JP3022458B2 - 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 for plating platinum on an ion exchange membrane used in a hydrogen / oxygen generator by electrolysis of water or an ozone generator by electrolysis of water.

[0002]

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 μm, and there is a defect that adhesion is weak, electric resistance is large, and ohmic loss is large.

[0003] Therefore, since platinum plating cannot be performed directly on an ion exchange membrane, palladium or a platinum catalyst must be present on the ion exchange membrane. Therefore, the ion-exchange membrane is subjected to a sensitizing treatment in a tin chloride solution, an activation treatment in a palladium chloride solution, a reduction treatment in a hydrazine monohydrate solution, and then a non-treatment in a chloroplatinic acid solution. There is a method of electroplating platinum (Japanese Patent Application No. 8-29)
No. 4383). In this case, the palladium remaining in the film becomes a hindrance to ozone generation in the ozone generator, and has a drawback that the generated concentration is significantly reduced. Further, the surface electric resistance of the ion-exchange membrane surface was about 5 × 10 ⁻³ Ωcm, which was difficult.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ion-exchange membrane with a platinum plating and a surface electric resistance of 5 × 10
^The purpose is to produce an ion exchange membrane having a high generation ability by reducing the ohmic loss to ^-5 Ωcm or less, and at the same time, preventing the obstruction of ozone generation by foreign metals such as palladium .
You .

Another object of the present invention is to make it possible to attach the same surface electric resistance to the same surface layer with the same plating layer for the front and back plating .
You.

[0006] Further, the plating area allows plating only on the required surface, thereby improving the economics involved in plating.
That is .

[0007]

In order to achieve the above-mentioned object, the present invention provides a method for applying an effective platinum plating to an ion-exchange membrane by (a) first forming the ion-exchange membrane by sandblasting or a fine abrasive. After the rough surface treatment, a hot water treatment in a boiling pure water solution is performed. (B) Secondly, after drying, the inside of the vacuum vessel reaches a predetermined degree of vacuum with a sputtering device, and then argon gas is supplied to the vacuum vessel. And the pressure is brought to around 10 ^-1 Pa,
A glow discharge is generated between the platinum target and the substrate on which the ion-exchange membrane is mounted, and argon cations are accelerated, collide with the platinum target, cause sputtering, and the platinum atoms released from the target are opposed to this. Make a thin film by attaching it to the ion exchange membrane on the substrate
(C) Third, the ion-exchange membrane after platinum deposition is heat-treated in pure water and hot water, and (d) fourth, hydrazine monohydrate (H
After the reducing agent treatment with ₂ NNH ₂ · H ₂ O) solution, (e) Fifth, plating frame, the sample stage, using the immersion cell type plating apparatus consisting fastener, after the reducing agent treatment on the sample stage Is placed on the ion exchange membrane, and the plating frame is placed on it and fixed to the sample table with the fastener. The chloroplatinic acid (H ₂ PtCl ₆ ) solution is poured on the ion exchange membrane surface in this frame, and the ion exchange membrane is leveled. A platinum plating method for an ion-exchange membrane, characterized in that platinum is applied to an ion-exchange membrane while maintaining a state in which the chloroplatinic acid solution is deposited in a stationary state on a bottom surface.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (a) In order to improve the adhesion of plating, the surface of an ion exchange membrane is roughened, and sand blasting, which is generally used for removing rust on metal surfaces, is used.
Fine glass beads at a pressure of 3-5 kgf / cm ² ,
Spray from a position 20 to 30 cm away, spray for 1 to 2 minutes so that the transparent film becomes frosted glass-like opaque state, or scatter the abrasive on the polishing plate using fine abrasive, Place the plate on top of it and move it to roughen the ion exchange membrane, but simply put a detergent containing abrasives on the sponge and rub the surface evenly and lightly to roughen the surface. After polishing, it can be washed well with detergent and washed with water.

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

(C) After boiling, the moisture of the ion exchange membrane 2 is extracted with a blotting paper or the like and air-dried.

(D) The dried ion-exchange membrane 2 is placed on a substrate in a vacuum chamber of a sputtering apparatus. Activate the vacuum pump, and when the degree of vacuum arrives between 10 ^{-3 and} 10 ^-4 Pa, introduce argon gas into the vacuum vessel, keep the pressure near 10 ^-1 Pa, and maintain the pressure between the platinum target and the substrate. Glow discharge is started during that time to accelerate argon cations. The accelerated argon cation collides with a platinum target, causing sputtering, releasing platinum atoms from the target, and attaching it to an ion exchange film on a substrate to form a platinum thin film.
The adhesion amount is 5 to 0.2 mg / cm ² .

(E) The ion-exchange membrane after the platinum deposition is subjected to a heat treatment in pure water and hot water to return to a state in which moisture is sufficiently absorbed for electroless plating.

[0013] The (f) Hydrazine monohydrate as a reducing agent _{(H 2 NNH 2 · H 2} O) was immersed in the solution, the solution in the rotation of the stirrer by magnetic stirrer so that the concentration of the solution keeping the uniform After stirring and immersing for a required time, it is pulled out of the liquid and washed with water.

(G) Sample table 4 of immersion cell type plating apparatus 1
Then, the ion-exchange membrane 2 after the treatment (f) is placed thereon. The sample stage 4 is a flat plate made of plastic such as vinyl chloride, and a flat plate packing is laid on an upper surface thereof. Silicon rubber, vidone rubber, or the like is used as a packing material. The plating frame 3 is placed on the ion exchange membrane 2, and the plating frame 3 is fixed to the sample table 4 by the fastener 5. The plating frame 3 is made of plastic such as vinyl chloride and has a rectangular frame shape, and a packing material is adhered to a bottom edge of the frame. The fastening tool 5 may be any method as long as the plating frame 3 can be fixed to the sample table 4 with the ion exchange membrane 2 interposed therebetween. FIG. 1 shows an example in which a plating frame 3 is pressed and fixed to a sample table 4 by tightening a wing nut 10 using an L-shaped bracket 9 using a screw 8.

(H) A required amount of a chloroplatinic acid solution is injected into the ion exchange membrane 2 in the plating frame and allowed to stand. Generation of small bubbles (hydrogen gas) is seen on the surface of the ion exchange membrane, and platinum is plated to change the surface to a platinum color. As the platinum plating progresses, the color of the solution disappears from yellow and eventually becomes colorless and transparent, indicating the end of the platinum plating. At this point, the plating solution is discharged, the fastener 5 is loosened, the plating frame 3 is removed, and the platinum-plated ion exchange membrane 2 is removed from the sample table 4. Rinse the plating surface lightly with a sponge.

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

(V) If the value is less than the required value, the substrate is immersed again in a hydrazine monohydrate solution, and the steps of platinum plating in an immersion cell type plating apparatus are repeated to obtain the required value.

(L) The above is a platinum plating process on one side. When platinum plating is performed on both surfaces, the surface is similarly immersed in a hydrazine monohydrate solution, washed with water, and the surface not subjected to platinum plating is raised. After mounting the plating frame and mounting a required amount of chloroplatinic acid solution in the frame, platinum plating is performed. Subsequent steps are the above (h)-
It is as (nu).

[0019]

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

Conventionally, as a pretreatment for platinum plating, a sensitizing treatment in a tin chloride solution and then an activation treatment in a palladium chloride solution were required. Instead, platinum deposition by platinum sputtering was performed. by this,
For ion exchange membranes conventionally used in ozone generators,
On the anode side, tin or palladium metal, which is originally unnecessary, is
The adverse effects of remaining in the on-exchange membrane were eliminated .

That is , as the ion exchange membrane of the ozone generator, lead dioxide is charged on the anode side as an ozone generation catalyst.
The attached anode power feeder is in close contact with the surface, but if there is palladium or platinum in the ion exchange membrane in contact with this surface, the ozonation rate will drop extremely, and in some cases, a phenomenon in which ozone is not generated will occur. Only the occurrence may be seen. According to the present invention, there is no fear that a metal other than platinum may enter, so that there is no concern about this phenomenon. Therefore, an ion exchange membrane having high ozone generation efficiency can be easily formed.

Although the surface resistance of the platinum film surface was about 5 × 10 ⁻³ Ωcm even when the plating process was repeated, it was confirmed that according to the present invention, the surface resistance could be 5 × 10 ⁻⁵ Ωcm or less. . In the deposition of platinum on the surface of the ion exchange membrane by sputtering, the ion exchange membrane is in a state in which the moisture in the membrane evaporates due to the reduced pressure in the vacuum vessel, and the dimensions of the membrane shrink. Since platinum atoms are attached here, a thin film (0.1
μm or less), but the surface resistance is extremely small, 5 ×
It indicates a short-circuit state of 10 ⁻⁵ Ωcm or less . However, when this is heat-treated in pure hot water, water is taken into the ion exchange membrane and the dimensions are expanded and stretched. Therefore, the platinum film is cut off and loses its connection, and the surface resistance becomes about 5 Ωcm. However, this platinum is used as a base material, the mutual bonding is regenerated by the subsequent platinum plating, and the plating layer also grows thick, and the surface resistance 5
It becomes a platinum film of × 10 ⁻⁵ Ωcm or less .

Since the surface resistance is small, the heat loss caused by the current flowing to electrolyze the water, that is, (current) ² × resistance is reduced, and the amount of generated heat can be reduced.
Power consumption has decreased.

[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 Ion exchange membrane 3 Plating frame 4 Sample stand 5 Clamping tool 6 Chloroplatinic acid solution 7 Packing 8 Screw 9 L-shaped fitting 10 Wing nut

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-193381 (JP, A) JP-A-58-185790 (JP, A) JP-A-58-185789 (JP, A) (58) Field (Int. Cl. ⁷ , DB name) C23C 18/00-18/54

Claims (1)

(57) [Claims] The present invention relates to a method for performing platinum plating on the surface of an ion exchange membrane of a hydrogen / oxygen generator by electrolysis of water using an ion exchange membrane 2 or an ozone generator by electrolysis of water. The surface of the ion-exchange membrane 2 is roughened using sandblasting or fine-grain abrasive, and then subjected to hot water treatment in a boiling water of pure water. (B) Secondly, after drying, the inside of the vacuum vessel is sputtered with a sputtering device. After arriving at a predetermined degree of vacuum, an argon gas is introduced into the vacuum vessel, the pressure is set at about 10 ^-1 Pa, and a glow discharge is generated between the platinum target and the substrate on which the ion exchange membrane is mounted, thereby forming argon cations. Accelerate
Collision with a platinum target, causing sputtering,
The platinum atoms released from the target are attached to the ion-exchange membrane 2 on the substrate located opposite thereto to form a thin film. (C) Thirdly, the ion-exchange membrane 2 after platinum deposition is placed in pure hot water. then subjected to heat treatment, (d) fourth, after the reducing agent treatment with hydrazine monohydrate _{(H 2 NNH 2 · H 2} O) solution, to the 5 (e), the plating frame 3, the sample stage 4, Using the immersion cell type plating apparatus 1 including the fasteners 5, the ion exchange membrane 2 after the reducing agent treatment is placed on the sample table 4, the plating frame 3 is placed thereon, and the sample is fixed to the sample table 4 with the fasteners 5. Chloroplatinic acid (H ₂ PtCl ₆ ) is applied to the surface of the ion exchange membrane 2 in this frame.
A solution is poured, and the ion exchange membrane 2 is formed as a horizontal bottom surface, and the chloroplatinic acid solution is deposited on the ion exchange membrane 2 in a stationary state, and platinum plating is performed on the ion exchange membrane 2. Platinum plating method.