Reference electrode

Abstract

The system provides a reference electrode that can be regenerated on the spot if its performance deteriorates. [Solution] A reference electrode embedded in concrete and used to measure the potential of a metal in the concrete, comprising a cylindrical resin container 40 housing an electrode body 10 in contact with a solid electrolyte 30, and a regenerative electrolysis counter electrode 20 in contact with at least one of the solid electrolyte 30 and the concrete, wherein the electrode body 10 has at least one of an oxide layer formed by oxidation of the metal constituting the electrode body 10 and a first coating layer 11 on at least a part of its surface 10a, the reference electrode 1.

Description

[Technical Field]

[0001] This invention relates to a reference electrode. [Background technology]

[0002] Steel materials such as reinforcing bars and pipes embedded in concrete structures can corrode due to the neutralization of the concrete. In addition, in concrete structures built particularly in coastal areas, chloride ions penetrate from the surface, and if the concentration exceeds the permissible level, corrosion of the steel materials occurs. To prevent corrosion of steel materials, for example, cathodic protection is applied. In this case, it is necessary to embed reference electrodes in the concrete to measure the potential of the steel materials and monitor the corrosion of the steel materials. The potential of a metal is expressed as the difference (potential difference) from the potential of a reference electrode.

[0003] When measuring the potential of steel materials, the electrode used as a reference is called a reference electrode. Examples of reference electrodes include the HS-205C (saturated silver chloride electrode) manufactured by TOA-DKK, the RE-5 type (saturated copper sulfate electrode) manufactured by MCMiller, and the AC-2 type (artificial seawater silver chloride electrode) manufactured by Nippon Shokuho Co., Ltd.

[0004] Furthermore, as a reference electrode used when measuring the potential of steel materials in concrete structures, for example, a silver-silver oxide reference electrode is known, which is a mixture of silver particles and silver oxide particles in a specific ratio (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 6-317553 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, when commercially available saturated silver-silver chloride electrodes or saturated copper sulfate electrodes stop showing normal potentials, they cannot be regenerated and must be discarded, which is uneconomical. In addition, although artificial seawater silver-silver chloride electrodes can be regenerated when they stop showing normal potentials, since it is necessary to disassemble the electrodes to prepare molten salts or set up an electrolysis system in a beaker, they cannot be regenerated on-site.

[0007] In addition, the invention of Patent Document 1 had the problem that the electrode potential changed in an environment containing chloride ions such as seawater. Furthermore, in the invention of Patent Document 1, silver oxide could be reduced depending on the constituent components. Also, there was a possibility that the electrode potential became unstable due to the reduction of silver oxide particles on the electrode surface by the weak current flowing during potential measurement.

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide a reference electrode that can be regenerated on-site when its performance deteriorates. [Means for Solving the Problems]

[0009] The present invention has the following aspects. [1] A reference electrode embedded in concrete and used for measuring the potential of a metal in the concrete, comprising: A cylindrical resin container that houses an electrode body in contact with a solid electrolyte; A counter electrode for regeneration electrolysis in contact with at least one of the solid electrolyte and the concrete, and The electrode body has at least one of an oxide layer and a coating layer formed by oxidizing the metal constituting the electrode body on at least a part of its surface. [2] The reference electrode according to [1], wherein the electrode body and the counter electrode for regeneration electrolysis are embedded in the same solid electrolyte. [3] The reference electrode according to [1], wherein the electrode body and the counter electrode for regeneration electrolysis are embedded in different solid electrolytes. [4] The reference electrode according to [1], wherein the metal constituting the electrode body is silver. [5] The verification electrode according to [1], wherein the counter electrode for regeneration electrolysis has a second coating layer covering at least a part of its surface. [6] The verification electrode according to [1], which has a liquid junction part for sealing the solid electrolyte. [7] The verification electrode according to [1], wherein the counter electrode for regeneration electrolysis is a metal embedded in concrete.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a verification electrode that can be regenerated in place when its performance deteriorates.

Brief Description of the Drawings

[0011] [Figure 1] It is a cross-sectional view schematically showing a verification electrode according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view schematically showing a verification electrode according to an embodiment of the present invention. [Figure 3] It is a cross-sectional view schematically showing a verification electrode according to an embodiment of the present invention. [Figure 4] It is a cross-sectional view schematically showing a verification electrode according to an embodiment of the present invention. [Figure 5] It is a cross-sectional view schematically showing a verification electrode according to an embodiment of the present invention. [Figure 6] It is a cross-sectional view schematically showing a verification electrode according to an embodiment of the present invention. [Figure 7] It is a diagram showing the result of measuring the change over time of the potential of the verification electrode in Example 1. [Figure 8] It is a diagram showing the result of evaluating the amount of silver oxide generated by electrolytic oxidation by a constant current reduction method in Example 2. [Figure 9] It is a diagram showing the result of measuring the potential of the verification electrode in a saturated calcium hydroxide solution in Example 3. [Figure 10] It is a diagram showing the result of measuring the potential of the electrode by immersing the electrode in a saturated calcium hydroxide solution in Example 4. [Figure 11]This figure shows the results of measuring the potential of the electrodes after immersing them in a saturated calcium hydroxide solution in Example 5. [Figure 12] This figure shows the results of measuring the potential of the reference electrode in Example 6, after immersing the reference electrode in a saturated calcium hydroxide solution. [Figure 13] This figure shows the results of measuring the potential of a reference electrode inside a concrete specimen during exposure in Example 7. [Modes for carrying out the invention]

[0012] The following description will explain a reference electrode according to an embodiment of the present invention with reference to the drawings. Note that, for convenience, the drawings used in the following description show enlarged versions of characteristic parts, and the dimensional ratios of each component may differ from those of the actual components. Furthermore, the materials, dimensions, etc., exemplified in the following description are merely examples, and the present invention is not limited to them. They can be modified as appropriate without altering the essence of the invention.

[0013] [Reference electrode] (First embodiment) Figure 1 is a schematic cross-sectional view showing a reference electrode according to one embodiment of the present invention. As shown in Figure 1, the reference electrode 1 of this embodiment includes an electrode body 10, a counter electrode 20 for regenerative electrolysis, a solid electrolyte 30, and a resin container 40. The electrode body 10 has a coating layer (hereinafter referred to as the "first coating layer") 11 that covers at least a portion of its surface 10a.

[0014] The resin container 40 has a hollow cylindrical shape, and the electrode body 10, the regenerative electrolysis counter electrode 20, and the solid electrolyte 30 are housed in its internal space 40a. The resin container 40 is open at both ends in its axial direction (longitudinal direction). One end 40A of the resin container 40 is sealed by the solid electrolyte 30. The other end 40B of the resin container 40 is sealed by the filling resin 50. The solid electrolyte 30 and the filling resin 50 are in contact within the resin container 40. The aforementioned end 40B of the resin container 40 is provided with a lead wire 70 connected to the electrode body 10 by a crimp terminal 60, and a lead wire 71 connected to the regenerative electrolysis counter electrode 20 by a crimp terminal 61. The crimp terminals 60 and 61 are embedded in the filling resin 50. The connection method between the electrode body 10 and the lead wire 70, and the connection method between the regenerative electrolysis counter electrode 20 and the lead wire 71, may be soldering, and any known connection method can be used.

[0015] "Electrode body" The electrode body 10 is embedded in the solid electrolyte 30. In Figure 1, the electrode body 10 is embedded in the solid electrolyte 30, but it is sufficient for the electrode body 10 to be in contact with the solid electrolyte 30. The electrode body 10 can be any metal that, when electrolytically oxidized, produces an oxide (also called an active material) on its surface. Examples include silver, lead, copper, zinc, and tin. These metal oxides have excellent chemical stability and are therefore preferred as metals for the electrode body 10. However, platinum, titanium, and manganese are excluded because their potential changes depending on the oxygen concentration.

[0016] The electrode body 10 may have an oxide layer (not shown) on at least a portion of its surface 10a, which is formed by the oxidation of the metal constituting the electrode body 10. If the electrode body 10 is made of silver, the oxide layer is made of silver oxide. If the electrode body 10 is made of lead, the oxide layer is made of lead oxide. If the electrode body 10 is made of copper, the oxide layer is made of copper oxide. If the electrode body 10 is made of zinc, the oxide layer is made of zinc oxide. If the electrode body 10 is made of tin, the oxide layer is made of tin oxide. The oxide layer is an active material formed by the oxidation of the metal constituting the electrode body 10, and an electrode potential is generated by an electrode reaction between the metal and the active material. In addition, although Figure 1 illustrates the case in which the electrode body 10 is embedded in the solid electrolyte 30, the electrode body 10 only needs to be in contact with the solid electrolyte 30. As long as the electrode body 10 is in contact with the solid electrolyte 30, regenerative electrolysis, as described later, is possible.

[0017] The thickness of the oxide layer is preferably 50 nm or more; if the thickness of the oxide layer is less than 50 nm, the potential becomes unstable.

[0018] The shape of the electrode body 10 is not particularly limited, but examples include linear, mesh-like, spherical, square, cylindrical, elliptical prism, and prismatic shapes. Among these, linear and mesh-like shapes are preferred because they are readily available.

[0019] "First coating layer" The first coating layer 11 covers the surface 10a of the electrode body 10 and at least a portion of the oxide layer. The thickness of the first coating layer 11 is preferably 0.005 mm or more and 50 mm or less, more preferably 0.01 mm or more and 10 mm or less, and even more preferably 0.02 mm or more and 3 mm or less. When the thickness of the first coating layer 11 is above the lower limit, the electrode potential tends to be more stable. When the thickness of the first coating layer 11 is below the upper limit, it is easier to suppress the peeling of the potential stabilizer from the surface of the electrode body 10. In addition, when the thickness of the first coating layer 11 is below the upper limit, it is cost-effective. The thickness of the first coating layer 11 can be determined, for example, by observing a cross-section of the first coating layer 11 in the thickness direction using a microscope or the like.

[0020] The potential stabilizer preferably contains an alkaline solid in addition to the active material, which is formed by oxidizing the metal constituting the electrode body 10, because it hardens easily to form the first coating layer 11. Examples of alkaline solids include calcium hydroxide powder, calcined gypsum powder, and cement. The alkaline solid may be used alone or in combination of two or more types.

[0021] The potential stabilizer is more preferably a composition containing the active material, calcium hydroxide powder, calcined gypsum powder, and water, or cement and water (hereinafter also referred to as the "stabilizer composition"). When the potential stabilizer is a stabilizer composition, it is easier to form the first coating layer 11 on the surface 10a of the electrode body 10 and on the surface of the oxide layer.

[0022] When the active material is silver oxide, the content of silver oxide powder in the stabilizer composition is preferably 10% to 95% by mass, and more preferably 35% to 85% by mass, based on the total mass (100% by mass) of the stabilizer composition. If the content of silver oxide powder is above the lower limit, the electrode potential is more easily stabilized. If the content of silver oxide powder is below the upper limit, the workability is good and an appropriate first coating layer 11 can be formed.

[0023] The amount of potential stabilizer can be appropriately set according to the service life of the reference electrode 1. For example, if the service life of the reference electrode 1 is set to 20 years or less, in line with the service life of the lead wire, the amount of potential stabilizer on the surface 10a of the electrode body 10 is 0.01 g / cm³. 2 More than 10g / cm 2 The following is preferable: 0.1 g / cm³ 2 More than 5g / cm 2 The following are preferable. When the content of the potential stabilizer is above the lower limit, the electrode potential tends to be more stable. When the content of the potential stabilizer is below the upper limit, it is more cost-effective. When an active material is included in the stabilizing agent composition, the decrease in the active material constituting the oxide layer due to diffusion can be suppressed. On the other hand, even if the stabilizing agent composition does not contain an active material, an electrode potential is generated by the electrode reaction between the electrode body 10 and the oxide layer, in other words, between the metal and the active material. That is, if there is a first coating layer 11 that covers the surface 10a of the electrode body 10 and at least a part of the oxide layer, the electrode potential tends to be stable, but the reference electrode 1 does not have to have the first coating layer 11. Therefore, if there is an electrode body 10 and at least one of the oxide layer and the first coating layer 11, an electrode potential is generated and it functions as a reference electrode 1. In Figure 1, an example is shown in which the electrode body 10 has a first coating layer 11 on at least a part of its surface 10a. However, in the reference electrode of the present invention, the electrode body may have both an oxide layer formed by the oxidation of the metal constituting the electrode body and the first coating layer 11 on at least a part of its surface, or it may have only an oxide layer formed by the oxidation of the metal constituting the electrode body 10, or it may have only the first coating layer 11.

[0024] "Counter electrode for regenerative electrolysis" The regenerative electrolysis counter electrode 20 can be made of any electronically conductive material, such as stainless steel, platinum, titanium, gold, silver, copper, and graphite. While Figure 1 illustrates a case where the regenerative electrolysis counter electrode 20 is embedded in the solid electrolyte 30, the regenerative electrolysis counter electrode 20 may simply be in contact with the solid electrolyte 30. Furthermore, the regenerative electrolysis counter electrode 20 may be in contact with concrete, and may even be made of steel (metal) embedded in concrete. The shape of the regenerative electrolysis counter electrode 20 is not particularly limited, but examples include linear, mesh-like, spherical, rectangular, cylindrical, elliptical, prismatic, and coil-like shapes. Among these, coil-like and mesh-like shapes are preferred because they allow for a large surface area. Furthermore, if the regenerative electrolysis counter electrode 20 is made of steel embedded in concrete, the surface area is significantly larger. A larger surface area of ​​the regenerative electrolysis counter electrode 20 can reduce power consumption during regenerative electrolysis.

[0025] On the other hand, if the electrode body 10 is made of silver, the silver oxide particles contained in the first coating layer 11 are reduced by the weak current flowing during potential measurement, and a portion of them becomes silver. The same thing can happen during regenerative electrolysis. If the shape of the regenerative electrolysis counter electrode 20 is, for example, linear, the silver oxide particles in the path of the current flowing from the electrode body 10 to the regenerative electrolysis counter electrode 20 during regenerative electrolysis are partially reduced to silver. If the silver parts conduct electricity with each other, there is a concern that eventually the electrode body 10 and the regenerative electrolysis counter electrode 20 will conduct electricity via the silver, in which case regenerative electrolysis will not be possible, and the potential measurement will also be negatively affected.

[0026] "Second coating layer" Although not shown in Figure 1, the regenerative electrolytic counter electrode 20 constituting the reference electrode 1 of this embodiment may have a coating layer covering its surface (hereinafter referred to as the "second coating layer"). The second coating layer covers at least a portion of the surface of the regenerative electrolysis counter electrode 20. The thickness of the second coating layer can be determined, for example, by observing a cross-section of the second coating layer in the thickness direction using a microscope.

[0027] The second coating layer may have the same configuration as the solid electrolyte 30 described later. Furthermore, the second coating layer may be a solid electrolyte containing a deliquescent salt or a hygroscopic salt. Examples of deliquescent salts include potassium carbonate, calcium nitrate, sodium hydroxide, magnesium chloride, and calcium chloride. By including a deliquescent salt, the increase in the surface resistance of the regenerative electrolysis counter electrode 20 can be suppressed. The content of the deliquescent salt or hygroscopic salt is preferably 1% by mass or more relative to the total mass of the second coating layer. Furthermore, the second coating layer may be a solid electrolyte containing an oxidizing agent. Examples of oxidizing agents include silver oxide, copper oxide, zinc oxide, iron oxide, manganese oxide, copper sulfate, iron sulfate, nickel sulfate, cobalt sulfate, cobalt chloride, and tin chloride. By including an oxidizing agent, the reduction reaction on the counter electrode for regenerative electrolysis during regenerative electrolysis can be promoted, and the voltage can be suppressed. The content of the oxidizing agent is preferably 1% by mass or more relative to the total mass of the second coating layer. Furthermore, the second coating layer may be a solid electrolyte containing an electronically conductive material. Examples of electronically conductive materials include metal powders such as zinc powder, silver powder, and copper powder, as well as graphite powder. By including an electronically conductive material, the apparent surface area of ​​the regenerative electrolysis counter electrode 20 can be increased, thereby suppressing the voltage during electrolysis. The content of the electronically conductive material is preferably 1% by mass or more relative to the total mass of the second coating layer. In addition, the second coating layer may be an electrolyte containing a gelling agent. Examples of gelling agents include sodium polyacrylate and carboxymethylcellulose. By including a gelling agent, the increase in the surface resistance of the regenerative electrolysis counter electrode 20 can be suppressed. The gelling agent content is preferably 1% by mass or more relative to the total mass of the coating layer 21. However, when using a gelling agent, it is necessary to provide a liquid junction as described later.

[0028] "Solid electrolyte" The solid electrolyte 30 is a solid electrolyte. The solid electrolyte 30 may be completely solidified or may be in gel form. Examples of the solid electrolyte 30 include a cured product of a composition containing calcium hydroxide powder, calcined gypsum powder, and water.

[0029] The thickness of the solid electrolyte 30 (axial length in the resin container 40) is preferably 10 mm or more, more preferably 50 mm or more, and even more preferably 100 mm or more. If the thickness of the solid electrolyte 30 is greater than or equal to the lower limit, substances that can react with the metal constituting the electrode body 10 are less likely to reach the electrode body 10, and the electrode potential is more easily stabilized. In other words, the solid electrolyte 30 functions as a diffusion suppression layer that suppresses the diffusion of substances that can react with the metal constituting the electrode body 10. The upper limit of the thickness of the solid electrolyte 30 is not particularly limited, but from the viewpoint of making the reference electrode 1 compact, for example, 200 mm or less is preferred.

[0030] The solid electrolyte 30 functions as a diffusion-inhibiting layer, making it difficult for substances that can react with the metal ions constituting the electrode body 10 to reach the electrode body 10. As a result, the oxide layer does not undergo chemical changes, and changes in the electrode potential can be suppressed. Consequently, the electrode potential becomes more stable.

[0031] The thickness of the solid electrolyte 30 can be appropriately set according to the service life of the reference electrode 1. For example, if the service life of the reference electrode 1 is 20 years or less, the thickness of the solid electrolyte 30 is preferably 180 mm or more.

[0032] The solid electrolyte 30 may be a cementitious body. When the solid electrolyte 30 is a cementitious body, substances that can react with the metal ions constituting the electrode body 10 are less likely to reach the electrode body 10. Therefore, the oxide layer does not undergo chemical changes, and changes in the electrode potential can be further suppressed. As a result, the electrode potential is more easily stabilized. Examples of hardened cement include hardened products of cement compositions containing cement and water. Examples of cements include various types of Portland cement such as ordinary Portland cement, moderate-heat Portland cement, and sulfate-resistant Portland cement, as well as various blended cements (blast furnace cement, fly ash cement, silica cement) obtained by mixing these Portland cements with blast furnace slag, fly ash, or silica. These cements may be used individually or in combination of two or more types.

[0033] The cement composition may contain fine aggregate other than cement and water. Examples of fine aggregate include river sand, mountain sand, land sand, crushed sand, silica sand, or mixtures thereof. The fine aggregate content is preferably 20% to 75% by mass relative to 100% by mass of the cement composition. If the fine aggregate content is above the lower limit, the strength of the solid electrolyte 30 can be further increased. If the fine aggregate content is below the upper limit, the fluidity of the cement composition is excellent, and the moldability of the solid electrolyte 30 can be further increased.

[0034] The solid electrolyte 30 preferably contains an active material. Examples of the active material include silver oxide, lead oxide, copper oxide, zinc oxide, and tin oxide, depending on the metal constituting the electrode body 10. The amount of active material contained in the solid electrolyte 30 is preferably 1% by mass or more relative to the total mass (100% by mass) of the solid electrolyte 30, which stabilizes the potential of the reference electrode 1.

[0035] The solid electrolyte 30 may include, for example, a substance that can remove anions that bind to the metal or active material constituting the electrode body 10 in an alkaline environment, i.e., an ion-exchangeable substance. By including an ion-exchangeable substance in the solid electrolyte 30, anions that penetrate from the environment can be excluded, so the oxide layer does not undergo chemical changes and changes in the electrode potential can be suppressed. As a result, the electrode potential is more easily stabilized. Examples of the aforementioned anions include halide ions, chlorate ions, chlorite ions, hypochlorite ions, cyanide ions, nitrate ions, sulfide ions, hydrogen sulfide ions, thiocyanate ions, sulfate ions, bicarbonate ions, carbonate ions, sulfite ions, and thiosulfate ions.

[0036] Examples of ion-exchangeable materials include clay minerals, diatomaceous earth, and calcium silicate hydrate. These materials contain hydroxide ions in their structure. Examples of clay minerals include kaolinite, smectite, allophane, and imogolite. These clay minerals may be used individually or in combination of two or more.

[0037] "Plastic container" The resin container 40 forms the outer shape of the reference electrode 1 and has a hollow cylindrical shape. The cross-sectional shape of the resin container 40 may be circular or elliptical, or it may be a polygon, etc. The material of the resin container 40 may be any material that can house the electrode body 10, the regenerative electrolysis counter electrode 20 and the solid electrolyte 30 and has electrical insulating properties. Examples include polyvinyl chloride, polystyrene, polyethylene, polypropylene, acrylic resin, tetrafluoroethylene resin (PTFE), vinylidene fluoride resin (PVDF), polyether-ether-ketone resin (PEEK), polycarbonate resin (PC), fiber-reinforced plastic, etc. From the viewpoint of excellent durability, polyvinyl chloride, PC, and fiber-reinforced plastic are preferred as the material of the resin container 40.

[0038] The length (axial length) of the resin container 40 is not particularly limited, but for example, 50 mm to 250 mm is preferred, 60 mm to 200 mm is more preferred, and 70 mm to 150 mm is even more preferred. If the length of the resin container 40 is greater than or equal to the lower limit, the thickness of the solid electrolyte 30 can be made sufficiently thick, making it difficult for substances that can react with the metal ions constituting the electrode body 10 to reach the electrode body 10. As a result, the oxide layer does not undergo chemical change, and changes in the electrode potential can be suppressed. As a result, the electrode potential is more stable. If the length of the resin container 40 is less than or equal to the upper limit, the reference electrode 1 can be made more compact, which is also cost-effective.

[0039] The inner diameter of the resin container 40 (the inner diameter of the opening of the resin container 40) is not particularly limited, but is preferably 3 mm or more and 30 mm or less, more preferably 5 mm or more and 25 mm or less, and even more preferably 7 mm or more and 20 mm or less. If the inner diameter of the resin container 40 is greater than or equal to the lower limit, the measurement accuracy of the reference electrode 1 can be further improved. If the inner diameter of the resin container 40 is less than or equal to the upper limit, the reference electrode 1 can be made more compact, which is also cost-effective. The wall thickness of the resin container 40 is not particularly limited, but is preferably 1 mm to 5 mm, and more preferably 2 mm to 4 mm. If the wall thickness of the resin container 40 is above the lower limit, the strength of the reference electrode 1 can be increased, and the electrode potential is more easily stabilized. If the wall thickness of the resin container 40 is below the upper limit, the reference electrode 1 can be made more compact, which is also cost-effective.

[0040] "Liquid junction" Although not shown in Figure 1, the reference electrode 1 of this embodiment may have a liquid junction. The liquid junction seals the solid electrolyte 30 and allows ions to move. Examples of materials that make up the liquid junction include cement, mortar, gypsum, etc. The reference electrode 1 does not necessarily have to have a liquid junction, but it is preferable that the reference electrode 1 has a liquid junction because it enhances durability and makes the electrode potential more stable.

[0041] The axial length of the liquid junction is preferably 5 mm or more, more preferably 10 mm or more, and even more preferably 15 mm or more. If the axial length of the liquid junction is greater than or equal to the lower limit, substances that can react with the metal ions constituting the electrode body 10 will have difficulty reaching the electrode body 10. As a result, the oxide layer will not undergo chemical changes, and changes in the electrode potential can be suppressed. Consequently, the electrode potential is more stable. The upper limit of the axial length of the liquid junction is not particularly limited, but for example, 180 mm is preferred. If the axial length of the liquid junction is less than or equal to the upper limit, the reference electrode 1 can be made more compact. Furthermore, from the viewpoint of making the electrode potential more stable and the reference electrode 1 more compact, the liquid junction may have a meandering liquid junction path (not shown). The liquid junction path is the path through which ions move within the liquid junction. By providing a liquid junction, the thickness of the solid electrolyte 30 can be reduced, but in the present invention, the function of the liquid junction is provided by the solid electrolyte 30, thus achieving a similar effect.

[0042] The total length of the reference electrode 1 (the axial length of the resin container 40) is preferably 300 mm or less, more preferably 275 mm or less, and even more preferably 250 mm or less. If the total length of the reference electrode 1 is less than or equal to the upper limit, the reference electrode 1 can be made more compact. The lower limit of the total length of the reference electrode 1 is not particularly limited, but for example, 100 mm is preferred. If the total length of the reference electrode 1 is greater than or equal to the lower limit, it is easier to install on concrete structures, etc.

[0043] "Filling resin" The filling resin 50 is a resin that seals the end of the resin container 40 opposite to the side containing the solid electrolyte 30. The filling resin 50 is not particularly limited and examples include epoxy resin, acrylic resin, silicone resin, urethane resin, etc. Epoxy resin is preferred as the filling resin 50 because of its excellent filling properties.

[0044] "Lead wire" Lead wires 70 and 71 are conductors for extracting the current flowing during potential measurement to the outside. Any material with electronic conductivity can be used as a lead wire, and copper wire is usually used. In this specification, the lengths of lead wires 70 and 71 are not included in the total length of the reference electrode 1.

[0045] In the reference electrode 1, it is preferable to position the portion of the electrode body 10 covered by the first coating layer 11 and the regenerative electrolysis counter electrode 20 at a distance from each other. This eliminates the possibility that during regenerative electrolysis, the active material constituting the first coating layer 11 may be partially reduced, and that the electrode body 10 and the regenerative electrolysis counter electrode 20 may become electrically conductive through the partially reduced active material.

[0046] (Second embodiment) Figure 2 is a schematic cross-sectional view showing a reference electrode according to one embodiment of the present invention. In Figure 2, components identical to those shown in Figure 1 are denoted by the same reference numerals, and their descriptions are omitted. As shown in Figure 2, the reference electrode 100 of this embodiment includes an electrode body 10, a counter electrode 20 for regenerative electrolysis, a solid electrolyte 30, and a resin container 40.

[0047] In the reference electrode 100 of this embodiment, the shape of the regenerative electrolysis counter electrode 20 is coil-shaped. By making the shape of the regenerative electrolysis counter electrode 20 coil-shaped, the current flowing from the electrode body 10 to the regenerative electrolysis counter electrode 20 during regenerative electrolysis can be dispersed, thereby delaying the partial reduction of silver oxide particles into silver and the electrical conductivity between the silver parts. A similar effect can also be achieved by making the shape of the electrode body 10 coil-shaped, for example.

[0048] (Third embodiment) Figure 3 is a schematic cross-sectional view showing a reference electrode according to one embodiment of the present invention. In Figure 3, components identical to those shown in Figure 1 are denoted by the same reference numerals, and their descriptions are omitted. As shown in Figure 3, the reference electrode 200 of this embodiment includes an electrode body 10, a counter electrode 210 for regenerative electrolysis, a solid electrolyte 30, and a resin container 40.

[0049] In the reference electrode 200 of this embodiment, a ring-shaped regenerative electrolysis counter electrode 210 is embedded in the filling resin 50. Furthermore, within the filling resin 50, the ring-shaped regenerative electrolysis counter electrode 210 is positioned in contact with the end face 30a of the solid electrolyte 30 on the filling resin 50 side (the interface between the solid electrolyte 30 and the filling resin 50). By making the shape of the regenerative electrolysis counter electrode 210 ring-shaped and positioning it in contact with the end face 30a of the solid electrolyte 30 on the filling resin 50 side, the current flowing from the electrode body 10 to the regenerative electrolysis counter electrode 210 during regenerative electrolysis can be dispersed, thereby delaying the partial reduction of silver oxide particles into silver and preventing electrical conductivity between the silver portions.

[0050] (Fourth embodiment) Figure 4 is a schematic cross-sectional view showing a reference electrode according to one embodiment of the present invention. In Figure 4, components identical to those shown in Figure 1 are denoted by the same reference numerals, and their descriptions are omitted. As shown in Figure 4, the reference electrode 300 of this embodiment includes an electrode body 10, a counter electrode 20 for regenerative electrolysis, a solid electrolyte 30, and a resin container 40.

[0051] One end 40A of the resin container 40 is sealed with a solid electrolyte 30(30A). The other end 40B of the resin container 40 is sealed with a filling resin 50. Furthermore, a solid electrolyte 30(30B) is positioned so as to be in contact with the end face 40b of the other end 40B of the resin container 40.

[0052] In the reference electrode 300 of this embodiment, the shape of the regenerative electrolysis counter electrode 20 is coil-shaped, similar to that of the second embodiment. The regenerative electrolysis counter electrode 20 is embedded in the solid electrolyte 30. By making the shape of the regenerative electrolysis counter electrode 20 coil-shaped, the current flowing from the electrode body 10 to the regenerative electrolysis counter electrode 20 during regenerative electrolysis can be dispersed, thereby delaying the partial reduction of silver oxide particles into silver and the electrical conductivity between the silver portions.

[0053] In the reference electrode 300 of this embodiment, the regenerative electrolysis counter electrode 20 is embedded in a solid electrolyte 30(30B) that is different from the solid electrolyte 30(30A) in which the electrode body 10 is embedded. By embedding the regenerative electrolysis counter electrode 20 in a solid electrolyte 30(30B) that is different from the solid electrolyte 30(30A) in which the electrode body 10 is embedded, it is possible to suppress electrical conductivity between the electrode body 10 and the regenerative electrolysis counter electrode 20 through the metal (for example, silver) that constitutes the electrode body 10. The same applies when the regenerative electrolysis counter electrode 20 is in contact with concrete, and when the regenerative electrolysis counter electrode 20 is made of steel embedded in concrete. In this way, when electrolytic oxidation is performed via concrete, there is no active material in the concrete, so there is no electrical conductivity between the electrode body 10 and the regenerative electrolysis counter electrode 20. In this embodiment, the solid electrolyte 30 (30B) in which the regenerative electrolysis counter electrode 20 is embedded is positioned in contact with the end face 40b on the end 40B side of the resin container 40. However, the solid electrolyte 30 (30B) may also be housed inside a resin container 40 that is extended axially (longitudinally) from the end 40B side of the resin container 40.

[0054] (Fifth embodiment) Figure 5 is a schematic cross-sectional view showing a reference electrode according to one embodiment of the present invention. In Figure 5, components identical to those shown in Figure 1 are denoted by the same reference numerals, and their descriptions are omitted. As shown in Figure 5, the reference electrode 400 of this embodiment includes an electrode body 10, a counter electrode 20 for regenerative electrolysis, a solid electrolyte 30, and resin containers 410 and 411. In the reference electrode 400 of this embodiment, the resin containers 410 and 411 are arranged adjacent to each other so as to be in contact on their outer surfaces. The electrode body 10 and the solid electrolyte 30 are housed in the resin container 410, and the counter electrode 20 for regenerative electrolysis and the solid electrolyte 30 are housed in the resin container 411. The counter electrode 20 for regenerative electrolysis is embedded in a different solid electrolyte 30 than the solid electrolyte 30 in which the electrode body 10 is embedded.

[0055] One end 410A of the resin container 410 is sealed with solid electrolyte 30. The other end 410B of the resin container 410 is sealed with filling resin 50. One end 411A of the resin container 411 is sealed with solid electrolyte 30. The other end 411B of the resin container 411 is sealed with filling resin 50. By embedding the regenerative electrolysis counter electrode 20 in a solid electrolyte 30 different from the solid electrolyte 30 in which the electrode body 10 is embedded, there is no active material in the concrete during regenerative electrolysis, so there is no electrical connection between the electrode body 10 and the regenerative electrolysis counter electrode 20.

[0056] (Sixth embodiment) Figure 64 is a schematic cross-sectional view showing a reference electrode according to one embodiment of the present invention. In Figure 6, components identical to those shown in Figure 1 are denoted by the same reference numerals, and their descriptions are omitted. As shown in Figure 6, the reference electrode 500 of this embodiment includes an electrode body 10, a counter electrode 310 for regenerative electrolysis, a solid electrolyte 30, and a resin container 40.

[0057] In the reference electrode 500 of this embodiment, a hollow cylindrical counter electrode 510 for regenerative electrolysis is positioned so as to be in contact with the end face 40b of the other end 40B of the resin container 40. One end 40A of the resin container 40 is sealed with a solid electrolyte 30. The other end 40B of the resin container 40 and the counter electrode 510 for regenerative electrolysis are sealed with a filling resin 50.

[0058] The regenerative electrolysis counter electrode 510 and the regenerative electrolysis counter electrode 20 are made of the same material. The regenerative electrolysis counter electrode 510 is connected to the lead wire 71 by a crimp terminal 61 on its inner surface 510a. The regenerative electrolysis counter electrode 310 is positioned in contact with the concrete. By making the shape of the regenerative electrolysis counter electrode 510 a hollow cylindrical shape and positioning it in contact with the concrete, there is no active material in the concrete during regenerative electrolysis, so there is no electrical contact between the electrode body 10 and the regenerative electrolysis counter electrode 20.

[0059] [Manufacturing method for reference electrodes] The manufacturing method of the reference electrode of this embodiment includes a polishing step of polishing the surface 10a of the electrode body 10; a forming step of forming an oxide layer on at least a part of the surface 10a of the electrode body 10 by electrolytic oxidation of the polished surface 10a of the electrode body 10 in an alkaline solution, wherein the metal constituting the electrode body 10 is oxidized; a coating step of applying a potential stabilizer to the electrode body 10 having the oxide layer; a polishing step of polishing the surface of the regenerative electrolysis counter electrode 20; and a coating step of applying a solid electrolyte or the like to the polished surface of the regenerative electrolysis counter electrode 20.

[0060] The manufacturing method for the reference electrode 1 shown in Figure 1 will be described below.

[0061] First, a cylindrical resin container 40 of a predetermined material and dimensions, an electrode body 10, a counter electrode 20 for regenerative electrolysis, and a composition that will be used as the raw material for the solid electrolyte 30 (hereinafter also referred to as the "electrolyte composition") are prepared. The electrode body 10 may be a commercially available product, or a cast product formed using a mold of any shape. A lead wire 70 is attached to one end of the electrode body 10 in the axial direction. Furthermore, the regenerative electrolysis counter electrode 20 may be a commercially available product or a molded product formed into any shape. A lead wire 71 is attached to one end of the regenerative electrolysis counter electrode 20 in the axial direction. However, if a steel material embedded in a concrete structure is used as the regenerative electrolysis counter electrode 20, the lead wire 71 may be attached to any part of the steel material or to an existing terminal rising from the steel material.

[0062] Next, the surface 10a of the electrode body 10 and the surface of the regenerative electrolysis counter electrode 20 are polished (polishing step). By polishing the surface 10a of the electrode body 10 and the surface of the regenerative electrolysis counter electrode 20, impurities (dirt and inclusions in the metal) and inert films can be removed from the surface 10a of the electrode body 10 and the surface of the regenerative electrolysis counter electrode 20, thereby making the surface 10a of the electrode body 10 and the surface of the regenerative electrolysis counter electrode 20 active. As a result, the efficiency of the electrode body 10 during electrolytic oxidation is increased, and the surface resistance of the regenerative electrolysis counter electrode 20 can be reduced. The polishing process may involve, for example, mechanical polishing, chemical polishing (wet etching or dry etching), or electrolytic polishing.

[0063] When mechanically polishing the surface 10a of the electrode body 10 and the surface of the regenerative electrolysis counter electrode 20, for example, abrasive paper may be used, and the coarseness of the abrasive paper is preferably medium, around #120 to #240. When wet etching the surface 10a of the electrode body 10, it is necessary to use a polishing solution suitable for the material of the electrode body 10. For example, if the electrode body 10 is made of silver, it is preferable to immerse the electrode body 10 in a polishing solution consisting of 10% by mass of ferric chloride and 90% by mass of distilled water for about 3 to 1800 seconds. When dry etching the surface 10a of the electrode body 10 and the surface of the regenerative electrolysis counter electrode 20, this can be done using a plasma of a gas that is reactive with the material of the electrode body 10 or the regenerative electrolysis counter electrode 20, or using an inert gas. When electrolytically polishing the surface 10a of the electrode body 10, it is necessary to use a polishing liquid suitable for the material of the electrode body 10. For example, when the electrode body 10 is made of silver, a polishing liquid composed of 40% by volume of concentrated phosphoric acid, 40% by volume of ethanol, and 20% by volume of distilled water is adjusted to 40 °C, the anode is silver (electrode body 10), the cathode is aluminum, and it is preferably carried out by applying a voltage of 25V to 30V for about 4 to 6 minutes. As described above, various types of polishing methods have been exemplified. However, in the polishing process, only one of them may be performed, or two or more of them may be performed.

[0064] After the polishing process, an oxide layer is formed by electrolytically oxidizing the polished surface 10a of the electrode body 10 in an alkaline solution (forming process). As the alkaline solution, a saturated calcium hydroxide solution is preferred. The current density during electrolytic oxidation is 0.005 mA / cm 2 or more and 20 mA / cm 2 or less is preferred, 0.01 mA / cm 2 or more and 15 mA / cm 2 or less is more preferred, 0.05 mA / cm[[ID=1十七]] 2 or more and 10 mA / cm 2 or less is even more preferred. When the current density during electrolytic oxidation is within the above numerical range, an oxide layer with sufficient thickness can be formed on the surface 10a of the electrode body 10, and the electrode potential is likely to be stable. In the electrolytic oxidation of the electrode body 10, the electrolytic charge is 30 mC / cm 2 or more and 500 mC / cm 2 or less is preferred, 50 mC / cm 2 or more and 400 mC / cm 2 or less is more preferred, 70 mC / cm 2 or more and 300 mC / cm 2 or less is even more preferred. When the electrolytic charge is not less than the lower limit value, an oxide layer with sufficient thickness can be generated. When the electrolytic charge is not more than the upper limit value, it is excellent in terms of cost. The time for electrolytic oxidation is adjusted so as to obtain the above electrolytic charge at the above current density. However, regardless of the current density, it is preferable to perform electrolysis for at least about 30 seconds. As a result, the electrode potential becomes stable.

[0065] When applying a potential stabilizer to the surface 10a of the electrode body 10, the stabilizer composition, which has been made into a paste by adding water, may be applied to the surface 10a of the electrode body 10 and the surface of the oxide layer, and solidified to form the first coating layer 11. The oxide layer is located between the electrode body 10 and the first coating layer 11.

[0066] After the forming process, with the electrode body 10 and the regenerative electrolysis counter electrode 20 held in appropriate positions within the resin container 40, the solid electrolyte 30 is filled into the resin container 40 and allowed to solidify. Next, the composition that will be the raw material for the filling resin 50 (hereinafter also referred to as the "filling resin composition") is filled into the opening of the resin container 40 on the side to which the lead wires 70 and 71 are attached, and allowed to solidify. The solid electrolyte 30 and the filler resin composition may be filled first with the solid electrolyte 30, first with the filler resin composition, or both may be filled simultaneously. When forming a liquid junction, a cylindrical frame is provided on the resin container 40 on the solid electrolyte 30 side using paper, for example, so that a liquid junction of the desired dimensions is formed on the solid electrolyte 30 side. The raw material composition (hereinafter also referred to as "liquid junction composition") is then filled into the frame to the desired dimensions and allowed to solidify. To create a meandering liquid junction, the liquid junction composition is filled into a flexible container, and the container is moved in a meandering manner to solidify the liquid junction composition. As a result, a liquid junction with a meandering liquid junction path is obtained. As shown in Figure 1, the formation of the solid electrolyte in which the regenerative electrolysis counter electrode 20 is embedded at the end of the resin container 40 filled with the filling resin 50 may be carried out in the same manner as when forming the liquid junction described above.

[0067] By going through the above steps, the reference electrode 1 is obtained.

[0068] The reference electrode 1 of this embodiment includes an electrode body 10 and a regenerative electrolysis counter electrode 20. Therefore, when the oxide layer on the surface 10a of the electrode body 10 decreases and the electrode potential fluctuates significantly, the oxide layer can be regenerated by applying a voltage to the regenerative electrolysis counter electrode 20 and regenerating electrolysis of the electrode body 10. Thus, the reference electrode 1 can be regenerated on the spot when its performance deteriorates.

[0069] In the regenerative electrolysis of the electrode body 10, the current density is 0.005 mA / cm². 2 More than 20mA / cm 2 The following is preferred: 0.01 mA / cm² 2 More than 15mA / cm 2 The following is more preferable: 0.05 mA / cm 2 More than 10mA / cm 2 The following are even more preferable: If the current density is above the lower limit, the oxide layer can be regenerated. If the current density is below the upper limit, it is cost-effective.

[0070] In the regeneration electrolysis of the electrode body 10, the amount of regeneration electrolysis electricity is 30 mC / cm 2 More than 500mC / cm 2 The following is preferable: 50 mC / cm 2 More than 400mC / cm 2 The following is more preferable: 70 mC / cm 2 More than 300mC / cm 2 The following is even more preferable: If the amount of regenerative electrolysis is equal to or greater than the lower limit, the oxide layer can be regenerated. If the amount of regenerative electrolysis is equal to or less than the upper limit, it is cost-effective.

[0071] In the regenerative electrolysis of the electrode body 10, the time for performing the regenerative electrolysis is adjusted so that the amount of electrolytic electricity can be obtained at the current density, but it is preferable to perform the electrolysis for at least 30 seconds, regardless of the current density. As a result, the electrode potential stabilizes.

[0072] In this embodiment, the reference electrode 1 uses a solid electrolyte 30, which makes it difficult for substances that can react with the active material to reach the electrode body 10. For example, when the active material is silver oxide, it exhibits a more stable electrode potential even in an environment with high concentrations of chloride ions. The reference electrode 1 of this embodiment is made compact by minimizing its length, making it easy to install in actual structures. The reference electrode 1 of this embodiment is cost-effective because it contains the minimum necessary amount of potential stabilizer.

[0073] Although the reference electrode of this embodiment has been described above, the present invention is not limited to the above-described embodiment and can be modified as appropriate without departing from the spirit of the invention. In the above-described embodiment, the shape of the reference electrode is cylindrical and extends in the axial direction, but the reference electrode may also be curved or branched. [Examples]

[0074] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0075] [Example 1] (Recovery of silver oxide electrode potential through regenerative electrolysis) A reference electrode with the same configuration as shown in Figure 1 was fabricated. Silver was used as the metal for the electrode body. The electrode potential of the obtained reference electrode was measured in a saturated calcium hydroxide solution. The potential measurement was performed using a saturated silver chloride reference electrode (SSE = Silver Silver chloride electrode) as a reference. The electrode potential of the reference electrodes in other examples was also measured using the SSE as a reference. After confirming the degradation of performance, regeneration electrolysis was performed in a saturated calcium hydroxide solution. Regeneration electrolysis was performed a total of two times, on the 38th and 90th days of the test. The results of measuring the change in the potential of the reference electrode over time are shown in Figure 7. As shown in Figure 7, the results confirm that by regenerating electrolysis, silver oxide can be generated on the surface of the silver constituting the electrode body, thereby regenerating the potential of the reference electrode to a normal potential (220±20mV vs. SSE), and that the potential of the reference electrode after regenerating electrolysis is reproducible.

[0076] [Example 2] A pure silver wire was immersed in a saturated calcium hydroxide solution, and the reading was 0.1 mA / cm². 2 ~0.6mA / cm 2 Electrolytic oxidation was performed at the specified current density. The amount of silver oxide produced by electrolytic oxidation was evaluated by a constant current reduction method. The results are shown in Figure 8. As shown in Figure 8, when producing silver oxide on the surface of silver by electrolytic oxidation, excessive current density leads to simultaneous active dissolution of silver and oxygen generation, reducing the efficiency of silver oxide production. Conversely, it was found that silver oxide is not produced at low current densities. In other words, the current density at which silver oxide is efficiently produced is 0.2 mA / cm². 2 0.4mA / cm or less 2 It was found that the following was true.

[0077] [Example 3] It has a similar configuration to that shown in Figure 1, and the electrolytic charge is 20 mC / cm². 2 ~100mC / cm 2 A reference electrode was fabricated. Silver was used as the metal for the electrode body. The potential of the obtained reference electrode was measured in a saturated calcium hydroxide solution. The results are shown in Figure 9. As shown in Figure 9, under the condition of low electrolytic charge (20 mC / cm²), 2 ~40 mC / cm² 2 Under conditions where the electrolytic charge was high (100 mC / cm²), the reference electrode showed a potential change from the beginning. 2 In this case, the potential remained stable for more than 60 days. From this, it was found that the greater the amount of electrolytic charge, the more stable the potential becomes.

[0078] [Example 4] Electrolytic oxidation (100mC / cm 2We fabricated electrodes consisting of silver wires that had been oxidized () and solidified with cement, as well as electrodes made solely from the silver wires that had been electrolytically oxidized. Each electrode was immersed in a saturated calcium hydroxide solution, and the potential of each electrode was measured. The results are shown in Figure 10. As shown in Figure 10, the electrode that remained electrolytically oxidized (liquid electrolyte in the figure) showed a stable potential for about 4 days before exhibiting a rapid change in potential. On the other hand, the electrode solidified with cement (solid electrolyte in the figure) initially showed a change in potential, but then maintained a stable potential for a long period of time. From this, it is thought that using a solid electrolyte to fabricate a reference electrode can extend its lifespan.

[0079] [Example 5] A reference electrode with the same configuration as shown in Figure 1 was fabricated. Silver was used as the metal for the electrode body. Two electrodes were fabricated: one containing a solid electrolyte with silver oxide powder added as the active material, and another containing a solid electrolyte without silver oxide powder. Each electrode was immersed in a saturated calcium hydroxide solution, and the potential of each electrode was measured. The results are shown in Figure 11. As shown in Figure 11, electrodes containing solid electrolytes without added silver oxide powder showed potential changes from the beginning of the test. In contrast, electrodes containing solid electrolytes with added silver oxide powder showed less potential change and exhibited a relatively stable potential. This indicates that adding an active material (silver oxide powder) to the solid electrolyte leads to improved potential stability.

[0080] [Example 6] A reference electrode with the same configuration as shown in Figure 1 was fabricated. Silver was used as the metal for the electrode body. An arbitrary amount of active material (silver oxide powder) was added to the solid electrolyte. The obtained reference electrode was immersed in a saturated calcium hydroxide solution, and the potential of the reference electrode was measured. The results are shown in Figure 12. As shown in Figure 12, from the start of the experiment until day 100, all reference electrodes with active material additions of 1% to 30% relative to the total mass (100% mass) of the solid electrolyte showed a stable potential (220±20mV vs. SSE). After 100 days, the electrode with 1% mass of active material showed a significant change in potential. The electrode with 5% mass of active material also showed a slight change in potential. The electrodes with 10% to 30% mass of active material showed a stable potential. From this, it was found that at least 1% mass of active material is required to add to the solid electrolyte. Furthermore, if long-term potential stability is expected, it is considered that an active material addition of 10% mass or more is necessary.

[0081] [Example 7] Concrete specimens with reference electrodes embedded inside, similar in configuration to those shown in Figure 2, were exposed outdoors. The potential of the reference electrodes inside the concrete specimens was measured during exposure. The results are shown in Figure 13. As shown in Figure 13, a decline in performance was observed around 200 days into the test. On day 230 of the test, the reading was 0.1 mA / cm². 2 Regenerative electrolysis of the reference electrode was performed for 1000 seconds at a constant current density. The amount of regenerative electrolysis electricity was 100 mC / cm². 2 As a result, we were able to confirm that the performance was restored through regenerative electrolysis. [Industrial applicability]

[0082] The reference electrode of the present invention can be used even in environments with high chloride ion concentrations, such as for measuring the potential of steel in concrete bridges, steel in reinforced concrete in seawater, piping in air mortar-filled sheathed pipes, steel in concrete structures using seawater, steel in improved soil, and steel in immersed tunnels. It can also be used for measuring the potential of steel in soil. Therefore, it has extremely large industrial applicability. [Explanation of Symbols]

[0083] 1,100,200,300,400,500 Reference electrodes 10 Electrode body 11 First coating layer 20,210,510 Counter electrode for regenerative electrolysis 30 Solid electrolyte 40,410,411 Plastic containers 50, Filling resin 60, 61 Crimp terminals 70, 71 Lead wires

Claims

1. A reference electrode embedded in concrete and used to measure the potential of metals in the concrete, A cylindrical resin container housing the electrode body in contact with the solid electrolyte, The solid electrolyte and the concrete are in contact with at least one of the following: The electrode body is a reference electrode having at least one of an oxide layer and a coating layer formed by the oxidation of the metal constituting the electrode body on at least a portion of its surface.

2. The reference electrode according to claim 1, wherein the electrode body and the counter electrode for regenerative electrolysis are embedded in the same solid electrolyte.

3. The matching electrode according to claim 1, wherein the electrode body and the counter electrode for regenerative electrolysis are embedded in different solid electrolytes.

4. The reference electrode according to claim 1, wherein the metal constituting the electrode body is silver.

5. The reference electrode according to claim 1, wherein the counter electrode for regenerative electrolysis has a second coating layer that covers at least a portion of its surface.

6. The reference electrode according to claim 1, having a liquid junction portion for sealing the solid electrolyte.

7. The reference electrode according to claim 1, wherein the counter electrode for regenerative electrolysis is a metal embedded in concrete.

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