JP3073819B2 - Electrode structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode structure used for salt electrolysis such as a diaphragm method and an ion exchange membrane method, and more particularly, to further improve the activity of an electrode substrate used for salt electrolysis and the like. The present invention relates to an electrode structure that has been made.

[0002]

2. Description of the Related Art Platinum, ruthenium, and the like are used as electrodes for chlorine generation electrolysis such as salt electrolysis on a porous electrode base made of a valve metal such as titanium or a titanium alloy or a valve metal alloy.
Electrodes coated with noble metals or noble metal oxides such as iridium and rhodium are commonly used. The electrode activity of this electrode gradually decreases as the electrolysis time elapses, and finally falls below a predetermined electrode activity required for electrolysis. It is possible to discard such a deteriorated electrode and use a new one. However, usually, the electrode is reactivated to recover the activity to a predetermined level or more and reused. For this reactivation, it is necessary to exfoliate the electrode substance with reduced activity on the electrode substrate by bubbling or the like to expose the electrode substrate, and then to coat the electrode substance. The removal of the material was troublesome, and was not desirable as a method for reactivating the electrode.

[0003] Also, electrolytic cells such as a diaphragm method and an ion exchange membrane method,
In particular, in an electrolytic cell constituted by accommodating an electrode having an open end in a bag-shaped ion exchange membrane, the projection at the open end of the electrode comes into contact with the ion exchange membrane, and the ion exchange membrane is damaged. It's easier. FIG. 1 illustrates a conventional expandable electrode. In this electrode, two insoluble metal plates C made of U-shaped titanium or the like are connected to a power supply rod A erected on the bottom of the electrolytic cell via two flexible thin plates B to form a rectangular shape in a plan view. Have been. This electrode has sharp open ends D at both upper and lower ends. When this electrode is housed in a bag-shaped ion exchange membrane, the open end D comes into contact with the ion exchange membrane and damages the ion exchange membrane. The ion exchange membrane is broken, and the electrolytes in the anode chamber and the cathode chamber are mixed, so that the electrolysis cannot be continued. In order to prevent such a situation, the protrusions at the open end of the electrode base are melted and rounded, and a wire is welded to the open end of the electrode base to prevent direct contact between the electrode base and the ion exchange membrane. For example, a fluororesin tape is wound around the open end to prevent the electrode substrate from directly contacting the ion exchange membrane. Among these methods, there is a drawback that the ion exchange membrane is damaged if the melting is troublesome and the melting is insufficient, and the method is sufficient from the viewpoint of preventing the ion exchange membrane from being damaged, but is processed into a product. However, there is an inconvenience that workability is poor due to the necessity. Further, in the case of a new electrode substrate, it may be desirable to improve the electrode activity depending on the use or the like. For this purpose, conventionally, the surface of the electrode substrate is further coated with an electrode substance.However, even if the coating amount is increased, the activity is slightly improved and the desired activity cannot be obtained. There is a disadvantage that it cannot be returned to.

[0004]

An object of the present invention is to solve the above-mentioned problems of the prior art, to easily improve and change the activity thereof, and to damage the ion exchange membrane even when the ion exchange membrane is used. It is intended to provide a non-electrode structure.

SUMMARY OF THE INVENTION The present invention comprises a porous electrode substrate having an electrode material coated on its surface and having an open end, and a porous active substrate having its surface coated with an electrode material. An electrode structure wherein the tip of the porous active substrate is bent and engaged with at least a part of the open end of the porous electrode substrate to be integrated.

Hereinafter, the present invention will be described in detail. The electrode structure of the present invention is an electrode structure in which a porous active substrate coated with an electrode substance is integrally engaged with a porous electrode substrate such as an expanded mesh or a perforated plate. By doing so, the activity of the entire electrode structure is made higher than that of the electrode base. Further, when used in an electrolytic cell using an ion exchange membrane, the membrane is effectively prevented from being damaged. As the electrode base, a box-shaped insoluble metal plate composed of two U-shaped titanium or the like is provided on a power supply rod provided on the bottom surface of an electrolytic cell that can be mainly used for salt electrolysis via two flexible thin plates. A so-called expandable electrode made of a corrosion-resistant material such as titanium connected can be used, and an electrode of any shape having an open end can also be used. The substrate is coated with an electrode material, for example, a noble metal or noble metal oxide such as platinum, ruthenium, iridium and rhodium. The electrode substrate is usually housed in a bag-shaped ion exchange membrane and is partitioned from the counter electrode.

The electrode substrate to be used in the present invention may be a substrate which has been used and has a reduced activity of the electrode material, or a substrate which has not been used and has a reduced activity of the electrode material. The present invention is particularly useful for reactivating an electrode substrate whose activity has decreased due to the use of the former for a relatively long time. In the former case, the activity of the entire electrode structure can be recovered and reactivated to an unused activity by using an active substrate coated with the same electrode substance as the electrode substrate. In any case, the activity of the entire electrode structure can be made higher or different from the activity of the electrode substrate by engaging the active substrate with the electrode substrate. For this purpose, the electrode substance to be coated on the active substrate may be made a more active substance, or the shape of the electrode substrate may be changed. The following effect of improving the activity can be obtained by the shape change. That is, by substantially increasing the surface area, the load on each part is reduced, and high activation is possible. By changing the shape of the surface, particularly in ion exchange membrane electrolysis, the current density in the ion exchange membrane having a higher resistance than the electrolytic solution can be reduced uniformly and uniformly, and the voltage can be reduced. By changing the surface shape, the supply of the electrolytic solution is substantially increased to change the apparent characteristics. Of these, there is no effect when the electrodes are installed at a sufficient distance in the liquid, but it is particularly important in the ion exchange membrane method electrolysis because the anode and the ion exchange membrane are operated in close contact with each other. .

[0007] The active substrate is formed of a corrosion-resistant material such as titanium similarly to the electrode substrate, and as described above, the electrode material to be coated may be the same as or different from the electrode material coated on the electrode substrate. Since the active base is engaged with the electrode base and does not require strength, it is desirable to reduce the thickness of the active base to reduce material cost and weight. Further, the pore size (opening) of the active substrate is made smaller than that of the substrate in consideration of sufficient evacuation of the generated gas and sufficient supply of the liquid to make the current distribution in the ion exchange membrane more uniform, It is desirable to reduce the voltage. The active substrate may have the same shape, which is slightly larger than the electrode substrate, and a portion corresponding to the open end of the electrode substrate may be bent to engage with the open end so that the active substrate covers the entire surface of the electrode substrate. Although desirable, only a necessary part may be covered. When the electrode substrate has a plurality of open ends, it is not necessary to engage the active substrate with all the open ends, and it is sufficient to engage only the positions necessary for integrating the two. However, when the electrode structure is separated from the counter electrode by using an ion exchange membrane, the bent active substrate is engaged with all the open ends of the electrode structure in contact with the ion exchange membrane, and It is desirable to protect the ion exchange membrane from damage by preventing direct contact with the ion exchange membrane. In other words, when the tip of the active substrate is bent so as to be able to engage with the open end of the electrode substrate, the bent portion necessarily has a rounded shape, and even if the bent portion comes into contact with the ion exchange membrane, the ion exchange membrane may be damaged. Therefore, damage to the ion exchange membrane due to the sharp open end is effectively prevented.

The electrode base and the active base are usually joined by spot welding or the like. However, when the active base is electrically connected to each other at a bent portion or the like, welding is not required. When the two are integrated only with each other, the active substrate can be easily attached to and detached from the electrode substrate. In addition, the above-mentioned wire or tape may be attached to the end of the already used electrode base to protect the ion exchange membrane,
In the conventional electrode structure, a means for preventing detachment of the wire or the like was required, but in the electrode structure of the present invention, the wire or the like was wrapped between the bent portion of the active substrate and the end of the electrode structure. Because it can hold and prevent detachment,
The means for preventing separation is not required.

Next, an example of an electrode structure according to the present invention will be described with reference to the accompanying drawings. FIG. 2 is a partial perspective view showing an example of an electrode structure formed by engaging an active substrate with a new electrode substrate that is an expandable electrode, and FIG.
FIG. 4 is a vertical sectional view taken along the line AA showing an engagement structure between an open end of the electrode substrate and a bent portion of the active substrate in FIG. An electrode material such as a platinum group metal oxide made of a corrosion-resistant material such as titanium in a horizontal U-shape is formed on a power supply rod 1 erected on the bottom surface of an electrolytic cell via two flexible thin plates 2. The coated box-shaped porous electrode substrate 3 is electrically connected, and a sharp open end 4 is formed at the upper and lower ends of the electrode substrate 3.

[0010] A thin porous active substrate 5 having substantially the same shape as the electrode substrate 3 and having a higher activity than the electrode material or coated with the same electrode material is provided around the electrode substrate 3 in contact therewith. An inwardly rounded bent portion 6 is formed at the upper and lower ends of the active base 5 (only the upper end is shown). The bent portion 6 sandwiches the open end 4 and integrally engages the electrode base 3 and the active base 5 while electrically connecting them to each other to supply electricity from the power supply rod 1 to the active base 5. Is possible. Although the pore diameters of the porous electrode substrate 3 and the porous active substrate 5 may be the same, the pore size of the active substrate 5 is determined in consideration of the current distribution in the ion exchange membrane and for uniform electrode reaction. It is desirable to make it smaller. The substrates 3 and 5 need to be porous in order to facilitate the flow of the electrolytic solution. For example, the substrates 3 and 5 have rhombic holes, and the directions of the holes match. If they are brought into contact with each other, the holes may be closed and the flow of the electrolyte may be obstructed. Therefore, it is desirable to connect the two so that the directions are shifted. In the illustrated structure, since the bent portion 6 prevents the open end 4 from contacting the ion exchange membrane, it is not necessary to use an auxiliary member such as a wire or a tape as in the related art.

FIG. 4 is a partial sectional view showing an example corresponding to the engagement structure of FIG. 3 in an existing electrode base, and FIG. 5 is a partial sectional view showing still another example. As shown in FIG. 4, a wire made of a corrosion-resistant material is used to prevent the open end 4 'of the used electrode base 3' having the open end 4 'from directly contacting the ion exchange membrane. 7 is fixed by welding or the like. A bent portion 6 'is formed at the end of the porous active substrate 5', and the open end 4 'is sandwiched between the bent portion 6' and the electrode substrate 3 'and the active substrate 5' are formed in the same manner as in FIG. The electrode structure is constituted by being integrally engaged. In the case of this used electrode substrate, the electrode substrate can be reactivated without being decomposed by the active substrate 5 'coated with a highly active electrode material instead of the electrode substrate 3' inactivated. . When the electrode substance on the active substrate 5 'is deactivated, the engagement between the active substrate 5' and the electrode substrate 3 'is released, and a new active substrate is engaged with the electrode substrate 3' to further activate the electrode. Can be reactivated. In the illustrated electrode structure, the wire 7 is accommodated in the bent portion 6 'and does not come off, so that a stable electrolysis operation can be continued. In the electrode structure of FIG. 5, the wire 7 of FIG.
4 shows an example in which the end of the electrode substrate 3 'is covered with a corrosion-resistant tape 8 made of fluororesin or the like, and the electrode structure is formed by the electrode substrate 3' and the active substrate 5 'in the same manner as in FIG. It is composed.

[0012]

EXAMPLES Next, examples in which the electrode structure of the present invention is used for salt electrolysis will be described, but the electrode structure of the present invention is not limited to these examples.

Example 1 Using the electrode structure shown in FIGS. 2 and 3, the increase and decrease of the electrolytic voltage when an active substrate was used was measured. A plurality of tubular nickel-plated soft iron cathodes were installed so as to be installed between facing wall surfaces in a box-shaped diaphragm type electrolytic cell. Two electrode substrates each having a 1.5-mm-thick horizontal U-shape in which a ruthenium (30 mol%)-titanium (70 mol%) oxide was coated on an expanded mesh titanium substrate were connected to a power supply rod as shown in the figure. . The active substance is coated with the same electrode substance as the electrode substrate, has a plate thickness of 0.5 mm, a hole diameter of 10 mm, and a length of 10 mm. An anode electrode structure was formed by engaging with the end and spot welding to the electrode substrate.

A Nafion 90209 ion exchange membrane manufactured by DuPont is formed in a bag shape, and the electrode structure is accommodated in the ion exchange membrane so that the active substrate is in close contact with the ion exchange membrane. The electrolytic cell was partitioned into an inner anode chamber and an outer cathode chamber by the ion exchange membrane. A 300 g / liter saline solution was supplied into the electrolytic cell, and electrolysis was performed under the conditions of a liquid temperature of 90 ° C. and a current density of 20 A / dm ² . After 24 hours, the electrolysis voltage was 3.045V. The operation was stopped, electrolysis was performed under the same conditions using only the electrode substrate as the anode, and the electrolysis voltage was 3.100 V after 24 hours. From this result, it is understood that the use of the active substrate greatly reduces the electrolytic voltage. Further, continuous operation for one year could be stably performed using the present electrode structure, and no abnormality was observed in the ion exchange membrane.

[0014]

EXAMPLE 2 An electrode similar to that of Example 1 was prepared and this electrode 44
An ion-exchange membrane electrolytic cell was formed from the sheets. For comparison, the same mesh was spot-welded to the same substrate surface by spot welding, and an electrode was prepared that was fitted to the substrate electrode end without bending the end.
A similar electrolytic cell was formed with this electrode. Long-term electrolysis was performed using both electrolyzers under the same conditions as in Example 1. After 6 months of continuous electrolysis, the oxygen in the chlorine generated in the electrolytic cell for comparison is 2
% From 2.5% to 2.5%, and an increase in the concentration of sodium hypochlorite in the anolyte was observed.
A pinhole was observed in the ion exchange membrane corresponding to the end of the electrode, which was considered to be caused by contact with the electrode. On the other hand, there was no change in the electrolytic cell and electrode of this example, and no pinhole was observed in the ion exchange membrane.

[0015]

The present invention comprises a porous electrode substrate having an electrode material coated on its surface and having an open end, and a porous active substrate having its surface coated with an electrode material. An electrode structure wherein the tip of the active substrate is bent and engaged with at least a part of the open end of the porous electrode substrate to be integrated. In the electrode structure of the present invention, the electrode substrate and the active substrate are integrated by engaging the both, so that the deficiency of the electrode activity of the electrode substrate is improved and changed by the electrode activity of the active substrate.
Even when the electrode substrate is already used and the activity of the electrode substance is reduced, the active substrate coated with the electrode substance whose activity has not been reduced is simply coated on the electrode substrate without trouble of peeling the electrode substance. The same effect as the recoating of the electrode material can be produced only by the combination. The active substrate is engaged with the electrode substrate. Since the electrode substrate has a sufficient mechanical strength, the active substrate can have a thin and finer structure. When a membrane is used, a lower voltage and more active electrolysis can be achieved by interaction with the ion exchange membrane. Further, it is also possible to optimize the electrolysis conditions by modifying the electrode shape by selecting a hole diameter or the like.

In the electrode structure of the present invention, since the tip of the active base is bent and engaged with at least a part of the sharp open end of the electrode base, the open end is maintained even when an ion exchange membrane is used. Without contact with the ion exchange membrane, the expensive ion exchange membrane can be protected from damage. In the conventional electrolytic cell, an auxiliary member such as a wire or a tape is provided for protecting the ion exchange membrane, and a means for preventing the auxiliary member from being detached is required. However, these are unnecessary in the electrode structure of the present invention, and Even in the case of installation, since these can be wrapped in the bent portion of the active base for engaging the active base and the electrode structure, a separate detachment preventing means is not required.

[Brief description of the drawings]

FIG. 1 is a partial perspective view illustrating a conventional expandable electrode.

FIG. 2 is a partial perspective view showing an example of an electrode structure configured by engaging an active substrate with a new electrode substrate that is an expandable electrode.

FIG. 3 is a vertical sectional view taken along line AA of FIG. 2, showing an engagement structure between an open end of an electrode substrate and a bent portion of an active substrate.

FIG. 4 is a partial cross-sectional view showing an example corresponding to the engagement structure of FIG. 3 in an existing electrode base.

FIG. 5 is a partial sectional view showing still another example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Power supply rod 2 ... Flexible thin plate 3, 3 '...
Porous electrode base 4, 4 '... open end 5, 5' ...
・ Active substrate 6, 6 ′ ・ ・ ・ Bending part 7 ・ ・ ・ Wire 8 ・ ・ ・ Tape

Claims (6)

(57) [Claims] 1. A porous electrode substrate having a surface covered with an electrode material and having an open end, and a porous active substrate having a surface coated with an electrode material, wherein a tip of the porous active substrate is provided. An electrode structure, wherein the electrode structure is bent and engaged with at least a part of an open end of the porous electrode substrate to be integrated. 2. The electrode structure according to claim 1, wherein the pore size of the porous active substrate is smaller than the pore size of the porous electrode substrate. 3. The electrode structure according to claim 1, wherein the thickness of the porous active substrate is smaller than the thickness of the porous electrode substrate. 4. The electrode structure according to claim 1, wherein the porous electrode substrate is an unused electrode. 5. The electrode structure according to claim 1, wherein the porous electrode substrate is a used electrode. 6. The electrode structure according to claim 5, wherein an auxiliary member is wrapped between the open end of the porous electrode substrate and the tip of the porous active substrate.