JP7784669B2 - Catalyst electrode for zero-gap water electrolysis device and method for producing ozone water using said electrode - Google Patents

Description

The present invention relates to a highly efficient electrode assembly for electrolysis devices, particularly an electrode assembly for a zero-gap water electrolysis device using an SPE (solid polymer electrolyte) membrane for producing ozone water.

Ozone water, an aqueous solution of ozone gas, has a high bactericidal effect, but also has low impact on the human body, as it does not irritate the skin when touched and is safe even if it gets into the eyes or mouth. Therefore, it is used for sterilization and infection control in a variety of facilities around the world, including medical institutions, food factories, and daycare centers.

Ozone gas can be easily produced by the anodic reaction in a water electrolysis cell.
3H ₂ O → O ₃ + 6H ⁺ + 6e ^-
2H ₂ O → O ₂ + 4H ⁺ + 4e ^-
O ₂ + H ₂ O → O ₃ + 2H ⁺ + 2e ^-
Various electrode materials, electrolytic cell configurations, and methods have been developed with the aim of optimizing the current efficiency in this electrolytic reaction, improving ozone generation efficiency, and extending electrode life.

As a catalytic electrode material to promote the above reaction, diamond that has been made electrically conductive by incorporating boron (boron-doped diamond, BDD) is preferred due to its excellent chemical and dimensional stability. It is often used as an anode material, coated as a film or as particles attached to a corrosion-resistant metal substrate that is resistant to electrolysis.

For example, there are known examples of electrode structures in which BDD is coated onto a titanium plate or mesh using chemical vapor deposition (CVD), or BDD particles are fixed between titanium meshes. However, due to ease of handling and the reliability of ozone generation, it is more common to form a thin film of BDD by chemical vapor deposition (CVD) on a flat metal plate with multiple holes. (Non-Patent Documents 1 and 2)

Meanwhile, a method has also been developed for electrolytic cells in which an anode and cathode are placed facing each other in a tight (zero-gap) contact with an SPE membrane such as Nafion (trade name) sandwiched between them, and the cell is immersed in water and a potential is applied (Patent Document 1). This cell structure has the advantage of a narrow reaction space, resulting in a short diffusion length for substances and rapid reaction. In other words, because ozone, hydrogen peroxide, and various water electrolysis intermediate products (ions and radicals) are present near the electrode surface during water electrolysis, anodic oxidation proceeds efficiently. For example, it is known that during wastewater purification, the reaction between pollutants in the water and the oxidant proceeds quickly, achieving high purification efficiency.

The electrode reaction that generates ozone occurs at the electrode's water contact point, particularly near the boundary between the BDD and SPE membrane, where a three-phase interface of gas, liquid, and solid phases is formed. Multiple small holes can be drilled in the electrode plate to allow water to penetrate or flow through, expanding the contact area. High current efficiency has also been reported in ozone generation reactions using an electrolysis device constructed by closely adhering a BDD-coated Ti plate anode and an SPE membrane. (Non-Patent Document 2)

Re-table No. 2020/171238 (Patent No. 7010529)

K. Arihara, et al. ElectroChem. Solid-State Lett., 9, D17 (2006) R&D Kobe Steel Technical Report 60 (1)Apr. 2010

When electrolytically generating ozone and other substances using a zero-gap electrolysis device with a BDD catalytic electrode and an SPE membrane, maximizing the area in contact with water between the diamond electrode and the SPE membrane is an important factor in optimizing operating conditions such as current efficiency. However, this cannot be said to be fully achieved with conventional electrode configurations, and there is room for improvement.

Conventional anodes include electrodes with a BDD supported on a titanium mesh or substrate. However, while mesh configurations ensure a supply of raw water as the treated water passes through the mesh, the metal mesh structure poses issues with adhesion between the BDD and the SPE membrane. Meanwhile, BDDs supported on a metal substrate ensure adhesion to the SPE membrane, but pose issues with the amount of raw water that can be supplied through the narrow gaps. Therefore, while numerous small holes are provided in the substrate to allow for the supply of raw water, the formation of a three-phase interface is primarily limited to the circumferential area of the small holes that come into contact with the SPE membrane.

Therefore, an object of the present invention is to improve the ozone generation efficiency per electrode area in such an electrolytic cell by expanding the reaction area that contributes to ozone generation.
In particular, the present invention provides an effective and clear network of water channels on the anode surface, thereby creating an efficient flow of water on the working surface and increasing the number of contact points between the diamond catalyst electrode where a three-phase interface is formed, the water, and the SPE membrane, thereby improving the efficiency of ozone generation.

The present invention is an electrode body for an electrolytic cell for water treatment, in which a water channel network is provided on the flat working surface of a substrate made of a conductive material, and water to be treated is moved along the water channel network. The main feature of this invention is that the water channel network includes continuous water channels formed as grooves in the thickness direction, and has an inlet on the upstream side for water flow, allowing water to flow in from the inlet to the outlet.

The electrode body of the present invention is intended to be mounted in a zero-gap electrolysis device and used for electrolytic generation of ozone water, etc. The manufacturing method basically includes the following steps.
(1) The anode body, which is formed by bonding boron-doped diamond (BDD) to a corrosion-resistant metal substrate, is placed in close contact with and face-to-face with the SPE membrane, a cathode is placed on the back of the SPE membrane and immersed in water, and a water flow is generated along the electrode working surface.
(2) Applying a potential between the two electrodes that can generate ozone ionizes the water in contact with the SPE membrane.
(3) BDD generates ozone by an anodic reaction.
(4) The generated ozone is dissolved in the surrounding water and collected.

In this invention, a wide network of water channels is installed on the anode working surface, consisting of numerous channels connecting the inlet and outlet of the raw water. The edges of both banks of the channels in contact with the SPE membrane are used as the three-phase interface formation area, allowing essentially the entire anode working surface to function as an effective ozone generation starting point. For example, parallel grooves (channels) 0.1 mm wide and 0.1 mm deep are formed at 0.1 mm intervals over the entire surface of a metal electrode substrate such as titanium or niobium. A thin BDD film is then formed on top of these, and the grooves are used as water channels. This creates a three-phase interface at the contact points between the diamond film, particles, and polymer electrolyte membrane present at the edges of the grooves, making it possible to essentially turn almost the entire surface of the electrode into a functional surface for ozone generation.

Furthermore, the electrode body of the present invention is capable of passing a large current at a low voltage, making it ideal as an electrode for producing ultra-high concentration ozone water, and it can also be used in a variety of applications in semiconductor processes.
Furthermore, since it is possible to produce ultra-high concentration ozone water using tap water without causing electrolytic deposition of minerals, it can also be used to produce industrial treated water, such as in pre-treatment processes for plating, and can be used in a variety of equipment and processes involving water treatment.

FIG. 1 is an explanatory view showing an example of an electrode assembly having a rectangular substrate and an active surface manufactured according to the present invention. FIG. 2 is an explanatory view showing an example of an electrode assembly having a circular substrate and an active surface manufactured according to the present invention. FIG. 3 is an enlarged explanatory view showing the shape of a water channel network (part) on the surface of an electrode body produced according to the present invention. FIG. 4 is an explanatory diagram of the water channel network of the electrode body of the present invention used in an example of operation for comparison with the conventional configuration. FIG. 5 is a graph showing current-voltage comparison in an example of operation using an electrode assembly of the present invention and a conventional configuration.

The ozone gas generation reaction on the anode surface is known to proceed in a three-phase interface region approximately 0.05 mm wide where the reaction field (water), the catalytic BDD electrode, and the SPE membrane meet. Therefore, in this invention, a network of numerous water channels is installed on the active surface of the anode, and the BDDs on both sides of the channels that contact the SPE membrane are used as the starting point for ozone generation.

Such an increase in the three-phase interface makes it possible to reduce the resistance of the BDD catalyst portion, which brings about the following advantages, particularly in the ozone generation process, and is therefore of great practical value.
・When operating at the same current density, the voltage can be reduced, which suppresses the electrolytic deposition of minerals at the cathode, enabling long-term operation.
・When operating at the same voltage, the current density can be increased, which increases the amount of ozone and hydrogen peroxide produced. In other words, a large amount of ozone water can be produced with a small device.
The actual electrodes will take on various shapes depending on the structure of the electrolysis device, but in any case, by providing multiple water channels connecting the inlet and outlet of the water to be treated, it is possible to increase the amount of functional water such as ozonated water and reduce water flow resistance.

When operating a zero-gap water electrolyzer, water to be treated is generally introduced between the closely-contacted working surface and the SPE membrane surface, creating a gentle flow that dissolves the generated ozone and hydrogen and allows them to pass through. However, the electrode body of the present invention is particularly designed to maximize the three-phase interface reaction area where the reaction progresses, and is equipped with a water channel network that can guide the water to be treated and efficiently guide and discharge it outside the electrode body.

The water channel network of the present invention comprises linear (straight or curved) open recesses or grooves formed on the surface, i.e., working surface, of an electrode substrate made of a metal such as titanium, niobium, or silicon that has excellent corrosion resistance and the ability to fix a deposited diamond layer via carbide. The substrate can be provided with distributed through-holes to expand the reaction area or to allow the water to be treated to flow from the opposite side (back surface) of the substrate. The distributed formation of through-holes on a substrate is itself well known, but by connecting them with water channels as described below, they can be used as a component of the water channel network of the present invention. The water channel network can be said to provide a flow path that guides the movement of the water to be treated on the working surface of the electrode body, and these flow paths can be configured in various ways by functionally connecting the water channels and through-holes, as described in detail below.

The shape of the electrode substrate varies depending on the design of the electrolytic cell , and can be circular, annular (circular with a through hole in the center), polygonal, or other shapes, with or without distributed through holes. The water channel network of the present invention can use any substrate as long as it has a flat surface, and is constructed by designing the water channel network pattern according to the geometric shape of the working surface and combining and arranging long and short water channels.
Each water channel is formed on the working surface by laser processing or other existing techniques as a groove with a width of at least 0.1 mm and a depth of at least 0.05 mm. In other words, the groove must be designed to be wider and deeper than the anchor grooves used to prevent the diamond film deposited on the substrate from falling off, and to function as a water channel. For rectangular, square, or other quadrilateral substrates, particularly on working surfaces without through-holes, it is simple to form multiple parallel straight water channels between the upstream outer edge and the opposite downstream outer edge of the substrate. However, for such processing, linear groove cutting by machining is preferable in terms of accuracy and processing time.

The water channel network of the present invention is designed according to the surface configuration of the electrode substrate, including the geometric shape and presence or absence of through-holes, and is composed of water channels formed as long, short, straight, or curved linear grooves on the surface. The through-holes also form part of the water channel network. This water channel network has multiple inlets opening at the upstream inlet end and multiple outlets opening at the downstream outlet end, providing multiple paths (flow paths) for guiding the water to be treated from the inlets to the outlets.

Each flow path can be constructed from a single, long channel with both an inlet and an outlet, but it is also effective to connect multiple shorter channels with connecting channels that are formed in the intersecting direction and open to each other to form a combined flow path. The former type of channel can be called a full channel, and the latter type of channel can be called a partial channel or connecting channel. In this way, the waterway network of the present invention provides multiple flow paths from the inlet end to the outlet end.

The configuration of the waterway network of the present invention can be designed, for example, as follows.
In the case of a simple surface without through-holes, in the case of a quadrilateral or other polygonal substrate, the water channel network can be composed solely of all-through channels extending from the upstream end to the downstream end, while in the case of a ring-shaped substrate (a circular substrate with a through-hole in the center), it can be composed of all-through channels extending from the periphery (inner periphery) of the central hole to the outer periphery. In the former case, it is efficient to form these all-through channels as a group of parallel straight lines, and in the ring-shaped substrate, it is efficient to form them extending radially. It is also effective to form connecting channels in a direction that intersects with these channels midway, i.e., orthogonal in the former case, or in one or multiple concentric circles of different radii in the ring-shaped substrate, and to form openings that reach and connect the multiple all-through channels.

When it is difficult to extend a full water channel on a substrate with a large number of distributed through-holes, the water channel network of the present invention can ensure a flow path from the upstream end to the downstream end of the substrate by connecting each through-hole and the through-hole to its upstream end with short channels. If there is a surface area where a flow path can be formed that does not go through through-holes, there is no problem in also using a combined flow path that connects a full water channel that does not go through through-holes or a partial water channel with a connecting channel.

Connecting water channels can be widely used as components to connect all of the above-mentioned water channels, between holes in a substrate with through-holes, or between the holes and the upstream or downstream end. Connecting the through-holes ensures a supply of water to be treated, but it is also possible to design them with an emphasis on averaging the water flow and reducing water flow resistance, thereby increasing the amount of water passing through.

In the present invention, in the case of a circular or annular substrate with a relatively large through-hole (main hole) in the center of the substrate, a typical example of a water channel network is the formation of radial full-length water channels that run in the direction of the water flow when a water flow is applied from the periphery to the center, or in the opposite direction. In this case, it is appropriate to connect adjacent full-length water channels with multiple concentric full-circle or partial-circle (arc) connecting channels of different radii. Inserting connecting channels increases the amount of water flow by reducing water flow resistance, and also increases the area of the three-phase interface, potentially increasing the amount of ozone generated. Laser or mechanical processing can be used to form the full-length water channels, just as in the case of quadrilateral substrates.

In the above, it is simple to space the channels at equal angles, but since the circumferential spacing increases on the outer periphery, it is preferable to make it as small as possible. However, as the angular spacing (pitch) becomes smaller, the density increases on the inner diameter side, while the spacing becomes too large on the outer periphery. Therefore, rather than making the main channel the entire length of the ring, it is also effective to form a channel with a smaller pitch that extends halfway across the ring width or a full channel from that point on, and connect the two channels with a connecting channel, creating a multi-pitch radial channel configuration.

Once the channel formation process is complete, the electrode substrate is then subjected to a CVD process for use as an anode plate, where boron-doped conductive diamond (BDD) particles or a film are deposited or coated on the substrate surface. However, if measures are taken to prevent the diamond from being altered by heat, laser groove cutting can also be performed on the BDD-coated anode plate as a post-processing step. Even in the case of a film, the BDD coating has many gaps, allowing the water to be treated to flow in from above the working surface. In the area where the BDD and SPE film on the working surface are close to each other, ozone is generated by an electrolytic reaction and dissolved in the water, which then travels along the main and connecting channels to the outlet.

In this invention, by providing multiple water channels on the anode surface and taking in the water to be treated into the channels, the water to be treated within the channels is used in the electrolysis reaction, making it possible to reduce electrical resistance by increasing the area of the three-phase interface. Furthermore, the formation of these water channels makes it possible to increase the current density (conduction of H+ ions), and when operating at the same voltage as conventional electrodes, it is possible to improve the water electrolysis rate.

Furthermore, the reduced electrical resistance makes it possible to operate at a lower voltage when operating at the same current density, i.e., the same water electrolysis rate, as conventional electrodes. As a result, even in areas where the hardness of tap water is high and the electrodeposition of minerals during water electrolysis is an obstacle, preventing the introduction of water electrolysis equipment, it is possible to suppress the electrodeposition reaction of minerals on the cathode surface, which is expected to extend the equipment's lifespan.

In Figure 1, which shows an example of a water channel network configuration in an electrode assembly according to the present invention, the electrode assembly, shown as an entirety 10, has a substrate 11 made of a square (rectangular) metal plate, with multiple parallel linear grooves 12 extending from one end to the other across the surface, each forming a full-length water channel, forming a water channel network 13. These full-length water channels intersect with connecting channels (connecting channels) 14-18 every few lines along their length, allowing water to flow between them.

When the working surface of the electrode substrate is circular, a hole (main hole) is provided at the center of symmetry or elsewhere, penetrating the entire thickness of the substrate, allowing water (water to be treated) to pass through from the opposite (back) side of the working surface of the substrate, and multiple water channels opening on the inner periphery edge extend radially from the edge of the substrate to the outer periphery. In this case, adjacent pairs of water channels may be connected by a water channel that reaches both of them.

In the example of a circular (annular) electrode body 20 with a through hole in the center in Figure 2, a metal plate 21 of the same type as above has a circular through hole 22 in the center, and multiple linear water channels 23 (24 in the figure) extend radially from this hole to the outer periphery. Connecting water channels 24 to 26 extend in an annular shape, intersecting these water channels midway along their length. This connection allows water to flow between the radial water channels, forming a water channel network 27 as a whole.

Figure 3 shows a detailed example of the configuration of a water channel network in an electrode substrate with many through-holes. In this diagram, each through-hole 31 is connected to adjacent surrounding through-holes by connecting water channels 32 extending in six directions, and these channels link together to guide the water to be treated to the downstream end. In this diagram, the water channel network is composed only of through-holes and connecting water channels, but if there are blank areas on the surface without through-holes, it is also possible to install a main water channel (not shown) that runs from the upstream inlet end to the downstream outlet end.

This adds a three-phase interface area formed at the interface between the SPE membrane and both banks of each water channel, in addition to the three-phase interface area approximately 0.05 mm wide formed by the interaction between the outer edge of the through-hole and the SPE membrane, making it possible to increase the electrolysis current and improve the amount of ozone generated.

The water channel of the present invention is generally called a microchannel, and substances produced by water electrolysis (e.g., oxidizing agents such as ozone and hydrogen peroxide) diffuse quickly within the channel, enabling their reaction with other substances contained in the water to be promoted. For example, if wastewater containing harmful impurities is passed through an electrolysis device incorporating the electrodes of the present invention and electrolyzed directly, the impurities in the wastewater can be efficiently oxidized and decomposed within the microchannel.

The channel-equipped electrode of the present invention is highly effective when used in processes and equipment that require the promotion of reactions between ozone or hydrogen peroxide generated by electrolysis and other substances contained in water. In other words, the channel-equipped electrode of the present invention is expected to be even more effective when incorporated into water electrolysis equipment for purposes such as wastewater purification and making river water drinkable.

An electrode substrate with a water channel network formed according to the present invention was prepared using a ring-shaped niobium plate with an outer diameter of 35 mm and an inner diameter of 11 mm (area of approximately 8.6 ^cm2 ) and a thickness of 0.5 mm, and which had a large number of fine through holes.For comparison, an electrode substrate with a conventional configuration without a water channel network was also prepared.

First, on the entire surface of the electrode substrate of the present invention, seven rows of through holes (small holes) with a diameter of 1.0 mm were formed at intervals of approximately 0.5 mm, with 28 rows of four holes radially arranged from the center hole (Figure 4).
Next, 56 main water channels, each 0.1 to 0.2 mm in width and depth, were formed between each row of through holes, extending from the central hole to the outer periphery, and connecting channels were formed from each through hole to four adjacent through holes, thereby connecting the adjacent through holes to the main water channels.On the other hand, the electrode substrate for comparison was used as is, without providing the above-mentioned water channels.

A BDD film approximately 5 μm thick was deposited on the inventive and comparative substrates by the hot filament deposition method. The region primarily responsible for ozone generation is the approximately 0.05 mm-wide three-phase interface where the anode-side catalytic material BDD, the polymer electrolyte membrane (Nafion membrane), and water meet. Therefore, the three-phase interface area per hole was 0.16 ^mm² (π × 1 mm × 0.05 mm), plus the sum of the three-phase interface areas on both sides of each channel, totaling approximately 0.15 ^mm². This roughly doubled the three-phase interface area compared to conventional products without grooves, thereby improving catalytic activity.

These electrodes were installed in the accelerated oxidation water production device with a built-in mixer described in Publication No. 2020-171238, and an ozone water generation test was conducted using tap water. This device is a home ozone water generation device with a circular water electrolysis device for generating ozone gas at the bottom of an acrylic container with an inner diameter of 50 mm and a length of 170 mm, and a mixer for dissolving ozone gas in water above.
The current-voltage characteristics in electrolysis using the electrode of the present invention are shown in FIG. 5 in comparison with those using a conventional electrode.

In an ozone water generator equipped with a conventional boron-doped diamond electrode without a water channel, a voltage of 9 V was required to pass a current with a current density of 0.2 A/cm ² (current value of 1.72 A), whereas it was found that a voltage of approximately 7.2 V was sufficient for the electrode of the present invention.

By lowering the operating voltage to approximately 7V, the amount of mineral deposition on the cathode can be reduced to as close to zero as possible, demonstrating the possibility of improving electrode life and the possibility of hard water electrolysis. That is, the amount of ^OH- ions generated on the cathode side during water electrolysis becomes noticeable at an applied voltage of around 8V, and it is known that these ^OH- ions trigger the deposition of ions such as Ca and Mg in the water on the cathode surface in the form of hydroxides or carbonates, which can cause problems. Therefore, water electrolysis at applied voltages of 8V or less is leading to a wide range of applications.

On the other hand, in water electrolysis at an applied voltage of 8 V, the current density was 0.15 A/ ^cm2 (current value 1.25 A) with the conventional electrode, but with the electrode of the present invention, the current density could be doubled to 0.3 A/ ^cm2 (current value 2.5 A). In other words, it became possible to generate twice the amount of ozone at an applied voltage of 8 V using an anode plate of the same apparent area.
From another perspective, the dissolved ozone concentration in ozonated water obtained by water electrolysis at 9 V, at which the problem of electrodeposit adhesion to the cathode surface becomes significant with conventional electrodes, is 0.48 mg/L. However, by using the electrode of the present invention and lowering the applied voltage by 1 V to 8 V, it is possible to obtain an ozone concentration of 0.75 mg/L, which is about 1.5 times higher, while avoiding the problem of electrodeposit adhesion, and a clear advantage has been recognized.

10 Electrode body 11 Substrate 12 Connecting water channel (linear)
13 Waterway network 14-18 Connecting waterway 20 Annular electrode body 21 Metal plate 22 Through hole 23 (Radial) waterway 24-26 Connecting waterway (Annular)
27 Waterway network 31 Through hole 32 Connecting waterway

Claims (13)

An electrode body of a zero-gap electrolysis device for ozone generation, wherein the substrate of the electrode body is made of a conductive material and has a flat working surface coated with a boron-doped diamond (BDD) catalyst layer,
The electrode body is
a water channel that is provided on the working surface of the electrode body, is open, and is formed as a depression in the thickness direction of the substrate relative to the working surface, for guiding water;
The electrode body is
the boron-doped diamond catalyst coating the working surface of the electrode body;
a solid polymer electrolyte (SPE) membrane covering the boron-doped diamond catalyst layer and closely covering the open surface of the water channel;
By adopting such a configuration, at least at the bank edge of the water channel, the water, the boron-doped diamond catalyst layer, and the solid polymer electrolyte membrane come together to form a three-phase interface region,
An electrode body in which a water channel network including a plurality of the water channels has respective openings, inlets and outlets, for the inflow or outflow of the water to be treated on the outer periphery and working surface of the substrate, and the water channels form a water flow path from the inlets to the outlets by being connected to other water channels individually or by the intersection of water channels with different directions. 2. The electrode assembly of claim 1, wherein the water channel network includes a plurality of linear water channels extending parallel to the substrate in the same direction, at least one of the water channels having an inlet opening opening outward at an upstream end of the working surface, and at least one of the water channels having an outlet opening opening outward at a downstream end of the working surface . The electrode assembly described in claim 2, wherein the water channel network includes a plurality of linear first water channels extending parallel to the substrate in the same direction, and linear second water channels extending and intersecting the first water channels, and at least one pair of adjacent first water channels are connected to each other by an intersecting second water channel. The electrode assembly described in claim 3, wherein the substrate is a quadrilateral or a polygon other than a quadrilateral, and the water channel network includes multiple linear water channels extending parallel to one another in the same direction. The electrode assembly described in claim 1, wherein the substrate is circular with a central through-hole penetrating the thickness of the substrate, and the water channel network includes a plurality of linear water channels extending radially from the periphery of the central through-hole. The electrode assembly described in claim 1, wherein the substrate is circular and has a central through-hole that penetrates the thickness of the substrate, the water channel network includes a plurality of linear first water channels extending radially from the periphery of the central through-hole, and second water channels extending on a circumference concentric with the outer periphery of the substrate, and at least one pair of adjacent first water channels intersects with the second water channel, and both water channels are connected by the second water channel. The electrode assembly of claim 1, wherein the water channel network includes a plurality of through-holes formed on the active surface and penetrating the entire thickness of the substrate, and a plurality of water channels extending between the through-holes and connecting adjacent through-holes to each other. 2. The electrode assembly of claim 1, wherein the water channel network includes a plurality of through holes formed on the active surface and penetrating the entire thickness of the substrate, and a plurality of water channels extending between the through holes and connecting adjacent through holes to each other, one or more of the water channels opening outward at the upstream end of the substrate and one or more of the water channels opening outward at the downstream end, each providing an inlet and an outlet. The electrode body according to claim 1, wherein the substrate is made of Ti, Nb, or Si. The electrode assembly of claim 1, wherein the width of the water channel is 0.1 mm or more. The electrode assembly according to claim 1, wherein the depth of the water channel is 0.05 mm or more. (1) An electrode body in which a substrate of an electrode body made of a conductive material has a flat working surface coated with a boron-doped diamond (BDD) catalyst, the working surface has a water channel network consisting of a collection of water channels or linear grooves formed as recesses in the thickness direction of the substrate, and openings for the inflow and outflow of the water to be treated into the water channel network are provided on the outer periphery of the substrate and on the working surface,
(2) The electrode body is used as an anode, and the working surface is closely attached to a solid polymer electrolyte (SPE) membrane. A cathode is placed on the back of the SPE membrane, and the working surface is placed horizontally in an electrolytic cell and immersed in water.
(3) A flow of water to be treated is formed, and the water is supplied to the SPE by flowing the water from the inlet through the water channel into the gap between the anode working surface and the SPE membrane;
(4) Applying an operating potential between the two electrodes capable of generating ozone to generate ozone at the three-phase interface along the water channel and to generate a water flow through the water channel;
(5) A method for producing ozone water, characterized in that the produced ozone is transported outside the action surface by the water flow, dissolved in the surrounding water, and collected and recovered. The method for generating ozone water described in claim 12, wherein the operating potential is 8 V or less.