TWI496953B - Anode for electrolysis and method of electrolytically synthesizing fluorine-containing substance using the anode for electrolysis - Google Patents

Description

Electrolysis anode and electrolytic synthesis method of fluorine-containing substance using the anode for electrolysis

The present invention relates to an anode material which, when used in an electrolytic application such as a hydrofluoric acid-containing electrolytic cell, does not produce an anode effect even when a high current density voltage is applied thereto, and which is not dissolved by an electrode The resulting severe sludge generation suppresses the generation of CF ₄ and can stably continue electrolysis without electrode disintegration. The invention further relates to an electrolysis process.

The industry has actually employed an electrolytic method of electrolytically synthesizing an inorganic fluorine compound, an organic fluorine compound, or a fluorine gas by using a solution prepared by dissolving an inorganic or organic compound in anhydrous hydrofluoric acid (anhydrous HF) as an electrolytic cell.

Since anhydrous HF has insufficient conductivity, when it is intended to operate at a high current density, an alkali metal fluoride (such as, for example, potassium fluoride (KF)) or an alkaline earth metal fluoride (hereinafter referred to as a conduction aid) is usually used. ) is added to the electrolytic cell.

The KF/HF electrolytic cell prepared by adding potassium fluoride (KF) as a conduction aid to HF by electrolysis is synthesized and widely used as a fluorinating agent in resin synthesis, chemical synthesis, pharmaceutical synthesis, and the like. Fluorine gas (F ₂ ). The NH ₄ F/HF electrolytic cell prepared by dissolving ammonia as a substance to be fluorinated in HF by electrolysis is synthesized to be widely used as a dry etchant or a cleaning gas in, for example, the semiconductor field. Nitrogen gas (NF ₃ ).

Further, there is a solution prepared by dissolving an inorganic or organic compound as a substance to be fluorinated in anhydrous HF as an electrolytic cell, and electrolyzing the electrolytic cell at a voltage lower than a voltage at which fluorine gas is generated, This is a method of synthesizing a perfluoro compound. This method is called the Simon method.

In all of these electrolysis methods, materials which are available as electrolyzers and electrode materials are limited due to the remarkable corrosiveness of HF. In particular, materials that can be used as anode materials are limited to nickel and carbon.

When nickel is used as the anode, the wear of this anode is significantly accelerated. Therefore, carbon is often used as an anode.

The advantages of carbon anodes include sensitivity to the reduction in electrode wear that occurs in nickel electrodes. However, carbon anodes generally cause problems in the phenomenon of electrode passivation (so-called anode effect), making it difficult to continue electrolysis.

In addition to the discharge reaction as the fluoride ion of the desired reaction, the anodic reaction which occurs when a carbon anode is used also includes a reaction for producing graphite fluoride. On the other hand, the produced fluorinated graphite is partially decomposed by the pyrolysis of the Joule heat generated by the electrode reaction or by the disproportionation reaction. Fluorinated graphite, which is a covalent compound, exhibits low wettability to the electrolytic cell. Therefore, when the rate of producing graphite fluoride is higher than the decomposition rate of the fluorinated graphite, the surface of the electrode is coated with fluorinated graphite to produce an anode effect. The rate of generation of fluorinated graphite depends on the current density, and therefore, the anode effect is more likely to occur when the current density is increased.

In the case where water is present in the electrolytic cell, decomposition reaction of water which is carried out at a potential lower than the discharge reaction of the fluoride ions is preferentially occurred, and at this time, the reaction of water with the carbon anode generates graphite oxide. This graphite oxide is chemically unstable, and therefore, it tends to undergo a substitution reaction with fluorine to produce graphite fluoride. Therefore, the higher the concentration of water in the electrolytic cell, the more the formation of fluorinated graphite is accelerated, and the more the anode effect occurs.

Therefore, in order to suppress the occurrence of an anode effect at the carbon anode, it is necessary to minimize the concentration of water in the electrolytic cell and to perform electrolysis at a current density lower than the current density (critical current density) at which the anode effect starts to occur. In actual industrial electrolysis, for the former purpose, complicated operations such as, for example, dehydration electrolysis, and for the latter purpose, a limited operating current density are used. Due to these measures, the rate at which the target substance is produced is limited, and this suppresses the profitability of the improved electrolytic synthesis.

On the other hand, HF is inserted into the carbon electrode to swell the electrode, and this expansion usually causes the electrode to crack or disintegrate. In order to prevent HF from penetrating into the carbon electrode, techniques such as, for example, coating the surface of the electrode with nickel by thermal spraying or electroplating have been actually employed. However, since nickel itself is also problematic as will be described later, no basic solution has been found. A technique for increasing the concentration of a conduction aid (e.g., KF) in an electrolytic cell, thereby reducing the vapor pressure of HF, is also applied. However, the increased concentration of the conduction aid increases the melting point of the cell and therefore requires a higher operating temperature. Therefore, this technology has limitations.

In electrolysis in an electrolytic cell prepared by adding a substance to be fluorinated such as, for example, ammonia, an alcohol, or an amine to anhydrous HF, nickel is widely used as an anode. Although the nickel anode has the advantage of not having an anode effect occurring in the carbon anode, the nickel anode wears during the electrolysis process.

The nickel anode wears in an amount equivalent to 3-5% of the applied amount of electricity, and the cost of replacing the worn nickel anode is almost equivalent to the cost of electricity for electrolysis. In addition, the dissolution of nickel in the electrolytic cell increases the viscosity of the electrolytic cell, making it difficult to control the temperature of the electrolytic cell. Therefore, it is also necessary to replace the electrolytic cell regularly. As described above, the replacement of the anode, the replacement of the electrolytic cell, and the operation associated with the replacement of the nickel anode are inevitable, and the factors that inhibit the profitability of the electrolytic synthesis improvement are inhibited.

Patent Document 1 discloses an electrode comprising a ruthenium substrate having a surface coated with a boron-doped diamond film; and an electrolytic fluorination method using the electrode. Patent Document 2 discloses: an electrode comprising a substrate of a conductive carbon material having a surface coated with a conductive diamond; and a method of electrolytically synthesizing a fluorine-containing substance using the electrode.

Patent Document 1: JP-A-2000-204492

Patent Document 2: JP-A-2006-249557

The inventors conducted serious research. As a result, it has been found that the invention described in Patent Document 1 has a problem that the substrate is HF-etched in the electrolytic cell, and therefore, it is difficult to maintain the electrode structure. Further, the invention described in Patent Document 2 has a high HF concentration when the electrolytic cell has a specific HF concentration, in particular, when the volume molar concentration of HF in the electrolytic cell is not lower than the volume of the substance to be fluorinated or the conductive auxiliary agent. When the ear concentration is three times, there is a problem that HF penetrates into the carbon substrate to cause the carbon substrate to disintegrate.

As described above, there is a need for an electrode which does not have an anode effect and disintegration occurring in a carbon electrode, and which does not have wear occurring in a nickel electrode, as an electrode for electrolysis in an electrolytic cell containing HF. .

The present invention provides an electrode for electrolysis comprising: a substrate comprising a conductive material, wherein the surface of the substrate is made of glassy carbon; and a conductive diamond film coating at least a portion of the substrate. The present invention further provides a method of electrolytically synthesizing fluorine or a fluorine-containing compound in an electrolytic cell containing HF using the electrode.

In other words, the invention includes the following aspects in its broadest configuration:

(1) An electrode for electrolysis comprising: a substrate comprising a conductive material, wherein a surface of the substrate is made of glassy carbon; and a conductive diamond film coated with at least a portion of the substrate.

(2) A method for electrolytically synthesizing fluorine or a fluorine-containing compound, wherein the method is included in an electrolytic cell comprising hydrofluoric acid and a substance to be fluorinated added thereto, using the electrode for electrolysis according to the above (1) Perform electrolysis.

(3) The method of electrolytically synthesizing fluorine or a fluorine-containing compound according to the above item (2), wherein the electrolytic cell further comprises an alkali metal fluoride or an alkaline earth metal fluoride (hereinafter referred to as a conduction aid).

(4) The method for electrolytically synthesizing fluorine or a fluorine-containing compound according to the above item (2) or (3), wherein the electrolytic cell has a volume molar concentration of a volume of a substance to be fluorinated or a conductive auxiliary agent in the electrolytic cell At least three times the concentration of hydrofluoric acid.

The invention will be described in detail below.

As a result of earnest research by the present inventors, it has been found that an electroconductive substrate whose surface is made of glassy carbon and an electrolysis electrode obtained by coating at least a part of the electroconductive substrate with a conductive diamond film have a high electrolysis cell. At the HF concentration, anode effect or electrode wear or electrode disintegration does not occur in electrolysis in an HF-containing electrolytic cell, and is an electrode which can be continuously electrolyzed for a long period of time.

The glassy carbon is a glass-like appearance and is made of cellulose, a cellulose resin, or a thermosetting resin (for example, a furan resin) as a precursor, and the molded precursor is subjected to solid phase carbonization by molding the precursor. And the carbon material produced. Features include high hardness, chemical stability, abrasion resistance, and impermeability to gases and liquids. The glassy carbon has a uniform amorphous structure free of crystal forms. Although there are many voids in the structure, most of the voids are closed cells, and therefore, there are almost no openings. In a conductive diamond electrode using glassy carbon having such characteristics as a conductive substrate, HF is less likely to be inserted into the inside of the substrate even in an electrolytic cell having a high HF concentration. Therefore, the electrode does not undergo electrode expansion and subsequent electrode disintegration.

Glassy carbon is also known as vitreous carbon. The glassy carbon to be used in the present invention is not particularly limited, and examples thereof include a GC series product manufactured by TOKAI CARBON CO., LTD., and an SPI-Glas series product manufactured by SPI Supplies. In particular, from the viewpoint of low gas permeability, GC-10 (trade name, manufactured by TOKAI CARBON CO., LTD.) and SPI-Glas 10 (trade name, manufactured by SPI Supplies) are preferred. A method of making glassy carbon is disclosed in U.S. Patent No. 6,241,956, incorporated herein by reference.

In addition, coating a portion of the substrate surface with conductive diamond prevents anode effects (which can be attributed to the formation of fluorinated graphite) and electrode wear.

For example, perfluorotrimethylamine can be efficiently synthesized using an electrolytic cell having the composition (CH ₃ ) ₄ NF‧5HF. In the case of a nickel electrode, CsF‧2HF is added to prevent passivation problems. However, even when CsF‧2HF is added, electrode wear still occurs. In the case where carbon is used as the anode, an anode effect occurs and HF penetration into the substrate occurs to cause electrode collapse. In the case of using a known electrode obtained by coating a surface of a conductive carbon material substrate with a conductive diamond, HF penetration into the substrate occurs to cause electrode collapse.

Conversely, in the case of using an electrode made by using a substrate including a conductive material in which the surface of the substrate is made of glassy carbon and at least a part of the surface of the substrate is coated with a conductive diamond film, the anode can be prevented Effects, electrode wear, and electrode disintegration occur, and long-term continuous electrolysis can be performed.

The present invention provides an electrode comprising a substrate comprising a conductive material, wherein the surface of the substrate is made of glassy carbon, and a conductive diamond film coating at least a portion of the surface of the substrate, and is used for For example, an inorganic fluorine compound, an organic fluorine compound, and a fluorine gas are synthesized by electrolyzing an electrolytic cell containing HF. The present invention further provides a method of electrolytically synthesizing fluorine or a fluorine-containing compound using the electrode.

The electrode and the synthesis method prevent anode effect, electrode wear, and electrode disintegration from occurring even in an electrolytic cell having a high HF concentration, and enable long-term continuous electrolysis. The productivity of the inorganic fluorine compound, the organic fluorine compound, and the fluorine gas is improved.

The electrode for electrolysis of the present invention will be described in detail.

The shape of the conductive substrate of the electrode of the present invention is not particularly limited as long as the substrate has a surface made of glassy carbon. A plate shape, a rod shape, a tube shape, or a spherical shape or the like can be used. The glassy carbon constituting the surface has a gas permeability of preferably 10 ^-7 cm 2 /sec or less, more preferably 10 ^{- 10} cm 2 /sec or less.

Examples of the glassy carbon satisfying the preferable gas permeability include GC-10 (trade name, manufactured by TOKAI CARBON CO., LTD.) and SPI-Glas 10 (trade name, manufactured by SPI Supplies) and SPI-Glas 20 (trade name) , manufactured by SPI Supplies).

In addition, examples of glassy carbons that satisfy better gas permeability include GC-10 and SPI-Glas 10.

The method of coating at least a part of the surface of the conductive substrate with the conductive diamond film is not particularly limited, and any desired method can be used. Typical manufacturing methods include a hot filament CVD (chemical vapor deposition) method, a microwave CVD method, a plasma-arc jet method, and a physical vapor deposition (PVD) method. Suitable methods can be selected from this.

Regardless of the method used to coat the conductive diamond film, a mixed gas composed of hydrogen and a carbon source is used as a raw material for the diamond. An element having a different valence number (hereinafter referred to as a dopant) is added in a trace amount to the mixed gas to impart conductivity to the diamond. The dopant is preferably boron, phosphorus, or nitrogen. The content of the dopant is preferably from 1 to 100,000 ppm, more preferably from 100 to 10,000 ppm (dopant atom to carbon atom ratio). Regardless of the method used to coat the diamond film, the deposited conductive diamond film is polymorphic, and the amorphous carbon and graphite components remain in the diamond film.

From the standpoint of the stability of the diamond film, the content of the amorphous carbon and the graphite component should preferably be low. In Raman spectroscopy, the I(D)/I(G) ratio (where I(D) indicates the peak intensity of the diamond appearing around 1,332 cm ^-1 (in the range of 1,312-1,352 cm ^-1 ) And I(G) indicates that the appearance of the G band of graphite in the vicinity of 1,560 cm ^-1 (in the range of 1,540-1,580 cm ^-1 ) should preferably be 1 or more. In other words, the diamond content should preferably be higher than the graphite content.

A hot filament CVD as a typical coating method for a conductive diamond film will be described.

An organic compound which acts as a carbon source, such as, for example, methane, alcohol, or acetone, and a dopant, together with hydrogen or the like, is supplied to the filament. Heating the filament to a temperature at which hydrogen radicals or the like are generated (ie, 1,800-2,800 ° C), and placing a conductive substrate in the atmosphere to have a temperature (750-950 ° C) in the region where diamond deposition occurs. . The supply rate of the mixed gas depends on the size of the reaction vessel. However, it is preferred to use a pressure of 15-760 Torr.

It is preferred to polish the surface of the conductive substrate because the polishing improves the adhesion between the substrate and the diamond layer. Preferably, the surface is abraded to produce an arithmetic mean roughness Ra of 0.1-15 microns and a maximum height Rz of 1-100 microns. Applying the diamond powder as a nucleus to the surface of the substrate can effectively grow a uniform diamond film. A layer of fine diamond particles having a diameter of 0.001 to 2 microns is typically deposited on the substrate. Although the thickness of the diamond film can be adjusted by changing the deposition time, the thickness is preferably from 1 to 10 μm from the viewpoint of profitability.

In the present invention, fluorine or a fluorine-containing compound is synthesized by an electrolytic synthesis method. The method is not particularly limited, but includes a method of performing electrolysis using an electrode for electrolysis according to the present invention in an electrolytic cell containing hydrofluoric acid and a substance to be fluorinated thereto.

The electrolytic cell may further comprise an alkali metal fluoride or an alkaline earth metal fluoride. These fluorides (i.e., conduction aids) may be used singly or in combination of two or more thereof.

In the method for electrolytically synthesizing fluorine or a fluorine-containing compound according to the present invention, the volume molar concentration of hydrofluoric acid can be adjusted so that it is at least three of the molar concentration of the substance to be fluorinated or the conduction aid in the electrolytic cell. Times.

Regarding the material of the electrolyzer, a mild steel, a nickel alloy, a fluororesin, or the like can be used from the viewpoint of corrosion resistance to HF. Preferably, the separator side, the separator, or the like is used to completely or partially separate the anode side from the cathode side to prevent mixing of the F ₂ or fluorine compound synthesized at the anode with the hydrogen gas generated at the cathode.

A small amount of HF is produced at the anode with an inorganic or organic fluorine compound or fluorine gas, and this HF can be removed by passing this product through a column filled with granular sodium fluoride. Small amounts of by-products such as nitrogen, oxygen, and nitrous oxide are also produced. Among these by-products, nitrous oxide can be removed by passing the product through water and sodium thiosulfate. Oxygen can be removed by activated carbon. Therefore, an inorganic or organic fluorine compound or a fluorine gas having a low by-product content can be obtained.

[Examples]

The invention will be described in detail below based on examples. However, the invention should not be construed as being limited to the following examples.

(Example 1)

A glassy carbon plate (GC-10, manufactured by TOKAI CARBON CO., LTD.) was used as a conductive substrate, and a conductive diamond electrode was produced under the following conditions by a hot filament CVD apparatus.

First, an abrasive material composed of diamond particles having a diameter of 1 μm was used to polish the surface of the substrate. The surface of the ground substrate has a Ra of 0.2 microns and a ten point surface roughness Rz of 6 microns. Diamond particles having an average particle diameter of 4 nm were then applied to the surface of the substrate as crystal nuclei. The substrate is then mounted to a hot filament CVD apparatus. The mixed gas prepared by adding 1% by volume of methane gas and 0.5 ppm of trimethylboron gas to hydrogen was continuously passed through the apparatus at a rate of 5 liters/min. When the gas was mixed as such, the internal pressure of the apparatus was maintained at 75 Torr and a voltage was applied to the filament to raise its temperature to 2,400 °C. At this point in time, the substrate has a temperature of 860 °C.

The CVD operation was continued for 8 hours. After the CVD operation is completed, the substrate is analyzed. It was confirmed by Raman spectroscopy and X-ray diffraction that the diamond had been deposited. In Raman spectroscopy, the ratio of the peak intensity at 1,332 cm ^-1 to the peak intensity at 1,560 cm ^-1 is 1/0.4. In addition, a portion of this substrate was destroyed and examined by SEM. As a result, it was found to have a thickness of about 4 μm.

The obtained conductive diamond electrode was mounted as an anode in an anhydrous HF bath maintained at 0 °C. A nickel plate and platinum were used as the cathode and the reference electrode, respectively, and the current-potential curve of the anode was detected by a constant current chronopotentiometry.

Shortly after the start of the test, the anode potential at a current density of 5 mA/cm 2 was 0.6 volts. The anode potential was measured by gradually increasing the current density at 5 mA/cm 2 each time. As a result, the anode potential at a current density of 200 mA/cm 2 was 3.2 volts.

The electrolysis was stopped and the anode was taken out and the appearance was examined. As a result, neither electrode disintegration nor peeling of the conductive diamond film was observed.

(Comparative Example 1)

Electrolysis was carried out under the same conditions as in Example 1, except that a graphite plate was used as the anode. The current-potential curve of the anode in an anhydrous HF bath maintained at 0 ° C was thus measured.

Shortly after the start of the test, the anode potential at a current density of 5 mA/cm 2 was 0.7 volt. The anode potential was measured by gradually increasing the current density at 5 mA/cm 2 each time. As a result, at a current density of 70 mA/cm 2 , the anode potential suddenly rises and almost no current flows, making it difficult to continue electrolysis.

Stop electrolysis and remove the anode. As a result, the anode was found to be broken into powder in the electrolyzer.

(Comparative Example 2)

Electrolysis was carried out under the same conditions as in Example 1, except that a nickel plate was used as the anode. The current-potential curve of the anode in an anhydrous HF bath maintained at 0 ° C was thus measured.

Shortly after the start of the test, the anode potential at a current density of 5 mA/cm 2 was 0.6 volts. The anode potential was measured by gradually increasing the current density at 5 mA/cm 2 each time. As a result, when the current density reached 50 mA/cm 2 , the anode potential began to rise with time. Finally, almost no current flows, making it difficult to continue electrolysis.

Stop electrolysis and remove the anode. As a result, no electrode disintegration was observed. Analyze the surface of this electrode. As a result, a Ni-F bond was observed. Therefore, it is presumed that an insulating NiF ₂ coating film has been formed on the surface of the electrode.

(Comparative Example 3)

A conductive diamond electrode was produced in the same manner as in Example 1 except that a ruthenium plate was used as the conductive substrate.

The current-potential curve of the electrode in the anhydrous HF bath maintained at 0 ° C was examined under the same electrolysis conditions as in Example 1, except that the obtained electrode was used as the anode.

Shortly after the start of the test, the anode potential at a current density of 5 mA/cm 2 was 0.6 volts. The anode potential was measured by gradually increasing the current density at 5 mA/cm 2 each time. As a result, the anode potential was 3.8 volts at a current density of 200 mA/cm 2 .

The electrolysis was stopped and the anode was taken out and the appearance was examined. As a result, it was found that the portion of the diamond film in which the anode was immersed in the electrolytic cell was peeled off, and it was observed that the exposed portion of the surface of the ruthenium substrate which was lost in the diamond film was subjected to corrosion.

(Comparative Example 4)

A conductive diamond electrode was produced in the same manner as in Example 1 except that a graphite plate was used as the conductive substrate.

The current-potential curve of the electrode in the anhydrous HF bath maintained at 0 ° C was detected by the same method as in Example 1, except that the obtained electrode was used as the anode.

Shortly after the start of the test, the anode potential at a current density of 5 mA/cm 2 was 0.6 volts. The anode potential was measured by gradually increasing the current density at 5 mA/cm 2 each time. As a result, at a current density of 70 mA/cm 2 , the anode potential suddenly rises and almost no current flows, making it difficult to continue electrolysis.

Stop electrolysis and remove the anode. As a result, the anode was found to be broken into powder in the electrolyzer.

(Example 2)

A glassy carbon plate was used as a conductive substrate in the same manner as in Example 1, and a conductive diamond electrode was produced by a hot filament CVD apparatus.

This electrode was mounted to the tank immediately after preparation of the (CH ₃ ) ₄ NF‧5HF electrolytic cell. A nickel plate and Cu/CuF _{2 were} used as the cathode and the reference electrode, respectively, and constant current electrolysis was performed at a current density of 100 mA/cm 2 . Shortly after the start of electrolysis, the anode potential was measured and found to be 4.6 volts. When the electrolysis was continued for 200 hours, the anode potential was 4.8 volts.

The electrolysis was stopped and the anode was taken out and the appearance was examined. As a result, neither electrode disintegration nor peeling of the conductive diamond film was observed. No anode effect was observed during the entire 200 hour electrolysis process.

(Comparative Example 5)

Electrolysis was carried out in the tank immediately after preparation of the (CH ₃ ) ₄ NF ‧ ₅ HF electrolytic cell in the same manner as in Example 2 except that a graphite plate was used as the anode.

Shortly after the start of electrolysis, the anode potential suddenly rises and almost no current flows, making it difficult to continue electrolysis.

Electrolysis was stopped, and the anode was taken out and the contact angle between the electrode surface and water was detected. As a result, the contact angle was measured to be 150 degrees. Therefore, it is confirmed that a so-called anode effect occurs.

(Comparative Example 6)

Electrolysis was carried out in the tank immediately after preparation of the (CH ₃ ) ₄ NF ‧ ₅ HF electrolytic cell in the same manner as in Example 2 except that a nickel plate was used as the anode.

Shortly after the start of electrolysis, the anode potential began to rise gradually. Finally, almost no current flows, making it difficult to continue electrolysis.

The electrolysis was stopped and the anode was taken out. Analyze the surface of this electrode. As a result, a Ni-F bond was observed. Therefore, it is presumed that an insulating NiF ₂ coating film has been formed on the surface of the electrode.

(Comparative Example 7)

A conductive diamond electrode was produced in the same manner as in Example 1 except that a ruthenium plate was used as the conductive substrate.

Electrolysis was carried out in the tank immediately after preparation of the (CH ₃ ) ₄ NF ‧ ₅ HF electrolytic cell in the same manner as in Example 2 except that the obtained electrode was used as the anode.

Shortly after the start of electrolysis, the anode potential was 4.6 volts. However, after 14 hours from the start of electrolysis, the anode potential began to gradually increase. Finally, almost no current flows, making it difficult to continue electrolysis.

The electrolysis was stopped and the anode was taken out and the appearance was examined. As a result, it was found that the diamond film of the portion of the anode which was immersed in the electrolytic cell was almost completely peeled off, and it was confirmed that the surface of the ruthenium substrate was corroded.

(Comparative Example 8)

A conductive diamond electrode was produced in the same manner as in Example 1 except that a graphite plate was used as the conductive substrate.

Electrolysis was carried out in the tank immediately after preparation of the (CH ₃ ) ₄ NF ‧ ₅ HF electrolytic cell in the same manner as in Example 2 except that the obtained electrode was used as the anode.

Shortly after the start of electrolysis, the anode potential was 4.6 volts. However, after 70 hours from the start of electrolysis, the anode potential began to gradually increase. Finally, almost no current flows, making it difficult to continue electrolysis.

The electrolysis was stopped and the anode was taken out. As a result, the anode was found to be broken into powder in the electrolyzer.

While the invention has been described with reference to the specific embodiments of the embodiments of the invention

The present application is based on Japanese Patent Application No. 2009-021157, filed on Feb. 2, 2009, the content of which is incorporated herein by reference.

Claims (4)

An electrode for electrolysis comprising: a substrate made of only glassy carbon and having a gas permeability of 10 ^-7 cm 2 /sec or less; and a conductive diamond film coated with at least a portion of the substrate. A method for electrolytically synthesizing fluorine or a fluorine-containing compound, wherein the method comprises electrolysis using an electrode for electrolysis according to the first aspect of the patent application, in an electrolytic cell containing hydrofluoric acid and a substance to be fluorinated thereto. A method of electrolytically synthesizing fluorine or a fluorine-containing compound according to claim 2, wherein the electrolytic cell further comprises an alkali metal fluoride or an alkaline earth metal fluoride as a conduction aid. The method for electrolytically synthesizing fluorine or a fluorine-containing compound according to the second or third aspect of the patent application, wherein the electrolytic cell has a volume molar concentration of at least three times the volume molar concentration of the substance to be fluorinated or the conductive auxiliary agent in the electrolytic cell. Hydrofluoric acid.