JP2013104090A - Electrode unit for use in electrolytic cell of zero-gap type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly economical electrode unit for use in electrolytic cells of a zero-gap type, whose manufacturing cost can be controlled to the extent practicable.SOLUTION: Of the constituent members of an electrode unit constituting an electrolytic cell of a gap type, an anode 20 and an electrode-supporting frame that supports the anode 20 on one side of a separation wall and a cathode on the other side are employed without modification in an electrode unit for use in electrolytic cells of a zero-gap type. In place of the cathode, a cathode structure 30 that supports an active cathode 33 via a conductive elastic body 32 in a manner of allowing the same to move back and forth, is attached to the front side of the cathode which is used as a back plate 31. Thus, an electrode unit used in electrolytic cells of a gap type is converted to an electrode unit for use in electrolytic cells of a zero-gap type, with slight modification.

Description

  The present invention relates to an electrode unit used in a zero-gap electrolytic cell, and more specifically, an existing and existing electrode unit used in a non-zero-gap electrolytic cell (gap-type electrolytic cell) that has been the mainstream in the past. The present invention relates to a highly economical zero gap type electrolytic cell electrode unit.

  In order to produce chlorine, hydrogen, and sodium hydroxide by electrolyzing an alkali metal salt aqueous solution, that is, a sodium chloride aqueous solution, the anode chamber and the cathode chamber are separated by a cation exchange membrane, and the anode and cathode chambers in the anode chamber are separated. It is well known that an ion exchange membrane salt electrolytic cell is used in which electrolysis is performed by passing an electric current between the cathode and the cathode, and many improvements have been made. For example, by developing a dimensionally stable electrode as the anode and an active cathode with a low hydrogen overvoltage as the cathode, the electrolysis voltage in ion exchange membrane salt electrolysis is reduced. In particular, the recent improvement in electrolysis technology is remarkable, and as one of them, a so-called zero gap type electrolytic cell in which an anode and a cathode are in close contact with a cation exchange membrane has been developed, and the electrolysis voltage is further lowered (patent) References 1 and 2).

  Regardless of the zero gap type electrolytic cell or the gap type electrolytic cell, the ion exchange membrane salt electrolytic cell uses an electrode unit that supports the anode on one side and the cathode on the other side across the partition wall. (Patent Document 3). Specifically, a plurality of electrode units are arranged in cascade and connected with a cation exchange membrane interposed therebetween. Thereby, as shown in FIG. 5, the ion exchange membrane I is arrange | positioned between the anode 2 and the cathode 3 of two adjacent electrode units, and an electrolytic cell is comprised. A plurality of electrode units arranged in tandem for electrolytic cell construction are electrically connected in series is called a bipolar (bipolar), and a parallel connection is called a monopolar (monopolar). . The piper electrolytic cell uses an electrode unit in which an anode chamber is provided between the anode and the back partition, and a cathode chamber is provided between the cathode and the back partition. The monopolar electrolytic cell uses, as electrode units, an anode chamber unit having an anode on both sides and a cathode chamber unit having a cathode on both sides. The anode 2 is in close contact with the ion exchange membrane I disposed between the adjacent electrode units, and the cathode 3 is opposed to the ion exchange membrane I with a predetermined gap G. What was made to do is a zero gap type electrolytic cell.

  That is, in the ion-exchange membrane method salt electrolytic cell, the anode is in close contact with the ion-exchange membrane from the beginning, and the zero-gap electrolytic cell in which the negative electrode is newly adhered. This is because the electrolyte pressure on the anode side and the cathode side of the ion exchange membrane is different (because the fluid pressure on the cathode side is larger than the fluid pressure on the anode side). Because it does. In this state, the zero gap type electrolytic cell further reduces the electrolysis voltage by intentionally and physically bringing the cathode into close contact with the ion exchange membrane to reduce the electrical resistance between the ion exchange membrane and the cathode. is there. In such a zero gap electrolytic cell, the pressure of pressing the ion exchange membrane against the anode increases as the cathode adheres to the ion exchange membrane.

  In order to cope with the increase in the pressing pressure, in the zero gap type electrolytic cell described in Patent Document 2, the anode has a rigid structure that is less deformed even when pressed against the ion exchange membrane while the anode is an electrode. Damage to the ion exchange membrane by making a flexible structure that maintains the zero gap by absorbing tolerances and deformation due to tolerances such as the support frame and interposing a conductive cushion mat between the back plate and the back. Instead, the adhesion between the ion exchange membrane and the anode and between the ion exchange membrane and the cathode is ensured. And regarding the structure of the anode which is a rigid structure, the electroconductivity which consists of a titanium expanded metal or a titanium metal net | network with an aperture ratio of 25 to 75% mainly from a viewpoint of ensuring liquid permeability between ion exchange membranes. It is recommended that a catalyst layer be formed on the surface of the substrate, the maximum value of the unevenness on the catalyst layer surface be 5 to 50 μm, and the thickness to be 0.7 to 2.0 mm.

  However, enormous costs are required to newly design and manufacture an electrode unit for a zero gap electrolytic cell as described in Patent Document 2.

JP 2001-262387 A Japanese Patent No. 4453973 JP 61-37355 A

  An object of the present invention is to provide an electrode unit for a zero-gap electrolytic cell with high economic efficiency that can suppress the manufacturing cost as much as possible even though it is used in a zero-gap electrolytic cell.

  In order to achieve the above-mentioned object, the present inventors investigated the difference in level of the unevenness on the surface of the catalyst layer for many anodes mounted on the gap type electrolytic cell electrode unit that has been used conventionally. As a result, it has been found that in most of the anodes, the maximum value of the height difference of the irregularities on the surface of the catalyst layer is almost in the range of 5 to 50 μm without exception. Further, regardless of whether the electrode unit for a gap electrolytic cell or the electrode unit for a zero gap electrolytic cell is used, an expanded metal made of titanium having an aperture ratio of 25 to 75% is known as an anode substrate, and is 0.7 to 2.0 mm. The anode thickness is also extremely common.

  That is, the rigid-structure anode for constituting the zero gap type electrolytic cell described in Patent Document 2 is not different from the anode incorporated in the gap type electrolytic cell electrode unit that has been used conventionally. . This is because even in the anode used in the electrode unit for the gap type electrolytic cell, the surface of the substrate is blasted or etched by several μm to several μm in order to expect an anchor effect for supporting the catalyst layer on the surface of the conductive substrate. Since the surface of the catalyst layer formed on the surface has a roughness of about 10 μm, the maximum value of the unevenness height difference is several along the unevenness of the surface, whether desired or not. This is because the surface becomes uneven within a range of μm to several tens of μm.

  Here, the relationship between the surface roughness of the conductive substrate and the maximum value of the uneven height difference on the catalyst layer surface will be briefly described. Since the unevenness of the substrate surface is relaxed by the coating of the catalyst layer on the substrate surface, when compared with the maximum unevenness height difference, the catalyst layer surface is smaller than the substrate surface, but even with the same unevenness size, In the case of the average roughness such as Ra and the maximum unevenness height difference, the latter is displayed larger than the former. As a result, they cancel each other, and the average roughness of the substrate surface and the maximum value of the uneven height difference on the surface of the catalyst layer are generally the same value.

  In short, the anode built into the gap type electrolytic cell electrode unit and the anode built into the zero gap type electrolytic cell electrode unit are both anodes that are in close contact with the ion exchange membrane. Since there are similar restrictions in use, it is natural that there is no difference in structure. For this reason, the difference in structure between the electrode unit for gap type electrolytic cell and the electrode unit for zero gap type electrolytic cell is only the flexible contact structure on the cathode side after all.

  If so, in order to produce a zero gap type electrolytic cell electrode unit, it is not necessary to recreate everything, and a conventional electrode manufactured and sold for the anode of a gap type electrolytic cell electrode unit. And a lot of parts including the electrode support frame can be diverted to the electrode unit for the zero gap type electrolytic cell, and it is concluded that the diverted one can produce the electrode unit for the zero gap type electrolytic cell with the effort of remodeling. Reached. By the way, the cathode in the gap type electrolytic cell electrode unit is not in close contact with the ion exchange membrane, so it is often a rigid structure like nickel expanded metal, and can be used as a back plate that supports the conductive cushion mat from the back. Has the rigidity.

  The electrode unit for a zero gap electrolytic cell of the present invention has been completed on the basis of such knowledge, and is an electrode unit used for constituting a zero gap electrolytic cell, and is an electrode for a gap electrolytic cell An anode made for the unit, an electrode support frame made for the gap type electrolytic cell electrode unit, supporting the anode on one side and supporting the cathode on the other side across the partition, and the electrode support The cathode structure in which the cathode in the frame is used as a back plate and the active cathode is stacked and supported on the front side of the frame via a conductive elastic body so as to be movable in the front-rear direction.

  In the zero gap type electrolytic cell electrode unit of the present invention, the anode is a diversion from the gap type electrolytic cell electrode unit. The electrode support frame is also a transfer product from the electrode unit for the gap electrolytic cell, and its cathode is used as the back plate of the conductive elastic body in the cathode structure. What is newly needed is a slight modification of the active cathode and conductive elastic body in the cathode structure and the electrode support frame for their attachment. Therefore, it becomes possible to produce the gap type electrolytic cell electrode unit that has been used for a long time at a low cost.

  The anode is preferably an active electrode in which a catalytic layer having activity is formed on the surface of a conductive substrate having liquid permeability, from the viewpoint of a decrease in electrolytic voltage. As the conductive substrate of the anode, a titanium expanded metal or a titanium punching metal is desirable from the viewpoint of corrosion resistance and the like, and a titanium expanded metal is particularly desirable from the viewpoint of economy. The aperture ratio in these conductive substrates is preferably 25 to 75% from the viewpoint of achieving both mechanical strength and liquid permeability.

  The thickness of the anode including the catalyst layer is preferably 0.7 to 2.0 mm from the viewpoint of achieving both mechanical strength and economical efficiency. That is, if the conductive substrate is too thin, the mechanical strength is lowered, and the surface is roughened to cause deformation and distortion. As a result, a gap is generated between the ion exchange membrane and the anode, and the electrolysis voltage increases. In addition, a conductive substrate that is too thin is not preferable because it may be deformed by the electrolytic pressure during operation. On the other hand, if it is too thick, the raw material cost increases and the economic efficiency decreases.

  The maximum value of the unevenness height difference on the catalyst layer surface is preferably 5 to 50 μm and more preferably 10 to 40 μm from the viewpoint of achieving both liquid permeability and ion exchange membrane protection, but the catalyst layer is provided on the surface side of the conductive substrate. In order to carry the substrate, the surface of the substrate has been subjected to a roughening treatment by blasting or etching, and the unevenness of the surface of the substrate is reflected on the surface of the catalyst layer. As described above, it is within the range.

  When measuring the surface roughness of the conductive substrate and the surface roughness of the catalyst layer surface, there are a contact type using a stylus and a non-contact type measurement method using optical interference or laser light. The non-contact method is expensive although it does not cause damage to the measurement object, and therefore a contact method is desirable. Mitutoyo's SJ-301 or the like is used for measuring the contact surface roughness using a stylus. This device measures the surface roughness by a method in which the stylus of the detector traces minute irregularities on the surface of the object to be measured, and the surface roughness is obtained from the vertical displacement and lateral movement of the stylus. To do.

  For the measured value on the surface of the workpiece, Ra arithmetic average roughness, ten-point average roughness, etc. can be measured. Here, the sum of the height from the average line to the highest peak and the depth to the deepest valley bottom is calculated. Use the maximum height found. The area to be measured can be arbitrarily selected, but it is desirable to measure an area of 10 μm to 300 μm square in order to grasp the unevenness of the substrate surface and the catalyst layer surface to some extent. In particular, when measuring an expanded metal or a catalyst layer on the surface thereof, it is desirable to measure an area of 50 μm to 150 μm square.

  The active cathode in the cathode structure is also preferably an active electrode in which a catalytic layer having activity is formed on the surface of a conductive substrate having liquid permeability, from the viewpoint of reduction in electrolytic voltage. As the conductive substrate of the cathode, nickel expanded metal, nickel punching metal or nickel fine mesh is desirable from the viewpoint of corrosion resistance, etc., and nickel is a flexible structure from the viewpoint of economy and reduction of damage to the ion exchange membrane. A fine mesh made is particularly desirable. As in the case of the anode, the aperture ratio in these conductive substrates is preferably 25 to 75% from the viewpoints of mechanical strength and liquid permeability, and the thickness of the cathode including the catalyst layer is mechanical strength and economical efficiency. From the viewpoint of achieving both, 0.7 to 2.0 mm is desirable.

  As the conductive elastic body in the cathode structure, a woven mesh (conductive cushion mat) formed by matting conductive metal wires is more preferable than a spring. This is because it is highly flexible and economical. As the material of the fine metal wire, nickel which is the same as the material of the cathode is preferable. The wire diameter of the fine metal wire is usually 0.05 to 0.3 mm, preferably 0.07 to 0.2 mm, and more preferably 0.1 to 0.15 mm.

The bulk density of the woven mesh (conductive cushion mat) is preferably 0.2 to ² kg / m ² , and the thickness is 5 to 10 mm in a state where no load is applied. After the electrode unit is connected, the bulk density is 4 in close contact with the ion exchange membrane. ˜8 mm is preferred. This is because the pressing pressure of the ion exchange membrane from the cathode to the anode cannot be secured unless it has a certain mechanical strength.

  The zero gap type electrolytic cell electrode unit of the present invention can be inexpensively used by remodeling the electrode unit by diverting many members and parts for the gap type electrolytic cell electrode unit that have been used in the past. Since it can be produced, it is very excellent in economic efficiency. In addition, the production period is shortened, and this point is also economical.

It is a vertical side surface which shows the schematic structure of the principal part of the electrode unit for zero gap type electrolytic cells which shows one Embodiment of this invention. It is a cross-sectional top view which shows schematic structure of the principal part, and is the sectional view on the AA line in FIG. It is a vertical side view which shows the detailed structure of the principal part, and is the B section enlarged view in FIG. It is a vertical side view which shows another detailed structure of the principal part, and is equivalent to the B section enlarged view in FIG. It is a vertical side surface which shows the detailed structure of the principal part of the electrode unit for gap type electrolytic cells. The change over time of the cell voltage (electrolysis voltage) when the main structure of the electrode unit for the zero gap type electrolytic cell is that shown in FIGS. It is a graph shown.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  The electrode unit for the zero gap type electrolytic cell shown in FIGS. 1 to 3 is used for a zero gap type ion exchange membrane salt electrolytic cell. Here, a predetermined number of electrode units U have the same polarity. The ion exchange membrane I is arranged between the adjacent units U and U to constitute an electrolytic cell.

  Each electrode unit U includes an electrode support frame 10 that supports a rigid anode 20 on one side of a partition wall 11 that is perpendicular to the column direction and perpendicular to the partition wall 11 and supports a cathode structure 30 on the other side. The electrode support frame 10 in the electrode unit U is manufactured on the assumption that the electrode support frame 10 is incorporated into an electrode unit for a conventional gap type electrolytic cell, and has a rigid structure with a predetermined gap on one side of the vertical partition wall 11. The anode 20 is supported, and the cathode structure 30 including the original cathode is supported on the other side.

  In order to support the anode 20 here, a plurality of vertical longitudinal ribs 12 arranged at predetermined intervals in the lateral direction are attached to one surface of the vertical partition wall 11, and the anode 20 is attached to the tip of these. It has been. Between the anode 20 and the partition wall 11 behind it is an anode chamber 20A, and each vertical rib 12 is provided with a plurality of through holes 12a so that the electrolyte can freely flow in the lateral direction in the anode chamber 20A. ing.

  Similarly, on the other surface of the vertical partition wall 11 of the electrode support frame 10, a plurality of vertical vertical ribs 13 arranged at predetermined intervals in the lateral direction are attached, and the cathode structure 30 is provided at the tip thereof. Installed. A space between the cathode structure 30 and the partition wall 11 behind it is a cathode chamber 30A, and each vertical rib 13 has a plurality of through-holes 13a so that the electrolyte can freely flow in the lateral direction in the cathode chamber 30A. Is provided.

  The anode 20 of the rigid structure in the electrode unit U is manufactured on the assumption that it is incorporated in the conventional gap type electrolytic cell electrode unit, like the electrode support frame 10, and the electrode units U are arranged in tandem. Thus, the ion exchange membrane I is sandwiched between the cathode structures 30 in the adjacent electrode units U. The anode 20 having a rigid structure is a highly rigid and plate-like conductive substrate having liquid permeability, here, a conductive substrate 21 made of titanium expanded metal having an aperture ratio of 25 to 75%, and the front surface of the conductive substrate 21. And an active catalyst layer 22 formed on the side surface.

  The rigid anode 20 has a thickness of 0.7 to 2.0 mm, the conductive substrate 21 has a thickness of 0.7 to 2.0 mm, and the catalyst layer 22 has a thickness of 5 to 50 μm. Moreover, the maximum value of the unevenness | corrugation height difference of the catalyst layer surface is 5-50 micrometers.

  The cathode structure 30 in the electrode unit U has an original cathode directly attached to the vertical ribs 13 of the electrode support frame 10 as a back plate 31 and a flexible structure active cathode 33 via a conductive elastic body 32 on the front side thereof. It has a three-layer structure in which are stacked. The original cathode used as the back plate 31 is made of nickel expanded metal and has a rigid structure because of material limitations. Here, the conductive elastic body 32 is a cushion mat (woven mesh) formed by combining conductive thin wires (nickel thin wires), and an active cathode 33 having a flexible structure is placed between the electrode unit U on the front side. This contributes to elastic contact with the arranged ion exchange membrane I. The active cathode 33 having a flexible structure has an active catalyst layer on the front surface of a conductive base 33a having flexibility, here, a conductive base 33a made of nickel fine mesh having an aperture ratio of 25 to 75%. This is an active electrode formed with 33b.

  The thickness of the active cathode 33 having a flexible structure is 0.7 to 2.0 mm, the thickness of the conductive substrate 33 a in the active cathode 33 is 0.7 to 2.0 mm, and the thickness of the catalyst layer 33 b is 1.0 to 50 μm. Similarly, the thickness of the back plate 31 having a rigid structure is 0.7 to 2.0 mm.

  Next, the function of the electrode unit for zero gap type electrolytic cells shown in FIGS. 1 to 3 will be described.

  A predetermined number of electrode units U are arranged in tandem with the same polarity while sandwiching the ion exchange membrane I therebetween, and a predetermined load is applied in the arrangement direction to constitute an electrolytic cell. Thereby, the ion exchange membrane I between the adjacent electrode units U and U is predetermined by the cathode structure 30 in the electrode unit U on the other side with respect to the rigid anode 20 in the electrode unit U on the one side. Pressed with a load. Specifically, in the cathode structure 30, the active cathode 33 is elastically pressed against the ion exchange membrane I by disposing the active cathode 33 on the front side of the back plate 31 via the conductive elastic body 32. The

  Moreover, since the back plate 31 made of the original cathode has a rigid structure with a nickel expanded metal as a base, the new active cathode 33 has a flexible structure with a nickel fine mesh as a base. Dispersion effect of electrode pressing load on I is large. As a result, no particular problem arises even though the rigid anode 20 incorporated in the conventional gap type electrolytic cell electrode unit is used as it is.

During operation, saline is supplied into the anode chamber 20A, and water is supplied into the cathode chamber 30A. In this state, a predetermined voltage is applied to a predetermined number of electrode units U electrically connected in series. As a result, chlorine gas (Cl ₂ ) is generated in the anode chamber 20, and sodium hydroxide (NaOH) and hydrogen gas (H ₂ ) are generated in the cathode chamber 30. And since the zero gap structure which made the active cathode 33 contact | adhere to the ion exchange membrane I is employ | adopted, the voltage rise in the meantime is blocked | prevented and a cell voltage (electrolytic voltage) falls.

  In each electrode unit U, the back plate 31 in the electrode support frame 10, the anode 20, and the cathode structure 30 is a diversion from the conventional gap type electrolytic cell electrode unit, and is electrically conductive on the front side of the back plate 31. Since the electrode unit U is manufactured only by modification to the extent that the active cathode 33 is supported via the elastic elastic body 32, the manufacturing cost is very low.

  In the zero gap type electrolytic cell electrode unit shown in FIG. 4, the active cathode 33 in the cathode structure 30 is composed only of a conductive substrate 33a made of nickel fine mesh, and the catalyst layer 33b is not formed on the surface thereof. The point differs from the electrode unit for zero gap type electrolytic cells shown in FIGS. Since the active cathode 33 in contact with the ion exchange membrane I does not have the catalyst layer 33b, the cell voltage (electrolysis voltage) rises, but the electrode unit U can be manufactured at low cost by using a diverted product from the electrode unit for gap electrolytic cell. These are the same as the zero gap type electrolytic cell electrode unit shown in FIGS.

  Next, examples of the present invention will be described, and the effects of the present invention will be clarified by comparing with comparative examples.

(Comparative example)
A gap-type electrolytic cell using two types of general-purpose electrodes, which were sold without limitation as of March 8, 1991, as an anode and a cathode was used for a comparative test. The electrolytic cell is configured by arranging electrode units U in tandem with the ion exchange membrane I interposed therebetween. As shown in FIG. 5, each electrode unit U supports an anode 2 on one side of a partition wall by an electrode support frame (not shown), supports a cathode 3 on the other side, and is arranged in tandem to constitute an electrolytic cell. In addition, the distance D between the anode 2 and the cathode 3 of both units facing each other is increased so that the anode 2 is in contact with the ion exchange membrane I disposed between the electrodes and the cathode 3 is not in contact. It is comprised so that it may be in a contact state (state which opposes with the predetermined gap G). The material of the electrode support frame in the electrode unit is SUS310S.

  The general-purpose anode 2 is a liquid-permeable type rigid structure electrode having a conductive base 2a made of a titanium expanded metal having an aperture ratio of 50%, and was manufactured as follows. The surface of the substrate was blasted with # 180 alumina and then etched in 10% 90 ° C. oxalic acid for 3 hours. The average roughness of the substrate surface after etching was 20 μm. An acidic solution containing a platinum group metal was applied to the surface of the conductive substrate 2a thus roughened, dried at 100 ° C. for 10 minutes, and then fired at 500 ° C. for 20 minutes. The anode 2 is fabricated by repeating this coating-drying-firing process to form a catalyst layer 2b having an active thickness of about 10 μm on the surface of the substrate. The thickness of the anode 2 including the catalyst layer 2b is 1 mm. The maximum difference in the uneven height on the surface of the catalyst layer 2b was 20 μm, which is the same as the average roughness of the substrate surface after etching.

  On the other hand, the cathode 3 is a liquid-permeable rigid structure electrode using nickel expanded metal having an aperture ratio of 50% as a conductive base. The cathode 3 is produced by performing activated carbon dispersion plating on the surface of the conductive substrate. The thickness of the cathode 3 is 1 mm.

  An inter-electrode distance D in a gap type electrolytic cell configured by connecting electrode units is 2 mm. The ion exchange membrane I disposed in contact with the anode between the electrodes is a DuPont cation exchange membrane Nafion 2030 (Nafion is a registered trademark), and has a thickness of about 150 μm.

In each of the electrode units in the gap type electrolytic cell, 250 g / L of saline solution as an electrolytic solution is supplied to the anode chamber, and 32% sodium hydroxide solution is supplied to the cathode chamber. The liquid temperature is 80 ° C. and the current density is 4 kA / m. Electrolytic operation has been conducted for 20 years under the conditions of ² . FIG. 6 shows changes with time in the cell voltage (electrolytic voltage) from the start of the comparative test. The cell voltage (electrolysis voltage) was initially 3.22 V, and increased by 10 mV after 360 days had elapsed since the start of the test.

Example 1
The electrode unit for a gap type electrolytic cell having a service period of 20 years used in the comparative example was modified to the electrode unit U for a zero gap type electrolytic cell shown in FIGS. Specifically, the anode 20 and the electrode support frame 10 used the anode 2 and the electrode support frame in the gap type electrolytic cell electrode unit as they were. Other than this, the active cathode 33 was supported on the front side of the cathode 3 having a rigid structure in the electrode support frame via a mat-like conductive elastic body 32 made of nickel woven mesh so as to be movable back and forth. The wire diameter of the nickel woven mesh constituting the conductive elastic body 32 is 0.1 mm, and the elastic body thickness in a state where no compression force is applied is about 8 mm.

  The active cathode 33 is a flexible structure electrode using a nickel fine mesh having an aperture ratio of 50% as a conductive substrate 33a. The surface of the conductive substrate 33a was blasted with # 180 alumina, and then etched in 10% hydrochloric acid for 60 minutes at room temperature. An acidic solution containing a platinum group metal was applied to the surface of the conductive substrate thus roughened, dried at 100 ° C. for 10 minutes, and then fired at 500 ° C. for 10 minutes. By repeating this coating-drying-firing process, an active catalyst layer 33b having an active thickness of about 5 μm was formed on the substrate surface, and the active cathode 33 was completed. The thickness of the active cathode 33 including the catalyst layer 33b is 1 mm.

  By placing the ion exchange membrane I between the anode 20 and the newly produced cathode structure 30 and arranging the electrode units U in tandem while the cathode structure 30 is in close contact with the ion exchange membrane I, a zero gap is obtained. An electrolytic cell was constructed. The thickness of the conductive elastic body 32 in the cathode structure 30 in this state is about 6 mm.

  The electrolysis operation was performed under the same conditions as in the comparative example. FIG. 6 shows changes with time in the cell voltage (electrolytic voltage). The cell voltage (electrolysis voltage) at the beginning of the operation was 2.96 V due to the zero gap and the activation of the cathode, which was 260 mV lower than the comparative example. The voltage increase after the elapse of 360 days from the start of operation was only 10 mV.

(Example 2)
In Example 1, the average roughness after the roughening treatment of the titanium expanded metal used as the conductive substrate 21 of the anode 20 was set to 60 μm. The maximum difference in the unevenness on the surface of the catalyst layer 22 in the completed anode 20 was 60 μm, which is the same as the average roughness of the substrate surface after the roughening treatment. FIG. 6 shows changes with time in the cell voltage (electrolytic voltage) from the start of operation. The cell voltage (electrolytic voltage) decreased by 240 mV compared to the comparative example.

(Example 3)
In Example 1, the catalyst layer 33b formed on the surface of the conductive substrate 33a of the active cathode 33 was omitted. That is, the zero gap type electrolytic cell electrode unit shown in FIG. 4 was used. FIG. 6 shows changes with time in the cell voltage (electrolytic voltage) from the start of operation. The cell voltage (electrolytic voltage) decreased by 210 mV compared to the comparative example.

U electrode unit I ion exchange membrane D distance between electrodes in gap type electrolytic cell G gap between cathode and ion exchange membrane in gap type electrolytic cell 10 electrode support frame 11 partition 12, 13 vertical rib 12a, 13a through hole 2, 20 Anode 20A Anode chamber 30 Cathode structure 30A Cathode chamber 31 Back plate 32 Conductive elastic body 3 Cathode 33 Active cathode

Claims (7)

  An electrode unit used to construct a zero-gap electrolytic cell, an anode made for a gap-type electrolytic cell electrode unit and a gap-type electrolytic cell electrode unit, with a partition wall in between An electrode support frame that supports the anode on one side and a cathode on the other side, and the cathode in the electrode support frame can be moved back and forth through a conductive elastic body on the front side of the cathode as a back plate An electrode unit for a zero gap type electrolytic cell comprising a cathode structure laminated and supported on the electrode unit.   The electrode unit for zero gap type electrolytic cells according to claim 1, wherein the anode is an active electrode in which an active catalyst layer is formed on the surface of a conductive substrate having liquid permeability. .   3. The electrode unit for a zero gap type electrolytic cell according to claim 2, wherein the anode has a rigid structure using a titanium expanded metal or a titanium punching metal having an aperture ratio of 25 to 75% as a conductive substrate, and a catalyst. A zero gap type electrolytic cell electrode unit having a thickness including a layer of 0.7 to 2.0 mm and a maximum difference in height of unevenness on the surface of the catalyst layer of 5 to 50 μm.   The electrode unit for zero gap type electrolytic cells according to any one of claims 1 to 3, wherein the cathode in the cathode structure is a nickel expanded metal having an aperture ratio of 25 to 75% as a conductive substrate having liquid permeability. An electrode unit for a zero gap electrolytic cell, which is an active electrode using nickel punching metal or nickel fine mesh and having an active catalyst layer formed on the surface thereof.   5. The electrode unit for a zero gap type electrolytic cell according to claim 4, wherein the cathode in the cathode structure is a flexible active electrode having a nickel fine mesh as a conductive substrate.   The electrode unit for a zero gap type electrolytic cell according to any one of claims 1 to 5, wherein the conductive elastic body in the cathode structure is a woven mesh formed by mating conductive metal wires into a mat shape. Electrode unit for electrolytic cell.   The electrode unit for zero gap type electrolytic cells according to claim 6, wherein the thin metal wire is a nickel wire having a wire diameter of 0.05 to 0.3 mm.

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