JP2008266718A - Ozone water generating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ozone water generating apparatus capable of easily and efficiently generating high purity and high concentration ozone without incorporating metals or the like from an anode and degradating the anode electrode or solid high molecular electrolyte membrane. <P>SOLUTION: The ozone water generating apparatus is provided with the solid high molecular electrolyte membrane, and the anode electrode and a cathode electrode which are arranged to face across the solid high molecular electrolyte membrane. The anode electrode has a conductive thin film made of diamond-like carbon in which crystalline component is mixed with amorphous component, and the conductive thin film is formed so as to cover at least a part of an anodic base material or the solid high molecular electrolyte membrane. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ozone water production apparatus, and more particularly to an ozone water production apparatus used in a water electrolysis method using a solid polymer electrolyte membrane (SPE).

Since the oxidizing power of ozone is very strong, ozone is used in various fields such as sterilization, oxidation, deodorization, and decolorization. As a method for directly generating ozone water, a water electrolysis method using a solid polymer electrolyte membrane (SPE) using PbO ₂ or Pt as an anode catalyst has been proposed (for example, Patent Documents 1 to 3). If the water electrolysis method is used, there is an advantage that high-concentration ozone water can be easily generated with a small apparatus.

In FIG. 1, the schematic diagram of the typical ozone water manufacturing apparatus used for the water electrolysis method by SPE is shown. As shown in FIG. 1, an ozone water production apparatus 10 includes a solid polymer electrolyte membrane 1, and an anode 2 and a cathode 3 arranged so as to face each other with the solid polymer electrolyte membrane 1 interposed therebetween. The anode 2 includes a metal substrate 2a and a metal thin film 2b such as PbO ₂ or Pt coated so as to cover the metal substrate 2a. The metal substrate 2a may be processed into a porous shape or a net shape for the purpose of increasing the liquid contact area with water.

In the water electrolysis method, the following reaction proceeds on the anode (anode) side.
2H ₂ O → O ₂ + 4H ⁺ + 4e ⁻ (1)
3H ₂ O → O ₃ + 6H ⁺ + 6e ⁻ (2)
H ₂ O + O ₂ → O ₃ + 2H ⁺ + 2e ⁻ (3)
Here, if the anode electrode is an insoluble electrode, the reaction (1) proceeds. However, when an ozone-generating catalyst metal such as PbO ₂ or Pt is used for the anode electrode, the reactions (2) and (3) above. Progresses and ozone is generated. Therefore, high-concentration ozone gas or ozone water can be obtained by supplying water to the anode side of the apparatus.

However, when PbO ₂ or Pt is used as an electrode, the electrode is consumed with electrolysis, and the metal is eluted. The elution of the metal causes deterioration of the solid polymer electrolyte membrane. Therefore, Patent Document 4 discloses a carbon electrode having a conductive diamond structure as a non-metallic electrode material replacing these metal electrodes. Patent Document 5 discloses an electrode made of a self-stereoscopic conductive diamond plate having a porous or net-like structure, thereby improving the adhesion to the substrate. However, diamond is expensive, and in the method of Patent Document 4, it is necessary to make the thickness of the conductive diamond plate as thick as 0.2 mm or more in order to ensure mechanical strength. Therefore, it is considered difficult to put to practical use.
Japanese Patent Laid-Open No. 1-312092 JP-A-8-134777 Japanese Patent No. 3375904 JP-A-9-268395 JP-A-2005-336607

  The present invention has been made in view of the above circumstances, and its purpose is that there is no mixing of metal from the anode, so that the anode electrode and the solid polymer electrolyte membrane are not deteriorated, and the purity and concentration are high. Another object of the present invention is to provide an ozone water production apparatus capable of producing ozone in a simple and efficient manner.

  The ozone water production apparatus of the present invention that has solved the above-described problems includes a solid polymer electrolyte membrane, and an anode electrode and a cathode electrode arranged so as to face each other with the solid polymer electrolyte membrane interposed therebetween. In the ozone water production apparatus, the anode electrode is characterized in that it has a diamond-like carbon conductive thin film.

  In a preferred embodiment, the conductive thin film is formed so as to cover at least a part of the anode base material or the solid polymer electrolyte membrane.

In a preferred embodiment, the conductive thin film, in Raman spectroscopic analysis, and has a clear peak in the range of 1340cm in the range of ^-1 ± 20 cm ^-1, and 1580cm ^-1 ± 20cm ^-1.

In a preferred embodiment, the conductive thin film, in Raman spectroscopic analysis, the integrated intensity of the peaks present in 1580 cm ^-1 ± 20 cm ^-1 and the integrated intensity Int <1340> of peaks present in 1340cm ^-1 ± 20cm ^-1 Int The ratio with <1580> satisfies the following formula (1).
Int <1340> / Int <1580> = 0.5 to 1.5 (1)

  If the ozone water production apparatus of the present invention is used, there is no problem of mixing of metals and the like and deterioration of the anode electrode and the solid polymer electrolyte membrane, and high-purity and high-concentration ozone can be produced simply and efficiently.

  In the ozone water production technology by water electrolysis using a solid polymer electrolyte membrane, the present inventor has a high-purity and high-concentration ozone at a low cost and easily compared with the case where conductive diamond is used as an anode material. In order to provide an ozone water production apparatus capable of generating water, studies have been made. As a result, the inventors have found that the intended purpose can be achieved if conductive diamond-like carbon (DLC) is used as the anode material, and the present invention has been completed.

  First, the conductive thin film characterizing the present invention will be described.

  The conductive thin film used in the present invention is made of diamond-like carbon (DLC) in which a crystalline component and an amorphous component are mixed. As described above, there is no conventional DLC used as an anode material for generating ozone.

DLC is an amorphous inorganic substance having intermediate properties between diamond and graphite. When DLC is compared with diamond and graphite, diamond and graphite have a crystal structure, whereas DLC is largely different in that DLC is amorphous. Further, when the bonding state between carbons is compared, diamond consists only of sp ³ hybrid orbitals (D band, covalent bond), and graphite consists only of sp ² hybrid orbitals (G band, double bond), whereas DLC. Is said to contain both carbon atoms with the properties of diamond and carbon atoms with the properties of graphite. Moreover, since it is usually necessary to maintain the substrate temperature at a high temperature of about 1000 K or higher when forming the diamond film, the difference in thermal expansion coefficient from the substrate when the temperature after film formation is returned to room temperature. The DLC film can be formed even at a low temperature of about 500K or less, and the problem is small, and the adhesion to the base material is excellent. ing.

  DLC has hardness close to that of diamond and has excellent slidability, wear resistance, gas barrier properties, biocompatibility, etc., for example, machine tools, semiconductor parts, automotive parts, food packaging containers, medical It is used in fields such as equipment.

However, there has been no report on the use of DLC as an electrode for generating ozone. On the other hand, Patent Document 4 and Patent Document 5 described above disclose a technique in which conductive diamond is used as an electrode for generating ozone. The reason why conductive diamond has attracted attention as an electrode for generating ozone is, for example, that the oxygen overvoltage, which is considered to be an indicator of ozone water generation efficiency, is as high as about 3 V (vs. standard electrode potential), and the specific resistance is 10 ^−3. It can be easily reduced to about Ω · cm. On the other hand, DLC has an oxygen overvoltage of about 1.2 to 2.5 V (vs. standard electrode potential), lower than that of conductive diamond, and a bulk specific resistance of about 10 ⁹ Ω · cm. Was considered not suitable as an electrode material for ozone generation.

  However, according to the results of the study by the present inventors, conductive DLC is useful as an electrode material for ozone generation, and not only can the ozone generation ability be almost the same as that when conductive diamond is used, but also conductivity. Because it has better adhesion to the substrate than diamond, the conductive DLC film formed on the substrate does not peel off from the substrate even if it is electrolyzed for a long time with a large current and voltage, and is extremely excellent in durability. (See Examples below). Such excellent characteristics can be exhibited well even when the thickness of the conductive DLC film is reduced to about 1 μm or less (see the examples described later). Therefore, compared with the case where conductive diamond is used. Advantages such as a reduction in film time and a reduction in cost can also be obtained.

DLC used in the present invention, in Raman spectroscopic analysis, and has a clear peak in the range of 1340cm in the range of ^-1 ± 20 cm ^-1, and 1580cm ^-1 ± 20cm ^-1. Specifically, the ratio of the 1340 cm ^-1 integrated intensity of the peaks present in the integrated intensity Int <1340> and 1580 cm ^-1 ± 20 cm ^-1 of peaks present in ± 20cm ^-1 Int <1580> (hereinafter, simply integrating (Sometimes referred to as intensity ratio) satisfies the following formula (1).
Int <1340> / Int <1580> = 0.5 to 1.5 (1)

Here, the conditions of Raman spectroscopic analysis are as follows.
Analysis method: Microscopic Raman spectroscopy Raman spectroscopic device: manufactured by JASCO Corporation, trade name: NR-1800 type Excitation light: Ar laser (514.5 nm)
Beam intensity: 1 mW sample Objective lens: 50 times Beam diameter: 2 μm
Resolution: 0.2cm ^-1

The Raman spectrum has a strong correlation with the crystal structure of carbon. For example, as shown in FIG. 2, the Raman spectrum of diamond (sp ³ bond) usually has a peak near 1340 cm ⁻¹ . The Raman spectrum of graphite (sp ² bond) usually has a peak in the vicinity of 1580 cm ⁻¹ . Therefore, the DLC film is often specified by, for example, the ratio of peak intensity (peak height) or the ratio of integrated intensity (area intensity). Therefore, also in the present invention, as described above, the DLC film is specified by the integrated intensity ratio or the like.

The integrated intensity ratio: Int <1340> / Int <1580> is also called sp ³ / sp ² and represents the abundance of carbon-bonded states inside the film. This integrated intensity ratio does not immediately indicate the sp ³ content (that is, the diamond content in the DLC film), but it can be used as an index indirectly indicating the structure of the DLC film.

In the present invention, defines a peak intensity attributed to sp ³ bond (diamond) in the range of 1340 cm ^-1 ± 20 cm ^-1, the range a peak intensity attributed to sp ² bonds (graphite) of 1580 cm ^-1 ± 20 cm ^-1 This is because the peak position of the Raman spectrum is considered to shift according to the internal stress of the film. In general, when the internal stress of the film is a compressive stress, the peak of the Raman spectrum tends to shift to the high wave number side, and conversely, when the internal stress of the film is a tensile stress, the peak tends to shift to the low wave number side. According to basic experiments of the present inventors, the peak around 1340 cm ^-1 due to the diamond, you generally present in 1320 cm ^-1 or 1360 cm ^-1 in the range, the peak around 1580 cm ^-1 due to the graphite but generally, if present in the range of 1560 cm ^-1 or 1600 cm ^-1 or less, it was confirmed that the higher ozone generation efficiency is achieved.

Note that the peak shape of the Raman spectrum may differ depending on the film forming conditions of the DLC film, and as shown in FIG. 3 to be described later, distribution patterns having clear peak centers in the vicinity of 1340 cm ⁻¹ and 1580 cm ⁻¹ are not necessarily obtained. It is never done. For example, when the substrate surface temperature at the time of film formation is close to room temperature, a clear peak center is not observed, and as shown in FIG. 2 described above, it spreads over both around 1340 cm ⁻¹ and 1580 cm ^−1. Even in such a case, it is possible to determine the integrated intensity ratio by performing peak separation from the peak shape. Detailed determination methods are described in, for example, Takashi Ohno et al. “Development of general-purpose waveform analysis system considering GUI”, Journal of Chemical Software Society, Vol. 6, no. 2 (2000) or the like.

  FIG. 3 is a Raman spectrum distribution of the conductive DLC film obtained by the method described in Example 1 described later. The integrated intensity ratio at this time is 0.8.

  In the present invention, those having an integrated intensity ratio of DLC in the range of 0.5 to 1.5 are excellent in ozone generation ability as shown in Examples described later. When the integrated intensity ratio of DLC is less than 0.5, the ozone generating ability is inferior. On the other hand, when the integrated intensity ratio is more than 1.5, the mechanical strength (wear resistance) is inferior. The integrated intensity ratio of the DLC film used in the present invention is preferably 0.5 or more, more preferably 1.0 or more, mainly from the viewpoint of ensuring ozone generation characteristics. On the other hand, from the viewpoint of ensuring mechanical strength characteristics, the integrated strength ratio of the DLC film is preferably 1.5 or less, and more preferably 1.0 or less.

The DLC film used in the present invention needs to have conductivity. As described above, the bulk specific resistance of DLC itself is as high as about 10 ⁹ Ω · cm and cannot be used as an electrode for generating ozone. For example, (a) boron, phosphorus, molybdenum, titanium, tungsten, nitrogen, etc. The specific resistance can be reduced to about 10 by adding a conductivity imparting component to the DLC film or (b) introducing a hydrogen into the DLC film and segregating hydrogen on the surface. It can be reduced to about ² Ω · cm. In the present invention, only the method (a) may be employed, only the method (b) may be employed, or both may be used in combination.

  Among these, when the conductivity imparting component is added to the DLC film as in the above (a), the conductivity imparting component contained in the DLC film is generally 0.01% by mass or more and 1.0% by mass or less. Preferably there is. When the conductivity-imparting component is less than 0.01% by mass, the conductivity is insufficient for use as an electrode for generating ozone. On the other hand, when it exceeds 1.0% by mass, the conductivity-imparting component segregates. There is a problem such as. A more preferable content of the conductivity imparting component is generally 0.01% by mass or more and 0.1% by mass or less.

  In the above (a), the conductivity imparting component used in the present invention is preferably at least one selected from the group consisting of boron, phosphorus, molybdenum, titanium, tungsten, and nitrogen. These elements are elements useful for imparting the necessary conductivity to the catalyst electrode for generating ozone water, and when added to the DLC film, generate electrons and holes that bear charges. These elements may be used alone or in combination of two or more. Among these, boron is an element that is usually used to make diamond conductive diamond, but other elements (other than boron) are not usually used, and are elements that are particularly added to obtain conductive DLC. .

  In the above (b), the average concentration of hydrogen contained in the DLC film is preferably about 1 atom% to 20 atom%. As will be described in detail later, since introduction of hydrogen into the DLC film is performed by, for example, a plasma CVD method or the like, hydrogen in the DLC film is highest on the outermost surface of the film and from the outermost surface toward the inside of the film It has a concentration distribution that reduces the hydrogen concentration. When the average concentration of hydrogen is less than 1 atomic%, the conductivity is insufficient for use as an electrode for ozone generation. On the other hand, when it exceeds 20 atomic%, there is a problem that the mechanical strength is lowered. A preferable range of the average concentration of hydrogen is approximately 5 atomic% or more and 15 atomic% or less.

  When the method (a) is used, the DLC film is substantially composed of carbon except for the conductivity-imparting component to be added. However, when the method (b) is used, the DLC film is substantially It consists only of carbon and hydrogen. Here, “consisting essentially of carbon” means that it consists of carbon and inevitable impurities that cannot be avoided in the film formation of DLC, and the hydrogen concentration in the DLC film is the maximum. However, it generally means that it is controlled to 1 atom% or less. On the other hand, “consisting essentially of carbon and hydrogen” means that it consists of carbon, hydrogen, and unavoidable impurities that cannot be avoided in the film formation of DLC. As described in the above (b), the concentration is about 1 atom% to 20 atom%.

  The surface of the conductive thin film is preferably hydrogenated, oxygenated or halogenated. According to the former (surface hydrogenation), the conductivity of the DLC film is improved. According to the latter (surface oxygenation or halogenation), the oxidation resistance is enhanced, the ozone resistance is improved, and the life of the ozone generating electrode is extended. In an ozone water generation environment, the anode material (thin film material) is exposed to a harsh oxidizing atmosphere and easily oxidized and eluted into water. For example, when using a diamond film, However, it has been difficult to introduce large molecules such as halogens, although the oxidation resistance has been improved by oxygenation of the surface. On the other hand, in the DLC film which is an object of the present invention, the surface can be easily halogenated, and as a result, ozone resistance is improved.

  The preferable average thickness of the conductive thin film is slightly different depending on whether the conductive thin film is formed on a metal substrate which is an anode substrate or a solid polymer electrolyte membrane.

  In the former case, that is, when the conductive DLC film is formed so as to cover at least a part of the metal substrate that is the anode substrate, the average thickness of the conductive thin film is generally about 0.01 to It is preferable to be in the range of 1 μm. Thereby, the outstanding ozone water production | generation effect | action can be exhibited, keeping the residual internal stress and electrical resistance of a DLC film low. When the average thickness of the conductive thin film is 0.01 μm, a continuous coating film cannot be obtained. On the other hand, when the average thickness exceeds 1 μm, there is a problem that peeling tends to occur and electrical resistance increases. A preferable average thickness of the conductive thin film is approximately 0.3 to 0.4 μm.

  In the latter case, that is, when the conductive DLC film is formed so as to cover at least a part of the solid polymer electrolyte membrane, the average thickness of the conductive thin film is generally 0.01 to 0.4 μm. It is preferable to be within the range. When the average thickness of the conductive thin film is 0.01 μm, the electrode area is small, so the ozone generating ability is low. On the other hand, when it exceeds 0.4 μm, the contact area between the solid polymer electrolyte membrane and water is small , Ozone generation ability is lowered. A preferable average thickness of the conductive thin film is about 0.1 to 0.3 μm.

  The conductive thin film (DLC film) used in the present invention has been described above.

  The ozone water production apparatus of the present invention includes a solid polymer electrolyte membrane (proton permeable membrane), and an anode electrode and a cathode electrode disposed so as to face each other with the solid polymer electrolyte membrane interposed therebetween. Has the conductive DLC thin film described above. The conductive DLC thin film is formed so as to cover at least a part of the anode base material or the solid polymer electrolyte membrane.

  Hereinafter, preferred embodiments of the device of the present invention will be described with reference to the drawings. FIG. 10 is a schematic view schematically showing an ozone water production apparatus according to the first and second embodiments of the present invention, and FIGS. 4 and 7 are enlarged views of the main part A in FIG. 10, respectively. It is. FIG. 4 is an enlarged view of relevant parts according to the first embodiment, and FIG. 7 is an enlarged view of relevant parts according to the second embodiment.

(First embodiment)
First, the basic configuration of the ozone water production apparatus and the principle of ozone water generation in this embodiment will be described with reference to FIG.

  As shown in FIG. 10, the ozone water production apparatus 20 is divided into an anode chamber 12 and a cathode chamber 13 by a solid polymer electrolyte membrane 11, and ozone is generated on the surface of the solid polymer electrolyte membrane on the anode chamber 12 side. An anode electrode of a noble metal (platinum or the like) having a catalytic function is arranged in contact with a cathode electrode of a noble metal (platinum, silver or the like) on the surface of the solid polymer electrolyte membrane on the cathode chamber 13 side. The anode chamber 12 and the cathode chamber 13 are each provided with a flow path 24 through which raw material water flows, and a DC power source is connected between the anode electrode and the cathode electrode. When a direct current is passed between the anode electrode and the cathode electrode, water electrolysis occurs between the noble metal catalyst for the anode and the noble metal catalyst for the cathode with the solid polymer electrolyte membrane sandwiched between them. Oxygen and ozone are generated on the cathode electrode side, and ozone generated on the anode electrode side is dissolved in water to obtain ozone water. The raw water is adjusted by a valve provided in the flow path so that more raw water flows on the anode side than on the cathode side. In order to efficiently obtain high-concentration ozone water, each of the anode electrode and the cathode electrode is provided with a compressor (not shown), so that it is uniformly pressed against the solid polymer electrolyte membrane. .

  Reference is now made to FIG. The anode chamber 12 has an anode electrode 12a in which a conductive DLC film is formed so as to cover at least a part of the metal substrate from the solid polymer electrolyte membrane 11 to the outside, a corrosion-resistant titanium lath net 12b, The ozone-resistant anode jacket 12c is arranged in this order. Here, in order to obtain high-concentration ozone water continuously and efficiently, an apparatus having a lath net superimposed on the outer peripheral surface of the anode electrode 12a is used. However, the present invention is not intended to be limited to this. .

  Specifically, the anode electrode 12a has a configuration in which the above-described conductive DLC thin film is formed on a metal mesh obtained by knitting a metal wire d as shown in FIG. The lath net 12b is formed by providing a large number of slits in a staggered pattern on a metal plate and extending the slits so as to form a net, and has, for example, the structure shown in FIG. The lath net and the metal net on which the conductive DLC thin film is formed have substantially the same size.

  On the other hand, the cathode chamber 13 includes a platinum mesh cathode electrode 13a, a titanium lath mesh 13b, and an ozone resistant cathode jacket 13c. The feature of this embodiment resides in the anode portion, and the cathode chamber may be the same as the conventional one, so that detailed description is omitted.

  This embodiment is characterized in that a conductive DLC film is used as the conductive thin film. The conductive DLC film does not necessarily need to be formed so as to cover the entire circumference of the wire mesh that is the anode base material, and covers at least a part of the wire mesh to the extent that desired high-concentration ozone water can be obtained. It suffices if it is formed so as to. The coverage is preferably about 50% or more.

  The type of metal substrate (anode substrate) or solid polymer electrolyte membrane used in the present embodiment is not particularly limited, and those generally used for conventional ozone generation electrodes can be employed.

  As the anode substrate, titanium, zirconium, niobium, tantalum, molybdenum, tungsten, platinum, palladium, iridium, gold and other commonly used metal substrates cannot be used in the production of diamond films, such as aluminum. Also low melting point metals can be used. A preferred metal substrate is a valve metal such as titanium or molybdenum, aluminum, or an alloy thereof. When these are used as a metal substrate, these oxide films are easily formed on the surface of the electrode in an ozone water generating environment, so that the entire surface of the metal substrate can be covered with the DLC film. As a result, the inefficient electrolytic reaction does not proceed on the metal substrate surface, and the ozone water generation reaction proceeds efficiently on the DLC film surface.

  As the anode substrate, it is preferable to use a substrate having a net shape such as a folded net or a lath net, a porous shape, or a porous shape (having holes penetrating like a net, a punching metal, or an expanded metal). As in the present embodiment, by using a lath net on a metal wire net, not only the contact area with water, which is a raw material for generating ozone water, is increased, but also the adhesion of the DLC film to the metal substrate is increased. To improve. Since the residual internal stress of the DLC film is generally large, the adhesion to the flat plate is not necessarily good, but a large adhesion can be obtained by making the substrate net-like or porous as described above. Specifically, the shape of the metal substrate is preferably a net-like, porous, or porous plate, tube, or rod. In this case, the thickness and diameter of the metal substrate are preferably in the range of about 0.1 to 100 μm. When the thickness or diameter of the metal substrate is less than 0.1 μm, the used metal or the like is exposed on the surface and the electrolysis efficiency is lowered. On the other hand, even if it exceeds 100 μm, the effect of improving the ozone generating ability cannot be obtained.

  The solid polymer electrolyte membrane (ion exchange membrane) used in the present invention is not particularly limited. For example, a fluorine-based cation exchange membrane excellent in ozone resistance is preferably used.

(Second Embodiment)
FIG. 7 is an enlarged view of a main part of an ozone water production apparatus according to the second embodiment of the present invention. The anode electrode has a configuration in which a conductive DLC film is formed so as to cover at least a part of the solid polymer electrolyte membrane. Here, in order to obtain high-concentration ozone water continuously and efficiently, an apparatus having a lath net superimposed on the outer peripheral surface of the anode electrode is used. However, the present invention is not intended to be limited to this.

  The ozone water production apparatus of this embodiment is different from that of the first embodiment shown in FIG. 4 described above only in that the conductive DLC film is directly formed on the solid polymer electrolyte membrane without a metal substrate. Is different. When both are compared, in this embodiment, there is no wire mesh in the first embodiment.

  Specifically, in the present embodiment, the anode electrode 12 a has a configuration in which a conductive DLC thin film is formed on the surface of the solid polymer electrolyte membrane 11. According to the present embodiment, compared to the first embodiment described above, high-concentration ozone water is obtained and the electrical resistance is low, and the like (see the examples described later).

  The ozone generation electrode of the present invention has been described above.

  Next, a method for producing the above-described ozone generating electrode will be described.

  The DLC film is formed by chemical vapor deposition (CVD) such as high-frequency plasma CVD, microwave plasma CVD, direct current plasma CVD, hot filament CVD, plasma jet, or thermal CVD, sputtering, or ionized vapor deposition. The film can be formed by a known method such as physical vapor deposition (PVD method). Among the above, the plasma CVD method has industrial advantages such as a substrate temperature (film formation temperature) generally low, from room temperature to 200 ° C., easy to form a uniform film even in a complicated shape, and a relatively short processing time. There are many.

  In the present invention, the above-described film forming method is not applied as it is. In particular, (a) in order to impart conductivity to the DLC film, a conductivity-imparting component is added to the source gas so that the DLC film is electrically conductive. Introduce property-imparting components, or add hydrogen to the source gas during film formation in the plasma CVD method to segregate hydrogen on the surface of the film. (B) It can withstand electrolytic conditions in large currents, large flow rates, and severe oxidizing atmosphere Good adhesion (adhesion with metal substrates and solid polymer electrolyte membranes) and good durability against mechanical stress such as the generation of bubbles mainly composed of oxygen (membrane smoothness) In order to achieve both, the incident energy during film formation is controlled, (c) the ozone resistance is increased, and the film is formed in an atmosphere containing a small amount of oxygen or halogen so that the thin film is not oxidized and eluted during electrolysis. Special measures are taken

  Hereinafter, the above (a) to (c) will be described in detail.

(A) Conductivity imparting means When a conductivity imparting component is added to the DLC film to develop conductivity, both the CVD method and the PVD method can be employed.

  On the other hand, in the case where hydrogen is segregated on the film surface to develop conductivity, it is preferable to use a CVD method such as a plasma CVD method, and it is preferable to add at least about 10 atomic% of hydrogen to the source gas. The higher the hydrogen concentration, the better. For example, it is more preferable to add 95 atomic% or more.

  Here, the substrate surface temperature during film formation is generally controlled to a low temperature range of 500 K or less (about 127 ° C. or less) or to a high temperature range of 800 to 1000 K (about 527 to 727 ° C.). Is preferred. Thereby, a DLC film having a concentration gradient in which the hydrogen concentration on the film surface is high and the hydrogen concentration decreases toward the inside of the film can be obtained efficiently. The difference from the diamond film formation method is that the DLC film can be formed not only in the high temperature range as in the latter but also in the low temperature as in the former.

(I) Means for improving film smoothness / adhesion with substrate In order to increase the smoothness of the DLC film and improve the adhesion with the substrate (metal substrate or solid polymer electrolyte membrane), It is preferable to control the incident energy within a range of 2 to 20 eV (more preferably within a range of 10 to 15 eV). The incident energy during the deposition of DLC is generally about 0.1 eV in the PVD method and about 1 eV in the CVD method, whereas the incident energy is set relatively high in the method of the present invention. . In the present invention, not only the initial stage of film formation but also the surface finishing stage of film formation, the incident energy is kept relatively high as described above to give sufficient energy to the carbon precursor in the film formation process. Therefore, not only when the substrate temperature is kept in a high temperature range of about 800 to 1000 K, but also when the substrate temperature is kept at a low temperature range of about 500 K or less, a good smooth surface is formed. become.

  In order to improve the adhesion between the base material and the DLC film, it is also useful to make the base material surface rough with shot blasting beforehand (average roughness: about 100 nm or less).

(C) Ozone resistance improving means In order to increase ozone resistance, it is preferable to form a film in an atmosphere containing oxygen or an oxygen-containing substance (specifically, acetone, ethanol, CO, CO ₂ ) or the like. Specifically, it is preferable to add about 0.01 to 2 atomic% of oxygen with respect to the carbon concentration in the raw material gas. Further, in order to increase ozone resistance, the film may be formed in an atmosphere containing carbon halide such as CF ₄ or CCl ₄ . Specifically, it is preferable to add about 0.01 to 1.0 atomic% of halogen with respect to the carbon concentration in the raw material gas. By applying such means, components having inferior ozone resistance are removed by etching during film formation, and a DLC film having excellent resistance to ozone water can be obtained.

  Hereinafter, embodiments of (I) sputtering method, (II) hot filament CVD method, and (III) microwave plasma CVD method, which are representative film forming methods of the conductive DLC film used in the present invention, will be specifically described. explain.

(I) Sputtering Method A plurality of graphite targets are placed in a reaction vessel, and a metal substrate is mounted on a substrate support that rotates between targets around the center point of the target. In the examples described later, a molybdenum metal substrate is used as the metal substrate. However, the present invention is not limited to this, and the above-described valve metals such as Ti, Al, and alloys thereof can be used. The metal substrate may be processed into a net shape or may be porous. Further, as the target, a target containing halogen or oxygen which is an ozone resistance improving component, or hydrogen which is a conductivity providing component may be used.

Next, after controlling the temperature of the metal substrate to about 400 K and controlling the degree of vacuum in the reaction vessel to an atmosphere of about 5 × 10 ⁻³ Pa, Ar gas is introduced from the supply port in the reaction vessel, and about While maintaining the atmosphere of 2 × 10 ⁻¹ Pa, the substrate surface was treated by applying a direct current voltage of about −1000 V to the substrate support with a bias power source, and then argon gas was temporarily discharged from the exhaust port in the reaction vessel. Exhaust. Here, the temperature of the base material is set to a low temperature range of about 400K, but may be set to a high temperature range of about 800 to 1000K.

Next, DLC is formed on the surface of the substrate by evaporating and ionizing the graphite target by discharge while introducing Ar gas again into the reaction vessel. The incident energy during film formation is about 2 to 20 eV, and the gas pressure is controlled within a range of about 0.1 Pa. At that time, components such as diborane (BH ₃ ) and trimethylboron [B (CH ₃ ) ₃ ] may be added to the Ar gas as a B supply source in order to impart conductivity. Further, hydrocarbon gas such as CH ₄ may be introduced into Ar gas to segregate hydrogen on the surface. During film formation, the DC bias voltage is maintained at a negative several hundred volts and the substrate surface temperature is maintained at about 400K. Here, the surface temperature of the substrate is set to a low temperature range of about 400K, but may be set to a high temperature range of about 800 to 1000K.

(II) Hot filament CVD method In the hot filament CVD method, the filament temperature is about 250 K or less, the gas pressure is about 4 to 20 kPa, the sample surface temperature (film formation temperature) is about 800 to 1000 K, and the incident energy is about 2 to 20 eV. The DLC film can be formed by controlling within the range and controlling the mixed gas of hydrogen gas and methane gas (methane gas concentration: 0.1 to 10 atomic%, total gas flow rate: about 1000 cc / min) as the source gas. preferable. In order to impart conductivity to the DLC film, a component such as diborane or trimethylboron may be added to the mixed gas as a B supply source. The B concentration is preferably controlled within a range of about 100 to 1000 ppm with respect to the carbon concentration in the mixed gas.

(III) Microwave plasma CVD method First, before vapor-phase synthesis of a diamond film, the base material is washed with alcohol or the like, or by using a diamond powder or a diamond paste, by surface-polishing or ultrasonic treatment. It is preferable to perform a damage treatment. Next, after the substrate is placed in the reaction vessel, the reaction vessel is evacuated. Next, the raw material gas is supplied from the raw material gas supply unit into the reaction vessel, and after the mixing ratio of the raw material gas and the gas pressure in the reaction vessel become constant, the microwave is introduced into the reaction vessel and the substrate is supported. Plasma is generated in the vicinity of the substrate placed on the table. At that time, a conductive DLC film can be obtained by introducing a conductivity-imparting component such as BH ₃ into the source gas. The source gas is decomposed by plasma, a part thereof is deposited as a diamond film on the substrate, and the remaining part is discharged through a pipe by an exhaust valve. The pressure in the chamber can be controlled by the supply amount of the source gas and the exhaust amount in the chamber. Moreover, although a base material is cooled from the back by water-cooling a base-material support stand, it is hold | maintained at constant temperature during the gas-phase synthesis | combination of a diamond thin film by balance with a microwave power.

  In the present invention, a conductive DLC film may be formed on the surface of the metal substrate using the film forming means described above, whereby the anode electrode shown in the first embodiment is obtained.

  Alternatively, a DLC film may be formed directly on the surface of the solid polymer electrolyte membrane without using a metal substrate, thereby obtaining the anode electrode shown in the second embodiment. As a film forming method in this case, it is particularly preferable to employ a sputtering method [particularly, an unbalanced magnetron sputtering (UBMS) method]. Specifically, a film is formed at 200 ° C. or less by the UBMS method, and a DLC film and a solid polymer electrolyte film are integrated. As a result, a dense and hard DLC film is formed with respect to the solid polymer electrolyte membrane. Further, since the solid polymer electrolyte membrane and the DLC membrane are uniformly contacted as a whole, the respective surface areas can be effectively utilized.

  For reference, the normal sputtering method and the UBM sputtering method will be described with reference to FIGS. 8 and 9.

  FIG. 8 is a diagram showing the structure of the cathode in a normal sputtering method. As shown in FIG. 8, in a normal sputtering method, ferrite magnets having the same magnetic characteristics are arranged in the central part and the peripheral part of a round target, and a closed loop of magnetic lines of force is formed in the vicinity of the target material. When a bias voltage is applied to the substrate, a substance constituting the target material is formed on the substrate. Although FIG. 8 shows an example of a ferrite magnet, an Sm-based rare earth magnet or an Nd rare earth magnet may be used.

  On the other hand, in the UBM sputtering method, as shown in FIG. 9, a magnet having different magnetic properties at the center and the periphery of the round target (in FIG. 9, a ferrite magnet at the center and an SmCo magnet at the periphery). ) Is arranged. When different magnets are arranged in this way, part of the lines of magnetic force generated by a stronger magnet reaches the vicinity of the substrate. As a result, plasma (for example, Ar plasma) generated during sputtering along the lines of magnetic force diffuses to the vicinity of the substrate. Therefore, according to the UBM sputtering method, more Ar ions and electrons reach the substrate along the magnetic field lines reaching the vicinity of the substrate than the normal sputtering (ion assist effect). Therefore, if UBM sputtering is used, it is possible to form a dense and hard DLC film. Further, a uniform amorphous layer can be formed by using the UBM sputtering method. In the present invention, it is particularly preferable to control the film forming temperature to about 200 ° C. or less.

The specific electrolysis conditions when generating ozone water using the ozone generating electrode of the present invention differ depending on the amount of water flow, the conductivity of raw water, etc., but generally the applied voltage is 3 to 20 V and the current density is 0. It is preferable to control within the range of 05-1.2 A / cm < ² >.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and is implemented with appropriate modifications within a range that can meet the purpose described above and below. Any of these may be included in the technical scope of the present invention.

Example 1
In this example, as the anode electrode (ozone generating electrode), (A) the first ozone water production apparatus of the present invention in which a conductive DLC film was formed on the surface of a net-like titanium substrate; A second ozone water production apparatus of the present invention in which a conductive DLC film is directly formed on the surface of a solid polymer electrolyte membrane without using the titanium base material of the above, and (C) conventional ozone water using a platinum net The ozone water concentration when using each manufacturing device was compared.

(A) Manufacture of the 1st ozone water manufacturing apparatus of this invention The 1st ozone water manufacturing apparatus of this invention has the same structure as FIG. 4 mentioned above. That is, the ozone water production apparatus includes a solid polymer electrolyte membrane 11 of a fluorine-based cation exchange membrane (thickness: 300 microns, size: 10 cm × 17 cm), an anode chamber 12, and a cathode chamber 13. The anode chamber 12 is a conductive DLC film (composed of an average thickness of about 0.4 μm) so as to cover the entire circumference of a titanium wire mesh (size: 8 cm × 15 cm, a wire having a diameter of 0.4 mm knitted into 80 mesh). The anode electrode 12a on which the film method will be described later) and a lath mesh 12b made of titanium (a titanium plate having a thickness of 1 mm is processed into a lath mesh under the conditions of an aperture ratio of 50% and a mesh size of about 2 cm ^2. And a maximum thickness after processing: about 2.4 mm, size: 8 cm × 15 cm) and an anode jacket 12 c made of an ozone resistant material. The structure of the cathode chamber 13 includes a platinum mesh cathode electrode 13a, a titanium lath mesh 13b, and a cathode jacket 13c made of an ozone resistant material.

The conductive DLC film was formed according to the method described in the column of “(I) Sputtering method” described above. Specific film forming conditions are as follows.
Incident energy: 10 eV
Deposition temperature: 400K
Gas pressure: 0.1 Pa
Gas type: CH ₄
Conductivity imparting means: tungsten dope Ozone resistance imparting means: 0.1% O ₂ added

The bulk resistance of the electrode including the conductive DLC film was 10 ⁻² Ω · cm or less.

  The result of the Raman spectrum of the electrode for ozone generation is shown in FIG. Here, a DLC film having a ratio of Int <1340> / Int <1580> (integrated intensity ratio) of 0.8 was obtained.

(B) Production of second ozone water production apparatus of the present invention The second ozone water production apparatus of the present invention has the same configuration as that of FIG. 7 described above. Conductivity having an average thickness of about 0.1 μm directly on one side of a solid polymer electrolyte membrane 11 of a fluorine-based cation exchange membrane (thickness: 300 microns, size: 10 cm × 17 cm) without a titanium wire mesh Except that the anode electrode 12a on which the DLC film is formed is used, it is the same as the first ozone water production apparatus. Here, the film was formed at 100 ° C. or lower using the UBMS method described above.

The bulk resistance of the electrode including the conductive DLC film was 10 ⁻² Ω · cm or less.

(C) Manufacture of Conventional Ozone Water Production Device The conventional ozone water production device has the same configuration as that of FIG. 4 described above, and the first of the present invention except that the platinum mesh anode electrode 12a is used. This is the same as the ozone water production system.

The bulk resistance of the electrode provided with the platinum film was 10 ⁻³ Ω · cm or less.

  Using the three types of ozone water production apparatuses (A) to (C), the ozone concentration when electrolysis was performed under the conditions shown in Table 1 was measured.

Specifically, when using the first and second ozone water producing apparatuses of the present invention, tap water (water temperature 20 ° C.) from which chlorine has been removed with activated carbon is used, and the water flow rate on the anode side is set to 9.3 L / The ozone water concentration (ppm) when the water flow rate on the cathode side is kept constant at 5 L / min and the voltage is changed within the range of 8 to 11 V and the current density is 0.35 to 1.4 A / cm ^2. , Measured by an iodine coulometric titration method using “Ozone Counter ZC-15” manufactured by Hiranuma.

In addition, when using a conventional ozone water production apparatus, an electrolysis experiment was performed in the same manner as above except that the water flow rate on the cathode side was set to 4.7 L / min, the voltage was set to 28 V, and the current density was set to 1 A / cm ^2. The ozone water concentration (ppm) was measured in the same manner.

  These results are summarized in Table 1. In Table 1, No. 1 to 4 show the experimental results when the first ozone water production apparatus of the present invention is used. Nos. 5 to 8 show the experimental results when using the second ozone water production apparatus of the present invention. 9 shows the experimental results when using a conventional ozone water production apparatus.

  From Table 1, if the 1st and 2nd ozone water manufacturing apparatus of this invention was used, compared with the case where the conventional ozone water manufacturing apparatus was used, high concentration ozone water could be obtained.

  Further, in the ozone water production apparatus of the present invention, when the first apparatus and the second apparatus are compared, the metal substrate is interposed between the first apparatus and the first apparatus in which the conductive DLC film is formed on the surface of the metal substrate. First, the second apparatus formed directly on the solid polymer electrolyte membrane was able to obtain high-concentration ozone water even under the same electrolysis conditions.

FIG. 1 is a diagram schematically showing a typical ozone water production apparatus used for a solid polymer electrolyte membrane (SPE). FIG. 2 is a graph showing Raman spectra of diamond and graphite. FIG. 3 is a graph showing a Raman spectrum of the conductive DLC film used in the first apparatus of the present invention in Example 1. FIG. 4 is a diagram schematically showing a main part of the ozone water producing apparatus diagram of the first embodiment according to the present invention. FIG. 5 is a diagram for explaining the configuration of the titanium wire mesh used in the first embodiment. FIG. 6 is a diagram for explaining a configuration of a lath net made of titanium used in the first embodiment. FIG. 7 is a diagram schematically showing a main part of the ozone water production apparatus according to the second embodiment of the present invention. FIG. 8 is a diagram showing the structure of the cathode in a normal sputtering method. FIG. 9 is a diagram showing the structure of the cathode in the UBM sputtering method. FIG. 10 is a schematic view schematically showing the ozone water production apparatus according to the first and second embodiments of the present invention.

Explanation of symbols

1,11 Solid polymer electrolyte membrane (SPE)
2 Anode 2a Metal substrate 2b Metal thin film 3 Cathode 10, 20 Ozone water production device 12 Anode chamber 12a Anode electrode 12b Las network 12c Anode jacket 13 Cathode chamber 13a Cathode electrode 13b Las network 13c Cathode jacket 14 Channel

Claims (4)

An ozone water production apparatus comprising: a solid polymer electrolyte membrane; and an anode electrode and a cathode electrode arranged to face each other across the solid polymer electrolyte membrane,
The ozone water production apparatus, wherein the anode electrode has a conductive film of diamond-like carbon.   The ozone water production apparatus according to claim 1, wherein the conductive thin film is formed so as to cover at least a part of the anode base material or the solid polymer electrolyte membrane. The conductive thin film, in Raman spectroscopic analysis, in the range of 1340 cm ^-1 ± 20 cm ^-1, and ozone water production according to claim 1 or 2 1580 cm ^-1 having a clear peak in a range of ± 20 cm ^-1 apparatus. The conductive thin film, in Raman spectroscopic analysis, 1340 cm ^-1 of the peaks present in ± 20 cm ^-1 integrated intensity Int <1340> and 1580 cm ^-1 of the peaks present in ± 20 cm ^-1 integrated intensity Int <1580> with The ozone water production apparatus according to any one of claims 1 to 3, wherein the ratio satisfies the following expression (1).
Int <1340> / Int <1580> = 0.5 to 1.5 (1)