阅读说明：本技术 电解合成用阳极和氟气的制造方法 (Anode for electrolytic synthesis and method for producing fluorine gas ) 是由 福地阳介 小黑慎也 小林浩 于 2019-07-29 设计创作，主要内容包括：提供一种电解合成用阳极和电解合成方法,其能够抑制电解电阻,以低功耗电解合成氟气或含氟化合物。用于电解合成氟气的电解合成阳极(3)具备由金属质材料形成的阳极基板(31)以及由碳质材料形成并配置在阳极基板(31)的表面上的碳质层(33)。并且,金属质材料是含有铁和镍的铁基合金。(Provided are an anode for electrolytic synthesis and an electrolytic synthesis method, which can suppress electrolytic resistance and electrolytically synthesize fluorine gas or fluorine-containing compounds with low power consumption. An electrolytic synthesis anode (3) for electrolytically synthesizing fluorine gas is provided with an anode substrate (31) formed from a metallic material and a carbonaceous layer (33) formed from a carbonaceous material and disposed on the surface of the anode substrate (31). Also, the metallic material is an iron-based alloy containing iron and nickel.)

1. An anode for electrolytic synthesis, which is an anode for electrolytic synthesis of fluorine gas,

the disclosed device is provided with: an anode base formed of a metallic material, and a carbonaceous layer formed of a carbonaceous material and disposed on a surface of the anode base,

the metallic material is an iron-based alloy containing iron and nickel.

2. The anode for electrolytic synthesis according to claim 1, wherein the metallic material is an iron-based alloy containing iron, nickel and cobalt.

3. The anode for electrolytic synthesis according to claim 1, wherein the metallic material is an iron-based alloy containing iron, nickel, cobalt and carbon.

4. The anode for electrolytic synthesis according to claim 1, wherein the iron-based alloy contains 32 mass% or more and 40 mass% or less of nickel.

5. The anode for electrolytic synthesis according to claim 2, wherein the iron-based alloy contains 30 mass% to 38 mass% of nickel and 3 mass% to 12 mass% of cobalt.

6. The anode for electrolytic synthesis according to claim 3, wherein the iron-based alloy contains 20 mass% to 36 mass% of nickel, 3 mass% to 20 mass% of cobalt, and 0.01 mass% to 1.5 mass% of carbon.

7. The anode for electrolytic synthesis according to any one of claims 1 to 6, wherein the carbonaceous layer comprises an inner layer in contact with the anode base and an outer layer on the outer side of the inner layer, the inner layer is a layer in which carbon is mixed with at least one of metals constituting the iron-based alloy, and the outer layer is a layer made of carbon.

8. A method for producing a fluorine gas, comprising: an electrolytic synthesis method for electrolytically synthesizing a fluorine gas by electrolyzing the hydrogen fluoride-containing electrolytic solution using the anode for electrolytic synthesis according to any one of claims 1 to 7.

Technical Field

The present invention relates to an anode for electrolytically synthesizing a fluorine gas or a fluorine-containing compound and an electrolytic synthesis method of a fluorine gas or a fluorine-containing compound.

Background

Fluorine gas and a fluorine-containing compound (for example, nitrogen trifluoride) can be synthesized by electrolyzing an electrolytic solution containing fluorine ions (electrolytic synthesis). In this electrolytic synthesis, a carbon electrode is generally used as an anode, but if a carbon electrode is used, there is a problem that the cell voltage required to obtain a predetermined current becomes a high voltage exceeding 12V even if electrolysis is performed at a very low current density. This phenomenon is called the anode effect.

The reason why the anode effect is generated is as follows. When the electrolytic solution is electrolyzed, fluorine gas generated on the surface of the anode reacts with carbon forming the anode, and thus a coating film having a covalent carbon-fluorine bond is formed on the surface of the anode. Since the coating is insulating and has poor wettability with the electrolyte, it is difficult for current to flow to the anode, and an anode effect occurs.

On the other hand, when a metal electrode is used as an anode, there are problems of dissolution of the metal electrode and high power consumption due to difficulty in flowing current caused by formation of an insulating coating film made of an oxide or a fluoride on the surface of the metal electrode.

In addition, when an electrode in which a metal substrate is coated with a conductive carbonaceous coating having a diamond structure (for example, see patent document 1) is used as an anode, electrolytic resistance can be suppressed to suppress power consumption, but the effect is not sufficient.

Documents of the prior art

Patent document 1: japanese patent laid-open publication No. 2011 46994

Disclosure of Invention

The invention provides an anode for electrolytic synthesis and an electrolytic synthesis method, which can suppress electrolytic resistance and electrolytically synthesize fluorine gas or fluorine-containing compound with low power consumption.

To solve the above problem, one embodiment of the present invention is as shown in the following [1] to [8 ].

[1] An anode for electrolytic synthesis, which is an anode for electrolytic synthesis of fluorine gas,

the disclosed device is provided with: an anode base formed of a metallic material, and a carbonaceous layer formed of a carbonaceous material and disposed on a surface of the anode base,

the metallic material is an iron-based alloy containing iron and nickel.

[2] The anode for electrolytic synthesis according to [1], wherein the metallic material is an iron-based alloy containing iron, nickel and cobalt.

[3] The anode for electrolytic synthesis according to [1], wherein the metallic material is an iron-based alloy containing iron, nickel, cobalt and carbon.

[4] The anode for electrolytic synthesis according to [1], wherein the iron-based alloy contains 32 mass% or more and 40 mass% or less of nickel.

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

[6] The anode for electrolytic synthesis according to [3], wherein the iron-based alloy contains 20 to 36 mass% of nickel, 3 to 20 mass% of cobalt, and 0.01 to 1.5 mass% of carbon.

[7] The anode for electrolytic synthesis according to any one of [1] to [6], wherein the carbonaceous layer comprises an inner layer in contact with the anode base and an outer layer outside the inner layer, the inner layer is a layer in which carbon is mixed with at least one of metals constituting the iron-based alloy, and the outer layer is a layer made of carbon.

[8] A method for producing a fluorine gas, comprising: electrolyzing the hydrogen fluoride-containing electrolytic solution using the anode for electrolytic synthesis according to any one of [1] to [7], thereby electrolytically synthesizing a fluorine gas.

According to the present invention, a fluorine gas or a fluorine-containing compound can be electrolytically synthesized with low power consumption while suppressing electrolytic resistance.

Drawings

Fig. 1 is a sectional view illustrating the structure of an electrolysis apparatus including an anode for electrolytic synthesis according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the electrolyzer of FIG. 1, which is virtually cut out in a plane different from that of FIG. 1.

FIG. 3 is a sectional view showing an example of an anode for electrolytic synthesis.

FIG. 4 is a sectional view showing another example of an anode for electrolytic synthesis.

Detailed Description

An embodiment of the present invention will be explained below. The present embodiment shows an example of the present invention, and the present invention is not limited to the present embodiment. Various changes and modifications may be made in the present embodiment, and the embodiments to which such changes and modifications are applied are also included in the present invention.

The structure of an electrolysis apparatus including the anode for electrolytic synthesis according to the present embodiment will be described with reference to fig. 1 and 2. Fig. 1 is a cross-sectional view showing an electrolytic apparatus virtually cut by a plane perpendicular to the plate surfaces of the anode for electrolytic synthesis 3 and the cathode for electrolytic synthesis 5 of the electrolytic apparatus and parallel to the vertical direction. Fig. 2 is a cross-sectional view showing the electrolytic apparatus virtually cut by a plane parallel to the plate surfaces of the anode for electrolytic synthesis 3 and the cathode for electrolytic synthesis 5 of the electrolytic apparatus and parallel to the vertical direction.

The electrolytic device shown in FIGS. 1 and 2 comprises: an electrolytic cell 1 for storing an electrolytic solution 10, and an anode 3 for electrolytic synthesis and a cathode 5 for electrolytic synthesis, which are disposed in the electrolytic cell 1 and immersed in the electrolytic solution 10. The inside of the electrolytic cell 1 is partitioned into an anode chamber 12 and a cathode chamber 14 by a cylindrical partition wall 7 extending vertically downward from a lid 1a of the electrolytic cell 1. That is, the inside region surrounded by cylindrical partition wall 7 is anode chamber 12, and the outside region of cylindrical partition wall 7 is cathode chamber 14.

The anode 3 for electrolytic synthesis is not limited in shape, and may be, for example, a columnar shape, but in this example, a plate shape, and is disposed in the anode chamber 12 such that the plate surface thereof is parallel to the vertical direction. The cathode 5 for electrolytic synthesis has a plate shape, and is disposed in the cathode chamber 14 so that the plate surface thereof is parallel to the plate surface of the anode 3 for electrolytic synthesis and the anode 3 for electrolytic synthesis is sandwiched between 2 cathodes 5, 5 for electrolytic synthesis.

Of the front and back plate surfaces of the cathodes 5 and 5 for electrolytic synthesis, a cooler for cooling the cathodes 5 and 5 for electrolytic synthesis and the electrolytic solution 10 is attached to the plate surface on the opposite side of the plate surface facing the anode 3 for electrolytic synthesis. In the example of the electrolysis apparatus shown in FIGS. 1 and 2, a cooling pipe 16 through which a cooling fluid flows is attached as a cooler to the cathodes 5 and 5 for electrolytic synthesis.

As the anode 3 for electrolytic synthesis, an electrode having the following structure can be used. That is, as shown in fig. 3, the anode 3 for electrolytic synthesis is an electrode including an anode base 31 made of a metallic material and a carbonaceous layer 33 made of a carbonaceous material and disposed on the surface of the anode base 31. The metal material forming the anode substrate 31 is an iron-based alloy containing iron and nickel. The iron-based alloy may be an alloy composed of iron, nickel and unavoidable impurities, or an alloy containing iron, nickel and other alloy components. The iron-based alloy in the present invention is an alloy containing iron as a main component, that is, an alloy containing the largest amount of iron in the alloy components.

Since the resistance of metal is much lower than that of carbon, by several tenths to several hundredths thereof, if a metal substrate is used as the substrate (anode substrate 31) of the anode 3 for electrolytic synthesis, the electrolytic resistance at the time of electrolytic synthesis can be reduced. Further, if the metallic material forming the anode base 31 is 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 to be low. Therefore, when 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, when electrolytic synthesis is performed using a carbon electrode as an anode in an electrolytic solution containing fluoride ions, the carbon electrode gradually collapses, the electrolytic voltage gradually rises, and the carbon electrode further collapses due to the rise in voltage, so that if the carbon electrode collapses to some extent, the electrolytic synthesis needs to be temporarily interrupted and the carbon electrode needs to be replaced. In addition, the carbon electrode used once cannot be coated with the diamond film, so that the used carbon electrode can be discarded only.

In contrast, the anode 3 for electrolytic synthesis according to the present embodiment is less likely to be broken down by electrolysis, and therefore stable electrolytic synthesis can be performed. Thus, maintenance of the electrolytic cell, such as replacement of the anode by interrupting electrolytic synthesis, is substantially unnecessary, and the maintenance frequency can be greatly reduced. Further, since the carbonaceous layer can be formed on the surface of the anode once used, the carbonaceous layer can be formed on the surface and used as long as the anode substrate does not disappear.

Furthermore, uranium hexafluoride (UF) may be chemically synthesized using fluorine gas obtained by electrolytic synthesis as a starting material₆) Sulfur hexafluoride (SF)₆) Carbon tetrafluoride (CF)₄) And fluorine-containing compounds such as nitrogen trifluoride. Fluorine-containing compounds such as fluorine gas, uranium hexafluoride, sulfur hexafluoride, carbon tetrafluoride, and nitrogen trifluoride are useful in the fields of atomic energy industry, semiconductor industry, medical and agricultural products, and civil use.

The carbonaceous material forming the carbonaceous layer 33 is not particularly limited as long as it is a material containing carbon, and examples of carbon contained in the carbonaceous material include crystalline carbon such as diamond and graphite, amorphous carbon such as carbon black, and further carbon nanotubes, graphene, diamond-like carbon, and the like.

The carbonaceous material forming the carbonaceous layer 33 may be a material composed of carbon alone, or may be a material composed of a mixture of carbon and another component (for example, a mixture of carbon and a metal, or a mixture of carbon and a ceramic). When the carbonaceous material is a mixture of carbon and a metal, the metal may be a metal (iron, nickel, cobalt, or the like) contained in the metallic material forming the anode base 31.

When the carbonaceous material is a mixture of carbon and other components, the carbon content in the carbonaceous material is preferably more than the carbon content in the metallic 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 carbon content in the carbonaceous material is preferably more than 0 mass% and less than 100 mass%, and when the metallic material forming the anode base 31 contains 1.5 mass% of carbon, the carbon content in the carbonaceous material is preferably more than 1.5 mass% and less than 100 mass%.

The nickel content in the iron-based alloy containing iron and nickel is not particularly limited, but is preferably 32 mass% or more and 40 mass% or less, and more preferably 34 mass% or more and 38 mass% or less, in order to suppress the electrolytic resistance of the carbonaceous layer 33 to be low.

The metallic material forming the anode substrate 31 may be an iron-based alloy containing iron, nickel, and cobalt. The iron-based alloy may be an alloy composed of iron, nickel, cobalt, and unavoidable impurities, or an alloy containing iron, nickel, and cobalt, and other alloy components.

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

The metal material forming the anode substrate 31 may be an iron-based alloy containing iron, nickel, cobalt, and carbon. The iron-based alloy may be an alloy containing iron, nickel, cobalt, carbon, and unavoidable impurities, or an alloy containing iron, nickel, cobalt, carbon, and other alloy components.

The nickel content in the iron-based alloy containing iron, nickel, cobalt, and carbon is not particularly limited, but is preferably 20 mass% or more and 36 mass% or less, and more preferably 21 mass% or more and 28 mass% or less, in order to suppress the electrolytic resistance of the carbonaceous layer 33 to be lower.

The cobalt content in the iron-based alloy containing iron, nickel, cobalt, and carbon is not particularly limited, but is preferably 3 mass% or more and 20 mass% or less, and more preferably 6 mass% or more and 16 mass% or less, in order to suppress the electrolytic resistance of the carbonaceous layer 33 to a lower level.

The carbon content in the iron-based alloy containing iron, nickel, cobalt, and carbon is not particularly limited, but is preferably 0.01 mass% or more and 1.5 mass% or less, and more preferably 0.5 mass% or more and 1.0 mass% or less, in order to suppress the electrolytic resistance of the carbonaceous layer 33 to a lower level.

Further, the carbonaceous layer 33 may have a one-layer structure as shown in fig. 3, but may have a two-layer structure as shown in fig. 4. That is, the carbonaceous layer 33 may be composed of an inner layer 331 in contact with the anode base 31 and an outer layer 332 outside the inner layer 331. Here, the inner layer 331 is a layer in which at least one of metals (iron, nickel, cobalt, and the like) 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.

As described above, the inner layer 331 is composed of carbon and a metal constituting the iron-based alloy forming the anode base 31, and the carbon content in the inner layer 331 is preferably larger than the carbon content in the metallic material forming the anode base 31 and smaller than 100 mass%. For example, in the case where the metallic material forming the anode base 31 does not contain carbon, the carbon content in the inner layer 331 is preferably more than 0 mass% and less than 100 mass%, and in the case where the metallic material forming the anode base 31 contains 1.5 mass% of carbon, the carbon content in the inner layer 331 is preferably more than 1.5 mass% and less than 100 mass%.

The method of forming the carbonaceous layer 33 on the surface of the anode base 31 is not particularly limited, but in the case of the carbonaceous layer 33 having a one-layer structure as shown in fig. 3, there are a method of forming the carbonaceous layer 33 on the surface of the anode base 31 and a method of forming the carbonaceous layer 33 by modifying the surface layer portion of the anode base 31. Examples of the film formation method include dry film formation methods such as a vacuum deposition method typified by a resistance heating deposition method and an electron beam deposition method, a sputtering method, an ion plating method, a hot wire chemical deposition (CVD) method, a microwave plasma CVD method, a plasma arc jet CVD method, and a plasma ion implantation method. Particularly, the carbonaceous layer 33 is preferably formed under the condition that the temperature of the anode substrate 31 is lower than 450 ℃. Further, as a modification method, an ion implantation method using a hydrocarbon gas or the like can be exemplified.

In the case of the carbonaceous layer 33 having a two-layer structure shown in fig. 4, a method of continuously forming the inner layer 331 and the outer layer 332 of the carbonaceous layer 33 on the surface of the anode base 31, and a method of modifying the surface layer portion of the anode base 31 to form the inner layer 331 and then forming the outer layer 332 on the inner layer 331 are exemplified.

In the case where the inner layer 331 and the outer layer 332 of the carbonaceous layer 33 are continuously formed on the surface of the anode base 31, for example, the following method may be employed: using the above-described dry film formation method, the inner layer 331 is formed on the surface of the anode base 31 while continuously changing the composition ratio of metal to carbon, and then the outer layer 332 is formed on the inner layer 331. When the inner layer 331 is formed by modifying the surface layer portion of the anode base 31 and then the outer layer 332 is formed on the inner layer 331, for example, the following method can be employed: the surface layer portion of the anode base 31 is modified by injecting carbon ions into the surface layer portion by an ion injection method using a hydrocarbon gas or the like to form the inner layer 331 in which the composition ratio of metal to carbon continuously changes, and then the outer layer 332 is formed on the inner layer 331 by the dry film formation method described above.

As the cathode 5 for electrolytic synthesis, a metal electrode may be used, and for example, an electrode made of iron may be used.

As the electrolyte 10, a molten salt can be used, and for example, molten potassium fluoride (KF) containing Hydrogen Fluoride (HF) can be used.

A current density of, for example, 0.01A/cm is supplied between the anode 3 for electrolytic synthesis and the cathode 5 for electrolytic synthesis²Above and 1A/cm²At the following current, fluorine gas (F) is generated at the anode 3 for electrolytic synthesis₂) The anode gas mainly containing hydrogen (H) is generated as a by-product at the cathode 5 for electrolytic synthesis₂) A cathode gas as a main component.

The anode gas is accumulated in the space above the liquid surface of the electrolyte 10 in the anode chamber 12, and the cathode gas is accumulated in the space above the liquid surface of the electrolyte 10 in the cathode chamber 14. Since the space above the liquid surface of the electrolyte 10 is divided by the partition wall 7 into the space in the anode chamber 12 and the space in the cathode chamber 14, the anode gas and the cathode gas are not mixed.

On the other hand, the electrolyte 10 is divided by the partition wall 7 at a portion above the lower end of the partition wall 7, and is continuous without being divided by the partition wall 7 at a portion below the lower end of the partition wall 7.

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

Hereinafter, the anode for electrolytic synthesis of the present embodiment and the electrolytic synthesis method of fluorine gas or fluorine-containing compound using the anode will be described in more detail.

(1) Electrolytic cell

The material of the electrolytic cell for carrying out the electrolytic synthesis is not particularly limited, but copper, mild steel, Monel (trademark), nickel alloy, fluororesin, or the like is preferably used from the viewpoint of corrosion resistance.

In order to prevent the fluorine gas or fluorine-containing compound electrolytically synthesized at the anode for electrolytic synthesis from mixing with the hydrogen gas generated at the cathode for electrolytic synthesis, it is preferable that the anode chamber in which the anode for electrolytic synthesis is disposed and the cathode chamber in which the cathode for electrolytic synthesis is disposed are entirely or partially divided by a partition wall, a diaphragm, or the like as in the electrolyzing apparatuses shown in fig. 1 and 2.

(2) Electrolyte solution

An example of an electrolytic solution used when fluorine gas is electrolytically synthesized will be described. In the case of electrolytically synthesizing a fluorine gas, a mixed molten salt of hydrogen fluoride and potassium fluoride may be used as the electrolytic solution. The molar ratio of hydrogen fluoride to potassium fluoride in the electrolyte can be, for example, 1.5-2.5: 1.

alternatively, a mixed molten salt of hydrogen fluoride and cesium fluoride (CsF), or a mixed molten salt of hydrogen fluoride, potassium fluoride, and cesium fluoride may be used as the electrolytic solution. The composition ratio of the electrolytic solution containing cesium fluoride can be as follows. That is, the molar ratio of cesium fluoride and hydrogen fluoride in the electrolytic solution may be 1: 1.0 to 4.0. In addition, the molar ratio of cesium fluoride, hydrogen fluoride, and potassium fluoride in the electrolytic solution may be 1: 1.5-4.0: 0.01 to 1.0.

Next, an example of an electrolytic solution used in the electrolytic synthesis of a fluorine-containing compound will be described. In the case of electrolytically synthesizing a fluorine-containing compound, a mixed molten salt of a compound having a chemical structure of the fluorine-containing compound to be synthesized before fluorination, hydrogen fluoride, and potassium fluoride may be used as the electrolytic solution. The compound having a chemical structure before fluorination may be formed into a gaseous state, and the electrolytic synthesis may be performed by blowing a mixed molten salt of hydrogen fluoride and potassium fluoride, or the electrolytic synthesis may be performed using an electrolytic solution obtained by dissolving the compound having a chemical structure before fluorination in a mixed molten salt of hydrogen fluoride and potassium fluoride. The compound having a chemical structure before fluorination reacts with fluorine gas generated in the reaction of the anode for electrolytic synthesis to become a fluorine-containing compound.

For example, in the case of electrolytically synthesizing nitrogen trifluoride, hydrogen fluoride and ammonium fluoride (NH) may be used₄F) The mixed molten salt of (3) or the mixed molten salt of hydrogen fluoride, potassium fluoride and ammonium fluoride is used as the electrolytic solution.

In the case of a mixed molten salt of hydrogen fluoride and ammonium fluoride, the molar ratio of hydrogen fluoride to ammonium fluoride in the electrolyte may be, for example, 1.5 to 2.5: 1.

the hydrogen fluoride generally contains 0.1 to 5 mass% of water. When the water content in the hydrogen fluoride is more than 3% by mass, the water content in the hydrogen fluoride may be reduced to 3% by mass or less and then used in the electrolytic solution by the method described in, for example, japanese patent application laid-open No. 7-2515. In general, it is difficult to easily reduce the amount of water in hydrogen fluoride, and therefore, in the case of industrially electrolytically synthesizing a fluorine gas or a fluorine-containing compound, it is preferable to use hydrogen fluoride having a water content of 3 mass% or less from the viewpoint of cost.

(3) Anode for electrolytic synthesis

The shape of the anode for electrolytic synthesis is not particularly limited, and a plate shape, a mesh shape, a punched plate shape, a shape in which a plate is rolled into a circular shape, a shape in which generated bubbles are guided to the back surface of the electrode, a three-dimensional structure in consideration of circulation of the electrolytic solution, or the like can be adopted.

(4) Cathode for electrolytic synthesis

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

Examples

The present invention will be described more specifically below with reference to examples and comparative examples.

Comparative example 1

Granular graphite "SIGRAFINE (registered trademark) ABR" manufactured by SGL carbon corporation was processed into a plate having a length of 2cm, a width of 1cm and a thickness of 0.5cm, a metal rod for power supply was attached, and an electrode surface was formed into a rectangular shape having a length of 1cm and a width of 1cm by using a mask to prepare an electrode.

An electrolyzer having the same structure as that shown in FIGS. 1 and 2 was produced using this electrode as the anode and a Monel (trade mark) plate as the cathode. The reference electrode is the corrosion potential of nickel. In addition, as the electrolyte, a mixed molten salt (KF · 2HF) of potassium fluoride and hydrogen fluoride was used.

Constant-voltage electrolysis was performed so that the potential of the anode was constant at 6V based on the corrosion potential of nickel, and fluorine gas was electrolytically synthesized. The current at this time was 0.148A, and the apparent current density was 0.148A/cm². Thus, the electrolytic resistance of the anode was 40.5 Ω (═ 6/0.148).

Comparative example 2

Electrolytic synthesis was performed in the same manner as in comparative example 1, except that a conductive diamond coating was formed on the surface of the anode by a thermal CVD method. The current at this time was 0.260A, and the apparent current density was 0.260A/cm². Thus, the electrolytic resistance of the anode was 23.1 Ω (═ 6/0.260).

Comparative example 3

Electrolytic synthesis was performed in the same manner as in comparative example 2, except that constant-current electrolysis was used instead of constant-voltage electrolysis. The current is 0.148A, and the current density is 0.148A/cm². The voltage of the anode with reference to the reference electrode at this time was 5.23V. Thus, electricity of the anodeThe resistance was 35.3 Ω (═ 5.23/0.148).

[ example 1]

Electrolytic synthesis was performed in the same manner as in comparative example 1 except that the following electrode was used as an anode. The anode used in example 1 includes an anode base made of a metallic material and a carbonaceous layer made of a carbonaceous material and disposed on a surface of the anode base. The metallic material forming the anode matrix was an iron-based alloy composed of iron, nickel, and cobalt, and had an iron content of 63.5 mass%, a nickel content of 31.5 mass%, and a cobalt content of 5.0 mass%. The anode substrate had a length of 2cm, a width of 1cm and a thickness of 1mm, and the electrode surface was formed into a rectangular shape having a length of 1cm and a width of 1cm through a mask.

The carbonaceous layer disposed on the surface of the anode substrate has a two-layer structure including an inner layer and an outer layer, and the inner layer is a layer composed of carbon and a metal (iron, nickel, cobalt) and the outer layer is a diamond-like carbon layer substantially composed of only carbon, as analyzed by X-ray photoelectron spectroscopy (XPS).

The inner layer is formed by modifying the surface layer portion of the anode base body by implanting carbon ions into the surface layer portion by a plasma ion implantation method. The outer layer is formed by laminating carbon on the inner layer by a plasma ion implantation method.

The current at constant voltage electrolysis was 0.454A, and the apparent current density was 0.454A/cm². Thus, the electrolytic resistance of the anode was 13.2 Ω (═ 6/0.454). The electrolytic resistance of the anode was about half that of comparative example 2, and it was found that the electrolytic resistance of the anode was rapidly decreased.

Comparative example 4

Electrolytic synthesis was performed in the same manner as in example 1, except that an anode base made of nickel was used. The current at this time was 0.27A, and the apparent current density was 0.27A/cm². Thus, the electrolytic resistance of the anode was 22.2 Ω (═ 6/0.27). If constant voltage electrolysis is continued, the current gradually becomes difficult to flow, the current decreases to 0.14A, and the electrolytic resistance of the anode increases to 42.9 Ω (═ 6/0.14).

Comparative example 5

Using an anode matrix formed of iron, except forExcept that the electrolytic synthesis was performed in the same manner as in example 1. The current at this time was 0.24A, and the apparent current density was 0.24A/cm². Therefore, the electrolytic resistance of the anode was 25.0 Ω (═ 6/0.24). If constant voltage electrolysis is continued, the current gradually becomes difficult to flow, the current decreases to 0.14A, and the electrolytic resistance of the anode increases to 42.9 Ω (═ 6/0.14).

[ example 2]

Electrolytic synthesis was performed in the same manner as in example 1, except that constant-current electrolysis was used instead of constant-voltage electrolysis. The current is 0.148A, and the current density is 0.148A/cm². The voltage of the anode with reference to the reference electrode at this time was 4.60V. Thus, the electrolytic resistance of the anode was 31.1 Ω (═ 4.60/0.148). Since the power consumption is proportional to the voltage, the power consumption is reduced by 20% or more (100-4.6/6 × 100) as compared with the case of comparative example 1.

While supplying hydrogen fluoride, constant current electrolysis was carried out at the same current for 500 hours. As a result, the voltage was not changed, the current efficiency of fluorine gas generation was 99%, and no deterioration was observed in the anode surface after the completion of the electrolysis.

[ example 3]

An electrolytic synthesis was performed in the same manner as in example 1 except that the metallic material forming the anode substrate was an iron-based alloy composed of iron, nickel, and cobalt, and the iron content was 61.8 mass%, the nickel content was 32.0 mass%, and the cobalt content was 6.2 mass%. The current at this time was 0.472A, and the apparent current density was 0.472A/cm². Thus, the electrolytic resistance of the anode was 12.7 Ω (═ 6/0.472).

[ example 4]

Electrolytic synthesis was performed in the same manner as in example 1 except that the metallic material forming the anode substrate was an iron-based alloy composed of iron, nickel, and cobalt, and the iron content was 52.0 mass%, the nickel content was 38.0 mass%, and the cobalt content was 10.0 mass%. The current at this time was 0.411A, and the apparent current density was 0.411A/cm². Thus, the electrolytic resistance of the anode was 14.6 Ω (═ 6/0.411).

[ example 5]

The metal material forming the anode matrix is an iron-based material composed of iron and nickelAn electrolytic synthesis was performed in the same manner as in example 1, except that the alloy contained 65.0 mass% of iron and 35.0 mass% of nickel. The current at this time was 0.373A, and the apparent current density was 0.373A/cm². Thus, the electrolytic resistance of the anode was 16.1 Ω (═ 6/0.373).

[ example 6]

An electrolytic synthesis was performed in the same manner as in example 1 except that the metallic material forming the anode substrate was an iron-based alloy composed of iron, nickel, cobalt, and carbon, and the iron content was 61.2 mass%, the nickel content was 30.0 mass%, the cobalt content was 8.0 mass%, and the carbon content was 0.8 mass%. The current at this time was 0.448A, and the apparent current density was 0.448A/cm². Thus, the electrolytic resistance of the anode was 13.4 Ω (═ 6/0.448).

[ example 7]

Electrolytic synthesis was performed in the same manner as in example 1, except that the carbonaceous layer disposed on the surface of the anode substrate was a diamond-like carbon layer having a one-layer structure formed by a plasma CVD method. The current at this time was 0.432A, and the apparent current density was 0.432A/cm². Thus, the electrolytic resistance of the anode was 13.9 Ω (═ 6/0.432).

TABLE 1

As is clear from table 1, in examples 1 to 7, since the anode in which the anode base is formed of the iron-based alloy containing iron and nickel and the carbonaceous layer is provided on the surface of the anode base is used, the resistance at the time of constant voltage electrolysis can be stably reduced as compared with comparative examples 1 and 2 using the carbon anode and comparative examples 4 and 5 using the metal anode. Further, it is found that when the anode base is formed of an iron-based alloy containing iron, nickel, and cobalt, the resistance during constant current electrolysis can be reduced as compared with comparative example 3 in which a carbon anode is used.

Description of the reference numerals

1 electrolytic cell

3 Anode for electrolytic synthesis

5 cathode for electrolytic synthesis

10 electrolyte solution

31 anode base

33 carbonaceous layer

331 inner layer

332 outer layer