JP5873071B2 - Method for producing anode catalyst body and method for producing electrolytic cell for ozone generation - Google Patents

Description

  The present invention relates to an anode catalyst body used in an electrolytic cell for ozone generation and related technology.

  As an apparatus for electrolyzing water, there is one utilizing a so-called zero gap type electrolysis cell in which an anode is closely attached to one surface of a cation exchange membrane and a cathode is closely attached to the other surface. Zero-gap electrolytic cells can reduce the electrolysis voltage because they do not energize the liquid phase, and can directly electrolyze pure water that cannot be electrolyzed by ordinary electrolysis methods because of their low conductivity. Since it can be easily made compact, it is widely used in water / electrolyzers for oxygen / hydrogen generation, electrolytic ozone generators, and electrolyzers using gas electrodes.

  As an electrode structure used in such an electrolysis cell, an electrode structure in which an electrode catalyst is integrally laminated on the surface of a current collector or a substrate is known for the purpose of improving electrolysis performance and stability (Patent Documents 1, 2, and 4). 3).

  The anode described in Patent Document 1 is obtained by forming two lead dioxide layers, an α-lead dioxide layer and a β-lead dioxide layer, as an electrode catalyst body on a valve metal such as titanium or an alloy substrate thereof. These lead dioxide layers are formed by electrolytic plating. For the formation of α-lead dioxide layer, a plating solution in which lead oxide is dissolved in an aqueous sodium hydroxide solution is used. For the formation of β-lead dioxide layer For this, an aqueous lead nitrate solution is used.

  Patent Document 2 discloses a method for producing a lead dioxide-containing film electrode material. The lead dioxide-containing film is produced through the following steps. First, trilead tetraoxide powder and polytetrafluoroethylene (PTFE) powder as a binder are kneaded with a liquid lubricant to prepare a paste. The paste is formed into a film and heated to remove the liquid lubricant. If necessary, it is further fired to obtain a porous film-like body. Then, the film-like body is acid-treated to convert trilead tetroxide into lead dioxide and a readily soluble lead (II) salt. Furthermore, when the readily soluble lead (II) salt is dissolved and removed, a lead dioxide-containing film-like body in which lead dioxide is dispersed in the resin is obtained. Polytetrafluoroethylene used as a binder has high ozone resistance and seems to be less deteriorated due to operation of the electrolytic cell.

  In the method for producing an electrode described in Patent Document 3, a catalyst layer is formed by applying and drying a slurry containing electrode catalyst particles such as iridium and a resin component on the surface of a porous substrate coated with a sealing agent, Thereafter, the sealing agent is eluted in water and removed.

Japanese Patent No. 3080971 (column 5, lines 19 to 50) Japanese Patent No. 2725799 (Claims, column 4, line 31 to column 6, line 7) JP 2005-166500 A (paragraph number 0014)

  The lead dioxide layer described in Patent Document 1 requires a two-step electrolytic plating process, and has many problems such as washing and drying in each plating process, resulting in low productivity. In addition, a large-scale treatment facility is required, and it is also necessary to treat lead-containing waste liquid and sludge generated along with the electrolytic plating treatment.

  In addition, when a metal fiber body made of a valve metal such as titanium is used as the base, it is difficult to obtain a fiber with a constant fiber shape and fiber length because the fiber forming process is difficult, resulting in non-uniformity. In addition, since it is difficult to obtain a fine product, the surface of the substrate has poor surface smoothness. Since the surface form of the plating film is almost the same as the surface form of the substrate, the surface smoothness is poor, and the plating film is a hard film. Since the electrolytic reaction is limited to the three-phase interface where the anode catalyst (lead dioxide plating film) / cation exchange membrane / pure water contacts, the contact area between the plating film and the cation exchange membrane is necessary for stable electrolysis. It is necessary to secure an electrolytic area by pressing the anode against the cation exchange membrane with a strong force to secure a contact area between the plating film having poor surface smoothness and the cation exchange membrane. At this time, the lead dioxide-plated metal fibers are in contact with each other so as to tear deeply into the cation exchange membrane that is a resin, and ozone is generated from the surface of the lead dioxide that has penetrated into the cation exchange membrane during electrolysis. The cation exchange membrane is a fluororesin and has ozone resistance, but hydroxy radicals generated during the self-decomposition process of ozone are known to have higher oxidizing power than ozone and decompose the cation exchange membrane. Yes. Therefore, at the three-phase interface during electrolysis, the cation exchange membrane is torn by pressing the anode with a strong force, vibrations due to gas generation, and reaction with radicals are generated. The exchange membrane decomposes and wears out and becomes thinner. When the cation exchange membrane is consumed and thinned, it does not function as a partition wall between both electrodes, and the life as an electrolytic cell is exhausted.

  For the above reasons, there is a problem that an electrolytic cell using an anode catalyst having a lead dioxide plating film on a metal fiber has a short life, and an electrolytic cell having a longer life is required.

  Since the lead dioxide-containing film-like body (electrode catalyst body) described in Patent Document 2 is a resin base, it is more supple and has higher surface smoothness than the plating film, and the anode catalyst is composed of a plating film. Thus, the electrolysis area between the cation exchange membrane and the anode catalyst can be secured without pressing with a strong force. However, since polytetrafluoroethylene having high ozone resistance is used as the binder, it is necessary to heat-treat the film-like body obtained by molding the paste at a melting point (327 ° C.) or higher of polytetrafluoroethylene. On the other hand, since lead dioxide is thermally decomposed when it exceeds 230 ° C., it cannot withstand the heat treatment of polytetrafluoroethylene. For this reason, in order to produce a lead dioxide-containing film, the film is formed using trilead tetroxide having high heat resistance as a starting material, and the film after heat treatment at 330 to 370 ° C. is acid-treated. Thus, it is necessary to go through a complicated process of converting trilead tetroxide to lead dioxide and dissolving and removing the easily soluble lead (II) salt as a by-product.

  Moreover, the quality of the electrode catalyst body using the lead dioxide produced | generated by the oxidation process of trilead tetroxide is bad, and there exists a tendency for ozone generation efficiency to be low, and for electroconductivity to be bad and for a cell voltage to become high. The cause is presumed to be that part of the lead dioxide produced by the acid treatment is reduced by water washing or drying performed as a post-treatment because an acid aqueous solution is used for the acid treatment. In addition, since the starting material, trilead tetraoxide, is in the form of particles, some of the used trilead tetraoxide molecules are not converted to lead dioxide, and there is a possibility that trilead tetraoxide remains mixed.

  In the electrode manufacturing method described in Patent Document 3, an aqueous resin is used as a sealing agent, and after the electrode catalyst layer is formed, the sealing agent is removed by elution with water. Before contact with water. For this reason, when lead dioxide is used as the electrode catalyst, lead dioxide is reduced to another substance before the anode catalyst body is incorporated into the electrolysis cell and energized, losing its conductivity and ozone generating ability, generating ozone. No anode catalyst body can be obtained. Even when other electrode catalysts are used, there is a problem that the number of steps is large because the sealing treatment and the removal of the sealing agent are necessary before and after the formation of the electrolytic catalyst layer.

  In view of the above-described prior art, the present invention provides a resin-based anode catalyst body to be incorporated in an electrolytic cell for ozone generation, particularly an anode catalyst body using lead dioxide as an electrode catalyst and related techniques.

  That is, this invention has the structure as described in following [1]-[20].

[1] The electrolysis of water is carried out by supplying a direct current to each catalyst body through a current collector, with the anode catalyst body in close contact with one surface of the fluororesin-based cation exchange membrane and the other surface. An anode catalyst body used in an electrolysis cell for generating ozone to obtain ozone gas as an anode gas,
An anode catalyst body comprising electrode catalyst particles capable of generating ozone by electrolysis and a resin, wherein the resin is made from a solution obtained by dissolving a resin component in a solvent.

  [2] The anode catalyst body according to [1], wherein the electrode catalyst is lead dioxide.

  [3] The anode catalyst body according to [1] or [2], wherein the resin component is a fluororesin having a structure in which some of the fluorine atoms are substituted with hydrogen atoms.

  [4] The anode catalyst body according to item 3 above, wherein the fluororesin is polyvinylidene difluoride.

  [5] The anode catalyst body according to item 3, wherein the fluororesin is a terpolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene difluoride.

  [6] The anode catalyst body according to the above item 5, which contains 30 mol% or more vinylidene difluoride in the monomer composition of the terpolymer.

  [7] The anode catalyst body according to item 4, wherein the solvent is N-methyl-2-pyrrolidone.

  [8] The anode catalyst body according to 5 or 6 above, wherein the solvent is ethyl acetate or methyl acetate.

  [9] Molding that forms a paste-like mixture containing lead dioxide, a fluororesin having a structure in which some of the fluorine atoms are replaced with hydrogen atoms, and a solvent that dissolves the fluororesin, and that does not contain water into a sheet-like body A method for producing an anode catalyst body comprising a step and a drying step of solidifying the molded sheet-like body by removing a solvent to form a sheet-like porous electrode material.

  [10] In the molding step, the paste-like mixture is applied onto the plate to form a sheet-like body, and the drying step is performed with the molded sheet-like body placed on the plate. 10. The method for producing an anode catalyst body according to 9 above, wherein the electrode material is taken out.

  [11] In the drying step, the sheet-like body in the middle of drying is peeled off from the plate, and the sheet-like body is turned over to place the exposed surface when applying the paste-like mixture on the plate, and further dried to remove the remaining solvent. 11. The method for producing an anode catalyst body according to 10 above.

  [12] The method for producing an anode catalyst body according to any one of 9 to 11 above, wherein the fluororesin is polyvinylidene difluoride.

  [13] The method for producing an anode catalyst body according to the above item 12, wherein the solvent is N-methyl-2-pyrrolidone.

  [14] The method for producing an anode catalyst body according to any one of items 9 to 11, wherein the fluororesin is a terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene difluoride.

  [15] The method for producing an anode catalyst body according to [14], wherein the solvent is ethyl acetate or methyl acetate.

  [16] The method for producing an anode catalyst body according to the above item 13, wherein the drying step is carried out at 50 to 90 ° C. for 15 to 120 minutes.

  [17] The method for producing an anode catalyst body as described in 15 above, wherein the drying step is carried out at room temperature to 90 ° C for 0.5 to 60 minutes.

[18] An anode catalyst body is adhered to one surface of a fluororesin-based cation exchange membrane, and a cathode catalyst body is adhered to the other surface, and water is supplied to each catalyst body by supplying a direct current through a current collector or a substrate. An electrolysis cell for ozone generation that performs electrolysis and obtains ozone gas as an anode gas,
An electrolysis cell for ozone generation, wherein the anode catalyst body is the anode catalyst body described in any one of 1 to 8 above.

  [19] The anode catalyst body is an anode catalyst body manufactured by the method according to any one of items 9 to 17, and the plate contact surface at the time of applying the paste-like mixture in the sheet-form forming step is cation exchange. 19. The electrolytic cell for ozone generation according to 18 above, which is disposed so as to be in contact with the membrane.

  [20] The electrolysis cell for ozone generation as described in 18 or 19 above, wherein a porous noble metal layer is provided between the anode catalyst body and the anode current collector or anode substrate.

  The anode catalyst body according to the invention described in [1] includes electrode catalyst particles and a resin made from a solution in which a resin component is dissolved in a solvent, and is flexible because it is a resin base. And excellent in surface smoothness. For this reason, it has good adhesion to the fluororesin cation exchange membrane and can increase the contact area between the two without pressing the anode catalyst body with a strong force, ensuring an electrolytic area and excellent ozone generation ability. Is obtained. Moreover, since the electrode catalyst particles do not bite into the cation exchange membrane by not pressing the anode catalyst body against the cation exchange membrane with a strong force, the consumption of the cation exchange membrane is reduced, thereby extending the life of the electrolysis cell. Can do.

  According to the invention described in [2] above, the above effect can be achieved in an anode catalyst body using lead dioxide as electrode catalyst particles.

  According to the invention described in the above [3], the above effect is exhibited in the anode catalyst body constituted by a fluororesin in which a part of the fluorine atoms of the fluorocarbon constituting the monomer is substituted with a hydrogen atom. Can do.

  According to the invention described in [4] above, the above effect can be achieved in an anode catalyst body using polyvinylidene difluoride having high solvent solubility and ozone resistance as the fluororesin.

  According to the invention described in [5] above, in the anode catalyst body using a terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene difluoride having high solvent solubility and ozone resistance as the fluororesin, There is an effect.

  According to the invention described in [6] above, since the monomer ratio of vinylidene difluoride in the ternary copolymer is 30 mol% or more, high solvent solubility is obtained, and the above effect is obtained in the anode catalyst body. Can play.

  According to the invention described in [7] above, the above effect can be achieved in an anode catalyst body obtained using a solution obtained by dissolving polyvinylidene difluoride in N-methyl-2-pyrrolidone as a raw material.

  According to the invention described in [8] above, in the anode catalyst body obtained using a solution in which a terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene difluoride is dissolved in ethyl acetate or methyl acetate as a raw material, The above effects can be achieved.

  According to the method for producing an anode catalyst body according to the invention described in [9] above, lead dioxide, a fluororesin in which a part of fluorine atoms of fluorocarbon constituting the monomer is substituted with hydrogen atoms, and a solvent are contained. A flexible sheet-like anode in which lead dioxide particles are molded using the fluororesin as a binder by two steps: a forming step for forming a paste-like mixture into a sheet-like body and a drying step for removing the solvent and solidifying the mixture. A catalyst body can be produced efficiently.

  The starting material of the electrode catalyst of the anode catalyst body is lead dioxide, and in the manufacturing process, acid treatment for converting lead from other substances into lead dioxide and dissolution treatment with water for removing by-products are not performed. Further, the paste-like mixture does not contain water, and the manufacturing process does not include a treatment in which lead dioxide comes into contact with water. From these things, in a manufacturing process, it is not converted into lead dioxide from other substances, and lead dioxide is not reduced. Therefore, there is no room for substances other than lead dioxide to be mixed in the production process, and an anode catalyst body containing only lead dioxide and excluding resin and having an excellent ozone generating ability can be produced.

  Since the method for producing an anode catalyst body according to the invention described in [10] above performs the forming step and the drying step on the plate, it depends on the material and shape of the other electrode material such as the electrode substrate. Thus, the anode catalyst body can be produced efficiently. Moreover, since the surface form of the plate is transferred to the plate contact surface when the paste mixture is applied, an anode catalyst body with high surface smoothness can be produced by using a plate with high smoothness.

  According to the invention described in [11] above, the solvent can be efficiently removed in the drying step.

  According to the invention described in [12] above, the above effect can be achieved in a production method using polyvinylidene difluoride as the fluororesin.

  According to the invention described in [13] above, the above effect can be achieved in a production method using polyvinylidene difluoride as the fluororesin and N-methyl-2-pyrrolidone as the solvent.

  According to the invention described in [14] above, the above effect can be achieved in a production method using a terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene difluoride as the fluororesin.

  According to the invention described in [15] above, in the production method using a terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene difluoride as the fluororesin and using ethyl acetate or methyl acetate as a solvent. The above effects can be achieved.

  According to the invention described in [16] above, in the production method using polyvinylidene difluoride as the fluororesin and N-methyl-2-pyrrolidone as a solvent, flexibility and An anode catalyst body having surface smoothness can be produced efficiently. Furthermore, when performing a shaping | molding process and a drying process on a plate, the anode catalyst body after a drying process can be easily taken out from a plate, without being damaged.

  According to the invention described in [17] above, in the production method using a terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene difluoride as the fluororesin and using ethyl acetate or methyl acetate as a solvent. The anode catalyst body having flexibility and surface smoothness can be efficiently produced under the prescribed drying conditions. Furthermore, when performing a shaping | molding process and a drying process on a plate, the anode catalyst body after a drying process can be easily taken out from a plate, without being damaged.

  In the electrolytic cell for ozone generation according to the invention described in [18], the resin-based anode catalyst body described in any one of the above [1] to [8] is used as the anode catalyst body of the anode, It is arranged in close contact with the cation exchange membrane. Since the anode catalyst body has flexibility and surface smoothness, it can achieve high adhesion without pressing against the cation exchange membrane with a strong force, and can secure a contact area between the two to obtain excellent ozone generation ability. . Further, since the electrode catalyst particles do not bite into the cation exchange membrane by not pressing with a strong force, the consumption of the cation exchange membrane is reduced, and the life of the electrolytic cell can be extended.

  The electrolytic cell for ozone generation according to the invention described in [19] above incorporates the anode catalyst body produced by the method described in any one of [11] to [17]. Since the anode catalyst body has no room for mixing substances other than lead dioxide in the production process and contains only lead dioxide except for the resin, the ozone generating electrolytic cell has an excellent ozone generating ability. In addition, since the plate contact surface at the time of applying the paste-like mixture, that is, the surface with higher surface smoothness of the two surfaces of the anode catalyst body is disposed in contact with the cation exchange membrane, High adhesion can be reliably obtained with the anode catalyst body.

  According to the invention described in [20] above, the noble metal layer reduces the contact resistance between the anode catalyst body and the anode current collector or the anode substrate, so that the electrolysis efficiency can be increased.

It is sectional drawing which shows the structure of one Embodiment of the electrolytic cell for ozone generation concerning this invention in a decomposition | disassembly state. It is typical sectional drawing which shows the process of the manufacturing method of the anode catalyst body concerning this invention.

  FIG. 1 shows one embodiment of an electrolytic cell for ozone generation according to the present invention in an exploded state. Hereinafter, the present invention will be described in detail with reference to FIG.

[Structure of anode catalyst body and electrolytic cell for ozone generation]
The electrolytic cell for ozone generation (1) has a porous anode (20) in close contact with one surface of a fluororesin cation exchange membrane (10) and a porous cathode (30) on the other surface. Is a zero-gap cell that is assembled with the anode side cell frame (11) and the cathode side cell frame (12) in close contact from the outside of the anode (20) and cathode (30). A pressing force is applied from the outside by a fastening means (not shown) to increase the adhesion between the members. (13) is an anode feeding terminal, and (14) is a cathode feeding terminal. The cell (1) is divided into an anode chamber (21) and a cathode chamber (31) by a fluororesin-based cation exchange membrane (10), an anolyte supply port (22) at the lower end of the anode chamber (21), An anolyte / gas outlet (23) is provided at the upper end, and a catholyte / gas outlet (33) is provided at the upper end of the cathode chamber (31).

  As the cation exchange membrane (10), a known solid polymer electrolyte membrane can be used. As the resin constituting the solid polymer electrolyte, a perfluorosulfonic acid resin having a sulfonic acid group having a cation exchange function and excellent in chemical stability is particularly preferable. The cation exchange membrane (10) also functions as a partition between the anode chamber (21) and the cathode chamber (31), and the anolyte and anode gas in the anode chamber (21) and the cathode chamber (31) Mixing of the catholyte and the cathode gas is prevented. Further, by preventing the substances in the bipolar chambers (21) and (31) from being mixed, the purity of the generated gas and electrolyte is maintained, and the function of preventing explosion and ignition due to mixing of the generated gas is provided.

  The anode (21) comprises an anode current collector or anode substrate (24), a noble metal layer (25), and an anode catalyst body (26).

  The anode current collector or anode substrate (24) is a porous structure made of a conductive metal, and is particularly preferably made of a metal having excellent corrosion resistance. Examples of metals that satisfy these conditions include valve metals such as titanium, tantalum, niobium, and zirconium. As porous structures, porous bodies, fiber bodies, nets, foams, and fibers are formed into required shapes by sintering or pressing. What was shape | molded can be illustrated.

  The anode catalyst body (26) is a porous thin film containing electrode catalyst particles capable of generating ozone by electrolysis and a resin, and the resin is made from a solution in which a resin component is dissolved in a solvent. . Examples of the electrode catalyst include lead dioxide and conductive diamond, and lead dioxide can be particularly recommended.

  The resin is required to have ozone resistance and be soluble in a solvent. Examples of such a resin include a fluororesin having a structure in which some of the fluorine atoms are substituted with hydrogen atoms, ethylene / chlorotrifluoroethylene, and the like.

A fluororesin having a structure in which a part of fluorine atoms is substituted with hydrogen atoms (abbreviated as “partially hydrogenated fluororesin” in the following description) has high solubility in a solvent and forms a sheet-like anode catalyst body. Suitable for Among such partially hydrogenated fluororesins, polyvinylidene difluoride (—CH ₂ CF ₂ —) and vinylidene difluoride as a monomer can be formed into a sheet at a temperature lower than the thermal decomposition temperature of lead dioxide and have high ozone resistance. A copolymer containing can be recommended.

“Structure in which a part of fluorine atoms are replaced with hydrogen atoms” and “partial hydrogenation” do not mean that fluorine atoms are replaced with hydrogen atoms in the process of polymerizing the monomer, but the resin structure. Means having a hydrogen atom. Therefore, in the process of polymerizing the monomer, the fluororesin that contains hydrogen atoms by substituting some of the hydrogen atoms of the hydrocarbons with fluorine atoms is referred to as “part of the fluorine atoms into hydrogen atoms” in the present invention. This corresponds to “a fluororesin having a substituted structure”. For example, polyvinylidene difluoride (—CH ₂ CF ₂ —) has a structure in which a part of fluorine atoms of polytetrafluoroethylene (—CF ₂ CF ₂ —) is substituted with hydrogen atoms.

The polyvinylidene difluoride is a resin having excellent ozone resistance as compared with other resins, although ozone resistance is slightly inferior to polytetrafluoroethylene used in Patent Document 2. Polytetrafluoroethylene (—CF ₂ CF ₂ —) in which fluorine atoms are not substituted with hydrogen has extremely high chemical stability and excellent ozone resistance, but is not dissolved in a solvent. On the other hand, polyvinylidene difluoride (—CH ₂ CF ₂ —) has a slightly lower ozone resistance than polytetrafluoroethylene by substituting some of the fluorine atoms of polytetrafluoroethylene with hydrogen. Solubility is increasing. Polyvinylidene difluoride is a fluororesin that has both ozone resistance necessary as an anode catalyst body for an electrolytic cell for ozone generation and solvent solubility necessary for forming a sheet.

A terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride can be recommended as a copolymer containing vinylidene difluoride. In the terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene difluoride (abbreviated as “THV copolymer” in the following description), a part of fluorine atoms of fluorocarbon is substituted with hydrogen. Having a vinylidene difluoride (—CH ₂ CF ₂ —) having a structure such that tetrafluoroethylene (—CF ₂ CF ₂ —) and hexafluoro which are solvent-soluble and in which the fluorine atom is not substituted with hydrogen By containing propylene (—CH ₂ CF (CF ₃ ) —), the fluororesin is chemically stable and has high ozone resistance. The THV copolymer contains tetrafluoroethylene and hexafluoropropylene as monomers, and thus has higher ozone resistance than the above-mentioned polyvinylidene difluoride. Further, the THV copolymer is suitable for the material of the sheet-like anode catalyst body because of its high flexibility.

  In the THV copolymer, the higher the vinylidene difluoride content in the monomer composition, the higher the solvent solubility, and the lower the vinylidene difluoride content, the lower the solvent solubility, making it difficult to form a sheet. . In the present invention, from the viewpoint of facilitating sheet formation, a THV copolymer containing 30 mol% or more of vinylidene difluoride in the monomer composition is recommended. A particularly preferred vinylidene difluoride content is 35 mol% or more. Although the chemical stability decreases as the vinylidene difluoride content increases, the above-mentioned polyvinylidene difluoride also has the ozone resistance necessary for the anode catalyst body. As long as it is a coalescence, it has ozone resistance necessary for the anode catalyst body. Therefore, there is no regulation on the upper limit value of the vinylidene difluoride content in the THV copolymer.

  The THV copolymer is available as a product of the Dionion THV series (THV220A, THV220G, THV221AZ, THV221GZ, THV500G, THV500GZ, THV600G, THV600GZ, etc.) manufactured by Sumitomo 3M Limited.

  Further, other copolymers containing vinylidene difluoride as a monomer, partially hydrogenated fluororesins other than vinylidene difluoride, or copolymers containing partially hydrogenated fluorocarbons other than vinylidene difluoride as monomers. The coalescence is also included in the present invention as long as it has ozone resistance and solvent solubility.

  In addition, since the method for producing an anode catalyst body of the present invention is used by dissolving a resin in a solvent, it can be used in a powder form or a pellet form. However, it is preferable to use a powder resin from the viewpoint of easy dissolution. .

  The solvent is not limited as long as it can dissolve the resin to be used, but it is preferable to use a solvent having a low boiling point. Since the solvent having a low boiling point can be removed in a short time even at a low temperature in the drying step of the production method described later, there is no possibility that lead dioxide is thermally decomposed and the working efficiency is good. N-methyl-2-pyrrolidone (boiling point 202 ° C.) can be exemplified as a solvent for dissolving polyvinylidene difluoride, and ethyl acetate (boiling point 77 ° C.) or methyl acetate (boiling point 57.5 ° C.) as a solvent for dissolving a THV copolymer. ° C).

  A method for producing the anode catalyst body (26) containing lead dioxide as the electrode catalyst and using polyvinylidene difluoride or THV fluororesin as the resin will be described in detail later.

  The noble metal layer (25) is a layer disposed between the anode catalyst body (26) and the anode current collector or anode substrate (24) in order to reduce the contact resistance between the anode catalyst body (26) and the anode current collector or anode substrate (24) to increase the electrolysis efficiency. It is. As the noble metal, platinum can be exemplified, and a porous foil in which a number of fine holes are formed in the noble metal foil can be exemplified. Although the thickness of the noble metal layer (25) is not limited, it is preferably 0.02 to 200 [mu] m, particularly preferably 0.02 to 0.2 [mu] m, for obtaining the above effect. In the electrolysis cell of the present invention, the noble metal layer is not an essential constituent element, and an electrolysis cell using an anode having no noble metal layer is also included in the present invention.

  The cathode (30) comprises a cathode substrate or cathode current collector (34) and a cathode catalyst body (36).

  The cathode substrate or the cathode current collector (34) is a porous structure made of a conductive metal. Examples of the conductive material include metals such as stainless steel, nickel, zirconium, titanium, and carbon. As the porous structure, as with the anode, a porous body, a fibrous body, a net-like body, a foamed body, and a fiber are sintered or pressed. What was shape | molded in the required shape can be illustrated. A particularly preferred porous structure is a stainless steel fiber sintered body that is excellent in workability as compared with a valve metal such as titanium, so that a uniform surface is easily obtained, and is excellent in corrosion resistance under negative polarization.

  The cathode catalyst body (36) is preferably platinum, platinum black, platinum-supported carbon or the like having a low hydrogen overvoltage as a catalyst, and a porous thin film in which these particles are dispersed in a fluororesin can be recommended.

  The electrolytic cell (1) comprises an anode current collector or anode substrate (24), a noble metal layer (25), an anode catalyst body (26), a cation exchange membrane (10), a cathode catalyst body (36), a cathode substrate or The cathode current collector (34) is placed in close contact, and the anode side cell frame (11) and the cathode side cell frame (12) are placed in close contact and assembled. Note that some members may be assembled in close contact prior to assembly of the entire cell.

In the electrolytic cell (1), when pure water is introduced into the anode chamber (21) from the anolyte supply port (22) and energized between both electrodes, the anode catalyst body / ion exchange membrane / pure water of the anode (20) In the three phases in contact with each other, the following electrolytic reactions (F1) and (F2) occur, and oxygen gas and ozone gas are generated. Hydrogen ions generated by the electrolytic reaction permeate the cation exchange membrane (10) by the potential gradient, and in the cathode chamber (31), the hydrogen ions come into contact with the cathode catalyst body (36) and are reduced by the reduction reaction (F3) below. Generate gas. The oxygen gas and ozone gas generated in the anode chamber (21) are released from the anolyte / gas outlet (23) together with pure water, and the hydrogen gas generated in the cathode chamber (31) is added together with pure water to the catholyte / gas. Released from the outlet (33).
(Anode reaction)
3H ₂ O → O ₃ + 6H ⁺ + 6e ⁻ (F1)
2H ₂ O → O ₂ + 4H ⁺ + 4e ⁻ (F2)
(Cathode reaction)
2H ⁺ + 2e ⁻ → H ₂ (F3)

[Preparation of anode catalyst body]
The anode catalyst body (26) is produced, for example, by the method of the present invention. The starting material for the anode catalyst body (26) is lead dioxide as an anode catalyst, a resin that serves as a binder for forming lead dioxide into a sheet (a fluorine resin having a structure in which some of the fluorine atoms are replaced with hydrogen atoms). It is a solvent for dissolving the resin. Lead dioxide is the anode catalyst chosen for its excellent electrical conductivity and ozone generation ability. When using polyvinylidene difluoride as the resin, N-methyl-2-pyrrolidone is used as the solvent, and when using the THV copolymer, ethyl acetate or methyl acetate is used as the solvent. Below, the manufacturing method of the anode catalyst body including a formation process and a drying process is explained in full detail, referring FIG.

(Molding process)
Lead paste particles, resin and solvent are thoroughly mixed to prepare a paste-like mixture in which lead dioxide particles are uniformly dispersed. As shown in FIG. 2A, the paste-like mixture is applied on a plate (40) having a smooth surface, spread to a required thickness, and formed into a sheet-like body (41). Since the paste-like mixture has viscosity, it is applied to a required thickness and area and formed into a sheet-like body (41), but is not solidified.

  In the anode catalyst body (26) to be produced, the higher the lead dioxide content, the higher the conductivity and the lower the power consumption during electrolysis. Therefore, it is preferable that the lead dioxide content be as high as possible. However, if the content of the resin as the binder is excessively low, it becomes difficult to take out the anode catalyst body (26) while maintaining the sheet shape after the drying step. Therefore, in the composition of the paste-like mixture, the content ratio of lead dioxide to the total amount of lead dioxide and resin can be set to 80 to 93% by mass, preferably 92 to 93% by mass, particularly 93% by mass. % Is preferred.

  The particle diameter of the lead dioxide is preferably 50 μm or less. If lead dioxide having a large particle size is used, the surface of the anode catalyst body (26) becomes rough, so that the adhesion with the cation exchange membrane (10) is deteriorated and the contact area is reduced. When the pressing force is increased to improve the adhesion of the anode catalyst body (26) with poor surface smoothness (coarse), the lead dioxide particles tend to bite into the cation exchange membrane (10), and the cation exchange membrane (10) This is not preferable because there is a possibility that the local consumption of the material increases. Moreover, if it is a particle | grain of 50 micrometers or less, there will be no difficulty in setting the lead dioxide content ratio with respect to the total amount of lead dioxide and resin in the suitable range mentioned above. On the other hand, by using lead dioxide having a small particle diameter, an anode catalyst body (26) that is thinner and has higher surface smoothness can be obtained. Such a thin anode catalyst body (26) having a high surface smoothness is preferable in that it has a large contact area with the cation exchange membrane (10), so that the cell voltage can be reduced and the power consumption can be reduced. However, if the desired cell voltage can be obtained, the purpose of using lead dioxide with a small particle size can be achieved, so that a thinner anode catalyst body (10) can be obtained using lead dioxide with a smaller particle size. Has little technical significance. From this viewpoint, the particle diameter of lead dioxide is preferably 0.1 to 50 μm, and particularly preferably 0.1 to 10 μm.

  Further, the ratio of the resin and the solvent in the paste-like mixture needs to be set to a viscosity at which the sheet-like body (41) can be applied to a desired thickness. When the ratio of the solvent is lowered, the viscosity is increased and the thickness after coating is maintained. However, when the viscosity is excessively increased, it is difficult to apply the desired thickness. From this viewpoint, the content ratio of the resin to the total amount of the resin and the solvent is preferably 5 to 12% by mass, and particularly preferably 12% by mass. As the solvent ratio increases, the viscosity of the paste-like mixture decreases and flows after application, making it difficult to maintain the desired thickness.

  Moreover, what set the thickness of the sheet-like body (41), ie, the coating thickness of a paste-form mixture, to the range of 60-1000 micrometers can be used. When the thickness of the sheet-like body (41) is thinner than the lower limit, the sheet strength of the anode catalyst body (26) after drying is low, and the electrolytic cell (1) can be removed from the plate (40) after the drying process. ) Be careful in handling even when incorporating into). On the other hand, as the thickness of the anode catalyst body (26) increases, the cell voltage during electrolysis increases, the operating power increases, and ozone generated by heat generation decomposes. For this reason, the thickness of the anode catalyst body (26), in other words, the coating thickness of the paste-like mixture is preferably thin as long as it can be handled without damage after drying. From such a viewpoint, the particularly preferable thickness of the sheet-like body (41) when applied is 100 to 200 μm.

(Drying process)
As shown in FIG. 2 (b), the sheet-like body (41) is dried on the plate (40) to remove the solvent. By this drying step, the paste-like mixture is solidified to form a porous anode catalyst body (26) in which lead dioxide particles are dispersed. Since the paste-like mixture is solidified, it can be peeled off from the plate (40) and taken out as a sheet-like anode catalyst body (26) as shown in FIG. The solidified anode catalyst body (26) is flexible and can be peeled off from the plate (40) without any trouble.

  The removal of the solvent from the sheet-like body (41) can be performed in a shorter time at a lower temperature as the boiling point of the solvent is lower. Accordingly, preferred drying conditions vary depending on the solvent.

  When N-methyl-2-pyrrolidone is used as the solvent, holding at 50 to 90 ° C. for 15 to 120 minutes is preferable. When the drying temperature is 50 ° C. or lower, it takes a long time to remove the solvent, resulting in poor production efficiency. Further, if the solvent remains, it becomes difficult to peel off the plate (40) while the unremoved portion is attached to the plate (40) and the sheet shape is maintained. On the other hand, since lead dioxide is thermally decomposed at 230 ° C. or higher, the drying temperature needs to be 230 ° C. or lower. However, the solidified anode catalyst body (26) when the drying temperature becomes high even in the temperature range of 230 ° C. or lower. May harden and decrease flexibility. The decrease in flexibility is presumed that the curing of the anode catalyst (26) is caused by the crystallization and aggregation of polyvinylidene difluoride. When the flexibility of the anode catalyst body (26) is reduced, phenomena such as being easily damaged when peeled from the plate (40) and the ozone generation efficiency are reduced. It is estimated that the decrease in ozone generation efficiency is due to the progress of lead dioxide phase transition. Further, when the flexibility of the anode catalyst body (26) is lowered, the adhesion with the cation exchange membrane (10) may be lowered. If the drying time is insufficient, the unremoved solvent remains in the anode catalyst body (26), and if it is too long, the anode catalyst body (26) is cured and the flexibility is lowered. Although much care is required for handling due to a decrease in flexibility due to drying for a long time, on the other hand, there is also an advantage that the removal of the solvent contained in the anode catalyst body (26) proceeds. The smaller the amount of unremoved solvent contained in the produced anode catalyst body (26), the smaller the amount of solvent that will elute from the anode catalyst body (26) during electrolysis, so it is connected to the inside of the electrolysis cell (1) and the electrolysis cell (1). The possibility that the inside of the equipment to be used and the liquid stored in those parts will be contaminated becomes low. Contamination with the solvent contributes to a decrease in electrolytic performance, so that the anode catalyst body (26) has high adhesion to the cation exchange membrane (10) and is flexible enough to be handled. It is preferable to dry it sufficiently. For these reasons, the drying temperature is preferably 50 to 90 ° C, particularly preferably 80 to 90 ° C. The drying time is preferably 15 to 120 minutes, particularly preferably 15 to 30 minutes.

  Further, since ethyl acetate or methyl acetate has a lower boiling point than N-methyl-2-pyrrolidone, the solvent is removed at a lower temperature and in a shorter time than the anode catalyst (26) using N-methyl-2-pyrrolidone. And can be dried at room temperature without heating. However, the smaller the amount of unremoved solvent contained in the anode catalyst body (26), the smaller the amount of solvent that elutes from the anode catalyst body (26) during electrolysis, so it is connected to the inside of the electrolysis cell (1) and the electrolysis cell (1). In order to reduce as much as possible the possibility of contamination of the inside of the equipment and the liquid stored in the inside, it is preferable to hold at room temperature of about 25 to 90 ° C. for 0.5 to 60 minutes. Further, since the THV copolymer is more flexible than polyvinylidene difluoride, it can be easily peeled off from the plate (40) even if it is sufficiently dried. A particularly preferable drying temperature is 25 to 90 ° C., and a particularly preferable drying time is 1 to 45 minutes.

  In the manufacturing process described above, the material constituting the plate (40) can be used as long as it does not change in quality due to the resin or solvent and does not thermally deform in the subsequent drying process. It is preferable that the catalyst body (26) is easily peeled off. From such a viewpoint, glass, stainless steel, polytetrafluoroethylene and the like can be recommended.

  Since the above-described forming process and drying process on the plate are independent processes, the resin base has flexibility and surface smoothness regardless of the material and shape of other electrode materials such as the electrode base. High anode catalyst body can be produced efficiently. Since the anode catalyst body that is flexible and excellent in surface smoothness has high adhesion to the cation exchange membrane and a large contact area, an electrolytic area can be secured and an excellent ozone generating ability can be obtained.

  In addition, since the surface morphology of the plate (40) is transferred to the plate contact surface (26a) when the paste mixture is applied, the surface roughness can be reduced by molding using a plate (40) having a small surface roughness and high smoothness. The anode catalyst body (26) having a small and high smoothness can be produced reliably. The anode catalyst body (26) having high surface smoothness and flexibility can achieve high adhesion without pressing against the cation exchange membrane (10) with a strong force, and can secure a contact area between the two. Moreover, since the lead dioxide particles do not penetrate into the cation exchange membrane (10) by not pressing with a strong force, the consumption of the cation exchange membrane (10) can be reduced, thereby extending the life of the electrolysis cell. .

  The anode catalyst body (26) formed by applying the paste-like mixture can be formed smoothly on the exposed surface (26b) when the paste mixture is applied, but as described above, the surface roughness of the anode catalyst body (26) Can be easily controlled by the plate (40) used at the time of molding, and high surface smoothness can be reliably obtained. And among the two surfaces of the anode catalyst body (26) taken out from the plate (40), the plate contact surface (26a) is disposed as an electrolytic surface so as to be in contact with the cation exchange membrane (10), and assembled. By transferring the plate surface roughness, high adhesion can be reliably obtained by the surface of the anode catalyst body whose surface roughness is controlled.

  Further, in the drying step, as shown in FIGS. 2B, 2C, and 2D, when part of the solvent is removed and the sheet-like body (41) can be peeled off, the sheet-like shape is being dried. The body (41) may be peeled from the plate (40) and turned over so that the exposed surface (26b) when the paste-like mixture is applied is placed on the plate (40) and further dried to remove the remaining solvent. If the plate (40) can be peeled even during drying, the surface smoothness of the plate (40) is transferred to the sheet (41), so the surface of the plate contact surface (26a) when applying the paste mixture Smoothness is achieved. Thus, by turning the sheet-like body (41) in the middle of drying, the solvent can be efficiently removed, and the unremoved solvent remaining on the anode catalyst body (26) can be reduced.

  The anode catalyst body has higher gloss as the surface roughness is smaller and surface smoothness is higher. Therefore, the surface smoothness of the anode catalyst body can be evaluated by the glossiness, and the ozone generation efficiency can be predicted and evaluated based on the adhesion to the cation exchange membrane (10). However, since the surface smoothness of the anode catalyst body produced with different resins differs in the resin size in the anode catalyst body, the level of glossiness of the anode catalyst body produced with a different resin indicates the level of ozone generation efficiency. Not exclusively. For example, when THV copolymer is used, the resin size in the anode catalyst body tends to be larger than that of polyvinylidene difluoride. Therefore, the glossiness of the anode catalyst body using THV copolymer is equal to that of polyvinylidene difluoride. It tends to be lower than the anode catalyst body using. However, the ozone generation efficiency is determined not only by the surface smoothness of the anode catalyst body (adhesion to the cation exchange membrane) but also by many factors such as the thickness of the anode catalyst body and the content of lead dioxide particles. It is difficult to evaluate anode catalyst bodies with different glossiness only by glossiness.

  As shown in FIG. 1, the porous anode catalyst body (26) prepared in the above process is incorporated into an electrolysis cell (1) together with other members and used for ozone generation by water electrolysis.

  Since the anode catalyst body of the present invention is resin-based, it has flexibility and can easily obtain surface smoothness. In addition, polyvinylidene difluoride used as a binder for lead dioxide is less ozone resistant than polytetrafluoroethylene used as a binder in Patent Document 2, so it can be dissolved and reduced by long-term operation of the electrolytic cell. There is sex. However, in the zero gap type electrolysis cell, since the pressure is applied to the cation exchange membrane from behind the two electrodes in order to maintain the contact state of each member, the polyvinylidene difluoride is temporarily reduced. However, the lead dioxide particles do not fall off, the lead dioxide particles are kept in close contact with the cation exchange membrane, and the electrolysis efficiency is maintained. Further, since the THV copolymer has higher ozone resistance than polyvinylidene difluoride, it does not dissolve even when it is operated for a long time, or the dissolved amount is less than that of polyvinylidene difluoride. In an electrolysis cell in the zero gap direction, the dissolution of the resin does not cause the lead dioxide particles to fall off, but the dissolved resin may contaminate the inside of the cell, so it is preferable that the dissolution of the resin is as small as possible. .

  The electrode catalyst particles of the anode catalyst body are lead dioxide from the starting material, and neither acid treatment nor dissolution treatment as in Patent Document 2 is performed in the manufacturing process. Therefore, conversion from other substances to lead dioxide is also possible. There is no reduction. For this reason, there is no room for substances other than lead dioxide to be mixed in the anode catalyst body, and an anode catalyst body containing only lead dioxide can be manufactured except for the resin. Moreover, since this invention can manufacture an anode catalyst body by a process fewer than the method described in patent document 2, production efficiency is good.

  Moreover, the paste-like mixture which is a manufacturing material of the anode catalyst body is a mixture of lead dioxide, resin and solvent, and does not contain water. Moreover, since the anode catalyst body manufactured in an independent process is incorporated in the electrolytic cell according to the present invention, the porous substrate is sealed and the sealing agent is eluted with water as in Patent Document 3, which forms a film on the porous substrate. Do not need. Furthermore, since there is no sealing agent elution step with water, lead dioxide as an electrode catalyst does not come into contact with water before energization, and there is no possibility that lead dioxide will be transformed into other substances by reduction or the like. Therefore, according to the present invention, there is no room to mix other things than lead dioxide, an anode catalyst body containing only lead dioxide can be produced except for the resin, and the electrolytic cell can be efficiently produced in a simpler process than that of Patent Document 3. Can be manufactured.

  In addition, the manufacturing method of the anode catalyst body of this invention is not limited to said process of producing a paste-like mixture on a plate and taking out from a plate. The present invention also includes a method in which a paste-like mixture is directly applied to a member to be brought into close contact with the anode catalyst body, the sheet is dried on the member, and a sheet-shaped body formed by extrusion or rolling is dried.

[Example]
[Example A: Production of anode catalyst body using polyvinylidene difluoride]
Using lead dioxide (manufactured by Nacalai Tesque Co., Ltd., special grade, particle size by SEM observation is 0.1 to 10 μm), and resin solution mixed with resin and solvent (trade name “KF Polymer # 1120” manufactured by Kureha Co., Ltd.) A sheet-like anode catalyst body was produced by the process shown in FIG. The resin solution is a mixture of polyvinylidene difluoride and N-methyl-2-pyrrolidone, and the content ratio of polyvinylidene difluoride in the resin solution is 12% by mass.

  First, lead dioxide and a resin solution in amounts shown in Nos. 1 to 18 in Table 1 were sufficiently mixed in a polypropylene test tube to prepare a paste-like mixture. This paste-like mixture was transferred to a glass plate (40) having a clean smooth surface, formed into a film using an applicator set to a coating width of 50 mm and a film thickness of 100 μm, and a sheet-like body ( 41) was molded. Table 1 shows the content ratio of lead dioxide to the total amount of lead dioxide and polyvinylidene difluoride in each No. pasty mixture.

  Next, the sheet-like body (41) formed on the glass plate (40) was dried for the time shown in Table 1 in a drier set at any temperature of 50 ° C., 90 ° C., 140 ° C., and 150 ° C. (40) A porous sheet-like anode catalyst body (26) was obtained. In No. 14, the sheet (41) was peeled off from the glass plate (40) 15 minutes after the start of drying, and turned over and the exposed surface (26b) when applying the paste-like mixture was placed on the glass plate (40). , And further dried for 30 minutes. The porosity of the produced anode catalyst body No. 3-18 (26) was 65-75%.

  The anode catalyst body (26) of each No. was peeled off from the glass plate (40) and taken out, and the film forming property was evaluated according to the following criteria depending on the state at the time of taking out. The results are shown in Table 1.

(Film formability)
A: The anode catalyst body has flexibility and can be easily peeled off from the glass plate without being damaged.
(Triangle | delta): Although the softness | flexibility of an anode catalyst body is inferior to (circle), it can peel from a glass plate. However, in order to peel it off so as not to break, it requires less care than handling ○, so it is not practical.
X: There is an undried portion on the surface of the sheet-like body, and the sheet shape cannot be peeled off from the glass plate. Or a sheet-like body is hard and it breaks when peeling from a glass plate.

  From Table 1, it was confirmed that the anode catalyst body could contain 93% by mass of lead dioxide with respect to the total amount of lead dioxide and polyvinylidene difluoride under the above test conditions. Furthermore, it confirmed that the suitable conditions of the drying process were 50-90 degreeC x 15-120 minutes.

[Content ratio of polyvinylidene difluoride in the resin solution]
As Nos. 21 to 23 shown in Table 2, a paste-like mixture was prepared using three types of resin solutions prepared by adjusting the content ratio of polyvinylidene difluoride in the resin solution to 12 mass%, 8 mass%, and 5 mass%. A 100 μm thick sheet was formed on the glass plate in the same manner as in Nos. 1 to 17. The drying process was 15 minutes at 90 ° C. About the produced anode catalyst body, the film formability was evaluated on the same basis as the above. These results are shown in Table 2.

  From Table 2, the film forming property was most excellent when a polyvinylidene difluoride content ratio of 12% by mass was used among the three types of resin solutions.

[Thickness of sheet-like body]
As Nos. 31 to 33 shown in Table 3, a paste-like mixture having the same composition as Nos. 3 to 17 was used, and sheet-like bodies were molded with three coating thicknesses of 50 μm, 100 μm, and 200 μm. The drying process was 15 minutes at 90 ° C. The porosity of the produced anode catalyst body was 65 to 75%.

  About the produced anode catalyst body, the film formability was evaluated on the same basis as the above. These results are shown in Table 3.

  From Table 3, it was confirmed that the film formability was good with a sheet-like body having a coating thickness of 100 μm or more.

[Electrolysis cell for ozone generation]
Using the anode catalyst bodies of No. 4, 8, 11, 13, 14, 17, 21, 32, and 33 in Table 1 and combining members other than the anode catalyst bodies described below, for generating ozone with the structure shown in FIG. An electrolytic cell (1) was produced.

A plurality of anode catalyst bodies (26) were prepared so that the electrolytic area was 1 dm ² .

  As a cation exchange membrane (10), a commercially available perfluorosulfonic acid type ion exchange membrane (manufactured by DuPont, trade name “Nafion 117”) is immersed in boiling pure water for 30 minutes and subjected to a swelling treatment with water. Was used.

  As an anode current collector (24), a titanium chatter fiber sintered body (manufactured by Tokyo Steel Co., Ltd.) having a diameter of 120 mm was degreased and washed with a neutral detergent.

  As the noble metal layer (25), a porous platinum foil in which a number of holes were formed in a platinum foil having a thickness of 0.2 μm was used.

  As the cathode catalyst body (36), a resin-based porous cathode catalyst sheet in which a platinum-supported carbon catalyst was dispersed in polytetrafluoroethylene was used. The cathode catalyst sheet was mixed with a dispersion of polytetrafluoroethylene (PTFE) dispersion (manufactured by Mitsui Fluorochemical Co., Ltd.) and a platinum-supported carbon catalyst dispersed in water, then dried, and solvent naphtha was added thereto. After kneading, it is produced through a rolling process, a drying process, and a firing process. PTFE is 40% by mass, platinum-supported carbon catalyst is 60% by mass, the film thickness is 120 μm, and the porosity is 55%.

  As the cathode current collector (34), a stainless fiber sintered body having a diameter of 120 mm (manufactured by Tokyo Seizuna Co., Ltd.) was used.

As shown in FIG. 1, the anode side cell frame (11), the anode current collector (24), the noble metal layer (25), the anode catalyst body (26), the cation exchange membrane (10), the cathode catalyst body ( 36), the cathode current collector (34), the assembly arranged in the order of the cathode-side cell frame (12), is brought into close contact with each member by applying a pressing force from the outside by clamping means not shown, the electrolysis area 1 dm ² An electrolytic cell (1) for generating ozone was prepared.

Using the electrolytic cell (1), pure water is electrolyzed at a current density of 2 A / cm ² and an electrolyte temperature of 30 ± 5 ° C., and a mixed gas of oxygen and ozone is supplied from the anode (20), and hydrogen gas is supplied from the cathode (30). Generated. The ozone current efficiency and cell voltage at this time are shown in Tables 1-3.

  Further, No. 11 and 13 were operated continuously for 2 months. Table 1 shows the ozone current efficiency and cell voltage after 2 months. Moreover, the electrolytic cell (1) was disassembled after continuous operation for two months, and when the consumption of the cation exchange membrane (10) was observed visually and by SEM, there was no consumption point. Further, the anode catalyst body (26) was in close contact with the cation exchange membrane (10), and almost no adhesion to the noble metal layer (25) was observed.

[Comparative example]
Instead of the anode (anode catalyst body, porous platinum foil, anode current collector) used in Example A, an electrolytic cell was prepared using the following anode.

  The anode current collector was obtained by degreasing and washing a titanium chatter fiber sintered body (manufactured by Tokyo Steel Co., Ltd.) with a neutral detergent, followed by acid washing with a 20 mass% 50 ° C. hydrochloric acid solution for 1 minute, and then platinum-titanium. -A coating made of tantalum (25-60-15 mol%) was formed by a thermal decomposition method and an underlayer was formed.

The anode current collector was subjected to a plating treatment using a 400 g / L lead nitrate aqueous solution as an electrolytic solution at 60 ° C. and 1 A / dm ² for 60 minutes to form a plating film made of lead dioxide. This plating film was used as an anode catalyst layer.

Using an electrolytic cell having the anode current collector having the anode catalyst layer as an anode, as in Example A, an electrolysis test for electrolyzing pure water at a current density of 2 A / cm ² and an electrolyte temperature of 30 ± 5 ° C. As a result, the ozone current efficiency was 15% and the cell voltage was 3.2V.

  Furthermore, when continuous operation was carried out for 2 months, the ozone current efficiency was 15.2% and the cell voltage was 3.3V. In addition, the electrolytic cell was disassembled after two months of continuous operation, and consumption of the cation exchange membrane was observed visually and by SEM. As a result, visual observation revealed that the chatter fiber sintered body had bite traces and electrolysis consumption on the entire anode side. Further, when the consumption thickness was determined from SEM observation, it was confirmed that the consumption was 15 μm. In addition, lead dioxide was not observed to adhere to the cation exchange, and remained on the chatter fiber as before electrolysis.

[Example B: Production of anode catalyst body using THV copolymer]
The same lead dioxide as in Example A was used. The resin solution was prepared by dissolving a powdery THV copolymer with ethyl acetate and adjusting the content ratio of the THV copolymer to 12% by mass. The THV copolymer used was THV221AZ manufactured by Sumitomo 3M Limited, and the monomer composition was tetrafluoroethylene: 40 mol%, hexafluoropropylene: 20 mol%, and vinylidene difluoride: 40 mol%.

  The amounts of lead dioxide and resin solution shown in Nos. 41 to 48 in Table 4 were thoroughly mixed in a polypropylene test tube to prepare a paste-like mixture. This paste-like mixture was transferred to a glass plate (40) having a clean smooth surface, formed into a film using an applicator set to a coating width of 50 mm and a film thickness of 100 μm, and a sheet-like body ( 41) was molded. Table 1 shows the content ratio of lead dioxide to the total amount of lead dioxide and THV terpolymer resin in each No. pasty mixture.

  Next, the sheet-like body (41) formed on the glass plate (40) was dried by holding No. 41 and No. 42 for 1 minute or 45 minutes without heating at room temperature (about 25 ° C.). Nos. 43 to 48 were dried for the time shown in Table 4 in a drier set at a temperature of 50 ° C., 70 ° C., or 90 ° C., and porous on the glass plate (40). (26) was obtained. The porosity of the produced No. 41 to 48 anode catalyst body (26) was 60 to 70%.

  Hereinafter, in the same manner as in Example A, the anode catalyst body (26) of each No. was peeled off from the glass plate (40) and evaluated for film formability. The results are shown in Table 4.

  Furthermore, using the anode catalyst bodies No. 41, No. 46 and No. 48 in Table 4, an electrolytic cell for ozone generation (1) having the structure shown in FIG.

Using the electrolytic cell (1), as in Example A, pure water was electrolyzed at a current density of 2 A / cm ² and an electrolyte temperature of 30 ± 5 ° C., and a mixed gas of oxygen and ozone from the anode (20), Hydrogen gas was generated from the cathode (30). Table 4 shows the ozone current efficiency and the cell voltage at this time.

  In addition, No. 48 was continuously operated for 2 months. Table 4 shows the ozone current efficiency and cell voltage after 2 months. Moreover, the electrolytic cell (1) was disassembled after continuous operation for two months, and when the consumption of the cation exchange membrane (10) was observed visually and by SEM, there was no consumption point. Further, the anode catalyst body (26) was in close contact with the cation exchange membrane (10), and almost no adhesion to the noble metal layer (25) was observed.

  From Table 4, it can be seen that the anode catalyst body can contain 93% by mass of lead dioxide with respect to the total amount of lead dioxide and THV copolymer under the above test conditions, and can generate ozone well. confirmed. It was also confirmed that the sheet could be formed at room temperature, and it was confirmed that the sheet could be formed in a short time even at a temperature lower than that of Example A using N-methyl-2-pyrrolidone as a solvent.

  The anode catalyst body of the present invention can be suitably used as an anode catalyst for an electrolysis cell for ozone generation of a zero gap method.

1 ... Electrolysis cell for ozone generation
10 ... Cation exchange membrane
20 ... Anode
21 ... Anode chamber
24 ... Anode current collector or anode substrate
25 ... Precious metal layer
26 ... Anode catalyst body
26a… Plate contact surface (glass plate contact surface) when applying paste-like mixture
26b… Exposed surface when applying paste-like mixture
30 ... Cathode
31 ... Cathode chamber
34 ... Cathode current collector or cathode substrate
36 ... Cathode catalyst body
40 ... Plate (glass plate)
41 ... Sheet

Claims (10)

The anode catalyst body is in close contact with one surface of the fluororesin-based cation exchange membrane, and the cathode catalyst body is in close contact with the other surface, and water electrolysis is performed by supplying a direct current through the current collector to each catalyst body. A method for producing an anode catalyst body used in an electrolysis cell for generating ozone to obtain ozone gas as a gas,
Electrode catalyst particles of lead dioxide or conductive diamond, a fluororesin having a structure in which some of the fluorine atoms are replaced with hydrogen atoms, and a solvent that dissolves the fluororesin, and a paste-like mixture that does not contain water. A molding step for forming into a body, and a drying step for solidifying by removing the solvent from the molded sheet-like body to form a sheet-like porous electrode material ,
In the molding step, a paste-like mixture is applied onto a plate to form a sheet-like body,
The drying process is performed in a state where the molded sheet-like body is placed on the plate, the sheet-like body in the middle of drying is peeled off from the plate, and the sheet-like body is turned over to expose the exposed surface when the paste-like mixture is applied on the plate. And then dried to remove the remaining solvent,
A method for producing an anode catalyst body, wherein the porous electrode material is removed from the plate after the drying . The method for producing an anode catalyst body according to claim 1 , wherein the fluororesin having a structure in which a part of the fluorine atoms is substituted with hydrogen atoms is polyvinylidene difluoride. Method for producing an anode catalyst body according to claim 2 wherein the solvent is N- methyl-2-pyrrolidone. 2. The anode catalyst body according to claim 1 , wherein the fluororesin having a structure in which some of the fluorine atoms are substituted with hydrogen atoms is a terpolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene difluoride. Production method. The method for producing an anode catalyst body according to claim 4 , wherein the solvent is ethyl acetate or methyl acetate. The manufacturing method of the anode catalyst body of Claim 3 performed by hold | maintaining the said drying process at 50-90 degreeC for 15 to 120 minutes. The manufacturing method of the anode catalyst body of Claim 5 performed by hold | maintaining the said drying process at room temperature-90 degreeC for 0.5 to 60 minutes. Water electrolysis is carried out by supplying an anode catalyst body to one surface of a fluororesin-based cation exchange membrane and a cathode catalyst body in close contact with the other surface, and supplying direct current to each catalyst body through a current collector or substrate. A method for producing an electrolytic cell for generating ozone, which obtains ozone gas as an anode gas,
The anode catalyst body is produced by the method according to any one of claims 1 to 7,
Ozone generation characterized by assembling the anode catalyst body in close contact with one surface of the cation exchange membrane, the cathode catalyst body in close contact with the other surface, and a current collector or substrate in close contact with each catalyst body For producing electrolytic cells for use in electric fields.   The method for producing an electrolytic cell for ozone generation according to claim 8, wherein a plate contact surface at the time of applying the paste-like mixture in the step of forming the sheet-like body of the anode catalyst body is brought into close contact with one surface of the cation exchange membrane. The method for producing an electrolytic cell for ozone generation according to claim 8 or 9 , wherein a porous noble metal layer is disposed between the anode catalyst body and the anode current collector or anode substrate.

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