JP7629776B2 - Electrode, anode for water electrolysis, electrolysis cell, and method for producing hydrogen - Google Patents

Description

The present invention relates to an electrode, an anode for water electrolysis, a bipolar electrolysis cell using the anode for water electrolysis, and a method for producing hydrogen using the anode for water electrolysis.

In recent years, hydrogen produced using renewable energy has been attracting attention as a clean energy source to solve problems such as global warming caused by _CO2 and dwindling reserves of fossil fuels. Hydrogen production using renewable energy requires low costs comparable to those of conventional hydrogen production by reforming fossil fuels. Therefore, hydrogen production using renewable energy requires high levels of energy efficiency and inexpensive equipment that could not be achieved with conventional technologies.

One method of producing hydrogen that can meet the above requirements is the electrolytic decomposition of water (water electrolysis). For example, several ideas have been proposed to produce hydrogen through water electrolysis using power generated by natural energies such as wind or solar power, and then store or transport it.

In water electrolysis, oxygen is generated at the anode and hydrogen is generated at the cathode by passing an electric current through the water. The main cause of energy loss in electrolysis is the overvoltage of the anode and cathode. Reducing this overvoltage makes it possible to produce hydrogen efficiently. In particular, the overvoltage of the anode is higher than the overvoltage of the cathode, and research and development into reducing the overvoltage of the anode is being widely pursued.

Among oxides having a perovskite structure, materials with high oxygen generating capacity are known, and they have attracted attention as anode materials for water electrolysis (Non-Patent Document 1). In order to use an oxide having a perovskite structure as an anode for alkaline water electrolysis, there is a method of forming an oxide layer on the surface of a conductive substrate. For example, Patent Document 1 discloses a water electrolysis anode with low oxygen overvoltage and high durability by forming a metal oxide layer with a high content of perovskite oxide in the crystalline component on the surface of a nickel porous substrate, and a water electrolysis device using the anode.

International Publication No. 2018/155503

Science, 2011, 334, 1383

The anode described in Patent Document 1 exhibits high durability when electricity is applied for long periods of time, but it has been found that there is a problem in that overvoltage increases when the anode is immersed in an alkaline electrolyte at a particularly high temperature in a state where no electricity is applied.

The present invention has been made in consideration of these problems, and aims to provide an electrode with low oxygen generation overvoltage and high high-temperature alkaline durability, an anode for water electrolysis, a bipolar electrolysis cell using the anode for water electrolysis, and a method for producing hydrogen using the anode for water electrolysis.

The present inventors have conducted extensive research and experiments to solve the above problems, and as a result have found that an electrode having a LaNi _x M _y O _3-z layer having a specific composition and structure formed on a substrate has low oxygen overvoltage and high high-temperature alkaline durability and can be used as an anode for water electrolysis, thereby completing the present invention.

That is, the present invention is as follows.
[1] An electrode having LaNi _x M _y O _3-z (x+y is 0.8 or more and 1.2 or less, y is 0.001 or more and 0.6 or less, z is -0.5 or more and 0.5 or less, and M contains at least one of Nb, Ta, Sb, Ti, Mn, and Zr) on a substrate, the XRD main peak position 2θ of LaNi _x M _y O _3-z being 32.6° or more and 33.2° or less.
[2] The electrode according to [1], wherein y is 0.002 or more and less than 0.2.
[3] The electrode according to [1] or [2], wherein the XRD main peak position 2θ of LaNi _x M _y O _3-z is 32.7° or more and 33.2° or less.
[4] The electrode according to any one of [1] to [3], wherein M is Nb.
[5] The electrode according to any one of [1] to [4], wherein the XRD main peak half width of LaNi _x M _y O _3-z is 0.6° or more and 0.85° or less.
[6] The electrode according to any one of [1] to [5], wherein the XRD main peak intensity of LaNi _x M _y O _3-z is 6,000 or more and 100,000 or less.
[7] An electrolytic cell comprising the electrode according to any one of [1] to [6] as an anode.
[8] A method for producing hydrogen by electrolyzing alkali-containing water in an electrolytic cell to produce hydrogen, the electrolytic cell comprising at least an anode and a cathode, the anode having LaNi _x M _y O _3-z (x+y is 0.8 or more and 1.2 or less, y is 0.001 or more and 0.6 or less, z is -0.5 or more and 0.5 or less, M is at least one of Nb, Ta, Sb, Ti, Mn and Zr) on a substrate, and the XRD main peak position 2θ of LaNi _x M _y O _3-z is 32.6° or more and 33.2° or less.

The present invention provides an inexpensive electrode that has low oxygen overvoltage and excellent durability against high-temperature alkali, a water electrolysis anode, and a water electrolysis cell equipped with this water electrolysis anode.

FIG. 1 is a side view showing an example of an entire electrolytic cell including an electrolytic cell having the electrode of the present embodiment as an anode. FIG. 2 is a diagram showing a cross section of the inside of an electrolytic cell of an electrolytic cell including the electrode of the present embodiment as an anode, the electrolytic cell being surrounded by a dashed rectangular frame in FIG. 1 . FIG. 1 is a diagram showing an outline of an electrolysis device used in Examples and Comparative Examples. FIG. 1 is a diagram showing an outline of a bipolar electrolytic cell used in an electrolysis test.

The following describes in detail the form for carrying out the present invention (hereinafter, referred to as the "present embodiment"). Note that the following present embodiment is an example for explaining the present invention, and is not intended to limit the present invention. Furthermore, the present invention can be modified in various ways without departing from the gist of the invention.

(electrode)
In this embodiment, the electrode has at least a substrate.
The substrate is preferably conductive. Examples of the conductive substrate include nickel, materials containing nickel as a main component, titanium, glassy carbon (GC), tantalum, zirconium, gold, platinum, and palladium. Examples of materials containing nickel as a main component include nickel-based alloys such as Monel, Inconel, and Hastelloy.
From the viewpoint of heat resistance in the firing step during electrode preparation, the material of the substrate is preferably a metal, and further preferably nickel or a material mainly composed of nickel, which is a metal that is not dissolved even at the oxygen generating potential in an alkaline aqueous solution and is available at a lower cost than precious metals, from the viewpoints of durability, electrical conductivity, and economy.
The shape of the conductive substrate of the electrode may be flat, or may be a porous body having a plate shape with many holes. Specific shapes of the porous body include expanded metal, punched metal, plain weave mesh, foam metal, or shapes similar thereto. Among these, expanded metal is preferred, and the dimensions are not particularly limited, but in order to achieve both an increase in the amount of gas generated due to an increase in the electrolysis surface area and efficient removal of the gas generated by electrolysis from the electrode surface, and from the viewpoint of mechanical strength, the center-to-center distance (SW) in the short direction of the mesh is preferably 2 mm or more and 5 mm or less, the center-to-center distance (LW) in the long direction of the mesh is preferably 3 mm or more and 10 mm or less, the thickness is preferably 0.2 mm or more and 2 mm or less, and the aperture ratio is preferably 20% or more and 80% or less. More preferably, SW is 3 mm or more and 4 mm or less, LW is 4 mm or more and 6 mm or less, the thickness is 0.8 mm or more and 1.5 mm or less, and the aperture ratio is 40% or more and 60% or less.

A second feature of this embodiment is that it has LaNi _x M _y O _3-z (x+y is 0.8 or more and 1.2 or less, y is 0.001 or more and 0.6 or less, z is −0.5 or more and 0.5 or less, and M includes at least one of Nb, Ta, Sb, Ti, Mn, and Zr).
In this embodiment, as a metal oxide having a perovskite structure, high oxygen generating ability can be realized by disposing Ni at least in a part of the B site. Furthermore, disposing element M at the B site together with Ni is one of the requirements for imparting durability to high-temperature alkali. Element M includes at least one of Nb, Ta, Sb, Ti, Mn, and Zr. M may include two or more of Nb, Ta, Sb, Ti, Mn, and Zr. As M, from the viewpoint of being able to impart durability to high-temperature alkali with a small amount of addition, Nb, Ta, Sb, Ti, and Zr are preferred, and from the viewpoint of excellent durability to high-temperature alkali, Ta, Sb, and Ti are more preferred, and from the viewpoint of being able to achieve both durability to high-temperature alkali and overvoltage with a small amount of addition, Nb is the most preferred.
From the viewpoint of high-temperature alkali resistance, x+y is 0.8 or more and 1.2 or less. From the viewpoint of achieving both high-temperature alkali resistance and overvoltage, x+y is preferably 0.8 or more and 1.05 or less, and more preferably 1.0 or more and 1.05 or less.
From the viewpoint of high-temperature alkali resistance, y is 0.001 or more and 0.6 or less. From the viewpoint of achieving both high-temperature alkali resistance and overvoltage, y is preferably 0.002 or more and less than 0.2, and more preferably 0.005 or more and 0.1 or less.
z is -0.5 or more and 0.5 or less. In the present invention, z is determined from the composition ratio 3-z of O calculated by assuming La to be trivalent, Ni to be trivalent, Nb to be pentavalent, Ta to be pentavalent, Sb to be pentavalent, Ti to be tetravalent, Mn to be trivalent, Zr to be tetravalent, and O to be -2 valent, so that the valence balance of the composition formula is matched. For example, in the composition formula LaNi _{x ZryO3 -z} , if x = 0.9 and y = 0.1, z = -0.05 is determined from the relational formula 3-z = (3 + 3 x 0.9 + 4 x 0.1) / 2.
The presence of LaNi _x M _y O _3-z (x+y is 0.8 or more and 1.2 or less, y is 0.001 or more and 0.6 or less, z is −0.5 or more and 0.5 or less, and M includes at least one of Nb, Ta, Sb, Ti, Mn, and Zr) on the substrate can be confirmed by a known method such as a method of peeling off a metal oxide layer on the substrate and dissolving it in an acid such as aqua regia, and performing a composition analysis by ICP-AES (inductively coupled plasma atomic emission spectroscopy), a method of peeling off a metal oxide layer on the substrate and performing a composition analysis by an X-ray fluorescence analyzer, or SEM-EDX analysis of the cross section of the electrode.

A third feature of this embodiment is that the XRD main peak position 2θ of LaNi _x M _y O _3-z is 32.6° or more and 33.2° or less.
In this embodiment, the XRD main peak position of LaNi _x M _y O _3-z shifts depending on the electrode, but when Cu Kα1 ray is used as the X-ray source and XRD (X-ray diffraction) of the electrode is measured, the peak in the vicinity of 2θ = 32.5° to 33.2° is determined to be the main peak position of LaNi _x M _y O _3-z , referring to the (104) plane main peak position 2θ = 33.166° of LaNiO ₃ on the PDF01-070-5757 card.
The main peak position of LaNi _x M _y O _3-z is calculated after shift-correcting the XRD spectrum using the "X-axis offset" tool so that the main peak position 2θ of NiO near 2θ = 43.276° becomes 2θ = 43.276° of the (200) plane of NiO in the PDF00-047-1049 card data.
The XRD main peak position 2θ of LaNi _x M _y O _3-z is 32.6° or more and 33.2° or less from the viewpoint of high temperature alkali resistance.

The present inventors have surprisingly found that LaNi _x M _y O _3-z , which is prepared by substituting a predetermined amount of Ni in LaNiO ₃ with element M or adding a predetermined amount of element M to LaNiO ₃ and controlling the _XRD main peak position 2θ to be 32.6° or more and _33.2 °, exhibits high durability to high-temperature alkali. The reason for this is unclear, but it is believed that by adjusting the _XRD main peak position 2θ of LaNi _x M _y O _3-z to be 32.6° or more and 33.2°, the concentration of oxygen defects that become reaction points between high-temperature alkali and LaNi _x M _y O _3-z is reduced, and by adding element M, the generation of oxygen defects in LaNi _x M _y O _3-z in high-temperature alkali is suppressed.

From the viewpoint of excellent durability to high-temperature alkali, it is preferably 32.7° or more and 33.2° or less, and from the viewpoint of achieving both durability to high-temperature alkali and overvoltage, it is more preferably 32.75° or more and 33.2° or less, and most preferably 32.8° or more and 33.2° or less.

In this embodiment, the XRD main peak half width of LaNi _x M _y O _3-z is preferably 0.6° or more and 0.85° or less from the viewpoint of durability to high-temperature alkali. The main peak half width refers to the half width calculated with a peak in the range of 2θ of 31° or more and 35° or less.
The XRD main peak half width of LaNi _x M _y O _3-z is more preferably 0.6° or more and 0.8° or less, and from the viewpoint of achieving both high-temperature alkali durability and overvoltage, is further preferably 0.6° or more and 0.75° or less.

In this embodiment, the XRD main peak intensity of LaNi _x M _y O _3-z is preferably 6,000 or more and 100,000 or less from the viewpoint of durability against high-temperature alkali. The main peak intensity refers to the intensity obtained by subtracting the baseline intensity from the measured intensity (Counts) at the peak position of the main peak measured using an XRD measurement device D8 ADVANCE (sold by Bruker Japan Co., Ltd.). The measurement conditions will be described later in the examples.
The XRD main peak intensity of LaNi _x M _y O _3-z is more preferably 6,500 or more and 5,0000 or less, further preferably 7,000 or more and 20,000 or less, and from the viewpoint of achieving both high-temperature alkali durability and overvoltage, it is most preferably 7,000 or more and 17,000 or less.

The electrode of this embodiment can be put to practical use as an anode for water electrolysis, and it is possible to provide an electrolysis cell for water electrolysis using the electrode of this embodiment as the anode, and a method for producing hydrogen using the anode for water electrolysis. Water containing an alkali may be used for water electrolysis.

(Preparation of Electrodes)
The electrode of this embodiment can be prepared by applying an aqueous solution (coating liquid) containing metal salts of La, Ni, and M to a substrate, drying and pre-firing the resulting solution, forming a predetermined weight of LaNi _x M _y O _3-z precursor on the substrate, and then firing the resulting precursor.

The metal salt may be a water-soluble salt such as a nitrate, oxynitrate, chloride, oxalate, tartrate, acetate, sulfate, etc. The metal salt may be either anhydrous or hydrated.
For La, Ni, and M, a water-dispersible sol of an oxide or hydroxide may be used instead of a metal salt.
When Nb is used as M, it is preferable to use niobium oxalate or ammonium niobium oxalate from the viewpoint of solubility. When Sb is used as M, it is preferable to use antimony tartrate.
It is preferable to add an organic ligand, such as an amino acid such as glycine, or a carboxylic acid such as oxalic acid or tartaric acid, to the coating liquid from the viewpoint of facilitating the preparation of LaNi _x M _y O _3-z , which has high resistance to high-temperature alkali.
In particular, when a coating solution in which glycine and a metal nitrate are dissolved is used, it becomes easy to prepare an electrode that has both high durability against high-temperature alkali and an overvoltage, and therefore glycine is a preferred organic ligand.

The concentration of the aqueous solution containing metal salts of La, Ni, and M is preferably 0.1 mol/kg or more and 4 mol/kg or less in terms of weight molar concentration based on LaNi _x M _y O _3-z. At 0.1 mol/kg or more, an electrode can be prepared with a small number of coatings. At 4 mol/kg or less, dissolution of metal salts and organic ligands becomes easy, which is preferable from the viewpoint of productivity of the coating solution. More preferably, it is 0.2 mol/kg or more and 2.0 mol/kg or less, and even more preferably, it is 0.2 mol/kg or more and 1.0 mol/kg or less.

The temperature at which the coating liquid is applied to the substrate and then dried is preferably 50° C. to 200° C. If the temperature is 50° C. or higher, the drying can be completed within 3 minutes to 1 hour, which is preferable from the viewpoint of productivity. If the temperature is 200° C. or lower, the cooling time of the substrate after drying can be shortened, which is preferable from the viewpoint of productivity.
The temperature for pre-baking the dried substrate is preferably 300° C. or higher and 500° C. or lower. If it is 300° C. or higher, the pre-baking is completed within 3 minutes to 1 hour, which is preferable from the viewpoint of productivity. If it is 500° C. or lower, the cooling time of the dried substrate is shortened, which is preferable from the viewpoint of productivity.

The coating, drying and calcination steps may be repeated to prepare an electrode having a desired amount of LaNi _x M _y O _3-z deposited thereon.

The temperature for the main firing can be from 500° C. to 1000° C., but firing at 800° C. or higher is preferred. When firing at 800° C. or higher, the XRD main peak position 2θ of LaNi _x M _y O _3-z can be controlled to 32.6° to 33.2° for a firing time of 10 minutes to 24 hours, making it possible to prepare an electrode that is highly durable against high-temperature alkali, which is preferred from the viewpoint of productivity.

The element M may be added by a method in which a coating liquid containing a water-dispersible sol of a metal salt, or an oxide or hydroxide of La or Ni is applied in advance, dried, and pre-baked, and then a coating liquid containing a water-dispersible sol of a metal salt, oxide, or hydroxide of element M is applied to the electrode in a topcoat manner, dried, pre-baked, and finally baked.
Alternatively, the element M may be added by a method in which a coating liquid containing a water-dispersible sol of a metal salt, oxide, or hydroxide of La or Ni is applied in advance, followed by drying, pre-baking, and main baking, and then a coating liquid containing a water-dispersible sol of a metal salt, oxide, or hydroxide of the element M is applied to the electrode in a topcoat manner, followed by drying, pre-baking, and main baking.

(Electrolytic cell)
FIG. 1 shows a side view of an example of an entire electrolytic cell including an electrolytic cell equipped with the electrode of this embodiment as an anode.
FIG. 2 shows a diagram of a zero gap structure of an example of an electrolytic cell including an electrolytic cell equipped with the electrode of this embodiment as an anode (a cross-sectional view of the part enclosed by the dashed square frame in FIG. 1).
In the bipolar electrolytic cell 50 (see FIG. 3) of this embodiment, the diaphragm 4 is in contact with the anode 2a and the cathode 2c to form a zero-gap structure Z (see FIG. 2).
The electrolysis apparatus used in the examples and comparative examples is shown in Fig. 3. The bipolar electrolytic cell used in the electrolysis tests is shown in Fig. 4.

(element)
As shown in FIG. 1, in a bipolar electrolytic cell 50, a bipolar element 60 is disposed between an anode terminal element 51 a and a cathode terminal element 51 c, and diaphragms 4 are disposed between the anode terminal element 51 a and the bipolar element 60, between adjacent bipolar elements 60, and between the bipolar element 60 and the cathode terminal element 51 c.
In this embodiment, in particular, the portion between the partition walls 1 between two adjacent bipolar elements 60 and the portion between the partition walls 1 between adjacent bipolar elements 60 and terminal elements in the bipolar electrolytic cell 50 are referred to as the electrolytic cell 65. The electrolytic cell 65 includes the partition wall 1, anode chamber 5a, anode 2a, and diaphragm 4 of one element, and the cathode 2c, cathode chamber 5c, and partition wall 1 of the other element.

(Electrode chamber)
2, in the bipolar electrolytic cell 50 of this embodiment, an electrode chamber 5 through which the electrolytic solution passes is defined by the partition wall 1, the outer frame 3, and the diaphragm 4. Here, the electrode chamber 5 on the anode side across the partition wall 1 is the anode chamber 5a, and the electrode chamber 5 on the cathode side is the cathode chamber 5c.
In this embodiment, the header pipe of the bipolar electrolytic cell may be of an internal header type or an external header type, and the space occupied by the anode and cathode themselves may be considered to be the space inside the electrode chamber. In particular, when a gas-liquid separation box is provided, the space occupied by the gas-liquid separation box may be considered to be the space inside the electrode chamber.

(rib)
In the bipolar electrolytic cell 65 for alkaline water electrolysis of this embodiment, the rib 6 is preferably physically connected to the electrode 2. With such a configuration, the rib 6 serves as a support for the electrode 2, making it easy to maintain the zero gap structure Z. In addition, the rib 6 is preferably electrically connected to the partition wall 1. Furthermore, the provision of the rib 6 can reduce convection that occurs in the electrode chamber 5 due to turbulence in the gas-liquid flow in the electrode chamber 5, thereby suppressing a local increase in the temperature of the electrolyte.
Here, an electrode may be provided on the rib, or a current collector, a conductive elastic body, and an electrode may be provided on the rib in this order.
In the above-described example of the bipolar electrolytic cell for alkaline water electrolysis, a structure is adopted in which the cathode rib-cathode current collector-conductive elastic body-cathode are stacked in this order in the cathode chamber, and a structure is adopted in which the anode rib-anode are stacked in this order in the anode chamber.
In the above-mentioned example of the bipolar electrolytic cell for alkaline water electrolysis, the above-mentioned "cathode rib-cathode current collector-conductive elastic body-cathode" structure is adopted in the cathode chamber, and the above-mentioned "anode rib-anode" structure is adopted in the anode chamber; however, the present invention is not limited to this structure, and the anode chamber may also have an "anode rib-anode current collector-conductive elastic body-anode" structure.
In detail, in the bipolar electrolytic cell for alkaline water electrolysis of the present embodiment, as shown in FIG. 2 , ribs 6 (anode rib, cathode rib) are preferably attached to the partition wall 1.
It is preferable that the ribs (anode ribs, cathode ribs) not only have a role of supporting the anode or cathode but also have a role of conducting current from the partition wall to the anode or cathode.
In the bipolar electrolytic cell for alkaline water electrolysis of the present embodiment, it is preferable that at least a part of the rib is conductive, and it is more preferable that the entire rib is conductive. With such a configuration, an increase in cell voltage due to electrode deflection can be suppressed.
The material of the rib is generally a conductive metal, such as nickel-plated mild steel, stainless steel, nickel, etc. The material of the rib is preferably the same as that of the partition wall, and most preferably nickel.
The distance between adjacent anode ribs or the distance between adjacent cathode ribs is determined taking into consideration the electrolysis pressure and the pressure difference between the anode chamber and the cathode chamber, etc.
If the interval between the anode ribs or the interval between the adjacent cathode ribs is too narrow, not only the flow of the electrolyte or gas is hindered, but also the cost is increased. If the rib pitch is 10 mm or more, gas escape to the back surface of the electrode is favorable. If the rib pitch is too wide, the electrodes (anode and cathode) held by a slight pressure difference between the anode chamber and the cathode chamber are deformed, and the number of anode ribs and cathode ribs is reduced, resulting in defects such as increased electrical resistance. If the rib pitch is 150 mm or less, the electrodes are less likely to bend. The number of ribs, the length of the rib, the angle between the rib and the partition wall, the number of through holes, and the interval (pitch) of the through holes in a given direction along the partition wall may be appropriately determined as long as the effects of the present invention are obtained. The ribs are preferably provided parallel to a given direction along the partition wall (for example, the vertical direction may be set, or the same direction as the direction of one of two pairs of opposing sides when the partition wall has a substantially rectangular shape in plan view as shown in FIG. 3). The rib pitch of the anode rib and the rib pitch of the cathode rib may be the same or different, and it is preferable that the rib pitch of the anode rib and the rib pitch of the cathode rib both satisfy the above range.
The anode ribs and cathode ribs are attached to the bulkhead by laser welding or the like.
The thickness of the rib may be from 0.5 mm to 5 mm, taking into consideration cost, ease of production, strength, etc., and is not particularly limited, with a thickness of from 1 mm to 2 mm being preferred.
The electrodes and current collectors are usually attached to the ribs by spot welding, but other methods such as laser welding may also be used, or they may be tied together with a wire or string-like member for close contact. The ribs are fixed to the partition wall by spot welding, laser welding, or other means, in the same manner as the anode and cathode.

(Method of producing hydrogen)
Next, a method for producing hydrogen by alkaline water electrolysis using the bipolar electrolytic cell of this embodiment will be described.
In this embodiment, hydrogen is produced at the cathode by applying a current to a bipolar electrolytic cell having an anode and a cathode as described above and circulating an electrolyte, thereby performing water electrolysis. In this case, for example, a variable power supply can be used as the power supply. A variable power supply is a power supply derived from a renewable energy power plant whose output fluctuates in units of a few seconds to a few minutes, unlike a power supply that provides a stable output, such as grid power. The method of generating renewable energy is not particularly limited, but examples include solar power generation and wind power generation.
For example, in the case of electrolysis using a bipolar electrolytic cell, the cationic electrolyte in the electrolytic solution moves from the anode chamber of an element through the diaphragm to the cathode chamber of an adjacent element, and the anionic electrolyte moves from the cathode chamber of an element through the diaphragm to the anode chamber of the adjacent element. Thus, the current during electrolysis flows in the direction in which the elements are connected in series. That is, the current flows from the anode chamber of one element to the cathode chamber of the adjacent element through the diaphragm. As a result of electrolysis, oxygen gas is produced in the anode chamber and hydrogen gas is produced in the cathode chamber.

The bipolar electrolytic cell 65 for alkaline water electrolysis of this embodiment can be used in the bipolar electrolytic cell 50, the electrolytic device 70 for alkaline water electrolysis, etc. Examples of the electrolytic device 70 for alkaline water electrolysis include a device including the bipolar electrolytic cell 50 of this embodiment, a liquid delivery pump 71 for circulating the electrolytic solution, a gas-liquid separation tank 72 for separating the electrolytic solution from hydrogen and/or oxygen, and a water supply device for supplying water consumed by electrolysis.
The alkaline water electrolysis apparatus may further include a rectifier 74, an oxygen concentration meter 75, a hydrogen concentration meter 76, a flow meter 77, a pressure meter 78, a heat exchanger 79, a pressure control valve 80, and the like.
In the alkaline water electrolysis method using the alkaline water electrolysis apparatus, the current density applied to the electrolytic cell is preferably 4 kA/m ² to 20 kA/m ² , and more preferably 6 kA/m ² to 15 kA/m ² .
In particular, when a variable power supply is used, it is preferable to set the upper limit of the current density within the above range.

The electrodes, electrolytic cells, and hydrogen production methods of the present invention have been illustrated and described above with reference to the drawings. However, the electrodes, electrolytic cells, and hydrogen production methods of the present invention are not limited to the above examples, and the above embodiments can be modified as appropriate.

Example 1
As a nickel porous substrate, a nickel expand metal having SW 3.0 mm, LW 4.5 mm, thickness 1.2 mm, and aperture ratio 54% was prepared. After blasting treatment was performed on this nickel expand metal, a substrate having a length of 10 cm and a width of 10 cm was cut out, which was then acid-treated in 6N hydrochloric acid at 50° C. for 6 hours, washed with water, and dried to obtain a substrate for coating.
Next, solutions A and B were prepared having the compositions of Example 1 in Table 1. Solution B was prepared by dissolving ammonium niobium oxalate in pure water, and the concentration of Nb was confirmed by ICP-AES (inductively coupled plasma atomic emission spectrometry).
Solution A was placed in a rectangular polyethylene container measuring 6 cm at the base and 10 cm at the height of 11 cm, and solution B was slowly mixed in while stirring with a magnetic stirrer to prepare the coating solution of Example 1.
While stirring the coating liquid, the substrate to be coated was held vertically and the lower half was immersed in the coating liquid, and then the substrate was turned upside down and the upper half was also immersed in the coating liquid. After the coating liquid was applied to the entire surface of the substrate, the substrate was kept vertically oriented and then subjected to an air blowing treatment with an air gun to blow off excess coating liquid.
Thereafter, the substrate was dried at 60° C. for 10 minutes and then baked at 400° C. for 10 minutes to form a metal oxide layer on the surface of the substrate.
This cycle of coating, drying and firing was repeated 13 times, and then firing was further performed at 800° C. for 1 hour to form a metal oxide layer with a deposition amount of 40 g/m ² on the coating substrate, thereby obtaining an anode for water electrolysis.

(Examples 2 to 6)
A substrate for application was prepared in the same manner as in Example 1. Liquids A and B having the compositions of Examples 2 to 6 in Table 1 were prepared. Liquids A and B were then mixed in a rectangular polyethylene container in the same manner as in Example 1 to prepare the coating solutions of Examples 2 to 6. Then, a cycle of application, drying, and firing was repeated in the same manner as in Example 1, and firing was performed at 800° C. for 1 hour to form a metal oxide layer with a deposition amount of 40 g/ ^m2 on the substrate for application, thereby obtaining water electrolysis anodes of Examples 2 to 6.

(Example 7)
9.30 g _of Ni( _NO3 ) _2.6H2O , 34.64 _g of La( _NO3 ) _3.6H2O , 30.03 g of glycine ( _{C2H5NO2 )} , and _13.78 g of Mn( _NO3 ) _2.6H2O were dissolved in 400 g of pure water to prepare a coating solution for Example 7. This coating solution was transferred to a polyethylene container having a base dimension of 13 cm x 13 cm and _a height of 10 cm.
A substrate for coating was prepared in the same manner as in Example 1. This substrate was completely immersed in the coating liquid in a container and then pulled out, the coating liquid was applied to the entire surface of the substrate, and the substrate was then turned vertically, and excess coating liquid was blown off by air blowing treatment using an air gun.
Thereafter, the substrate was dried at 60° C. for 10 minutes and then baked at 400° C. for 10 minutes to form a metal oxide layer on the surface of the substrate.
This cycle of coating, drying and firing was repeated 13 times, and then firing was further performed at 800° C. for 1 hour to form a metal oxide layer with a deposition amount of 40 g/m ² on the coating substrate, thereby obtaining an anode for water electrolysis.

(Example 8)
18.61 _g of Ni( _NO3 ) _2.6H2O , 34.64 _g of La( _NO3 ) _3.6H2O , and 27.63 g of glycine were dissolved in 200 g of pure water to obtain a solution A of Example 8. A _TiO2 sol having a primary particle size of 10 nm was diluted with pure water to prepare a _TiO2 sol having a Ti concentration of 80 mmol/kg sol, which was obtained as a solution B of Example 8.
Solutions A and B were mixed in a rectangular polyethylene container in the same manner as in Example 1 to prepare a coating solution for Example 8. After repeating a cycle of coating, drying, and baking in the same manner as in Example 1, baking was performed at 800° C. for 1 hour to form a metal oxide layer with a deposition amount of 40 g/ ^m2 on the coating substrate, thereby obtaining an anode for water electrolysis of Example 8.

(Example 9)
A coating solution of Example 7 was prepared by dissolving 20.93 _g of Ni(NO ₃ ) 2.6H ₂ O, 34.64 g of La(NO ₃ ) _{3.6H 2} O, 30.03 g of glycine, and 2.14 _g of ZrO(NO ₃ ) 2.2H ₂ O in 400 g of pure water.
Thereafter, the same procedure as in Example 7 was carried out to obtain an anode for water electrolysis of Example 9.

(Example 10)
A coating solution of Example 10 was prepared by dissolving 26.75 g of _Ni (NO ₃ ) 2.6H ₂ O, 34.64 g of La ₍ NO ₃ ) 3.6H ₂ O, 31.83 g of glycine, and 1.43 g of TaCl ₅ in 400 g of pure water.
Thereafter, the same procedure as in Example 7 was carried out to obtain an anode for water electrolysis of Example 10.

Example 11
_{17.45 g of Ni(NO3)2.6H2O , 34.64 g} of La( _NO3 ) _3.6H2O , and 27.03 g of glycine were dissolved in 200 g of pure water to prepare Solution A of Example 11. Antimony tartrate was dissolved in pure water to prepare an antimony tartrate solution with an Sb concentration of 20 mmol/kg, which was used as Solution B of Example 11. The Sb concentration was confirmed by ICP-AES (inductively coupled plasma-atomic emission spectroscopy).
Similarly to Example 1, solutions A and B were mixed in a rectangular polyethylene container to prepare a coating solution for Example 11. After repeating a cycle of coating, drying, and baking in the same manner as in Example 1, baking was performed at 800° C. for 1 hour to form a metal oxide layer with a deposition amount of 40 g/ ^m2 on the coating substrate, thereby obtaining an anode for water electrolysis for Example 11.

Example 12
A coating solution of Example 12 was prepared by dissolving 23.26 g of _Ni (NO ₃ ) 2.6H ₂ O, 34.64 g of La(NO ₃ ) _{3.6H 2} O, and 30.03 g of glycine in 400 g of pure water.
A substrate for application was prepared in the same manner as in Example 1, and the coating liquid was applied to both sides of the substrate using a spray coating device (rCoater sold by Asahi Sunac Corporation). The substrate was then dried at 60°C for 10 minutes and then baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface.
This cycle of coating, drying and baking was repeated 24 times.
Furthermore, Nb ₂ O ₅ sol having a primary particle size of 5 nm or less was diluted to prepare Nb ₂ O ₅ sol having an Nb concentration of 200 mmol/kg sol.
This _{Nb2O5 sol} was applied to both sides using a spray coater, dried at 60°C for 10 minutes, and the weight increase relative to the substrate before application was calculated to be 38mg. Since the amount of _LaNiO3 supported on the substrate was 1.4g, the weight of 1 mole _of LaNiO3 was 245.6g, and the weight of ₁ mole of _Nb2O5 was 265.2g, it was found that 0.05 moles of Nb was applied to 1 _mole of _LaNiO3 by applying 38mg of _Nb2O5 .
The substrate dried at 60° C. for 10 minutes was baked at 400° C. for 10 minutes and further baked at 800° C. for 1 hour to form a metal oxide layer with a deposition amount of 144 g/m ² , thereby obtaining an anode for water electrolysis of Example 12.

Example 13
A coating solution for Example 13 was prepared in the same manner as in Example 12. Thereafter, this coating solution was transferred to a polyethylene container having a base dimension of 13 cm×13 cm and a height of 10 cm.
A substrate for coating was prepared in the same manner as in Example 1. This substrate was completely immersed in the coating solution in the container and then pulled out, the coating solution was applied to the entire surface of the substrate, and the substrate was then turned sideways and the excess coating solution was blown off by air blowing using an air gun. Thereafter, the substrate was dried at 60°C for 10 minutes and further baked at 400°C for 10 minutes to form a metal oxide layer on the substrate surface.
This cycle of coating, drying and baking was repeated 24 times.
Ammonium niobium oxalate was dissolved in pure water to prepare an aqueous solution of ammonium niobium oxalate with a Nb concentration of 43.8 mmol/kg. The aqueous solution of ammonium niobium oxalate was transferred to a polyethylene container having a base of 13 cm×13 cm and a height of 10 cm.
The substrate with a metal oxide layer formed on the substrate surface was completely immersed in an aqueous solution of ammonium niobium oxalate and pulled out, and the entire substrate surface was coated with the coating solution. The substrate was then turned sideways and a weak wind was applied from an air gun to remove the coating solution that had clogged the substrate. When the weight of the substrate was measured after the air gun treatment, 1.3 g of an aqueous solution of ammonium niobium oxalate was applied to the substrate. Since the amount of LaNiO3 supported on _the substrate was 1.4 g and the weight of 1 mole _of LaNiO3 was 245.6 g, it was found that 1.3 _g of an aqueous solution of ammonium niobium oxalate with an Nb concentration of 43.8 mmol/kg was applied, and Nb was applied at a ratio of 0.01 mole to 1 mole of LaNiO3.
The substrate coated with the aqueous solution of ammonium niobium oxalate was dried at 60° C. for 10 minutes, then baked at 400° C. for 10 minutes and further baked at 800° C. for 1 hour to form a metal oxide layer with a deposition amount of 141 g/ ^m2 , thereby obtaining an anode for water electrolysis of Example 13.

(Example 14)
In the same manner as in Example 13, the cycle of drying and firing was repeated 24 times, and then firing was carried out at 800° C. for 1 hour to form a metal oxide layer on the surface of the substrate.
Ammonium niobium oxalate was dissolved in pure water to prepare an aqueous solution of ammonium niobium oxalate with a Nb concentration of 87.7 mmol/kg. The aqueous solution of ammonium niobium oxalate was transferred to a polyethylene container having a base of 13 cm×13 cm and a height of 10 cm.
The substrate with a metal oxide layer formed on the substrate surface was completely immersed in an aqueous solution of ammonium niobium oxalate and pulled out, and the entire substrate surface was coated with the coating solution. The substrate was then turned sideways and a weak wind was applied from an air gun to remove the coating solution that had clogged the substrate. When the weight of the _substrate was measured after the air gun treatment, 1.3 g of an aqueous solution of ammonium niobium oxalate was applied to the substrate. Since the amount of LaNiO3 supported on the substrate was 1.4 g and the weight of 1 mole _of LaNiO3 was 245.6 g, it was found that 1.3 g of an aqueous solution of ammonium niobium oxalate with an Nb concentration of 87.7 mmol/kg was applied, and thus 0.02 moles of Nb were applied to 1 mole of _LaNiO3 .
The substrate coated with the aqueous solution of ammonium niobium oxalate was dried at 60° C. for 10 minutes, then baked at 400° C. for 10 minutes and further baked at 800° C. for 1 hour to form a metal oxide layer with a deposition amount of 142 g/ ^m2 , thereby obtaining an anode for water electrolysis of Example 14.

(Example 15)
In the same manner as in Example 13, the cycle of drying and firing was repeated 33 times, and then firing was carried out at 800° C. for 1 hour to form a metal oxide layer on the surface of the substrate.
Thereafter, an aqueous solution of ammonium niobium oxalate with an Nb concentration of 125 mmol/kg was prepared, and in the same manner as in Example 14, Nb was applied at a ratio of 0.02 mol per 1 mol of LaNiO ₃ , dried at 60° C. for 10 minutes, baked at 400° C. for 10 minutes, and further baked at 800° C. for 1 hour to form a metal oxide layer with a deposition amount of 202 g/m ² , thereby obtaining an anode for water electrolysis of Example 15.

(Comparative Example 1)
A substrate for application was prepared in the same manner as in Example 1.
Next, lanthanum acetate 1.5 hydrate and nickel nitrate hexahydrate were mixed to have concentrations of 0.20 mol/L and 0.20 mol/L, respectively, to prepare a coating liquid.
A vat containing the above coating liquid was placed at the bottom of the coating roll, the coating liquid was soaked into an EPDM coating roll, a roll was placed on top of it so that the roll and the coating liquid were always in contact with each other, and a PVC roller was placed on top of it to apply the coating liquid to the substrate (roll method). The substrate was quickly passed between two EPDM sponge rolls before the coating liquid dried. After that, it was dried at 50°C for 10 minutes, and then baked at 400°C for 10 minutes in a muffle furnace to form a metal oxide layer on the substrate surface.
This cycle of roll coating, drying and firing was repeated 13 times, and then firing was further performed at 800° C. for 1 hour to form a metal oxide layer with a deposition amount of 42 g/m ² , thereby obtaining an anode for water electrolysis.

(Comparative Example 2)
A substrate for application was prepared in the same manner as in Example 1.
Next, coating solutions were prepared so that lanthanum nitrate hexahydrate, nickel nitrate hexahydrate, ammonium niobium oxalate n-hydrate, and glycine had concentrations of 0.20 mol/L, 0.16 mol/L, 0.04 mol/L, and 0.36 mol/L, respectively.
In the same manner as in Comparative Example 1, a cycle of roll coating, drying and firing was repeated 40 times by the roll method, and then firing was further performed at 700° C. for 1 hour to form a metal oxide layer, thereby obtaining a water electrolysis anode with a coating weight of 145 g/ ^m2 .

(XRD Measurement Method)
The test anode was cut to 2 cm x 2 cm and measured using an XRD measuring device D8 ADVANCE (sold by Bruker Japan Co., Ltd.). The test anode was located at the center of the bulk sample holder (groove φ40 mm, depth 6 mm, material PMMA), and pieces of clay were placed under the four corners of the sample electrode so that the surface height was the same as the height of the edge of the holder, and the sample electrode was pressed down and fixed from above. The measurement was performed by rotating the sample at 15 rpm, dividing the range of 2θ = 10 ° to 70 ° into 3080 steps, and measuring one step for 4 seconds. X-rays were used, and the voltage of the X-ray source was 40 kV and the current was 40 mA. A divergence slit of 0.8 ° was used. In addition, the settings (overview data) of the device such as the detector and filter that can be confirmed with the measurement condition setting software XRD WIZARD are shown in Table 2.
Using the analysis software DIFFRAC.EVA, a peak search of the XRD spectrum was performed using the "peak search" tool, and the 2θ of the peak position of each peak was determined.
The main peak position of LaNi _x M _y O _3-z was calculated by detecting the main peak of NiO near 2θ = 43.276° by peak search, and then shift-correcting the XRD spectrum using the "X-axis offset" tool so that the detected value of the NiO main peak position 2θ was 2θ = 43.276° of the (200) plane of the NiO PDF00-047-1049 card data.
The main peak position of LaNi _x M _y O _3-z shifts depending on the sample, but the peak position near 2θ = 32.5° to 33.2° was determined to be the main peak position of LaNi _x M _y O _3-z by referring to the (104) plane main peak position 2θ = 33.166° on the PDF01-070-5757 card.
The main peak intensity of LaNi _x M _y O _3-z was taken as the net intensity of the main peak of LaNi _x M _y O _3-z calculated using the "Peak Search" tool.
The half-width of the main peak of LaNi _x M _y O _3-z was determined by using the "Create Area" tool of the analysis software DIFFRAC.EVA to select an area by setting the left end to 31° and the right end to 35°, and calculating the half-width.

(Alkaline resistance test)
The test anode was cut to a size of 2 cm x 2 cm, and XRD was measured to calculate the main peak intensity of LaNi _x M _y O _3-z .
The alkali resistance test was carried out according to the following procedure.
The test anode was placed in a 19 mL PFA sealed container (outer diameter 30 mmφ, height including lid 44 mm, capacity), the container was filled with an 8 mol/L potassium hydroxide aqueous solution (sold by Kanto Chemical Co., Ltd.) and sealed.
Thereafter, the PFA sealed container was placed in an air-blowing constant temperature incubator (product name DKN402, manufactured by Yamato Scientific Co., Ltd.) and heated so that the temperature of the liquid in the sealed container reached 90°C. The liquid was kept at this temperature for 24 hours, after which the sealed container was removed from the air-blowing constant temperature incubator and cooled on ice.
The electrode was taken out of the sealed container, washed with water and dried, and then the XRD was measured again to calculate the main peak intensity of LaNi _x M _y O _3-z .
As an index of alkali resistance, the peak strength retention rate was calculated by the following formula.
(Peak strength retention rate (%))=(XRD main peak strength of LaNi _x M _y O _3-z after alkali resistance test)/(XRD main peak strength of LaNi _x M _y O _3-z before alkali resistance test)×100
The evaluation results for Examples 1 to 15 and Comparative Examples 1 and 2 are shown in Table 3.

(Measurement of oxygen overvoltage after alkaline resistance test of anode)
The oxygen overvoltage of the anode after the alkali resistance test was measured by the following procedure.
After the alkali resistance test, the anode (2 cm x 2 cm) was fixed to a nickel rod coated with PTFE with a nickel screw. A platinum mesh was used as the counter electrode, and electrolysis was performed at 80°C in a 32 wt% aqueous sodium hydroxide solution at a current density of 6 kA/ ^m2 to measure the oxygen overvoltage. The oxygen overvoltage was measured by the three-electrode method using a Luggin capillary in order to eliminate the influence of ohmic loss due to solution resistance. The distance between the tip of the Luggin capillary and the anode was always fixed at 1 mm. A potentiogalvanostat "1470E system" manufactured by Solartron was used as the oxygen overvoltage measuring device. Silver-silver chloride (Ag/AgCl) was used as the reference electrode for the three-electrode method. The electrolyte resistance that could not be completely eliminated even by using the three-electrode method was measured by an AC impedance method, and the oxygen overvoltage was corrected based on the measured electrolyte resistance.
A Cole-Cole plot was obtained by plotting the real and imaginary parts using a frequency response analyzer "1255B" manufactured by Solartron, and the electrolyte resistance and double layer capacitance were calculated by analyzing the plot using equivalent circuit fitting.
The ohmic loss that could not be completely eliminated even by using the three-electrode method was measured by the AC impedance method, and the oxygen overvoltage was corrected based on the measured ohmic loss. The ohmic loss was measured using a frequency characteristic analyzer "1255B" manufactured by Solartron.
The evaluation results for Examples 1 to 15 and Comparative Examples 1 and 2 are shown in Table 3.

(Example 16)
An electrolytic cell for alkaline water electrolysis and a bipolar electrolytic cell were prepared as follows.
-anode-
It was prepared in the same manner as in Example 14.
-cathode-
The conductive substrate used was a plain weave mesh substrate made of nickel thin wires having a diameter of 0.15 mm woven at 40 meshes, on which platinum was supported.
- Partition walls, outer frames -
The bipolar element used had a partition wall separating the anode and cathode and an outer frame surrounding the partition wall. All of the materials of the members that come into contact with the electrolyte, such as the partition wall and the frame of the bipolar element, were made of nickel.
-Conductive elastic body-
The conductive elastic body used was made by weaving nickel wires having a wire diameter of 0.15 mm and corrugating them to a wave height of 5 mm.
-diaphragm-
A coating solution having the following component composition was obtained using zirconium oxide (product name "EP Zirconium Oxide", manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.), N-methyl-2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.), polysulfone ("Udel" (registered trademark), manufactured by Solvay Advanced Polymers), and polyvinylpyrrolidone (weight average molecular weight (Mw) 900,000, manufactured by Wako Pure Chemical Industries, Ltd.).
Polysulfone: 15 parts by weight Polyvinylpyrrolidone: 6 parts by weight N-methyl-2-pyrrolidone: 70 parts by weight Zirconium oxide: 45 parts by weight The above coating liquid was applied to both surfaces of a substrate, a polyphenylene sulfide mesh (manufactured by Kureha Co., Ltd., film thickness 280 μm, mesh size 358 μm, fiber diameter 150 μm). Immediately after coating, the substrate coated with the coating liquid was exposed to steam, and then immersed in a coagulation bath to form a coating film on the substrate surface. The coating film was then thoroughly washed with pure water to obtain a porous film.
-gasket-
The gasket used was a square gasket with inner dimensions of 504 mm square, 4.0 mm thick and 18 mm wide, with an opening on the inside of the same dimensions as the electrode chamber in a plan view, and a slit structure for inserting and holding the diaphragm.
-Zero gap type multi-pole element-
The external header type zero gap type cell unit 60 was a rectangle of 540 mm x 620 mm, and the area of the current-carrying surface of the anode 2a and cathode 2c was 500 mm x 500 mm. The cathode side of the zero gap type bipolar element 60 has a cathode chamber 5c in which the cathode 2c, conductive elastic body 2e, and cathode current collector 2r are laminated and connected to the partition wall 1 via a cathode rib 6, and an electrolyte flows. The anode side has an anode chamber 5a in which the anode 2a is connected to the partition wall 1 via an anode rib 6, and an electrolyte flows (FIG. 2).
The depth of the anode chamber 5a (anode chamber depth, the distance between the partition wall and the anode in FIG. 2 ) was 25 mm, and the depth of the cathode chamber 5c (cathode chamber depth, the distance between the partition wall and the cathode current collector in FIG. 2 ) was 25 mm and made of nickel. The thickness of the nickel partition wall 1 to which the nickel anode rib 6 with a height of 25 mm and a thickness of 1.5 mm and the nickel cathode rib 6 with a height of 25 mm and a thickness of 1.5 mm were attached by welding was 2 mm.
A nickel expand base material that had been previously subjected to blasting was used as the cathode current collector 2r. The thickness of the base material was 1 mm, and the aperture ratio was 54%. The conductive elastic body 2e was fixed by spot welding onto the cathode current collector 2r. By stacking this zero-gap type bipolar element via a gasket that holds the diaphragm, a zero-gap structure Z in which the anode 2a and the cathode 2c are pressed against the diaphragm 4 can be formed.

(Comparative Example 3)
A zero-gap type bipolar element was produced in the same manner as in Example 16 , except that an anode prepared in the same manner as in Comparative Example 2 was used.

Using the electrolysis devices of Example 16 and Comparative Example 3, the electrolyte was kept at 90° C. and circulated while standing for 24 hours, and then the electrolyte temperature was lowered to 80° C., and a positive current was applied continuously for 500 hours so that the current density was 6 kA/m ² , to perform water electrolysis. The voltage versus each cell of Example 16 and Comparative Example 3 was monitored, and the progress of the voltage versus each cell was recorded. The cell voltage of each cell was compared by taking the average value of three cells of each of Example 16 and Comparative Example 3.
In Example 16, the three-cell average voltage after 500 hours of current application was a low value of 1.77 V, whereas in Comparative Example 3, the three-cell average voltage after 500 hours of current application was a high value of 1.95 V. Therefore, it can be concluded that the anode of Example 16 has higher alkali durability than Comparative Example 3, and thus a low cell voltage was achieved even during long-term operation.

The electrode of the present invention has a low overvoltage for oxygen generation and is highly resistant to high-temperature alkali, making it suitable for use as an anode in a water electrolysis cell for electrolyzing water containing alkali.

REFERENCE SIGNS LIST 1 Partition wall 2 Electrode 2a Anode 2c Cathode 2e Conductive elastic body 2r Cathode current collector 3 Outer frame 4 Diaphragm 5a Anode chamber 5c Cathode chamber 6 Rib 7 Gasket 50 Bipolar electrolytic cell 51g Fast head, loose head 51i Insulating plate 51a Anode terminal element 51c Cathode terminal element 51r Tie rod 60 Bipolar element 65 Electrolytic cell 70 Electrolytic device 71 Liquid delivery pump 72 Gas-liquid separation tank 74 Rectifier 75 Oxygen concentration meter 76 Hydrogen concentration meter 77 Flow meter 78 Pressure gauge 79 Heat exchanger 80 Pressure control valve Z Zero gap structure

Claims (8)

An electrode comprising LaNi _x M _y O _3-z (x+y is 0.8 or more and 1.2 or less, y is 0.001 or more and 0.15 or less, z is -0.5 or more and 0.5 or less, M contains at least one of Nb and Sb ) on a substrate, and the XRD main peak position 2θ of LaNi _x M _y O _3-z is 32.6° or more and 33.2° or less. The electrode according to claim 1, wherein y is equal to or greater than 0.002 and less than 0.2. 3. The electrode according to claim 1, wherein the XRD main peak position 2θ of the LaNi _x M _y O _3-z is 32.7° or more and 33.2° or less. An electrode according to any one of claims 1 to 3, wherein M is Nb. 5. The electrode according to claim 1, wherein the XRD main peak half width of the LaNi _x M _y O _3-z is 0.6° or more and 0.85° or less. 6. The electrode according to claim 1, wherein the XRD main peak intensity of the LaNi _x M _y O _3-z is 6,000 or more and 100,000 or less. An electrolytic cell characterized by using the electrode according to any one of claims 1 to 6 as an anode. A hydrogen production method for producing hydrogen by electrolyzing alkali-containing water in an electrolytic cell, the electrolytic cell comprising at least an anode and a cathode, the anode having LaNi _x M _y O _3-z (x+y is 0.8 or more and 1.2 or less, y is 0.001 or more and 0.15 or less, z is -0.5 or more and 0.5 or less, M contains at least one of Nb and Sb ) on a substrate, and the XRD main peak position 2θ of LaNi _x M _y O _3-z is 32.6° or more and 33.2° or less.

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