TW202016358A - Electrolytic synthesis anode and method for producing fluorine gas - Google Patents

Abstract

Provided are an electrolytic synthesis anode and an electrolytic synthesis method capable of electrolytically synthesizing fluorine gas or a fluorine-containing compound with low power consumption by suppressing electrolytic resistance. An electrolytic synthesis anode (3) for electrolytically synthesizing fluorine gas includes: an anode substrate (31) formed of a metallic material; and a carbonaceous layer (33) that is formed of a carbonaceous material and that is disposed on a surface of the anode substrate (31). In addition, the metallic material is an iron-based alloy containing iron and nickel.

Description

Anode for electrolytic synthesis, and method for producing fluorine gas

The invention relates to an anode for electrolytic synthesis of fluorine gas or fluorine-containing compound, and an electrolytic synthesis method of fluorine gas or fluorine-containing compound.

Fluorine gas or fluorine-containing compounds (for example, nitrogen trifluoride) can be synthesized by electrically decomposing an electrolyte containing fluoride ions (electrolytic synthesis). In this electrolytic synthesis, a carbon electrode is generally used as an anode. However, if a carbon electrode is used, even if it is electrically decomposed at a very small current density, the electrolytic cell voltage necessary to obtain a predetermined current may exceed 12V. The problem of high pressure. This phenomenon is called the anode effect. The reason for the anode effect is as follows. When the electrolytic decomposition of the electrolyte is carried out, the fluorine gas generated on the surface of the anode will react with the carbon forming the anode, so that a carbon-fluorine-bonded film having covalent bonding will be formed on the surface of the anode. This coating is insulative and has poor wettability with the electrolyte. Therefore, it becomes difficult for current to flow to the anode, which causes an anode effect.

On the other hand, when a metal electrode is used as the anode, the problem of dissolution of the metal electrode may occur, or an insulating film formed of oxide or fluoride on the surface of the metal electrode may make it difficult for current to flow and consume power. The amount becomes higher. In addition, when an electrode formed by coating a metal substrate with a conductive carbon film having a diamond structure (for example, refer to Patent Document 1) is used as an anode, although the electrolytic resistance may be suppressed and the amount of power consumption may be suppressed, the effect is not high. full. Prior technical literature Patent Literature

Patent Literature 1: Japanese Patent Publication Gazette No. 46994 of 2011

Problems to be solved by the invention

The problem to be solved by the present invention is to provide an anode for electrolytic synthesis and an electrolytic synthesis method capable of electrolytically synthesizing a fluorine gas or a fluorine-containing compound with low power consumption while suppressing electrolytic resistance. Technical means to solve problems

To solve the aforementioned problem to be solved, one aspect of the present invention is as described in the following [1] to [8]. [1] An anode for electrolytic synthesis, which is an anode for electrolytic synthesis of fluorine gas, Equipped with: an anode substrate formed of a metallic material, and a carbonaceous layer formed of a carbonaceous material and arranged on the surface of the anode substrate; The aforementioned metallic material is an iron-based alloy containing iron and nickel.

[2] The anode for electrolytic synthesis as described in [1], wherein the metallic material is an iron-based alloy containing iron and nickel and cobalt. [3] The anode for electrolytic synthesis according to [1], wherein the metallic material is an iron-based alloy containing iron and nickel and cobalt and carbon. [4] The anode for electrolytic synthesis according to [1], wherein the iron-based alloy contains 32% by mass or more and 40% by mass or less of nickel.

[5] The anode for electrolytic synthesis according to [2], wherein the iron-based alloy contains 30% by mass or more and 38% by mass or less nickel, and 3% by mass or more and 12% by mass or less cobalt. [6] The anode for electrolytic synthesis according to [3], wherein the iron-based alloy contains 20% by mass or more and 36% by mass or less nickel, 3% by mass or more and 20% by mass or less cobalt, and 0.01% by mass or more 1.5% by mass or less of carbon.

[7] The anode for electrolytic synthesis according to any one of [1] to [6], wherein the carbonaceous layer is composed of an inner layer in contact with the anode substrate and an outer layer outside the inner layer In the configuration, the inner layer is a layer in which at least one of the metals constituting the iron-based alloy is mixed with carbon, and the outer layer is a layer formed of carbon. [8] A method for producing fluorine gas, comprising using the anode for electrolytic synthesis according to any one of [1] to [7] to electrically decompose an electrolyte containing hydrogen fluoride, and electrolytically synthesize fluorine gas. Effect of invention

According to the present invention, it is possible to suppress the electrolytic resistance and electrolytically synthesize a fluorine gas or a fluorine-containing compound with low power consumption.

An embodiment of the present invention will be described below. In addition, this embodiment is merely an example of the present invention, and the present invention is not limited to this embodiment. In addition, various changes or improvements can be applied to the present embodiment, and the forms to which these changes or improvements are applied may also be included in the present invention.

1 and 2, the structure of an electrolysis device provided with an anode for electrolytic synthesis according to this embodiment will be described. In addition, FIG. 1 is a schematic cross-sectional view of the plane of the electrolytic synthesis anode and the cathode 5 for electrosynthesis that are orthogonal to the planes of the electrolysis apparatus and parallel to the vertical direction. In addition, FIG. 2 is a schematic cross-sectional view of a plane in which the electrolytic device is virtually cut with a plane parallel to the plate surfaces of the electrolytic synthesis anode 3 and the electrolytic synthesis cathode 5 of the electrolytic device and parallel to the vertical direction.

The electrolytic device shown in FIGS. 1 and 2 includes an electrolytic cell 1 for storing the electrolytic solution 10, and an anode 3 for electrolytic synthesis and a cathode 5 for electrolytic synthesis disposed in the electrolytic cell 1 and immersed in the electrolytic solution 10. The inside of the electrolytic cell 1 is divided into an anode chamber 12 and a cathode chamber 14 by a cylindrical partition 7 extending downward from the cover 1 a of the electrolytic cell 1 in the vertical direction. That is, the area inside the cylindrical partition 7 is the anode chamber 12, and the area outside the cylindrical partition 7 is the cathode chamber 14.

The anode 3 for electrolytic synthesis is not limited in shape and may be, for example, cylindrical, but in this example, it has a plate shape, and its plate surface is arranged in the anode chamber 12 so as to be parallel to the vertical direction. In addition, the cathode 5 for electrolytic synthesis has a plate shape, the plate surface of which is parallel to the surface of the anode 3 for electrolytic synthesis, and is arranged on the cathode such that the anode 3 for electrolytic synthesis is sandwiched between the cathodes 5 and 5 for electrolytic synthesis Room 14. In addition, between the front and back surfaces of the cathodes 5 and 5 for electrolytic synthesis, the surface opposite to the surface of the anode 3 for electrolytic synthesis is equipped with a cathode 5, 5 or electrolyte 10 for electrolytic synthesis Cooler for cooling. In the example of the electrolysis device shown in FIGS. 1 and 2, the cooling pipe 16 through which the cooling fluid flows is installed in the cathodes 5 and 5 for electrolytic synthesis as a cooler.

As the anode 3 for electrolytic synthesis, an electrode having the following configuration can be used. That is, as shown in FIG. 3, the anode 3 for electrolytic synthesis includes an anode base 31 formed of a metallic material and a carbonaceous layer 33 formed of a carbonaceous material and disposed on the surface of the anode base 31. Electrode. In addition, the metallic material forming the anode base 31 is an iron-based alloy containing iron and nickel. The iron-based alloy may be an alloy made of iron and nickel and unavoidable impurities, or may be an alloy containing iron and nickel and other alloy components. In addition, the iron-based alloy in the present invention means an alloy containing iron as a main component, that is, an alloy having the largest content of iron among alloy components.

The resistance of the metal is much lower than that of carbon, which is one tenth to one hundredth. Therefore, if a metal substrate is used as the substrate of the anode 3 for electrosynthesis (anode substrate 31), it can reduce the Electrolytic resistance. In addition, if the metallic material forming the anode base 31 is made of an iron-based alloy having a specific alloy composition, the electrolytic resistance of the carbonaceous layer 33 disposed on the surface of the anode base 31 can be suppressed low. Therefore, if the anode 3 for electrolytic synthesis of the present embodiment is used, it is possible to electrolytically synthesize a fluorine gas or a fluorine-containing compound with low power consumption while suppressing the electrolytic resistance.

In addition, in the case of electrolytic synthesis using a carbon electrode as an anode in an electrolyte containing fluoride ions, the carbon electrode will gradually collapse and the electrolytic voltage will gradually rise, and the rise of the voltage will further induce the collapse of the carbon electrode. Therefore, if the carbon electrode collapses to a certain extent, it is necessary to temporarily interrupt the electrolytic synthesis and replace the carbon electrode. In addition, the used carbon electrode cannot be covered with a diamond film, so the used carbon electrode can only be discarded.

On the other hand, the anode 3 for electrolytic synthesis of the present embodiment is less likely to collapse due to electrolysis, so stable electrolytic synthesis can be performed. Therefore, there is almost no need to interrupt the electrolytic synthesis and replace the anode to perform maintenance of the electrolytic cell, so that the maintenance frequency can be reduced. In addition, even if the anode is used once, a carbonaceous layer can still be formed on the surface, so as long as the anode substrate does not disappear, a carbonaceous layer can still be formed on the surface and continue to be used. In addition, it can also use electrolytically synthesized fluorine gas as the starting material to contain uranium hexafluoride (UF ₆ ), sulfur hexafluoride (SF ₆ ), carbon tetrafluoride (CF ₄ ), nitrogen trifluoride, etc. Fluorine compounds are chemically synthesized. Fluorine gas, or fluorinated compounds such as uranium hexafluoride, sulfur hexafluoride, carbon tetrafluoride, and nitrogen trifluoride, are useful in the nuclear energy industry, semiconductor industry, medical pesticides, and civilian use fields.

The carbonaceous material forming the carbonaceous layer 33 is not particularly limited as long as it contains carbon, but examples of the carbon contained in the carbonaceous material include crystalline carbon such as diamond and graphite, and amorphous materials such as carbon black. Carbon, in addition to carbon nanotubes, graphene, diamond-like carbon and so on. In addition, the carbonaceous material forming the carbonaceous layer 33 may be a material made of only carbon, or a mixture of carbon and other components (such as a mixture of carbon and metal or a mixture of carbon and ceramic) . When the carbonaceous material is a mixture of carbon and metal, the metal may also be the metal (iron, nickel, cobalt, etc.) contained in the metal material forming the anode base 31.

When the carbonaceous material is a mixture of carbon and other components, the carbon content of the carbonaceous material is preferably greater than the carbon content of the metal material forming the anode base 31 and less than 100 mass %. For example, when the metallic material forming the anode base 31 does not contain carbon, the content of carbon in the carbonaceous material is preferably more than 0% by mass but less than 100% by mass. When the metallic material forming the anode base 31 contains When carbon is 1.5% by mass, the content of carbon in the carbonaceous material is preferably more than 1.5% by mass and less than 100% by mass.

The content of nickel in the iron-based alloy containing iron and nickel is not particularly limited, but in order to suppress the electrolytic resistance of the carbonaceous layer 33 to be lower, it is preferably set to 32% by mass or more and 40% by mass or less. It is set to 34% by mass or more and 38% by mass or less. The metallic material forming the anode base 31 can also be defined as an iron-based alloy containing iron and nickel and cobalt. The iron-based alloy may be an alloy made of iron, nickel, cobalt and unavoidable impurities, or it may be an alloy containing iron, nickel, cobalt and other alloy components.

The content of nickel in the iron-based alloy containing iron and nickel and cobalt is not particularly limited, but in order to suppress the electrolytic resistance of the carbonaceous layer 33 to be lower, it is preferably set to 30% by mass or more and 38% by mass or less, More preferably, it is set at 31% by mass or more and 35% by mass or less. In addition, the content of cobalt in the iron-based alloy containing iron and nickel and cobalt is not particularly limited, but in order to suppress the electrolytic resistance of the carbonaceous layer 33 to be lower, it is preferably set to 3% by mass or more and 12% by mass In the following, it is more preferably 4% by mass or more and 7% by mass or less.

In addition, the metallic material forming the anode base 31 can also be defined as an iron-based alloy containing iron and nickel and cobalt and carbon. The iron-based alloy may be an alloy made of iron, nickel, cobalt, and carbon and inevitable impurities, or may be an alloy containing iron, nickel, cobalt, and carbon and other alloy components. The content of nickel in the iron-based alloy containing iron and nickel and cobalt and carbon is not particularly limited, but in order to suppress the electrolytic resistance of the carbonaceous layer 33 to be lower, it is preferably set to 20% by mass or more and 36% by mass Below, it is more preferably set to 21% by mass or more and 28% by mass or less.

In addition, the content of cobalt in the iron-based alloy containing iron and nickel and cobalt and carbon is not particularly limited, but in order to suppress the electrolytic resistance of the carbonaceous layer 33 to be lower, it is preferably set to 3% by mass or more 20 If the mass% or less, it is more preferable to set it as 6 mass% or more and 16 mass% or less. In addition, the content of carbon in the iron-based alloy containing iron and nickel and cobalt and carbon is not particularly limited, but in order to suppress the electrolytic resistance of the carbonaceous layer 33 to be lower, it is preferably set to 0.01% by mass or more and 1.5 The mass% or less, more preferably 0.5 mass% or more and 1.0 mass% or less.

In addition, the carbonaceous layer 33 may have a one-layer structure as shown in FIG. 3 or a two-layer structure as shown in FIG. 4. In other words, the carbonaceous layer 33 may also be composed of an inner layer 331 that is in contact with the anode base 31 and an outer layer 332 that is outside the inner layer 331. Here, the inner layer 331 is a layer in which at least one of metals (iron, nickel, cobalt, etc.) constituting the iron-based alloy forming the anode base 31 is mixed with carbon, and the outer layer 332 is a layer formed of carbon.

The inner layer 331 is composed of metal and carbon constituting the iron-based alloy forming the anode base 31 as described above, but the content of carbon in the inner layer 331 is preferably higher than that of the metallic material forming the anode base 31 The carbon content is still large and less than 100% by mass. For example, when the metallic material forming the anode base 31 does not contain carbon, the content of carbon in the inner layer 331 is preferably more than 0% by mass but less than 100% by mass. When the metallic material forming the anode base 31 contains In the case of 1.5% by mass of carbon, the content of carbon in the inner layer 331 is preferably more than 1.5% by mass and less than 100% by mass.

The method of forming the carbonaceous layer 33 on the surface of the anode substrate 31 is not particularly limited, but in the case of the one-layer structured carbonaceous layer 33 as shown in FIG. 3, the surface of the anode substrate 31 may be A method of forming the carbonaceous layer 33 or a method of modifying the surface layer portion of the anode substrate 31 to form the carbonaceous layer 33. As the film forming method, for example, a vacuum vapor deposition method typified by a resistance heating vapor deposition method, an electron beam vapor deposition method, a sputtering method, an ion plating method, a thermal filament chemical vapor deposition (CVD) method , Microwave plasma CVD method, plasma arc jet (plasma arc jet) CVD method, plasma ion implantation method and other dry film forming methods. In particular, it is preferable to form the carbonaceous layer 33 under the condition that the temperature of the anode base 31 becomes lower than 450°C. In addition, as a modification method, for example, an ion implantation method using a hydrocarbon-based gas or the like can be mentioned.

In addition, in the case of the carbonaceous layer 33 having a two-layer structure as shown in FIG. 4, a method of forming the inner layer 331 and the outer layer 332 of the carbonaceous layer 33 in succession on the surface of the anode base 31 may be mentioned. Or a method of modifying the surface layer portion of the anode substrate 31 to form the inner layer 331 and then forming the outer layer 332 on the inner layer 331.

In the case where the inner layer 331 and the outer layer 332 of the carbonaceous layer 33 are formed on the surface of the anode substrate 31 in succession, for example, the following method can be adopted, that is, the above-described dry film forming method can be used to continuously change the metal and After forming the inner layer 331 on the surface of the anode substrate 31 with the carbon composition ratio, the outer layer 332 is formed on the inner layer 331. In addition, when the surface layer portion of the anode substrate 31 is modified to form the inner layer 331 and then the outer layer 332 is formed on the inner layer 331, for example, the following method can be adopted, that is, by using a hydrocarbon-based gas The plasma implantation method implants carbon ions in the surface layer portion of the anode substrate 31 to modify the surface layer portion to form an inner layer 331 in which the composition ratio of metal to carbon continuously changes, and then the above-mentioned dry film formation Method The outer layer 332 is formed on the inner layer 331.

As the cathode 5 for electrolytic synthesis, a metal electrode can be used, and an electrode made of iron, for example, can be used. As the electrolytic solution 10, a molten salt can be used, and for example, molten potassium fluoride (KF) containing hydrogen fluoride (HF) can be used. When an electric current of, for example, a current density of 0.01 A/cm ² or more and 1 A/cm ² or less is supplied between the anode 3 for electrolytic synthesis and the cathode 5 for electrolytic synthesis, fluorine gas (F ₂ ) is generated in the anode 3 for electrolytic synthesis The anode gas as the main component generates cathode gas containing hydrogen gas (H ₂ ) as a by-product in the cathode 5 for electrolytic synthesis.

The anode gas is accumulated in the space on the liquid surface of the electrolyte 10 in the anode chamber 12, and the cathode gas is accumulated in the space on the liquid surface of the electrolyte 10 in the cathode chamber 14. The space on the liquid surface of the electrolyte 10 is partitioned by the partition 7 into a space in the anode chamber 12 and a space in the cathode chamber 14, so that the anode gas and the cathode gas are not mixed. On the other hand, the electrolyte 10 is partitioned by the partition 7 for the portion above the lower end of the partition 7, but is not partitioned by the partition 7 for the portion below the lower end of the partition 7 continuous.

In addition, the anode chamber 12 is provided with an exhaust port 21 for exhausting the anode gas generated in the anode 3 for electrolytic synthesis from the anode chamber 12 to the outside of the electrolytic cell 1, and the cathode chamber 14 is provided with a The cathode gas generated by the cathodes 5 and 5 is discharged from the cathode chamber 14 to the exhaust port 23 outside the electrolytic cell 1.

Hereinafter, the anode for electrolytic synthesis according to this embodiment and the electrolytic synthesis method using the fluorine gas or fluorine-containing compound will be described in further detail. (1) Electrolysis cell The material of the electrolytic cell for electrolytic synthesis is not particularly limited, but from the viewpoint of corrosion resistance, copper, mild steel, Monel (trademark), nickel alloy, fluororesin, etc. are preferably used. In order to prevent the fluorine gas or fluorine-containing compound that is electrolytically synthesized at the anode for electrolytic synthesis from being mixed with the hydrogen gas generated at the cathode for electrolytic synthesis, the anode chamber provided with the anode for electrolytic synthesis and the cathode chamber provided with the cathode for electrolytic synthesis are Preferably, as in the electrolysis device shown in FIGS. 1 and 2, all or a part of it is partitioned by partition walls, diaphragms, and the like.

(2) Electrolyte An example of the electrolyte used when electrolytically synthesizing fluorine gas will be described. In the case of electrolytic synthesis of fluorine gas, a mixed molten salt of hydrogen fluoride and potassium fluoride can be used as an electrolyte. The molar ratio of hydrogen fluoride to potassium fluoride in this electrolyte can be set to 1.5 to 2.5:1, for example. Alternatively, a mixed molten salt of hydrogen fluoride and cesium fluoride (CsF), or a mixed molten salt of hydrogen fluoride and potassium fluoride and cesium fluoride can also be used as the electrolyte. The composition ratio of the electrolyte containing cesium fluoride can also be set as follows. In other words, the molar ratio of cesium fluoride to hydrogen fluoride in the electrolyte can also be set to be 1: 1.0 to 4.0. In addition, the molar ratio of cesium fluoride, hydrogen fluoride, and potassium fluoride in the electrolyte can also be set at 1:1.5 to 4.0:0.01 to 1.0.

Next, an example of the electrolyte used when electrolytically synthesizing a fluorine-containing compound will be described. In the case of electrolytically synthesizing a fluorine-containing compound, a compound having a chemical structure before fluorination of the fluorine-containing compound to be synthesized, a mixed molten salt with hydrogen fluoride and potassium fluoride can be used as an electrolyte. Compounds with the chemical structure before fluorination can be made into a gaseous state, while spraying a mixed molten salt of hydrogen fluoride and potassium fluoride for electrolytic synthesis, or using compounds with the chemical structure before fluorination dissolved in hydrogen fluoride and Electrolyte is synthesized by electrolytic solution of potassium fluoride mixed with molten salt. The compound having the chemical structure before fluorination will react with the fluorine gas generated in the reaction of the anode for electrolytic synthesis to become a fluorine-containing compound.

For example, in the case of electrolytic synthesis of nitrogen trifluoride, a mixed molten salt of hydrogen fluoride and ammonium fluoride (NH ₄ F), or a mixed molten salt of hydrogen fluoride and potassium fluoride and ammonium fluoride can be used as an electrolyte. In the case of a mixed molten salt of hydrogen fluoride and ammonium fluoride, the molar ratio of hydrogen fluoride and ammonium fluoride in the electrolyte can be set to 1.5 to 2.5:1, for example. Hydrogen fluoride generally contains 0.1% by mass or more and 5% by mass or less of water. When the water content in hydrogen fluoride is more than 3% by mass, the water content in hydrogen fluoride can be reduced to 3% by mass or less by the method described in Japanese Patent Laid-Open No. 7-2515, for example. Electrolyte. Generally speaking, it is not easy to simply reduce the amount of water in hydrogen fluoride, so in the case of industrially electrolytically synthesizing fluorine gas or fluorine-containing compounds, from the cost side, it is preferable to use the water content It is hydrogen fluoride of 3% by mass or less.

(3) Anode for electrolytic synthesis The shape of the anode for electrolytic synthesis is not particularly limited, such as a plate shape, a mesh shape, a punched plate shape, bending the plate into a round shape, guiding the generated bubbles to the back surface of the electrode, etc. Those who consider the three-dimensional structure of the cycle considered, because the anode substrate is formed of a metallic material, so the shape can be freely selected.

(4) Cathode for electrolytic synthesis As described above, a metal electrode can be used as a cathode for electrolytic synthesis. Examples of the type of metal forming the metal electrode include iron, copper, nickel, and Monel (trademark). The shape of the cathode for electrolytic synthesis is similar to the anode for electrolytic synthesis. Examples

Examples and comparative examples are disclosed below to explain the present invention more specifically. [Comparative Example 1] Granular graphite "SIGRAFINE (registered trademark) ABR" manufactured by SGL Carbon was processed into a plate 2 cm long, 1 cm wide, and 0.5 cm thick, and a metal rod for power supply was installed. It is masked in a rectangular shape of 1 cm to make an electrode. This electrode was designated as the anode, and the Monel (trademark) plate was designated as the cathode, to produce an electrolytic device having the same configuration as the electrolytic device shown in FIGS. The reference electrode is defined as the corrosion potential of nickel. In addition, as the electrolyte, a mixed molten salt of potassium fluoride and hydrogen fluoride (KF·2HF) is used. Under the reference of the corrosion potential of nickel, constant-voltage electrolysis was carried out so that the potential of the anode became constant at 6 V, and the fluorine gas was electrolytically synthesized. The current at this time was 0.148A, and the apparent current density was 0.148A/cm ² . Therefore, the electrolytic resistance of the anode is 40.5Ω (=6/0.148).

[Comparative Example 2] A conductive diamond film was formed on the surface of the anode by a thermal CVD method. Except for this point, as in Comparative Example 1, electrolytic synthesis was performed. The current at this time was 0.260 A, and the apparent current density was 0.260 A/cm ² . Therefore, the electrolytic resistance of the anode is 23.1Ω (=6/0.260).

[Comparative Example 3] Instead of constant voltage electrolysis but constant current electrolysis, other than this point, as in Comparative Example 2, electrolytic synthesis was performed. The current was 0.148A, and the current density was 0.148A/cm ² . The voltage of the anode of the reference electrode reference at this time was 5.23V. Therefore, the electrolytic resistance of the anode is 35.3Ω (=5.23/0.148).

[Example 1] As the anode, the electrode described below was used, and except for this point, as in Comparative Example 1, electrolytic synthesis was performed. The anode used in Example 1 includes an anode base formed of a metallic material and a carbonaceous layer formed of a carbonaceous material and disposed on the surface of the anode base. The metallic material forming the anode matrix is an iron-based alloy formed of iron, nickel, and cobalt. The iron content is 63.5% by mass, the nickel content is 31.5% by mass, and the cobalt content is 5.0% by mass. In addition, the size of the anode substrate was 2 cm long, 1 cm wide, and 1 mm thick, and the electrode surface was masked so as to have a rectangular shape of 1 cm long and 1 cm wide.

The carbonaceous layer arranged on the surface of the anode substrate has a two-layer structure composed of an inner layer and an outer layer. By analysis using X-ray photoelectron spectroscopy (XPS), the inner layer is composed of carbon and metals (iron, nickel , Cobalt) layer, the outer layer is essentially a drilled carbon layer made of only carbon. This inner layer is formed by implanting carbon ions in the surface layer portion of the anode substrate by plasma ion implantation to modify the surface layer portion. In addition, the outer layer is formed by laminating carbon on the inner layer by plasma ion implantation.

The current during constant voltage electrolysis was 0.454A, and the apparent current density was 0.454A/cm ² . Therefore, the electrolytic resistance of the anode is 13.2Ω (=6/0.454). The value of the electrolytic resistance of this anode is about half that of Comparative Example 2, and it can be seen that the electrolytic resistance of the anode is greatly reduced.

[Comparative Example 4] An anode substrate made of nickel was used, and the electrolysis synthesis was performed as in Example 1 except for this point. The current at this time was 0.27A, and the apparent current density was 0.27A/cm ² . Therefore, the electrolytic resistance of the anode is 22.2Ω (=6/0.27). In addition, when constant-voltage electrolysis continues, the current gradually becomes difficult to flow, the current decreases to 0.14A, and the electrolytic resistance of the anode increases to 42.9Ω (=6/0.14).

[Comparative Example 5] An anode substrate made of iron was used, and the electrolysis synthesis was performed as in Example 1 except for this point. The current at this time was 0.24A, and the apparent current density was 0.24A/cm ² . Therefore, the electrolytic resistance of the anode is 25.0Ω (=6/0.24). In addition, as the constant-voltage electrolysis continues, the current gradually becomes difficult to flow, the current decreases to 0.14A, and the electrolytic resistance of the anode increases to 42.9Ω (=6/0.14).

[Embodiment 2] Instead of constant voltage electrolysis but constant current electrolysis, except for this point, electrolysis synthesis was performed as in Example 1. The current was 0.148A, and the current density was 0.148A/cm ² . The voltage of the anode of the reference electrode reference at this time was 4.60V. Therefore, the electrolytic resistance of the anode is 31.1Ω (=4.60/0.148). The power consumption is proportional to the voltage, so compared to the case of Comparative Example 1, the power consumption will be reduced by more than 20% (100-4.6/6×100). While supplying hydrogen fluoride, constant current electrolysis was performed at the same current for 500 hours. As a result, the voltage did not change, the current efficiency of fluorine gas generation was 99%, and no deterioration was observed on the surface of the anode after the electrolysis.

[Example 3] The metallic material forming the anode substrate is an iron-based alloy composed of iron, nickel, and cobalt. The iron content is 61.8% by mass, the nickel content is 32.0% by mass, and the cobalt content is 6.2% by mass, except for this point, as in Example 1, electrolytic synthesis was performed. The current at this time was 0.472A, and the apparent current density was 0.472A/cm ² . Therefore, the electrolytic resistance of the anode is 12.7Ω (=6/0.472).

[Example 4] The metallic material forming the anode substrate is an iron-based alloy formed of iron, nickel, and cobalt. The iron content is 52.0% by mass, the nickel content is 38.0% by mass, and the cobalt content is 10.0% by mass, except for this point, as in Example 1, electrolytic synthesis was performed. The current at this time was 0.411A, and the apparent current density was 0.411A/cm ² . Therefore, the electrolytic resistance of the anode is 14.6Ω (=6/0.411).

[Example 5] The metallic material forming the anode substrate is an iron-based alloy formed of iron and nickel. The iron content is 65.0% by mass, and the nickel content is 35.0% by mass. 1. Perform electrolytic synthesis. The current at this time was 0.373A, and the apparent current density was 0.373A/cm ² . Therefore, the electrolytic resistance of the anode is 16.1Ω (=6/0.373).

[Example 6] The metallic material forming the anode substrate is an iron-based alloy composed of iron and nickel and cobalt and carbon. The iron content is 61.2% by mass, the nickel content is 30.0% by mass, and the cobalt content The amount was 8.0% by mass and the carbon content was 0.8% by mass. Except for this point, as in Example 1, electrolytic synthesis was performed. The current at this time was 0.448A, and the apparent current density was 0.448A/cm ² . Therefore, the electrolytic resistance of the anode is 13.4Ω (=6/0.448).

[Example 7] The carbonaceous layer disposed on the surface of the anode substrate is a diamond-like carbon layer having a one-layer structure formed by the plasma CVD method. Except for this point, as in Example 1, electrolytic synthesis is performed. The current at this time was 0.432A, and the apparent current density was 0.432A/cm ² . Therefore, the electrolytic resistance of the anode is 13.9Ω (=6/0.432).

As can be seen from Table 1, Examples 1 to 7 use an iron-based alloy containing iron and nickel to form the anode substrate, and the anode substrate has a carbonaceous layer on the surface of the anode substrate, so compared with the use of carbon anode Examples 1 and 2 or Comparative Examples 4 and 5 using metal anodes can stably reduce the resistance during constant voltage electrolysis. In addition, it can be seen that when an anode substrate is formed of an iron-based alloy containing iron, nickel, and cobalt, the resistance during constant current electrolysis can also be reduced compared to Comparative Example 3 using a carbon anode.

1: electrolytic cell 3: anode for electrolytic synthesis 5: Cathode for electrolytic synthesis 10: electrolyte 31: anode substrate 33: Carbonaceous layer 331: inner layer 332: outer layer

[Fig. 1] A cross-sectional view illustrating the structure of an electrolytic device equipped with an anode for electrolytic synthesis according to an embodiment of the present invention. [Fig. 2] A schematic cross-sectional view of the electrolytic device of Fig. 1 being cut imaginarily on a plane different from that of Fig. 1. [Figure 3] A schematic cross-sectional view of an example of an anode for electrolytic synthesis. [Fig. 4] Another schematic sectional view of an anode for electrolytic synthesis.

3: anode for electrolytic synthesis

31: anode substrate

33: Carbonaceous layer

Claims (8)

An anode for electrolytic synthesis is an anode for electrolytic synthesis of fluorine gas, Equipped with: an anode substrate formed of a metallic material, and a carbonaceous layer formed of a carbonaceous material and arranged on the surface of the anode substrate; The aforementioned metallic material is an iron-based alloy containing iron and nickel. The anode for electrolytic synthesis as described in item 1 of the scope of the patent application, wherein the metallic material is an iron-based alloy containing iron and nickel and cobalt. The anode for electrolytic synthesis as described in item 1 of the patent application range, wherein the metallic material is an iron-based alloy containing iron and nickel and cobalt and carbon. The anode for electrolytic synthesis as described in item 1 of the patent application range, wherein the iron-based alloy contains 32% by mass or more and 40% by mass or less of nickel. The anode for electrolytic synthesis as described in item 2 of the patent application range, wherein the iron-based alloy contains 30% by mass or more and 38% by mass or less nickel, and 3% by mass or more and 12% by mass or less cobalt. The anode for electrolytic synthesis as described in item 3 of the patent application range, wherein the iron-based alloy contains 20% by mass or more and 36% by mass or less nickel, 3% by mass or more and 20% by mass or less cobalt, and 0.01% by mass or more 1.5% by mass or less of carbon. The anode for electrolytic synthesis according to any one of claims 1 to 6, wherein the carbonaceous layer is composed of an inner layer in contact with the anode substrate and an outer layer outside the inner layer, The inner layer is a layer in which at least one of the metals constituting the iron-based alloy is mixed with carbon, and the outer layer is a layer formed of carbon. A method for producing fluorine gas includes using an anode for electrolytic synthesis as described in any one of claims 1 to 7 to electrically decompose an electrolyte containing hydrogen fluoride, and electrolytically synthesize fluorine gas.

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