

[0108] In the cross section obtained by cutting the gasket 7 with a plane parallel to the third main surface 21a of the first electrode 21, the length L2 of the gasket 7 along the alkaline aqueous solution flow direction A1 is preferably less than or equal to twice the length L3 of the gasket 7 in the direction perpendicular to the alkaline aqueous solution flow direction A1. Thus, while suppressing the pressure loss during liquid feeding, the gas extrusion effect of the entire electrode and the effect of suppressing gas retention in the electrode are improved.

[0109] like Figure 5 As shown, in the present invention, the length L2 refers to the maximum value of the distance between two points where a straight line along the flow direction of the alkaline aqueous solution is drawn in the cross section obtained by cutting the gasket 7 with a plane parallel to the third main surface 21a of the first electrode 21, and the outer edge 7B of the gasket 7 intersects. In the present invention, the length L3 refers to the maximum value of the distance between two points where a straight line perpendicular to the flow direction of the alkaline aqueous solution is drawn in the cross section obtained by cutting the gasket 7 with a plane parallel to the third main surface 21a of the first electrode 21, and the outer edge 7B of the gasket 7 intersects.

[0110] The first electrode 21 preferably has a pressure loss of 1 atm or less when water at 20°C is passed through the electrode at a flow rate of 3 m / s in the normal direction of the third main surface 21a of the electrode. As a result, the required capacity of the liquid delivery pump is reduced, and the equipment cost can be reduced. The pressure loss is measured as follows: an 80 mm square electrode sample is prepared, water is pumped in a manner that passes through the electrode sample in the normal direction of the third main surface 21a, the rear of the electrode sample is opened, and the pressure of the water before passing through the electrode sample is measured by a pressure sensor.

[0111] In embodiment 1, the fourth main surface 21b of the first electrode 21 is arranged in contact with the fifth main surface 4a of the bipolar plate, but the fourth main surface 21b of the first electrode 21 and the fifth main surface 4a of the bipolar plate can also be electrically connected via an elastomer. In this case, depending on the raw material and shape of the elastomer, the alkaline aqueous solution may pass through the elastomer. Therefore, in order to minimize the amount of alkaline aqueous solution passing through the elastomer and increase the amount of alkaline aqueous solution passing through the first electrode 21, the elastomer is preferably a raw material with a small thickness and through which the alkaline aqueous solution will not pass or is difficult to pass. As such a raw material, for example, Ni pad (Nimattress) can be cited. The thickness of the elastomer can be, for example, 0.5 mm to 2 mm.

[0112] The manner in which the alkaline water electrolysis device comprises an elastomer can be specified as follows:

[0113] An alkaline water electrolysis device, comprising:

[0114] A diaphragm comprising a first main surface and a second main surface opposite to the first main surface;

[0115] A first electrode including a third main surface and a fourth main surface opposite to the third main surface, wherein the third main surface is disposed opposite to the first main surface of the diaphragm;

[0116] A first bipolar plate comprising a fifth main surface, the fifth main surface being disposed opposite to the fourth main surface of the first electrode; and

[0117] an elastic body, which is disposed between the first electrode and the first bipolar plate and is in contact with the first electrode and the first bipolar plate, respectively;

[0118] The first electrode is composed of a first porous metal body having a three-dimensional network structure.

[0119] Example

[0120] This embodiment is specifically described by way of examples, but this embodiment is not limited to these examples.

[0121] [Example 1]

[0122] In Example 1, the Figure 1 As the first electrode 21 and the second electrode 22, an alkaline water electrolysis device having Figure 4 The first and second spectra shown in the figure are metal porous bodies with a three-dimensional network structure (material: nickel, average pore size: 0.45 nm, area of ​​the third main surface: 250 mm 2, thickness in the normal direction of the third main surface: 1 mm). The electrolysis voltage was evaluated using the alkaline water electrolysis device of Example 1. Specifically, a 7 mol / L KOH aqueous solution was supplied to the first electrode 21 and the second electrode 22 at a flow rate of 10 m / min, respectively, and electrolysis was performed at a liquid temperature of 30°C and a current value of 37.5 A, and the average voltage from 90 seconds to 100 seconds after the start of electrolysis was obtained. The result was 2.47 V.

[0123] [Comparative Example 1]

[0124] In Comparative Example 1, Figure 1 An alkaline water electrolysis device of the structure shown. As the first electrode 21 and the second electrode 22, a metal porous body having a three-dimensional network structure in which P2 / P1 is greater than 0.5 in the first spectrum and the second spectrum is used. The alkaline water electrolysis device of Comparative Example 1 is used to evaluate the electrolysis voltage. The specific method is the same as that of Example 1. The result is 2.68V.

[0125] Although the embodiments and examples of the present invention have been described above, it is intended from the outset that the configurations of the above-described embodiments and examples may be appropriately combined or variously modified.

[0126] The embodiments and examples disclosed this time should be considered in all respects as illustrative and non-restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0127] Description of Reference Numerals

[0128] 2A: first alkaline aqueous solution supply channel; 2B: first alkaline aqueous solution recovery channel; 2C: alkaline aqueous solution supply channel; 3A: second alkaline aqueous solution supply channel; 3B: second alkaline aqueous solution recovery channel; 3C: alkaline aqueous solution recovery channel; 4A: first bipolar plate; 4a: fifth main surface; 4B: second bipolar plate; 4b: eighth main surface; 5: reference electrode; 6A: cathode side current collecting member; 6B: anode side current collecting member; 7: gasket; 7A: through channel; 7B: outer edge of gasket; 8: channel frame; 8A: internal space; 9: Pressure vessel; 10A: first circulation path; 10B: second circulation path; 10C: third circulation path; 10D: fourth circulation path; 11: nitrogen injection port; 13: diaphragm; 13a: first main surface; 13b: second main surface; 18: power supply; 21: first electrode; 21a: third main surface; 21b: fourth main surface; 21A: outer edge of third main surface; 22: second electrode; 22a: sixth main surface; 22b: seventh main surface; 30: alkaline aqueous solution; 31: cathode; 32: anode; 33: valve; 40: alkaline electrolytic water tank.

Claims

1. An alkaline water electrolysis device, comprising: a diaphragm comprising a first major surface and a second major surface opposite to the first major surface; a first electrode including a third main surface and a fourth main surface opposite to the third main surface, wherein the third main surface is disposed opposite to the first main surface of the diaphragm; and A first bipolar plate includes a fifth main surface, wherein the fifth main surface is disposed in contact with the fourth main surface of the first electrode, The first electrode is composed of a first metal porous body having a three-dimensional network structure.

2. The alkaline water electrolysis device according to claim 1, comprising: a second electrode including a sixth main surface and a seventh main surface opposite to the sixth main surface, wherein the sixth main surface is disposed opposite to the second main surface of the diaphragm; and a second bipolar plate comprising an eighth main surface, wherein the eighth main surface is disposed in contact with the seventh main surface of the second electrode, The second electrode is composed of a second metal porous body having a three-dimensional network structure.

3. The alkaline water electrolysis device according to claim 1 or 2, wherein: In the first spectrum of the first electrode at a flow rate of 1 m / min and the second spectrum at a flow rate of 10 m / min, The first spectrum has a maximum peak in a frequency range of 0.2 Hz to 10 Hz. In the first spectrum, the frequency at the amplitude P1 of the maximum peak is F1, The ratio P2 / P1 of the amplitude P2 of the second spectrum at the frequency F1 to the amplitude P1 is less than 0.5, The first spectrum at the flow rate of 1 m / min and the second spectrum at the flow rate of 10 m / min are as follows: the third main surface is made into a 1 cm×1 cm square, and constant current electrolysis is performed for 100 seconds at a current of 1.5 A under the conditions of an air pressure of 0.1 MPa and a flow rate of the potassium hydroxide aqueous solution of 1 m / min or 10 m / min to obtain potential oscillation data every 1 ms, and the data obtained by multiplying the potential oscillation data by a window function is Fourier transformed, and the results of the Fourier transform are shown in a coordinate system with the X-axis as the frequency and the Y-axis as the amplitude.

4. The alkaline water electrolysis device according to claim 2, wherein: In the third spectrum of the second electrode at a flow rate of 1 m / min and the fourth spectrum at a flow rate of 10 m / min, The third spectrum has a maximum peak in a frequency range of 0.2 Hz to 10 Hz. In the third spectrum, the frequency at the amplitude P3 of the maximum peak is F3, The ratio P4 / P3 of the amplitude P4 of the fourth spectrum at the frequency F3 to the amplitude P3 is less than 0.5, The third spectrum at the flow rate of 1 m / min and the fourth spectrum at the flow rate of 10 m / min are as follows: the sixth main surface is made into a 1 cm×1 cm square, and constant current electrolysis is performed for 100 seconds at a current of 1.5 A under the conditions of an air pressure of 0.1 MPa and a flow rate of the potassium hydroxide aqueous solution of 1 m / min or 10 m / min to obtain potential oscillation data every 1 ms, and the data obtained by multiplying the potential oscillation data by a window function are Fourier transformed, and the results of the Fourier transform are shown in a coordinate system with the X-axis as the frequency and the Y-axis as the amplitude.

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