US20160186336A1

US20160186336A1 - Electrode unit, electrolytic cell comprising electrode unit and electrolytic device

Info

Publication number: US20160186336A1
Application number: US15/065,332
Authority: US
Inventors: Katsuyuki Naito; Norihiro Yoshinaga; Wu Mei; Norihiro Tomimatsu; Ryosuke YAGI; Masahiro Yokota; Hideo Oota
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 2014-09-19
Filing date: 2016-03-09
Publication date: 2016-06-30
Also published as: JP6407963B2; WO2016042802A1; JPWO2016042802A1; CN106661744A

Abstract

According to one embodiment, an electrode unit of an electrolytic device includes a first electrode including a first surface, a second surface located on an opposite side to the first surface, a plurality of first pores opened in the first surface, a plurality of second pores opened in the second surface and having an opening area greater than that of the first pores, and a plurality of the first pores communicating with a respective one of the second pores, a second electrode opposing the first surface of the first electrode, and a continuous porous membrane arranged between the first electrode and the second electrode, so as to cover the first surface of the first electrode.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of PCT Application No. PCT/JP2015/056547, filed Mar. 5, 2015 and based upon and claiming the benefit of priority from Japanese Patent Application No. 2014-192015, filed Sep. 19, 2014, the entire contents of all of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to an electrode unit, an electrolytic cell comprising the electrode unit and an electrolytic device.

BACKGROUND

In recent years, an electrolytic device for electrolyzing water and producing electrolyzed water which has various functions, such as ionized alkaline water, ozone water or aqueous hypochlorous acid has been provided. Of the electrolyzed water, aqueous hypochlorous acid has excellent sterilizing power and also is safe to human health; therefore it has been approved as a food additive.
As an electrolytic device, an electrolyzed-water production device comprising, for example, a three-chamber electrolytic cell is proposed. The inside of the electrolytic cell is divided into three chambers, namely, an intermediate chamber, and also an anode chamber and a cathode chamber located on both side of the intermediate chamber. The anode chamber and the cathode chamber are provided with an anode and a cathode, respectively. As the electrodes, a porous-structure type is employed, in which a great number of pores are made by processing such as expanding, etching or punching in a metal plate matrix.
In this type of electrolytic device, for example, salt water is supplied to the intermediate chamber, and water is supplied to the anode and cathode chambers. The salt water in the intermediate chamber is electrolyzed by the cathode and the anode. In this manner, aqueous hypochlorous acid is produced from gaseous chlorine produced by the anode. Aqueous sodium hydroxide is produced in the cathode chamber. The produced hypochlorous acid is used as sterilizing water. The aqueous sodium hydroxide is used as a cleaning solution.
In the three-chamber electrolytic cell, the anion-exchange membrane is degraded easily by chlorine or hypochlorous acid. When the electrode having a porous configuration adheres tightly to the ion-exchange membrane (electrolyte membrane), stress is easily concentrated on the edge portion of the pores of the electrode. Thus, the diaphragm formed of, for example, a thin electrolyte membrane which is weak mechanically, is deteriorated easily. In consideration of this factor, the following technique is suggested. To reduce the degradation of the electrode by chlorine, nonwoven fabric having overlaps or slits is inserted between the electrode having a porous configuration and the electrolyte membrane.
However, if a porous membrane such as nonwoven fabric is inserted between the electrode and the electrolytic membrane, stress is applied to the porous membrane, causing variation in thickness in the porous membrane. In other words, the thickness of the porous membrane becomes uneven. The porous membrane of an uneven thickness causes irregular electrolytic reaction, resulting in reduction of the reactivity of the electrolytic device or degradation of the electrolytic membrane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an electrolytic device according to a first embodiment.

FIG. 2 is a sectional view showing an electrode unit of the electrolytic device according to the first embodiment.

FIG. 3 is an exploded perspective view of the electrode unit.

FIG. 4 is a sectional view showing a manufacturing process of an electrode.

FIG. 5 is a sectional view of an electrolytic device according to a second embodiment.

FIG. 6 is a perspective view of the electrode unit according to the second embodiment.

FIG. 7 is a sectional view of an electrode unit of an electrolytic device according to a third embodiment.

FIG. 8 is a perspective view of an electrode unit according to a fourth embodiment.

FIG. 9 is a sectional view of an electrolytic device according to a fifth embodiment.

FIG. 10 is a sectional view of an electrolytic device according to a sixth embodiment.

FIG. 11 is a sectional view of an electrode unit according to the third embodiment.

FIG. 12 is a perspective view of a first electrode and a second electrode according to a modification.

FIG. 13 is a sectional view schematically showing a porous membrane containing inorganic oxide and including pores formed in a planarly or three-dimensionally irregular manner.

FIG. 14 is a sectional view schematically showing a porous membrane consisting of a multi-layered film.

DETAILED DESCRIPTION

Various embodiments will be described in detail with reference to drawings. In general, according to one embodiment, an electrolytic device comprises an electrode unit. The electrode unit comprises: a first electrode including a first surface; a second surface located on an opposite side to the first surface, a plurality of first pores opened in the first surface, a plurality of second pores opened in the second surface and having an opening area greater than that of the first pores, and a plurality of first pores communicating with a respective one of the second pores; a second electrode opposing the first surface of the first electrode; and a continuous porous membrane interposed between the first electrode and the second electrode, so as to cover the first surface of the first electrode.
Throughout the embodiments, common structural members are designated by the same reference symbols, and the explanation thereof will not be repeated. Further, the drawings are schematic diagrams designed to assist the reader to understand the embodiments easily. Thus, there may be sections where the shape, dimensions, ratio, etc. are different from those of the actual devices, but they can be re-designed as needed with reference to the following explanations and publicly known techniques. For example, the electrodes are illustrated in plane in these figures, but they may be curved or formed in cylindrical according to the shape of the respective electrode units.

First Embodiment

FIG. 1 is a diagram briefly showing an electrolytic device according to the first embodiment. The electrolytic device 10 comprises, for example, a two-chamber electrolytic cell 11, and an electrode unit 12 provided in the electrolytic cell 11. The electrolytic cell 11 is formed into a flat rectangular box, the inside of which is divided by an electrode unit into two compartments, namely, an anode chamber 16 and a cathode chamber 18 by a dividing wall 14 and electrode unit 12.
The electrode unit 12 comprises a first electrode (anode) 20 located in the anode chamber 16, a second electrode (a counterelectrode or a cathode) 22 located in the cathode chamber 18, and a porous membrane 24 and a diaphragm provided between the first and second electrodes.
The electrolytic device 10 comprises a power supply 30 to drive the first and second electrodes 20 and 22 of the electrode unit 12, an ammeter 32, a voltmeter 34 and a control device 36 that controls the members. A flow channel for liquid may be provided in the anode chamber 16 and the cathode chamber 18. For example, a pipe or a pump for supplying liquid from outside or discharging liquid may be connected to the anode chamber 16 and the cathode chamber 18. A porous spacer may be provided between the electrode unit 12 and the anode chamber 16 or the cathode chamber 18.
Next, the electrode unit 12 will be described in detail. FIG. 2 is a sectional view of the electrode unit. FIG. 3 is an exploded perspective view of the electrode unit.
As shown in FIGS. 2 and 3, the first electrode 20 has a porous structure in which numerous through-holes are formed in a matrix 21 of, for example, a rectangular metal plate. The matrix 21 includes a first surface 21 a and a second surface 21 b opposing and substantially parallel to the first surface 21 a. The interval between the first surface 21 a and the second surface 21 b, in other words, the thickness of the matrix 21, is defined as T1. The first surface 21 a opposes the porous membrane 24 and the second surface 21 b opposes the anode chamber 16.
A plurality of first pores 40 of, for example, a square shape, are formed in the first surface 22 a of the matrix 21 to open on the first surface 22 a. Moreover, a plurality of second pores 42 are formed in the second surface 22 b to open on the second surface 22 b. The opening area of the second pores 42 is greater than that of the first pores 40. The first pores 40 made on the porous membrane 24 side, have a dimension R1 of the opening, which is less than a dimension R2 of the openings of the second pores 42 of, for example, a square shape. Further, the first pores 40 are more in number than the second pores 42. The depth of the first pores 40 is T2 and the depth of the second pores 42 is T3, and T2+T3=T1. In this embodiment, the holes are made such that T2<T3.
In this embodiment, the second pores 42 are formed into, for example, a square shape to be arranged in a matrix on the second surface 22 b. The circumferential wall which defines each second pore 42 may be formed to have a tapered surface 42 a or curved surface so that the hole enlarges toward the second surface 22 b side from the bottom of the hole to the opening. The interval between adjacent second pores 42, that is, the width of a linear portion 60 a of the electrode is set to W2. Note that the second pores 42 are not limited to a rectangular shape, but may take various other forms. Moreover, the second pores 42 may not necessarily be arranged regularly, but may be at random.
The opening diameter of the first pores 40 is preferably less in order to make the pressure uniform. However, the first pores 40 need to be large to the extent that substance diffusion can be prevented. In case of a square, the length of each side of the opening is preferably 0.1 to 2 mm, and is more preferably 0.3 to 1 mm. The opening may take a variety of forms such as a square, a rectangle, a rhomboid, a circle and an ellipse, and the vertices of a square, a rectangle or a rhomboid may be rounded. The opening area is preferably 0.01 to 4 mm²in the same manner as the above-described square. The opening area is more preferably 0.1 to 1.5 mm². The opening area is further preferably 0.2 to 1 mm². The ratio of the opening area to the electrode area including the opening (in other words, the opening ratio) is preferably 0.05 to 0.5, and is more preferably 0.1 to 0.4, and is further preferably 0.15 to 0.3. If the opening ratio is excessively less, outgassing is difficult. If the opening ratio is excessively great, electrode reaction is inhibited.
The first pores 40 are formed into, for example, a square shape and are arranged in a matrix on the first surface 21 a. The circumferential wall which defines each first pore 40 may be formed to have a tapered surface 40 a or curved surface so that the dimension enlarges from the bottom of the hole to the opening, in other words, to the first surface 22 a. In this embodiment, a plurality, for example, nine of first pores 40 oppose a respective second pore 42 and communicate therewith to be made all the way through the matrix 21. An interval W1 between adjacent first pores 40 is set so as to be less than an interval W2 between second pores 42. With this structure, the number density of the first pores 40 in the first surface 21 a is sufficiently greater than that of the second pores 42 in the second surface 21 b.
Various shapes may be employed for each second pore 42, such as a square, a rectangle, a rhomboid, a circle or an ellipse. The opening dimension of each second pore 42 is preferably great in order to facilitate outgassing. However, if the opening dimension is great, the electrical resistance is increased. Therefore, the second pores 42 cannot be significantly enlarged. In the case of the square opening, one side is preferably 1 to 40 mm, more preferably 2 to 30 mm, and further preferably 3 to 20 mm. The opening may take a variety of forms such as a square, a rectangle, a rhomboid, a circle and an ellipse, while the opening area is preferably 1 to 1600 mm²in the same manner as the above-described square. The opening area of the second pores 42 is more preferably 4 to 900 mm², and is further preferably 9 to 400 mm². For example, the opening may be shaped as a rectangle or an ellipse which is long in one direction so as to connect an end and the other end of the electrode.
For the matrix 21 of the first electrode 20, a valve metal such as titanium, chromium or aluminum, or an alloy of these, or a conductive metal can be used. Out of these materials, titanium is preferable. It may be desirable, depending on the electrolytic reaction, to form an electrolytic catalyst (catalyst layer) on the first surface and the second surface of the electrode. When used as an anode, it is desirable to use a precious metal catalyst such as platinum or an oxide catalyst such as iridium oxide, as the matrix itself of the electrode. The amount of electrocatalyst per unit area on one surface of the electrode may differ from that on the other surface thereof. In this manner, for example, a side reaction may be prevented.
Further, the first pores 40 may not necessarily be arranged regularly, but may be at random. Furthermore, all the first pores 40 may not necessarily communicate with the second pores 42, but there may be some first pores not communicating with a second pore 42. Thus, some first pores 40 may not communicate with the anode chamber 16. For example, as shown in FIG. 12, the first pores 40 and 44 may be rectangles extending from near one end of the electrode to near the other end, within which a plurality of openings 41 a and 45 a communicating with the second pores 42 and 46 are arranged at certain interval. Only some of the first pores 40 and 44 may communicate with the second pores 42 and 44. The first pores 40 and 44 which do not communicate with the second pores 42 and 44 can increase the electrode area.
Preferably, 85% or more of all of the first pores 40 and 44 have an opening area of 0.01 to 4 mm². More preferably, 90% or more, and further preferably, 95% or more of all of the first pores 40 have an opening area of 0.01 to 4 mm².
The first electrode 20 can be manufactured by, for example, an etching method using a mask. FIG. 4 briefly shows the manufacturing method thereof. As shown in FIGS. 4(a) and (b), one flat matrix 21 is prepared. Resist films 50 a and 50 b are applied to the first and second surfaces 22 a and 22 b of the matrix 21. Then, as shown in FIG. 4(c), the resist films 50 a and 50 b are exposed using an optical mask (not shown) and thus etching masks 52 a and 52 b are formed, respectively. As shown in FIG. 4(d), wet etching is applied to the first and second surfaces 22 a and 22 b of the matrix 21 via the masks 52 a and 52 b with solution. In this manner, a plurality of first pores 40 and a plurality of second pores 42 are formed. Subsequently, the first electrode 20 is obtained by removing the masks 52 a and 52 b.
The shape of the tapered or curved surface of the first and second pores 40 and 42 can be controlled based on the material of the matrix 21 and etching conditions. The depth of the first pores 40 is T2, and the depth of the second pores 42 is T3. As stated above, the first and second pores are formed such that T2<T3. In etching, both surfaces of the matrix 21 may be etched at the same time, or may be etched separately. The type of etching is not limited to wet etching. For example, dry etching may be employed. Moreover, not only etching but also processing by laser, precision cutting or the like may be employed to manufacture the first electrode 20.
As shown in FIGS. 1 to 3, in this embodiment, the second electrode (counterelectrode) 22 is structured in the same manner as the first electrode 20. More specifically, the second electrode 22 has a porous configuration in which a large number of through-holes are formed in a matrix 23 made of, for example, a rectangular metal plate. The matrix 23 includes a first surface 23 a and a second surface 23 b opposing and substantially parallel to the first surface 23 a. The first surface 23 a oppose a diaphragm 26. The second surface 23 b opposes the cathode chamber 18.
A plurality of first pores 44 are formed in the first surface 23 a of the matrix 23 to open on the first surface 23 a. Further, a plurality of second pores 46 are formed in the second surface 23 b to open on the second surface 23 b. The opening area of the first pores 42 on the diaphragm 26 is less than that of the second pores 44. Further, the first pores 44 are more in number than the second pores 46. The depth of the first pores 44 is less than that of the second pores 46.
A plurality, for example, nine of first pores 44 are provided to oppose one second pore 46. Each of these first pores 44 communicates with the second pore 26 so as to be made through the matrix 23. The interval between adjacent first pores 44 is set so as to be less than the interval between the second pores 46. With this structure, the number density of the first pores 44 on the first surface 23 a is sufficiently greater than that of the second pores 46 on the second surface 23 b.
The porous membrane 24 and the diaphragm 26 are interposed between the first surface 22 a of the first electrode 20 and the first surface 23 a of the second electrode 22. The continuous porous membrane 24 is formed in, for example, a rectangular shape so as to have dimensions substantially equal to those of the first electrode 20, and opposes the whole first surface 21 a. As the porous membrane 24, for example, a nonwoven fabric, cloth or a porous membrane which is formed by a sol-gel method can be used, and various materials may be used for the porous membrane. The porous membrane needs to be chemically stable. In particular, it needs stability to, especially, chlorine, hypochlorous acid or oxygen, or resistance to acid or alkali. Further, when used to process foods, for example, the following requirements should be met. That is, when it is a polymer, monomers or the like must not dissolve at amount determined by the law or more, or when it is an inorganic material, heavy metal ion must not dissolve at amount determined by the law or more. Mechanically, when the porous membrane is solely used without an undercoat member, it is important for the membrane to be handled easily, and therefore the thickness thereof is preferably 20 to 500 μm. If the porous membrane is formed directly on an electrode, it may be thin, but in order for the membrane to exhibit its properties, the thickness is preferably 50 nm or greater. Of these porous membranes, a polymer membrane containing a fluorine atom or a chlorine atom in its main chain, glass cloth or a membrane including irregular continuous pores and containing inorganic oxide, is especially chemically stable and preferable. As the polymer membrane, Teflon is particularly preferable. Hydroxide, alkoxide, oxyhalide or hydrate may be contained in the inorganic oxide. When the inorganic oxide is prepared by the hydrolysis of metal halide or metal alkoxide, a composite thereof may be easily obtained though it depends on the temperature of the subsequent treatment. The polymer membrane, glass cloth and inorganic oxide may be combined, and for example, the polymer membrane and glass cloth may be covered by an inorganic oxide. As shown in FIG. 13, if an inorganic oxide film having irregular pores in a plane or in a three-dimensional manner is used as the porous membrane 24, it may also function as a diaphragm. In other words, the diaphragm 26 may be omitted.
As shown in FIG. 14, for the porous membrane 24, a multilayer film including a plurality of porous membranes 27 a and 27 b having different pore diameters may be used. In this case, if the pore dimension of the porous membrane 27 b located on the diaphragm 26 side is set greater than that of the porous membrane 27 b located on the first electrode 20 side, migration of ions is more facilitated, and the stress concentration due to the pores of the electrode can be reduced. This is because as the opening on the diaphragm 26 side is greater, the ion migration by diffusion becomes easier. When the first electrode 20 is used for the anode, a positive potential is applied. Therefore, even if the pore diameter on the first electrode 20 side is less, anions are easily attracted to the first electrode 20. If the pore diameter on the electrode 20 side is great, the produced chlorine or like is easily diffused to the porous membrane 24 side.
The pore diameter on the surface of the porous membrane 24 can be measured by a high-resolution scanning electron microscope (SEM). The pores inside the porous membrane can be measured by cross-sectional SEM observation.
As shown in FIGS. 2 and 3, the diaphragm 26 is formed into, for example, a rectangular shape with dimensions substantially equal to those of the first electrode 20, and also provided between the first surface 23 a of the electrode 22 and the porous membrane 24. The diaphragm 26 is tightly attached to the entire first surface 23 a of the second electrode 22, and further to the porous membrane 24.
The diaphragm 26 located between the first and second electrodes 20 and 22 is a film which allows ions and/or liquid to pass therethrough. For the diaphragm 26, various electrolyte membranes and porous membranes having nanopores may be used. For the electrolyte membrane, a polymer electrolyte membrane, for example, a cation-exchange solid polymer electrolyte membrane, more specicially, a cation-exchange membrane, an anion-exchange membrane or a hydrocarbon-based film may be used. Examples of the cation-exchange membrane are NAFION 112, 115 and 117 (trademark of E. I. du Pont de Nemours & Co.), Flemion (trademark of Asahi Glass Co., Ltd.), ACIPLEX (trademark of Asahi Chemical Co., Ltd.) and GOA SELECT (trademark of W. L. Goa and associates co.). An example of the anion-exchange membrane is A201 of Tokuyama, Inc. Usable examples of the porous membranes having nanopores are porous ceramics such as porous glass, porous alumina, porous titania and porous zeolite, and porous polymers such as porous polyethylen, porous propylene, porous teflon and porous polyimide.
The first electrode 20, the porous membrane 24 and the second electrode 22 having the above-described structures are brought into contact with each other by pressing them in a state where the porous membrane 24 is interposed between the first electrode 20 and the second electrode 22. In this manner, the electrode unit 12 is obtained.
As shown in FIG. 1, the electrode unit 12 is provided in the electrolytic cell 11 and is attached to the dividing wall 14. The electrolytic cell 11 is divided into the anode chamber 16 and the cathode chamber 18 by the dividing wall 14 and the electrode unit 12. Thus, the electrode unit 12 is disposed in the electrolytic cell 11 so that the direction where the components which constitute this are in contact with each other is, for example, horizontal. The first electrode 20 of the electrode unit 12 faces the anode chamber 16. The second electrode 22 faces the cathode chamber 18.
In the electrolytic device 10, both poles of the power supply 30 are electrically connected to the first electrode 20 and the second electrode 22. The power supply 30 applies a voltage to the electrode unit 12 under the control of the control device 36. The voltmeter 34 is electrically connected to the first electrode 20 and the second electrode 22 and detects the voltage applied to the electrode unit 12. The detection data is supplied to the control device 36. The ammeter 32 is connected to the voltage application circuit of the electrode unit 12 and detects the current flowing in the electrode unit 12. The detection data is supplied to the control device 36. The control device 36 controls the application of voltage or load for the electrode unit 12 by the power supply 30 based on the detected data in accordance with the program stored in the memory. The electrolytic device 10 applies a voltage or load between the first electrode 20 and the second electrode 22 in a state where the substance for reaction is supplied to the anode chamber 16 and the cathode chamber 18. In this manner, the electrochemical reaction for electrolysis is advanced. The electrolytic device 10 of the present embodiment should preferably electrolyze an electrolyte containing chloride ions.
According to the electrolytic device and the electrode unit having the above-described structure, in the first electrode 20, the diameter (opening area) of the first pores 40 formed in the first surface 22 a on the porous membrane 24 side is made less than that of the second pores 42. Thus, the number density thereof is increased. This structure allows the reduction in the concentration of stress applied from the first electrode 20 side to the porous membrane 24. As a continuous membrane, the porous membrane 24 is brought into contact with the whole first surface 21 a of the first electrode 20. Thus, the holes of the first electrode 20 are covered by the porous membrane 24. The distance between the first electrode 20 and the diaphragm 26 can be easily maintained equally over the whole surface. That is, distribution in the thickness of the porous membrane 24 can be prevented and it becomes possible to maintain the thickness of the porous membrane 24 uniformly. This structure enables the electrolytic reaction to occur uniformly, thereby improving the reaction efficiency of the electrolytic device and preventing the degradation of the electrolyte membrane.
Further, the first electrode 20 is formed to have the first pores 40 with a tapered or curved shape which enlarges towards the first surface side of the electrode. With this structure, the contact angle between the first pores 40 and the porous membrane 24 is obtuse, thereby making it possible to further reduce the concentration of stress on the porous membrane 24 from the first electrode 20 side. Note that the first surface 22 a on the porous membrane 24 side of the first electrode 20 is preferably substantially flat except for recess portions. The recess portions may be the first pores described above or recessed sections which will be described later.
When the opening area of the second pores 42 formed in the second surface 22 b of the first electrode 20 is increased and the number density is reduced, width W2 of the linear portions between the second pores 42 can be made sufficiently great. Thus, the mechanical strength of the first electrode 20 can be maintained high and the electric resistance can be reduced.
In the first embodiment having the above-described structures, it is possible to obtain a long-life, high-reaction-efficiency electrode unit and electrolytic device.
Note that in the first embodiment, the second electrode 22 has a porous structure with the first and second pores with different diameters, but it is not limited to this. For example, a plate electrode without a through-hole may be employed. Or such an electrode may be employed as well, that an electrode substrate is processed to have through-holes of the same diameter on the first surface and the second surface. The second electrode 22 and the diaphragm 26 may be in contact with each other, or a separate structural member may be interposed therebetween.
Next, an electrolytic cell and an electrolytic device according to another embodiment will be described. Note that in the other embodiments described below, the same reference symbols are given to the same structural elements as the first embodiment above, and the detailed explanations thereof are omitted. The portions different from those of the first embodiment will be mainly discussed.

Second Embodiment

FIG. 5 is a sectional view showing an electrode unit of an electrolytic device according to the second embodiment and FIG. 6 is a perspective view of an electrode.
According to the second embodiment, in the electrode unit 12, the first surface 22 a of the first electrode 20 is formed flat, and the first pores 40 described above are formed in the first surface 22 a so as to be made through the matrix 21. A plurality of recess portions 54 are formed in the first surface 22 a of the first electrode 20. In other words, the first electrode 20 includes recess portions 54, which are recesses which are not made through the matrix 21. The recess portions 54 are formed from, for example, continuous grooves extending between the first pores 40. Or the recess portions 54 may be a great number of independent dot-like recesses.
The porous membrane 24 is tightly attached to the first surface 22 a of the first electrode 20 and further opposes the first pores 40 and recess portions 54 to stop them.
The first surface 22 a of the first electrode 20 is preferably flat except for the first pores 40 and the recess portions 54. With the recess portions 54, the electrode area can be increased, and also, flow channels for extracting the produced gas can be created. By forming the first surface 22 a of the first electrode 20 substantially plate-like except for the recess portions 54, the concentration of the stress on the porous membrane 24 can be further reduced. Although it vary depending on the thickness of the porous membrane 24, the flatness of the first surface 22 a, or the average surface roughness, is preferably 10% or less of the average thickness of the porous membrane 24, more preferably, 5% or less, or further preferably, 2% or less. The average surface roughness can be examined by cross-sectional SEM observation.
Note that not only the first electrode 20, but also the first surface 23 a of the second electrode 22 may be provided with a plurality of recess portions.

Third Embodiment

FIG. 7 is a sectional view showing an electrode unit of an electrolytic device according to the third embodiment. According to the third embodiment, an electrically insulating film 56 which does not allow liquid to pass, is formed on at least a portion of the surface of the first electrode 20. In the first electrode 20, gas such as chlorine produced by the reaction is not easily discharged on the first surface 22 a, which is widely in contact with the porous membrane 24 on the diaphragm 26 side. For this reason, the diaphragm 26 is deteriorated easily by the produced gas. Here, by covering the region of the first surface 22 a where the first pores 40 are not formed with the insulating film 56, the production of the reactive gas is suppressed in this region, and thus the deterioration of the diaphragm 26 can be prevented. In this embodiment, the insulating film 56 is formed on both the surfaces of the broad linear portion (width W2) of the first electrode 20.
However, the reactive area of the first electrode 20 decreases by forming the insulating film 56. Therefore, it is desirable to have the reaction of the first electrode 20 occur sufficiently in the portion where the produced gas can easily escape. Further, an electrically insulating film 57 may be formed for cover on the second surface 22 b of the first electrode 20 located on the opposite side to the diaphragm 26. When such an electrode unit 12 is used for a three-chamber electrolytic cell, a side reaction on the second surface 22 b side can be reduced. Note that a portion of the insulating film may protrude in the sectional direction of the electrode.

Fourth Embodiment

FIG. 8 is a perspective view showing an electrode unit of an electrolytic device according to the fourth embodiment. According to the fourth embodiment, an interval W3 between adjacent first pores 40 formed in the central portion of the electrode is set to be greater than an interval W1 between those formed in the peripheral portion of the electrode. With this structure, the opening ratio (the ratio of the opening area to the electrode area including the opening area) of the central portion of the first electrode 20 is smaller than that of the peripheral portion of the first electrode 20. Therefore, the electric resistance can be made lower in the central portion of the first electrode 20 than in the peripheral portion, thereby making it possible to reduce the voltage rise in the central portion of the electrode even in the case where power is supplied from the periphery of the electrode to the electrode. In order to reduce the opening ration, the opening area of the first pores 40 formed in the central portion of the first electrode 20 can be reduced by reducing the open area of those formed in the periphery as shown in FIG. 8, or the number of pores can be reduced in the central portion.

Fifth Embodiment

FIG. 9 is a sectional view showing an electrolytic device according to the fifth embodiment. In the fifth embodiment, an electrolytic cell 11 of an electrolytic device 10 is structured as a one-chamber electrolytic cell comprising only one electrolytic chamber 17. An electrode unit 12 is provided in the electrolytic chamber 17. For example, a pipe or a pump for supplying an electrolyte from outside or discharging an electrolyte may be connected to the electrolytic chamber 17.
In the one-chamber electrolytic cell 11, a second electrode (counterelectrode) 22 of the electrode unit 12 preferably has a porous configuration in a manner similar to that of the first electrode 20. The porous configuration enables the electrode area to be increased.

Sixth Embodiment

FIG. 10 is a sectional view showing an electrolytic device according to the sixth embodiment and FIG. 11 is a sectional view of an electrode unit in the electrolytic device.
As shown in FIG. 10, an electrolytic device 10 comprises a three-chamber electrolytic cell 11 including an electrode unit 12. The electrolytic cell 11 is formed into a flat rectangular box shape, the inside of which is divided into three chambers, specifically, an anode chamber 16, a cathode chamber 18 and an intermediate chamber 19 formed between the electrodes, by a dividing wall 14 and the electrode unit 12.
The electrode unit 12 comprises a first electrode (anode) 20 disposed in the anode chamber 16, a second electrode (counterelectrode or cathode) 22 disposed in the cathode chamber 18, two diaphragms 26 a and 26 b provided between the first and second electrodes, a porous membrane 24 a interposed between the first electrode 20 and the diaphragm 26 a, and a porous membrane 24 b interposed between the second electrode 22 and the diaphragm 26 b. The diaphragms 26 a and 26 b oppose each other with an intervening space such that they are parallel to each other. The intermediate chamber (electrolyte chamber) 19 which holds an electrolyte is formed between the diaphragms 26 a and 26 b. A holder 25 which holds an electrolyte may be provided in the intermediate chamber 19. The first and second electrodes 20 and 22 may be connected to each other by a plurality of insulating bridges 60.
The electrolytic device 10 comprises a power supply 30 which applies a voltage to the first and second electrodes 20 and 22 of the electrode unit 12, an ammeter 32, a voltmeter 34 and a control device 36 which controls these elements. A flow channel for liquid may be provided in the anode chamber 16 and the cathode chamber 18. For example, a pipe or a pump for supplying liquid from outside or discharging liquid may be connected to the anode chamber 16 and the cathode chamber 18. A porous spacer may be provided between the electrode unit 12 and the anode chamber 16 or the cathode chamber 18 depending on the case.
As shown in FIGS. 10 and 11, in the electrode unit 12, the first and second electrodes 20 and 22 are formed to have a porous configuration similar to that of the first embodiment discussed above. The continuous porous membrane 24 is formed in, for example, a rectangular shape so as to have dimensions substantially equal to those of the first electrode 20, and opposes the whole first surface 21 a. As the porous membranes 24 a and 24 b, for example, a nonwoven fabric, cloth or a porous membrane which is formed by a sol-gel method can be used, and various materials may be used for the porous membranes. Of these porous membranes, a polymer membrane containing a fluorine atom or a chlorine atom in its main chain, glass cloth or a membrane including irregular continuous pores and containing inorganic oxide, is especially chemically stable and preferable. If an inorganic oxide film having irregular pores is used as the porous membranes 24 a and 24 b, they can also function as diaphragms. The porous membranes 24 and 27 may be multilayer films of a plurality of porous membranes having different pore-diameters.
The diaphragm 26 a is formed in, for example, a rectangular shape so as to have dimensions substantially similar to those of the first electrode 20, and opposes the first surface 22 a of the first electrode 20. The porous membrane 24 a is interposed between the first surface 22 a of the first electrode 20 and the diaphragm 26 a, and adheres tightly to the first electrode 20 and the diaphragm 26 a.
The diaphragm 26 b is formed in, for example, a rectangular shape so as to have dimensions substantially equal to those of the second electrode 22, and opposes the first surface 23 a of the second electrode 22. The porous membrane 24 b is interposed between the first surface 23 a of the second electrode 22 and the diaphragm 26 b, and adheres tightly to the second electrode 22 and the diaphragm 26 b.
The diaphragms 26 a and 26 b are films which allow ions and/or liquid to pass therethrough. For the diaphragm 26, various electrolyte membranes and porous membranes having nanopores may be used.
In the sixth embodiment having the above-described structure, effects similar to those of the first embodiment can be obtained. It is possible to obtain a long-life, high-reaction-efficiency electrode unit and electrolytic device.
Next, various examples and comparative example will be described.

Example 1

For the electrode matrix 21, a flat titanium plate having a thickness (T1) of 0.5 mm is employed. This titanium plate is etched as shown in FIG. 4. In this manner, an electrode is manufactured. In this electrode, a thickness T2 of a region including the smaller-dimension first pores 40 (depth of the first pores) is 0.15 mm, and a thickness T3 of a region including the larger-dimension second pores 42 (depth of the second pores) is 0.35 mm. The first pores 40 have a square shape whose vertices are rounded, and one side R1 of the square obtained by extrapolating the straight line part is 0.57 mm. The second pores 42 have a square shape, and one side R2 thereof is 2 mm. A width W1 of a linear portion formed between adjacent first pores 40 is 0.1 mm and a width W2 of a wide linear portion formed between adjacent second pores 42 is 1.0 mm.
The electrode matrix 21 is processed in advance in a 10-wt % oxalic acid aqueous solution at 80° C. for an hour. 1-butanol is added to iridium chloride (IrCl₃.nH₂O) to be adjusted to 0.25M (Ir) and the mixture is applied to the surface (first surface) of the electrode matrix 21 in which the first pores 40 are formed, followed by drying and burning. In this case, drying is performed at 80° C. for 10 minutes, and the burning is performed at 450° C. for 10 minutes. The above-described application, drying and burning are repeated five times. The electrode matrix made through this process is cut out such that the reactive electrode area can be 3 cm×4 cm. In this manner, the first electrode (anode) 20 is manufactured. The average coarseness of the flat portion of the first electrode 20 except for the recess portions is measured by AFM to be 1 μm.
Further, the second electrode (a counterelectrode, a cathode) 22 is produced by sputtering platinum onto the first surface of the electrode matrix in which the first pores are formed.
The electrode unit 12 shown in FIG. 11 is manufactured, using the first and second electrodes thus obtained. For the diaphragm 26 a, an anion-exchange membrane, A201 of Tokuyama, Inc is employed, and for the diaphragm 26 b, NAFION (trademark) 117 is employed. A glass cloth (75-μm-thick) is used for the porous membranes 24 a and 24 b. As the holder 25 which holds the electrolyte, porous polystyrene having a thickness of 5 mm is provided in the intermediate chamber (electrolyte chamber) 19. The first and second electrodes, the porous membrane, the dividing wall and porous polystyrene are put and fixed together using silicone seal adhesive and a screw, to form the electrode unit 12. Using this electrode unit 12, the electrode unit 12 and the electrolyte device 10 shown in FIG. 10 are manufactured.
The anode chamber 16 and the cathode chamber 18 of the electrolytic cell 11 are each formed from a vinyl-chloride container in which a straight pathway is formed. The control device 36, the power supply 30, the voltmeter 34 and the ammeter 32 are provided. A pipe and a pump for supplying water to the anode and cathode chambers 16 and 18 are connected to the electrolytic cell 11. Further, a saturated salt water tank, a pipe and a pump for circulating a saturated salt water to the holder (porous polystyrene) 25 of the electrode unit 12 are connected to the electrode unit. The electrolytic device 10 is operated for electrolysis at a voltage of 5V and a current of 1.5 A. Aqueous hypochlorous acid is produced on the anode 20 side, and aqueous sodium hydroxide is produced on the cathode 22 side. Even after continuous operation for 1000 hours, no substantial rise in voltage or change in product concentration is observed. Thus, a stable electrolytic treatment can be carried out.

Example 2

With a different mask used in the etching, a first electrode 20 is manufactured from an electrode matrix of 3×4 cm, having a central portion of 1×1.4 cm, where first pores 40 each having a square shape whose one side R1 has a length of 0.7 mm are formed and a width W1 of a linear portion is 0.2 mm. The second pores 42 have a square shape whose one side has a length of 2 mm. The second pore formed in the central portion included the first pores in an arrangement of 2×2. The other structures are the same as those of Example 1. On these conditions, the electrode unit 12 and the electrolytic device 10 are manufactured.
The electrolytic device 10 is operated for electrolysis at a voltage of 4.8 V and a current of 1.5 A. Aqueous hypochlorous acid is produced on the anode 20 side, and aqueous sodium hydroxide is produced on the cathode 22 side. Even after continuous operation for 1000 hours, no substantial rise in voltage or change in product concentration is observed. Thus, a stable electrolytic treatment can be carried out.

Example 3

As the porous membrane, a nonwoven fabric made from polyvinylidene chloride is used instead of the glass cloth. The other structures are the same as those of Example 1. On these conditions, the electrode unit 12 and the electrolytic device 10 are manufactured.
The electrolytic device 10 is operated for electrolysis at a voltage of 5.1 V and a current of 1.5 A. Aqueous hypochlorous acid is produced on the anode 20 side, and aqueous sodium hydroxide is produced on the cathode 22 side. Even after continuous operation for 1000 hours, no substantial rise in voltage or change in product concentration is observed. Thus, a stable electrolytic treatment can be carried out.

Example 4

As the porous membrane, a porous titanium oxide membrane including irregular pores is used instead of the glass cloth. The other structures are the same as those of Example 1. On these conditions, the electrode unit 12 and the electrolytic device 10 are manufactured.
The electrolytic device 10 is operated for electrolysis at a voltage of 5.2 V and a current of 1.5 A. Aqueous hypochlorous acid is produced on the anode 20 side, and aqueous sodium hydroxide is produced on the cathode 22 side. Even after continuous operation for 1000 hours, no substantial rise in voltage or change in product concentration is observed. Thus, a stable electrolytic treatment can be carried out.

Example 5

As the porous membrane, a nonwoven fabric made from Teflon is used instead of the glass cloth. The other structures are the same as those of Example 1. On these conditions, the electrode unit 12 and the electrolytic device 10 are manufactured.
The electrolytic device 10 is operated for electrolysis at a voltage of 5.0 V and a current of 1.5 A. Aqueous hypochlorous acid is produced on the anode 20 side, and aqueous sodium hydroxide is produced on the cathode 22 side. Even after continuous operation for 1000 hours, no substantial rise in voltage or change in product concentration is observed. Thus, a stable electrolytic treatment can be carried out.

Example 6

A first electrode 20 is manufactured as in Example 1 and electric-insulating polyvinyl chloride is applied selectively on a wide linear portion (having a width of W2) to form an insulating film by screen printing. The other structures are the same as those of Example 1. On these conditions, the electrode unit 12 and the electrolytic device 10 are manufactured.
The electrolytic device 10 is operated for electrolysis at a voltage of 5.3 V and a current of 1.5 A. Aqueous hypochlorous acid is produced on the anode 20 side, and aqueous sodium hydroxide is produced on the cathode 22 side. Even after continuous operation for 1000 hours, no substantial rise in voltage or change in product concentration is observed. Thus, a stable electrolytic treatment can be carried out.

Example 7

A second electrode (counterelectrode) 22 of a porous structure is manufactured as in Example 1. As the diaphragm 26, a porous glass film (50-μm-thick) is employed. As the porous membrane 24, a glass cloth (75-μm-thick) is employed. They are then put together using a silicone sealing material and screws to form an electrode unit 12.
Using the electrode unit 12, a one-chamber electrolytic cell 11 and an electrolyte device 10 shown in FIG. 9 are manufactured. A control device 36, a power supply 30, a voltmeter 34 and an ammeter 32 are provided. A pipe and a pump for supplying salt water to an electrolytic chamber 17 are provided. The electrolytic device 10 is operated for electrolysis at a voltage of 4.3 V and a current of 1.5 A to produce aqueous hypochlorous acid. Even after continuous operation for 1000 hours, no substantial rise in voltage or change in product concentration is observed. Thus, a stable electrolytic treatment can be carried out.

Example 8

As the porous membrane, a polyphenylene sulfide porous membrane coated with a film containing titanium oxide is employed instead of the glass cloth. The polyphenylene sulfide porous membrane coated with a film containing titanium oxide is used to also serve as the diaphragms 26 a and 26 b. The other structures are the same as those of Example 1. On these conditions, the electrode unit 12 and the electrolytic device 10 are manufactured.
The electrolytic device 10 is operated for electrolysis at a voltage of 4.8 V and a current of 1.5 A. Aqueous hypochlorous acid is produced on the anode 20 side, and aqueous sodium hydroxide is produced on the cathode 22 side. Even after continuous operation for 2000 hours, no substantial rise in voltage or change in product concentration is observed. Thus, a stable electrolytic treatment can be carried out.

Example 9

As the porous membrane, a glass-made nonwoven fabric (filter paper) coated with a film containing titanium oxide is employed instead of the polyphenylene sulfide porous membrane coated with a film containing titanium oxide. The other structures are the same as those of Example 8. On these conditions, the electrode unit 12 and the electrolytic device 10 are manufactured.
The electrolytic device 10 is operated for electrolysis at a voltage of 4.7 V and a current of 1.5 A. Aqueous hypochlorous acid is produced on the anode 20 side, and aqueous sodium hydroxide is produced on the cathode 22 side. Even after continuous operation for 2000 hours, no substantial rise in voltage or change in product concentration is observed. Thus, a stable electrolytic treatment can be carried out.

Example 10

As the porous membrane, a glass-made nonwoven fabric (filter paper) coated with a film containing zirconium oxide is employed instead of the polyphenylene sulfide porous membrane coated with a film containing titanium oxide. The other structures are the same as those of Example 8. On these conditions, the electrode unit 12 and the electrolytic device 10 are manufactured.
The electrolytic device 10 is operated for electrolysis at a voltage of 4.8 V and a current of 1.5 A. Aqueous hypochlorous acid is produced on the anode 20 side, and aqueous sodium hydroxide is produced on the cathode 22 side. Even after continuous operation for 2000 hours, no substantial rise in voltage or change in product concentration is observed. Thus, a stable electrolytic treatment can be carried out.

Example 11

As the porous membrane, a membrane further coated with a more precise film containing zirconium oxide on an electrode-side surface of the porous membrane is employed instead of the polyphenylene sulfide porous membrane coated with a film containing titanium oxide. The other structures are the same as those of Example 8. On these conditions, the electrode unit 12 and the electrolytic device 10 are manufactured.
This electrolytic device 10 is operated for electrolysis at a voltage of 4.9 V and a current of 1.5 A. Aqueous hypochlorous acid is produced on the anode 20 side, and aqueous sodium hydroxide is produced on the cathode 22 side. Even after continuous operation for 2000 hours, no substantial rise in voltage or change in product concentration is observed. Thus, a stable electrolytic treatment can be carried out.

Example 12

As the porous membrane, a membrane coated with a Teflon porous membrane further coated with a film containing zirconium oxide is employed instead of the polyphenylene sulfide porous membrane coated with a film containing titanium oxide. The other structures are the same as those of Example 8. On these conditions, the electrode unit 12 and the electrolytic device 10 are manufactured.
This electrolytic device 10 is operated for electrolysis at a voltage of 4.9 V and a current of 1.5 A. Aqueous hypochlorous acid is produced on the anode 20 side, and aqueous sodium hydroxide is produced on the cathode 22 side. Even after continuous operation for 2000 hours, no substantial rise in voltage or change in product concentration is observed. Thus, a stable electrolytic treatment can be carried out.

Example 13

For the electrode matrix 21, a flat titanium plate having a thickness T1 of 0.5 mm is employed. This titanium plate is etched as shown in FIG. 4 to manufacture an electrode. In this electrode, a thickness T2 of a region including the smaller-dimension first pores 40 (depth of the first pores) is 0.15 mm, and a thickness T3 of a region including the larger-dimension second pores 42 (depth of the second pores) is 0.35 mm. The first pores 40 have a rhomboid shape whose long diagonal is 0.69 mm and short diagonal is 0.4 mm. The second pores 42 have a rhomboid shape whose long diagonal line has a length of 6.1 mm and short diagonal line has a length of 3.5 mm. A width W1 of a linear portion formed between adjacent first pores 40 is 0.15 mm and a width W2 of a wide linear portion formed between adjacent second pores 42 is 1 mm. The other structures are the same as those of Example 1. On these conditions, the electrode unit 12 and the electrolytic device 10 are manufactured.
This electrolytic device 10 is operated for electrolysis at a voltage of 5.3 V and a current of 1.5 A. Aqueous hypochlorous acid is produced on the anode 20 side, and aqueous sodium hydroxide is produced on the cathode 22 side. Even after continuous operation for 1000 hours, no substantial rise in voltage or change in product concentration is observed. Thus, a stable electrolytic treatment can be carried out.

Example 14

For the electrode matrix 21, a flat titanium plate having a thickness T1 of 0.5 mm is employed. This titanium plate is etched as shown in FIG. 4 to manufacture an electrode. In this electrode, a thickness T2 of a region including the smaller-dimension first pores 40 (depth of the first pores) is 0.15 mm, and a thickness T3 of a region including the larger-dimension second pores 42 (depth of the second pores) is 0.35 mm. The first pores 40 have a square shape whose one side R1 has a length of 0.57 mm. The second pores 42 have a rectangular shape whose long side has a length of 40 mm and short side has a length of 4 mm. A width W1 of a linear portion formed between adjacent first pores 40 is 0.1 mm and a width W2 of a wide linear portion formed between adjacent second pores 42 is 1.0 rum. The other structures are the same as those of Example 1. On these conditions, the electrode unit 12 and the electrolytic device 10 are manufactured.
This electrolytic device 10 is operated for electrolysis at a voltage of 5.8 V and a current of 1.5 A. Aqueous hypochlorous acid is produced on the anode 20 side, and aqueous sodium hydroxide is produced on the cathode 22 side. Even after continuous operation for 1000 hours, no substantial rise in voltage or change in product concentration is observed. Thus, a stable electrolytic treatment can be carried out.

Comparative Example 1

An electrolytic device is manufactured in a similar manner to that of Example 1 except that the continuous porous membrane is not employed in this example. This electrolytic device is operated for electrolysis at a voltage of 5 V and a current of 1.5 A. Aqueous hypochlorous acid is produced on the anode side, and aqueous sodium hydroxide is produced on the cathode side. After continuous operation for 1000 hours, a significant rise in voltage and a decrease in product concentration are observed. Thus, this device did not exhibit a long-term stability.

Comparative Example 2

An electrolytic device is manufactured by forming through-holes having a diameter of 1 mm in an electrode matrix by punching to have the same opening ratio as that of the electrode of Example 1. The other structures are the same as those of Example 1. On these conditions, the electrode unit and the electrolytic device are manufactured.
This electrolytic device is operated for electrolysis at a voltage of 5.2 V and a current of 1.5 A. Aqueous hypochlorous acid is produced on the anode side, and aqueous sodium hydroxide is produced on the cathode side. After continuous operation for 1000 hours, a significant rise in voltage and a decrease in product concentration are observed. Thus, this device did not exhibit a long-term stability.
The present invention is not limited to the embodiments and modifications described above but the constituent elements of the invention can be modified in various manners without departing from the spirit and scope of the invention. Various aspects of the invention can also be extracted from any appropriate combination of a plurality of constituent elements disclosed in the embodiments. For example, some constituent elements may be deleted in all of the constituent elements disclosed in the embodiments. Further, the constituent elements described in different embodiments may be combined arbitrarily.
For example, the first electrode and the second electrode are not limited to rectangular shapes, but various other forms may be selected. The first and second pores of the first electrode are not limited to square shapes, and may have various other shapes such as a rectangular, rhomboid, circular or elliptical shape. Further, the material of each structural component is not limited to that employed in the embodiments or examples discussed, but various other materials may be selected as needed. The electrolytic cell of the electrode device is not limited to a three-chamber type, but it may as well be applied to a two-chamber- or single-chamber type or any electrolytic cells with electrodes in general. The electrolytes and product are not limited to salt or hypochlorous acid, but may be developed into various electrolytes and products.

Claims

1: An electrode unit comprising:

a first electrode including: a first surface, a second surface located on an opposite side to the first surface, a plurality of first pores opened in the first surface, a plurality of second pores opened in the second surface and having an opening area greater than that of the first pores, a plurality of the first pores communicating with a respective one of the second pores;

a second electrode opposing the first surface of the first electrode; and

a continuous porous membrane arranged between the first electrode and the second electrode, so as to cover the first surface of the first electrode.

2: The electrode unit of claim 1, wherein an opening area of the first pores opened in the first surface is 0.01 to 4 mm².

3: The electrode unit of claim 1, wherein an opening area of the second pores opened in the second surface is 1 to 1600 mm².

4: The electrode unit of claim 1, wherein a number density of the first pores per unit area is higher than that of the second pores per unit area.

5: The electrode unit of claim 1, wherein a catalytic layer is formed on the first surface and the second surface of the electrode, and an amount of the catalytic layer per unit area differs from the first surface to the second surface.

6: The electrode unit of claim 1, wherein the first pores are formed to have a tapered surface or a curved surface which widens towards the first surface.

7: The electrode unit of claim 1, wherein the first electrode includes recess portions formed in the first surface, and the first surface is formed flat except for the first pores and the recess portions.

8: The electrode unit of claim 7, wherein an average surface roughness of a flat portion of the first electrode is 10% or less of an average thickness of the porous membrane.

9: The electrode unit of claim 1, wherein an opening ratio of first pores located in a central portion of the first electrode is less than an opening ratio of first pores located in a peripheral portion of the first electrode.

10: The electrode unit of claim 1, further comprising: an electrically insulating film which inhibits liquid from passing therethrough and is provided on at least a portion of the first surface of the first electrode.

11: The electrode unit of claim 1, wherein the second electrode has a porous structure including a plurality of through-holes.

12: The electrode unit of claim 1, wherein the porous membrane is a polymer membrane containing a fluorine atom or a chlorine atom in a main chain thereof.

13: The electrode unit of claim 1, wherein the porous membrane is a glass cloth.

14: The electrode unit of claim 1, wherein the porous membrane is a membrane including in-planerly or three-dimensionally irregular pores and containing inorganic oxide.

15: The electrode unit of claim 1, wherein the porous membrane is a multi-layer film in which a plurality of porous films having different pore diameters are stacked one on another.

16: The electrode unit of claim 1, further comprising: a diaphragm provided between the first surface of the first electrode and the second electrode, which allows at least one of ion and liquid to pass therethrough, and

wherein the porous membrane is interposed between the first surface of the first electrode and the diaphragm.

17: The electrode unit of claim 1, further comprising:

two diaphragms provided between the first electrode and the second electrode so as to oppose each other; and

an electrolyte holding structure located between the two diaphragms to hold electrolyte.

18: An electrolytic cell comprising: an electrolytic chamber and an electrode unit of claim 1, provided in the electrolytic chamber.

19: An electrolytic device comprising:

an electrolytic cell including an electrolytic chamber;

an electrode unit of claim 1, provided in the electrolytic chamber; and

a power supply which applies a voltage to the first electrode and the second electrode of the electrode unit.

20: The electrolytic device of claim 19, wherein an electrolyte containing chloride ions is electrolyzed by the electrode unit.