JP2974627B2 - Platinum plating method for ion exchange membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of platinum plating an ion exchange membrane used for obtaining oxygen gas and hydrogen gas by electrolyzing water.

[0002] Since water itself is difficult to conduct electricity, conventionally, electrolysis was carried out by placing an electrode in an electrolyte solution such as a sodium hydroxide solution or a potassium hydroxide solution and passing a direct current thereto. With the progress of the technology, water is directly electrolyzed by the ion exchange membrane by utilizing the property that hydrogen ions move in the ion exchange membrane.

[0003]

2. Description of the Related Art In order to form a platinum thin film on the surface of an ion exchange membrane, there is a method in which prepared platinum catalyst fine particles are formed into a film with a binder and then pressure-bonded by heat.
0 to 50 [mu] m, the adhesive force was weak, and the electrical resistance was high and the ohmic loss was large.

The inventor of the present invention has previously filed a patent application (Japanese Patent Application No. 8-206476) as a method of directly plating platinum on an ion-exchange membrane in order to improve the above-mentioned disadvantages.

In this method, platinum plating is extremely thin,
The adhesion was also good by the ultraviolet irradiation etching, and the surface electric resistance was reduced to several hundred Ω / cm.

However, as a new problem to be improved, platinum plating is a method in which both surfaces are simultaneously formed. Therefore, technical skills are required to obtain uniform plating on both surfaces, and platinum plating is an ion-implanting method. Adheres to the entire surface of the exchange membrane,
In the water electrolyzer, the ion exchange membrane is attached to an electric insulating frame, but a surface that actually contacts water and is related to electrolysis is a surface in the electric insulating frame, and platinum plating is applied only to this portion. Since the necessary frame portion is wasted and is an expensive material, there are disadvantages such as an economic problem.

[0007]

The problems to be solved with respect to the method of platinum plating an ion exchange membrane used for obtaining oxygen / hydrogen gas by electrolyzing water are as follows. The goal is to reduce the ohmic loss with a surface electrical resistance of several ohms / cm or less by plating directly on the ion exchange membrane surface.

[0008] The goal is to allow the front and back plating to adhere to the same surface electrical resistance with the same plating thickness.

[0009] A plating area is a goal of enabling plating only on a required surface and improving the economical efficiency relating to plating.

[0010] The contents described above are issues required for the development of a porous plating method which has a strong adhesion to an ion exchange membrane and is porous.

[0011]

In order to achieve the above-mentioned object, the present invention relates to a method for applying effective platinum plating to both surfaces of an ion-exchange membrane according to the present invention. (A) First, the ion-exchange membrane 8 is roughened using sandblasting or a fine abrasive, and then treated with hot water in a boiling pure water solution.
And then subjected to a sensitivity treatment in a tin chloride (SnCl ₂ ) solution,
(C) Thirdly, an activation treatment in a palladium chloride (PdCl ₂ ) solution, and (d) fourthly, a sensitivity treatment in a tin chloride solution → an activation treatment procedure in a palladium chloride solution (E) Fifth, after a reduction treatment in a hydrazine monohydrate (H ₂ NNH ₂ .H ₂ O) solution, a transparent top lid plating cell 4, a sample stage 2. Using the immersion cell type plating apparatus 1 composed of the clamp 5, the ion exchange membrane 8 after the reduction treatment is placed on the sample table 2, the upper lid-like plating cell 4 is covered thereon, and the sample table 2 is clamped with the clamp 5. And the upper lid-shaped plating cell 4 are tightened. A chloroplatinic acid (H ₂ PtCl ₆ ) solution 13 is poured from a liquid inlet 6 provided in the upper lid-shaped plating cell 4. And the state in which the chloroplatinic acid solution 13 is deposited in a stationary state I, to allow the observation of the plated surface from the outside of the upper cover-like plating cell 4, platinum plating method to the ion-exchange membrane, characterized in that the platinum plating.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

(A) In order to improve the adhesion of plating, the surface of the ion exchange membrane is roughened. In general, sandblast used for removing rust on the metal surface is used, and fine glass beads are used at 3 to 5 kgf / cm. ^At a pressure of ² , spray from a distance of 20 to 30 cm, spray the abrasive on the polishing plate using a fine abrasive or spray for 1 to 2 minutes so that the transparent film becomes a ground glass opaque state, Place the ion-exchange membrane on top of it, move the flat plates together to roughen the ion-exchange membrane, but simply apply a detergent containing abrasive to the sponge and rub the surface evenly and lightly to polish the surface. If platinum plating is performed on both surfaces of the ion exchange membrane, it is necessary to perform the surface roughening. After polishing, both surfaces are thoroughly washed with a detergent and washed with water.

(B) Next, it is immersed in a boiling bath for 1 to 2 hours, and boiled to discharge impurities contained in the ion exchange membrane.

(C) Then, a method is adopted in which the filter is immersed in a tin chloride (SnCl ₂ ) solution and a filter is provided in the middle of the circulation by a pump to constantly remove impurities generated in the solution.
Then, withdraw from the bath and wash.

(D) Next, palladium chloride (PdC)
l ₂ ) It is immersed in a solution, circulated by a pump, and provided with a filter in the middle to constantly remove impurities generated in the solution.

(E) The above steps of immersion in a tin chloride solution, washing with water, immersing in a palladium chloride solution, and washing with water are repeated two or three times to deposit palladium on the ion exchange membrane.

(F) Next, the sample is immersed in a hydrazine monohydrate (H ₂ NNH ₂ .H ₂ O) solution as a reducing agent, and the mixture is stirred and the concentration is made uniform by rotating a stirrer with a magnetic stirrer. After the immersion for a required time, pull up from the liquid and wash with water.

(G) Sample table 2 of immersion cell type plating apparatus 1
The sample stage 2 is a flat plate made of plastic such as vinyl chloride, and a flat packing 3 is laid on the upper surface thereof. Silicon rubber, viton rubber, or the like is used as a packing material. The transparent upper-plated plating cell 4 comprises a transparent upper lid-shaped plating cell 4 and a fastening tool 5. The transparent upper-lid-shaped plating cell 4 is a box-shaped or tea-tube-shaped upper lid-shaped plastic made of vinyl chloride or the like. The upper surface is made of a transparent material to enable observation. The upper surface is provided with a liquid inlet 6 and an air vent 7, and
The transparent top lid-like plating cell 4 is covered on the ion exchange membrane 8 placed on the sample table 2, and the transparent top lid-like plating cell 4 is fixed to the sample table 2 by press-fitting with a fastening tool 5.
Any method may be used as long as the plating cell 4 can be fixed to the sample table 2 by pressure bonding. Use of a screw, use of a spring, use of air pressure, or the like is considered. In FIG. This is an example in which the wing nut 11 is tightened using an L-shaped fitting to press the plating cell 4 against the sample table 2 and fix it by pressure bonding.

(H) A funnel 12 is attached to the injection port 6, a chloroplatinic acid solution 13 is charged at a required liquid level, and left, and small bubbles (hydrogen gas) are generated on the surface of the ion exchange membrane 8.
It can be observed that the platinum is plated and the surface changes to a platinum color. The chloroplatinic acid solution 13 in the initial stage of the injection is yellow, but with the progress of the platinum plating, the color disappears and eventually becomes colorless. At this point, the immersion cell type plating apparatus was tilted, drained from the air vent 7, the fastener 5 was loosened, the plating cell 4 was removed, and the platinum-plated ion exchange membrane 8 was placed on the sample stage. Remove from 2 and wash with water while gently rubbing the plating surface with a sponge.

(I) The surface resistance of the plated surface is measured, and if it is within the required value, the plating is completed.

(V) If the value is less than the required value, the substrate is immersed again in a hydrazine-hydrate solution, and the platinum plating process is repeated with an immersion cell type plating apparatus to obtain the required value.

(L) The above is the step of platinum plating on one side. In the case of plating platinum on both sides, similarly, after immersing in a hydrazine-hydrate solution, washing with water,
The platinum-plated surface is placed on the sample stand 2 with the surface not plated with platinum facing up, the plating cell 4 is attached, the required level of the chloroplatinic acid solution 13 is charged, and platinum plating is carried out.
-(Nu).

[0023]

The present invention is embodied in the form described above and has the following effects.

According to the present invention, the roughening of the pretreatment of the ion-exchange membrane contributes to the improvement of the adhesion of the platinum plating, and its effect is judged by the "plating adhesion test method" (J
When the adhesion of platinum plating was examined by the “tape test method” described in ISH8504), it was found that the adhesion was good without peeling of the plating.

In the conventional method, although platinum plating can be performed simultaneously on both surfaces, there is a time saving, but technical skill is required to finish plating with the same performance.

On the other hand, in the present invention, platinum plating can be performed on one side at a time, and replating can be repeated until the required performance is reached. Therefore, it is extremely easy to make the performances on both sides uniform.

The area of the ion-exchange membrane to be plated with platinum is determined by the dimensions of the plating cell, and if this dimension and area are combined with the dimensions of the electric insulation frame of the water electrolyzer, the desired required area can be obtained. Only platinum plating is easy,
Platinum plating on unnecessary parts has been eliminated, which has helped to improve the economic efficiency of platinum plating.

By repeating the platinum plating step, the surface resistance can be reduced to a low resistance value of several Ω / cm or less, and the surface area of the platinum plating increases due to the rough surface ratio. The ohmic loss at the time of heating became extremely small, and even when a large current was passed, the calorific value could be reduced. When it was incorporated into the apparatus and the durability under actual use conditions was determined, the plating film did not peel off due to gas generation, and the increase in ohmic loss was 90%.
Not detected until 00 hours.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of an immersion cell type plating apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Immersion cell type plating apparatus 2 Specimen stand 3 Packing 4 Top-plated plating cell 5 Clamping tool 6 Injection port 7 Air release 8 Ion exchange membrane 9 Screw 10 L-shaped fitting 11 Wing nut 12 Funnel 13 Chloroplatinic acid solution

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Taniguchi 5-4-1-14 Shinjuku, Shinjuku-ku, Tokyo Suga Test Equipment Co., Ltd. Examiner Koichi Kimura (58) Field surveyed (Int. Cl. ⁶ , DB Name) C23C 18/00-18/54

Claims (1)

(57) [Claims] The present invention relates to a method of platinum plating an ion-exchange membrane used for electrolysis of water. (A) First, after roughening the ion-exchange membrane 8 using sandblasting or fine abrasive, a pure water boiling liquid is obtained. (B) secondly, a sensitizing treatment in a tin chloride (SnCl ₂ ) solution, and (c)
Third, an activation treatment is performed in a palladium chloride (PdCl ₂ ) solution. (D) Fourth, a sensitizing treatment in a tin chloride solution → the activation treatment in a palladium chloride solution is performed in two steps. 3
(E) Fifth, after a reduction treatment in a hydrazine monohydrate (H ₂ NNH ₂ .H ₂ O) solution, a transparent top lid-shaped plating cell 4, a sample table 2, and a fastening tool The ion-exchange membrane 8 after the reduction treatment is placed on the sample stage 2 by using the immersion cell type plating apparatus 1 composed of chloroplatinic acid (H _2). PtCl ₆ )
The solution is poured, and the ion exchange membrane 8 forms the horizontal bottom surface of the upper lid-shaped plating cell 4, and the chloroplatinic acid solution 13 is kept stationary on the ion exchange membrane 8. Platinum plating method for ion-exchange membrane, characterized in that platinum plating is possible.