JP3092771B2 - Electrolytic cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic cell for producing a gas such as hydrogen or chlorine by a diaphragm electrolysis method.

[0002]

2. Description of the Related Art Heretofore, as one type of such an electrolytic cell, there has been used an electrolytic cell in which a plate-like electrode made of carbon fiber having a space through which an electrolytic solution can flow is closely attached to both surfaces of a thin film-like diaphragm. However, in order to reduce power consumption during electrolysis, an activation overvoltage is reduced by carrying a catalyst on an electrode. Examples of such a supporting form include a method in which a catalyst is directly supported on the plate-like electrode through which an electrolyte can flow, and a method in which the catalyst is supported on a thin carbon sheet. Method of sandwiching the catalyst electrode between the diaphragm and the plate electrode
No. 50490) is known.

[0003]

However, when a catalyst is directly supported on a plate-like electrode, the electrode used in the conventional electrolytic cell has a reaction permeation to the inside of the felt-like electrode. The generated gas stayed in the electrode, and the generated gas reduced the apparent conductivity of the electrolytic solution and increased the voltage drop in the electrolytic solution. This voltage drop occurs in the thickness direction of the plate electrode,
The electrode reaction was concentrated in the vicinity of the diaphragm, and the catalyst was not effectively used in a portion far from the diaphragm.

[0004] When an expensive catalyst such as a platinum group metal is used as a catalyst, it is a major problem that the catalyst is not effectively used. There is a problem that a process is required and the production cost increases.

A method of sandwiching a carbon sheet carrying a catalyst between a diaphragm and a plate-like electrode also involves a method in which a gas generated inside a carbon sheet composed of carbon fibers stays and a voltage generated by an electrolytic solution is similarly increased. There has been a problem that the drop increases, that is, the electrolytic voltage increases and the power consumption increases. Therefore, an object of the present invention is to provide an electrolytic cell capable of reducing the electrolysis voltage by using an electrode in which gas does not easily remain in the electrode, and further reducing the amount of catalyst used by effectively using an expensive catalyst. And

[0006]

In order to solve the above-mentioned problems, an electrolytic cell according to the present invention comprises a plate-like electrode made of carbon fiber having a space through which an electrolytic solution can flow, which is closely attached to both surfaces of an ion exchange membrane. In an electrolytic cell having these sandwiched between end plates, at least one between the ion-exchange membrane and the electrode is provided with a space through which an electrolyte can flow, made of carbon fiber, carrying a catalyst, and A carbon sheet having a number of slits in the direction is interposed. As a carbon sheet composed of carbon fibers and having fine voids, carbon felt, carbon cloth, and the like can also be used. Further, as the slit, a linear, downward dendritic, or other shape is used. As the ion exchange membrane, an anion exchange membrane or a cation exchange membrane can be selected according to the purpose of the reaction. The electrolytic cell of the present invention may be used singly, or may be stacked in series to form a filter press type cell.

[0007]

In the above means, the carbon sheet serving as the electrode functions as a reaction layer, and the gas generated by the electrolysis is released through the slit of the electrode, so that the electrolysis voltage can be reduced and the electrolysis efficiency can be improved. At the same time, all the supported catalysts can be used effectively.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing one embodiment of the electrolytic cell of the present invention. In this electrolytic cell, an anode electrode 2 made of carbon felt is arranged in close contact with one side of an ion exchange membrane (cation exchange membrane) 1 and an ion exchange membrane (cation exchange membrane) 1
As shown in FIG. 2, a carbon sheet 4 having a large number of slits 3 in the vertical direction is interposed and a cathode electrode 5 made of carbon felt is placed in close contact with the remaining one side, and these are connected to anolyte inlets and outlets 6a, 6b. And an anode-side end plate 6 having a catholyte inlet and outlets 7a and 7b.

[0009] Here, as shown in FIG.
0.3mm thick carbon sheet 1 with 16 slits 9 of 2mm width and 230mm length at equal intervals in the area excluding 10mm height 9mm width around 200mm carbon sheet 8
(Example) and 0.56 mg / cm ² of platinum (Pt) as a catalyst were supported on each of a carbon sheet (comparative example 1) having a thickness of 250 mm and a width of 200 mm without slits and a thickness of 0.3 mm (Comparative Example 1). A catalyst-attached carbon sheet for Example 1 was produced. The catalyst is supported by diluting an organic solvent with a chloroplatinic acid solution.
(In this embodiment, 2-propanol is diluted with pure water)
Each of the carbon sheets was impregnated and supported with the chloroplatinic acid diluted solution to which was added, and then subjected to hydrogen reduction.

[0010] A carbon sheet with a catalyst and a carbon sheet without a slit (both 0.56 mg / cm ²
(Pt supported) was used in the above-mentioned electrolytic cell, and an electrolysis experiment was carried out simultaneously under the following conditions.
It became as shown in. (Electrolysis conditions) Temperature: 60 ° C Anolyte: 1.0 mol / l FeSO ₄ , 0.5 mol / l H ₂ SO
₄ aqueous solution Catholyte: 0.5 mol / l H ₂ SO ₄ aqueous solution Electrolysis method: constant current electrolysis 50, 100 A (100, 200 mA / cm ²
Anode and cathode: 5mm thick carbon felt

FIG. 4 shows that when electrolysis was performed at 100 mA / cm ² , there was almost no difference in the electrolysis voltage.
^At the current density of ^2, the electrolysis voltage of the carbon sheet with slits is about 0.07 V lower than that of the carbon sheet without slits. This is because in the electrolytic cell of the present invention, the gas staying in the vicinity of the electrode is effectively exhausted from the slit, and the effect is apparent at a high current density where a large amount of gas is generated.

Further, the same carbon sheet with a slit having a catalyst as described above (supporting 0.56 mg / cm ² Pt) (Example) and 0.56 m
g / cm ² Pt-supported (Comparative Example 2) and 1.5 mg / cm ² Pt-supported (Comparative Example 3) carbon felts with catalyst were used for the electrolytic cell under the same conditions as above (except that the current density was 100 A (200 mA / c).
(equivalent to m ² )), and the change with time in the electrolysis voltage was as shown in FIG.

FIG. 5 shows that the electrolytic cell of the present invention using the catalyst-carrying carbon sheet with slits has the same performance as the electrolytic cell using the catalyst-carrying carbon felt as an electrode with a platinum amount of 1/3. It can be seen that the platinum catalyst supported on the carbon sheet was effectively used.

Next, as shown in FIG.
5mm in diameter excluding 20mm around the carbon sheet 10mm
Holes (punches) 11 at 10mm intervals in 17 rows and 22 rows total 374
A holed carbon sheet 10 having the same catalytic effective area as that of the slitted carbon sheet of the example was produced, and platinum (Pt) was added in the same manner as described above to 0.56 mg / cm ² of platinum (Pt).
The supported catalyst electrode was prepared as an electrode of Comparative Example 4. A carbon sheet with a catalyst and a slit (0.56 mg / cm ² Pt supported) (Example) and a 0.36 mm thick carbon sheet with a catalyst-carrying hole supporting 0.56 mg / cm ² Pt (Comparative Example 4) were used in the electrolytic cell. Use the same conditions as above (except that the current density is 100A
(200mA / cm ² equivalent) only)
The change with time of the electrolysis voltage was as shown in FIG. FIG.
This indicates that the electrolysis voltage of the slit is 0.04 to 0.07 V lower than that of the pores, and that the electrolytic cell having the slit carbon sheet can obtain a more efficient reaction. This is because the slit is easy for gas to escape upward,
It is conceivable that the vacancies caused gas retention above each of the holes, making it difficult to escape.

From the above, it can be seen that the electrolytic cell of the present invention is more effective in reducing the amount of catalyst carried on the electrode and the power consumption.

In the above embodiment, the case where platinum is used as the catalyst supported on the carbon sheet used in the electrolytic cell of the present invention has been described. However, the present invention is not limited to this. For example, gold, silver, A simple substance such as palladium or rhodium, an alloy, an oxide, or the like may be used as a catalyst.
Further, the slit is not limited to a linear shape in the up-down direction, but may be a tree-like shape facing downward, or a shape in which gas can easily escape.

[0017]

As described above, according to the electrolytic cell of the present invention, the carbon sheet functions as a reaction layer, and the gas generated by electrolysis is released through the slit. The retention can be reduced, the amount of the catalyst can be significantly reduced as compared with the related art, and the electrolysis can be performed at a low electrolytic voltage, and the power consumption can be reduced. Especially when many electrolytic cells of the present invention are stacked in series,
The effect due to the reduction in the electrolytic voltage is further increased, and greatly contributes to the reduction in power consumption.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the electrolytic cell of the present invention.

FIG. 2 is a front view of a slitted carbon sheet used in the electrolytic cell shown in FIG.

FIG. 3 is a front view of a carbon sheet with holes used in Comparative Example 4.

FIG. 4 is an explanatory diagram showing a change with time of an electrolytic voltage in an electrolytic cell using a carbon sheet with and without a slit with a catalyst.

FIG. 5 is an explanatory diagram showing a change over time of an electrolytic voltage in an electrolytic cell using a carbon sheet with a slit with a catalyst and a carbon felt with a conventional catalyst.

FIG. 6 is an explanatory diagram showing a change with time of an electrolytic voltage in an electrolytic cell using a carbon sheet with a slit with a catalyst and a carbon sheet with a hole with a catalyst.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cation exchange membrane 2 Anode electrode made of carbon felt 3 Slit 4 Carbon sheet with pores with catalyst 5 Cathode electrode made of carbon felt

Claims (1)

(57) [Claims] 1. An electrolytic cell comprising: a plate-like electrode made of carbon fibers having a void through which an electrolyte can flow; At least one between the membrane and the electrode is provided with a space through which an electrolyte can flow, a carbon sheet made of carbon fiber, carrying a catalyst, and having a number of vertical slits inserted therein. An electrolytic cell characterized by the following.