WO2008065727A1

WO2008065727A1 - Process for producing electrode with platinum film

Info

Publication number: WO2008065727A1
Application number: PCT/JP2006/325980
Authority: WO
Inventors: Kazuhide Nagano
Original assignee: Shimane Prefectural Government
Priority date: 2006-11-28
Filing date: 2006-12-26
Publication date: 2008-06-05
Also published as: JPWO2008065727A1; JP5071741B2; TW200824170A; TWI383529B

Abstract

This invention provides a process for producing an electrode with a platinum film, which is useful as a counter electrode of a dye-sensitized solar cell. The process for producing an electrode with a platinum film is characterized by comprising successively carrying out (a) the step of providing a cathode, an anode, an electrolysis solution, and a power supply, wherein a substrate with an electroconductive film stacked thereon is provided as the cathode and an aqueous platinum solution having a pH value of 2 or more is provided as an electrolysis solution, (b) the step of connecting the cathode to a negative electrode in the power supply, connecting the anode to a positive electrode in the power supply, immersing both the electrodes in the electrolysis solution, applying voltage across the electrodes for electroplating to form a platinum film on the electroconductive film in the cathode, and (c) the step of taking out the cathode with the platinum film formed thereon.

Description

Method for producing electrode having platinum film

Technical field

The present invention relates to a method for producing an electrode having a platinum film, and more particularly to a method for producing an electrode having a platinum film useful as a counter electrode of a dye-sensitized solar cell.

Background art

[0002] A new type of dye-sensitized solar cell announced by Gretzell et al. Of Lausanne University of Technology in 1991 in Switzerland is less expensive than conventional silicon solar cells. Since the manufacturing process is relatively simple, there is a possibility that manufacturing costs can be greatly reduced, and practical application is expected.

[0003] In such a dye-sensitized solar cell, an oxidation-reduction pair (for example, I-, Γ, etc.) present in the electrolytic solution rapidly reacts on the surface of the electrode with the acid strength (for example, I + 2e— = 3Γ

3 3

There is a need for a counter electrode with a catalytic function. As this counter electrode, a material in which a highly catalytic white metal is supported on a conductive substrate provided with a conductive film [for example, indium stannate] or SnO] is often used. As a method for supporting platinum, a sputtering method (see Patent Document 1) and a vapor deposition method (see Patent Document 2) are generally used. However, these methods require equipment with a large vacuum chamber when considering mass production and large area, and the productivity is low and the equipment costs are high, so the manufacturing cost is not reduced. . In addition, it has been reported that counter electrodes produced by these methods are not durable because platinum dissolves in iodine electrolyte.

[0004] As another method, Patent Document 3 discloses a method in which platinum particles are supported on the surface of a conductive layer by electric plating. However, this method is considered to have a problem in durability because of low adhesion strength because platinum particles are supported by the particles. In addition, this method uses a strong acid called nitric acid as the electrolytic solution, and in the electroplating under such strong acidity, a substrate using a conductive film weak in acid (for example, ITO, SnO, etc.) or a metal substrate, There are problems such as dissolution and substrate dissolution.

[0005] In addition, in the case of performing electrical plating or electroless plating on a metal material, the surface of the metal material is oxidized. The membrane must be removed by acid treatment, etc., the pretreatment process is complicated, harmful substances are generated, and there are environmental problems.

[0006] Patent Document 1: Japanese Unexamined Patent Publication No. 2000-173680

Patent Document 2: Japanese Unexamined Patent Publication No. 2000-36330

Patent Document 3: Japanese Patent Laid-Open No. 2003-36897

Disclosure of the invention

[0007] The present invention has been made to solve the above-described problems in the prior art, and a method for producing an electrode having a more excellent platinum film, particularly a platinum film useful as a counter electrode of a dye-sensitized solar cell. It is an object of the present invention to provide a method for manufacturing an electrode having the following.

[0008] As a result of repeated studies to solve the above problems, the present inventors have performed electroplating using a platinum aqueous solution having a pH of 2 or more as an electrolytic solution, thereby providing sufficient adhesion strength on the conductive film. The present invention was completed by finding that uniform and uniform platinum was formed into a film.

That is, the method for producing an electrode having a platinum film of the present invention includes:

(a) a step of preparing a cathode, an anode, an electrolytic solution and a power source, a step of preparing a substrate on which a conductive film is stacked as a cathode and a platinum aqueous solution having a pH of 2 or more as an electrolytic solution;

(b) by connecting the cathode to the negative electrode of the power source, connecting the anode to the positive electrode of the power source, and immersing both electrodes in the electrolyte and applying a voltage between the two electrodes to perform electrical measurement. Forming a platinum film on the conductive film of the negative electrode; and

(c) removing the cathode on which the platinum film is formed,

Are performed in order.

[0010] Further, the present invention is characterized in that an electrode produced by the method is used as a counter electrode of a dye-sensitized solar cell.

[0011] According to the present invention, an electrode by an electroplating method in an aqueous platinum solution can be used with an acid-sensitive material such as indium tin oxide (ITO), and can be selectively deposited on a conductive film in a short time. A white metal film can be formed. The electroplating method is a cheaper manufacturing method compared to the conventional sputtering method and can contribute to the reduction of the manufacturing cost of the dye-sensitized solar cell. In addition, the formed platinum film is superior in durability to the sputtering method, and can contribute to the production of a durable dye-sensitized solar cell. Brief Description of Drawings

FIG. 1 is a schematic cross-sectional view showing a form of an electric plating.

FIG. 2 is a schematic cross-sectional view showing a basic configuration when the electrode of the present invention is used as a counter electrode of a dye-sensitized solar cell.

3 is a schematic cross-sectional view of an electrode used as a counter electrode of the dye-sensitized solar cell shown in FIG.

FIG. 4 is an electron micrograph (magnified 80,000 times) of the ITO glass conductive film surface before electroplating in Example 1.

FIG. 5 is an electron micrograph (100,000 times) of the ITO glass conductive film surface after electroplating in Example 1.

Explanation of symbols

1 container

2 Platinum aqueous solution

3 Ash electrode

4 Counter electrode

5 DC power supply

6 Board

7 Conductive layer

8 Platinum membrane

9 Semiconductor electrode

10 Transparent conductive layer

11 Transparent substrate

12 Photoelectrode

13 Electrolyte

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] (1) About step (a)

This step is a step of preparing a cathode, an anode, an electrolytic solution and a power source necessary for the production method of the present invention.

[0015] (i) Electrolyte As the electrolytic solution used in the method of the present invention, a platinum aqueous solution having a pH of 2 or more is used.

[0016] As a platinum compound used in the platinum aqueous solution used in the present invention, a power suitable for electroplating can be arbitrarily used. Potassium tetrachromate platinum (II) potassium [K PtCl], di-

2 4 Chlorotetraammineplatinum (II) [Pt (NH) C1 ·] O], dinitrodiammineplatinum (II) [Pt (N

3 4 2 2

O) (NH)], hexacloplatinum (IV) hexahydrate [H PtCl · 6Η 0], hexammine

2 2 3 2 2 6 2

Platinum (IV) methanesulfonate [Pt (NH) (CH 2 SO 4)] and other water-soluble divalent or tetravalent

3 6 3 3 4

A valent platinum compound is particularly preferably used.

[0017] As the concentration of each platinum compound, as the weight of platinum, a concentration of 0.1 to: LOgZL can be suitably used, and a concentration range of 1.5 to 2.5 gZL can be more preferably used. .

[0018] If necessary, an additive such as hydrazine as a reducing agent or hydroxylamine salt as a stabilizer may be added.

[0019] It is important that the pH of the solution is 2 or more. If the pH of this solution is less than 2, even if the plating is continued until the platinum film is formed, the obtained platinum film may be peeled off immediately and good battery performance cannot be expected (patent) Reference 1, paragraph number 0031). The optimum pH can be adjusted in consideration of the properties of the substrate, the deposition rate of platinum, etc., but from the viewpoint of protecting the conductive film on the substrate, the pH range of 4 to 13 is preferred. Particularly preferred is ~ 11 (excluding 7). As the pH adjusting agent, nitric acid, aqueous ammonia, potassium hydroxide or the like can be preferably used.

[0020] (ii) Cathode

The cathode used in the present invention is a substrate on which conductive films are laminated.

[0021] As the substrate, a glass substrate, a plastic substrate, a metal substrate or the like can be used, and the material of the substrate is not particularly selected. As will be described later, in particular, according to the method of the present invention, even when a metal substrate is used, it is not necessary to remove the oxide film on the surface, and electrical plating can be performed easily. As the metal material used for the metal substrate, titanium, stainless steel, etc. are preferred from the viewpoint of corrosion resistance against iodine.

[0022] From the viewpoint of low resistivity, the conductive layer is preferably an oxide tin or indium stannate oxide (ITO) film that may contain an additive (tin oxide is preferably contained in indium oxide. Is 5 Fluorine or antimony-doped tin oxide may be used, which is preferably about 15% by weight. These conductive layers can be laminated on the substrate by known methods such as sputtering, vapor deposition, and spin coating. When the conductive film (first conductive layer) on the surface is laminated smoothly by sputtering, vapor deposition, etc., ITO nanoparticles dispersed in an organic solvent or the like (particle size 5 ~: LOOnm, It is more preferable to apply particles such as 10 to 50 nm on the first conductive layer to form a second conductive layer and increase the surface area because the catalyst performance is improved.

[0023] (iii) Other

In addition, as the anode and the power source, those normally used for electric plating can be used.

[0024] As the anode, for example, a carbon electrode, a platinum electrode or the like can be suitably used.

[0025] (2) Regarding step (b)

This step is a step of performing electrical plating.

[0026] The bath temperature can be suitably used from room temperature to 80 ° C, more preferably from room temperature to 60 ° C.

° C can be used.

[0027] current as the density, in terms of deposition rate control, generally at 0. 1: more preferably preferably instrument performed by controlling the a current density LOAZdm ² 2. the 5～6AZdm ² Control and do.

[0028] The plating time is affected by temperature, current density, etc., but from the viewpoint of catalyst performance and cost, 0.1-5 minutes, more preferably 0.25-1.0 minutes is used! I can do it.

[0029] Through this electroplating step, a platinum film can be selectively formed on the cathode conductive film. By forming platinum as a film on the conductive film, the mechanical strength is good due to adhesion and denseness, and the reflected light contributes to power generation by reflecting light from the platinum film, improving efficiency. Has the advantage of being connected.

[0030] (3) About process (

This step is a step of taking out the cathode formed with the platinum film manufactured by the above steps (a) and (b).

[0031] The taken-out cathode can be suitably used as a counter electrode of a dye-sensitized solar cell after washing and drying. [0032] Hereinafter, the present invention will be described in more detail with reference to examples.

Example

[0033] FIG. 1 shows a schematic diagram of the electrical plating.

[0034] A substrate 6 having a conductive layer 7 laminated on one side and a counter electrode 3 were immersed in an aqueous platinum solution 2 in a container 1.

As the platinum aqueous solution, except for Example 4, an aqueous solution of hexammineplatinum (IV) methanesulfonate adjusted to ρΗΙΟ.8 with aqueous ammonia (content 25% by weight) was used. The concentration of hexammineplatinum (IV) methanesulfonate in the platinum aqueous solution was 6.9 g / L (2 gZL as platinum), and the liquid temperature of the platinum aqueous solution was 19 ° C.

[0036] A carbon electrode was used as the counter electrode.

[0037] In the electrical plating, the substrate 6 on which the conductive layer 7 is laminated is connected to the negative pole of the DC power source 5, and the counterpart electrode 3 is connected to the positive pole of the DC electrode 5. When a voltage is applied so that the current becomes 0.lAZdm ^{2 to} l OAZdm ² , a platinum film 8 is selectively formed on the surface of the conductive layer 7 laminated on the substrate 6, and the counter electrode as shown in FIG. 4 can be done.

In more detail, the counter electrode 4 was produced in each of Examples 1 to 3 and Comparative Examples 1 and 2 as follows. As in Example 1, when electroplating is performed in a platinum aqueous solution having a pH of 2 or more, more preferably 7 or more, platinum plating can be performed without damaging the ITO even in an acid-sensitive conductive layer such as ITO. it can.

[0039] Further, as in Example 3, a metal material having an acid film on the surface, such as titanium metal, cannot be etched unless the acid film is removed with a normal electric plating. By laminating a conductive layer on the surface, electric plating can be easily performed without performing a complicated pretreatment step of removing the acid film. Since the electrical plating is selectively coated on the surface on which the conductive layer is laminated and not on the surface without the conductive layer, it is very advantageous for manufacturing the counter electrode.

[0040] (Example 1)

As the substrate 6 having the conductive layer 7 laminated on one side, a glass substrate in which indium tin oxide (ITO, containing approximately 10% by weight of tin oxide in indium oxide) was deposited as a conductive film was used ( Film thickness 200nm). Fig. 4 shows an electron micrograph of the surface of the conductive film deposited with ITO before electroplating. [0041] The current density of the electrical plating was 5 A / dm ² and the time was 0.5 minutes. After electroplating, the substrate on which the white metal film was formed was washed with water and dried at 110 ° C. (platinum film thickness 5 nm). Fig. 5 shows an electron micrograph of the surface of the conductive film on which ITO was deposited after electroplating. Since platinum particles with no difference in the surface state before and after the plating are not observed, it is considered that platinum is uniformly deposited in the form of a film.

[Example 2]

As in Example 1, a glass substrate on which ITO was deposited as a conductive film was prepared, and an organic solvent solution (organic solvent: isopropyl alcohol) having an ITO particle concentration of 10% by mass was further spin-coated on this substrate. Then, it was dried at 110 ° C. for 5 minutes, and electroplating was performed using this as a cathode (spin coat film thickness 400 nm).

[0043] The current density of the electrical plating was 5 A / dm ² and the time was 0.5 minutes. After electroplating, the substrate on which the white metal film was formed was washed with water and dried at 110 ° C. (platinum film thickness 5 nm).

[0044] (Comparative Example 1)

The same substrate as in Example 1 was prepared by depositing ITO as a conductive layer on a glass substrate, and platinum was deposited on the surface of this conductive layer using a sputtering device (Hitachi E-1030 ion sputtering). It was supported to a thickness of 20 nm.

[0045] (Example 3)

As a substrate, an organic solvent solution (organic solvent: isopropyl alcohol) having an ITO particle concentration of 10% by mass with an average particle diameter of 12 nm was spin-coated on a titanium metal plate and dried at 110 ° C. for 5 minutes. (Film thickness 400nm).

[0046] The current density of the electrical plating was 5 A / dm ² and the time was 0.5 minutes. After electric plating, it was washed with water and dried at 110 ° C (platinum film thickness 5 nm).

[0047] (Comparative Example 2)

As in Example 2, a titanium metal plate was used as the substrate, and platinum was supported on this surface to a thickness of 20 nm by a sputtering apparatus.

[0048] (Example 4)

As the platinum aqueous solution, a hexaammineplatinum (IV) methanesulfonate aqueous solution adjusted to pH 2.1 with ammonia water (12.5 wt% contained) was used. Hexa at this time The concentration of ammineplatinum (IV) methanesulfonate was 6.9 gZL (2 gZL as platinum), and the solution temperature was 19 ° C.

[0049] substrate, use the same as in Example 1 in which ITO is deposited as a conductive film on a glass substrate, a current density of the electric plated is a 5AZdm ^2, time was 5 minutes 0.5.

[0050] After electroplating, it was washed with water and dried at 110 ° C (platinum film thickness was 4 nm).

[0051] (Performance evaluation)

Using the respective electrodes produced in Examples 1, 2, 3, 4 and Comparative Examples 1 and 2 as counter electrodes, dye-sensitized solar cells in FIG. 3 were produced.

[0052] Thus, using an IV tester, conversion efficiency 7% [%], open-circuit voltage Voc [V], short-circuit current sc [mAZcm ² ], and fill factor FF were determined. The performance of the dye-sensitized solar cell in which each electrode of the comparative example was incorporated as a counter electrode was evaluated. The results are shown in Table 1.

[0053] From the results shown in Table 1, the electric plating method showed good battery performance similar to the sputtering method. Further, by adding additional ITO particles to the surface as in Example 2, the surface area can be increased and the conversion efficiency can be further improved.

[0054] In Example 4, as a result of making the pH of the electrolytic solution acidic (2.1), the platinum film thickness was slightly thinner than that of Example 1. For this reason, the catalyst performance was slightly lower than that of Example 1.

[0055] [Table 1]

[0056] (Invention durability evaluation)

In order to investigate the durability of the electrode, iodine and lithium iodide were dissolved in 3-methoxypropio-tolyl at concentrations of 0.03M and 0.3M, respectively, to prepare an electrolyte solution. The electrode of Example 2 was immersed in and held at 80 ° C. for 48 hours. Then take this A dye-sensitized solar cell as shown in Fig. 3 was prepared using the electrode as a counter electrode, and the performance was evaluated in the same manner as described above. The results are shown in Table 2.

[0057] (Comparison product durability evaluation)

In order to compare with the durability of the electrode of the present invention, an electrolyte solution similar to the above-mentioned invention product durability evaluation was prepared, and the electrode of Comparative Example 1 was immersed in this electrolytic solution and held at 80 ° C. for 48 hours. . Thereafter, this was taken out, a dye-sensitized solar cell as shown in Fig. 3 was produced using the electrode as a counter electrode, and the performance was evaluated in the same manner as described above. The results are shown in Table 2.

[0058] [Table 2]

[0059] From the results shown in Table 2, it was confirmed that the electrical plating method was superior in durability and / or superior to the sputtering method.

Industrial applicability

[0060] The electrode produced by the method of the present invention forms a uniform film of platinum on the surface of the conductive film and has sufficient adhesion strength, and is useful as a counter electrode of a dye-sensitized solar cell. is there.

[0061] Further, according to the present invention, by forming the conductive film only in the necessary portion, the platinum film can be selectively formed only in the necessary portion, so that the cost can be reduced. The Further, even when the method of the present invention is used for a metal plate or the like, treatment such as removal of the oxide film on the surface is not necessary, and if a conductive film is formed on the surface, electric plating can be easily performed.

Claims

The scope of the claims

[1] (a) A step of preparing a cathode, an anode, an electrolytic solution and a power source, a step of preparing a substrate on which a conductive film is stacked as a cathode and a platinum aqueous solution having a pH of 2 or more as an electrolytic solution,

(c) removing the cathode on which the platinum film is formed,

The method of manufacturing the electrode which has a platinum film | membrane characterized by performing sequentially.

[2] The method for producing an electrode having a platinum film according to [1], wherein the platinum aqueous solution has a pH force of ˜13.

In [3] the step (b), 0. 1~: method for manufacturing an electrode having a platinum film of claim 1 which controls the current density of LOAZdm ² and performs the electric plated with.

[4] The production of the electrode having a platinum film according to [1], wherein the conductive film is formed from tin oxide or indium stannate that may contain an additive. Method.

[5] The platinum according to claim 1, wherein the conductive film has a first conductive layer and a second conductive layer made of particles having a particle size of 5 to LOONm applied thereon. The manufacturing method of the electrode which has a film | membrane.

6. The method for producing an electrode having a platinum film according to claim 1, wherein the substrate is a metal material.

[7] An electrode having a platinum film that can be produced by the method according to any one of claims 1 to 6.

[8] A dye-sensitized solar cell in which the electrode according to claim 7 is incorporated as a counter electrode.