JP5227194B2 - Laminated electrode - Google Patents

Description

  The present invention relates to a laminated electrode. More specifically, the present invention relates to a laminated electrode that can be suitably used for a dye-sensitized solar cell, a fuel cell, an electrode used for electrolyzing an electrolyte solution, and the like.

  In solar cells using inexhaustible and clean solar energy, dye-sensitized solar cells that have a low production cost and use abundant raw materials have been proposed as a new type of solar cell that replaces silicon solar cells (for example, (See Table No. 5-504023 and O'Regan, Brian, Graetzel, Michael, Nature Vol. 353 (1991), page 737 (published by Nature Publishing Group)). In this dye-sensitized solar cell, a transparent conductive film is formed on one surface of a substrate made of glass or plastic, a porous semiconductor film made of oxide semiconductor particles such as titanium oxide is formed on the transparent conductive film, and A photoelectrode is formed by supporting an organic dye thereon. On the other hand, a counter electrode made of a metal film such as platinum is provided on the side of the photo electrode on the substrate disposed opposite to the photo electrode, and iodine / iodine ions are provided between the counter electrode and the photo electrode. An electrolyte solution containing a redox pair such as is enclosed.

  In addition, as a next-generation clean power generation system, fuel cells have been studied in various fields, and full-scale practical use is awaited. In this fuel cell, a fuel electrode made of platinum or carbon in contact with hydrogen is used as a negative electrode, an air electrode made of platinum or carbon in contact with oxygen is used as a positive electrode, and phosphoric acid or An electrolyte such as lithium carbonate / potassium carbonate or a cation exchange membrane is sandwiched, and a current flows as hydrogen ions move from the fuel electrode to the air electrode in the electrolyte.

  Further, the electrolysis of the electrolyte solution is performed by immersing an anode that emits electrons and a cathode that receives electrons in an electrolyte solution composed of an aqueous solution such as an acidic aqueous solution, a basic aqueous solution, or a metal salt. The compound generated in the electrode by applying electrolysis by connecting the positive electrode and the negative electrode is applied to the production of chemicals and the like.

  Thus, the electrolyte solution used for the electrolysis of the dye-sensitized solar cell, the fuel cell, or the electrolyte solution includes a corrosive electrolyte such as an acidic solution, a basic solution, a metal salt solution, and an organic solvent. Yes. Therefore, the metal electrodes used for these have excellent corrosion resistance that is not easily affected by these electrolytes, are materials with low resistivity, and have catalytic activity that promotes the transfer of electrons at the electrodes. It is hoped to show.

  In general, copper, aluminum, and the like are widely used as electrode materials because of their low electrical resistance and low cost. However, these metal materials are easily corroded with respect to acidic solutions, basic solutions, metal salt solutions, organic solvents, and the like, and therefore their use is limited to use under conditions where corrosion does not occur. Further, there are silver, gold and the like as metal materials having low resistance, but since these are all expensive, it is not practical to use a large amount.

  The present inventors have used a solid electrolyte of copper iodide (CuI) as a redox electrolyte, thereby enabling practical use of an all-solid-state dye-sensitized solar with improved mechanical strength and battery characteristics as a solar battery. A battery has been proposed (see, for example, JP-A-2003-331938). The present inventors have further proposed a method for manufacturing a porous titanium oxide thin film using the SPD method, a highly efficient dye-sensitized solar cell electrode using the titanium oxide thin film for solar cells, and a method for manufacturing the same. (For example, refer to JP2003-176130A and JP2004-079610A). The counter electrode of the dye-sensitized solar cell manufactured by these methods has excellent corrosion resistance, low electrical resistance, and a catalyst on a glass substrate or a thin film of tin oxide doped with fluorine formed on the glass substrate. It is formed by forming a platinum thin film exhibiting activity.

  In addition, a highly sensitive and long-life NOx sensor has been proposed by using an electrode made of a metal material containing platinum as a main component as an electrode of an electrochemical element using an oxygen ion conductive solid electrolyte. (For example, refer to Japanese Patent Laid-Open No. 06-258283). Further, in a dye-sensitized solar cell, an electrode having a laminated structure including a nickel film formed on a substrate as a counter electrode and a platinum film formed on the nickel film has been proposed (for example, JP, 2005-56613, A).

  As described above, electrode materials used for electrolysis of fuel cells and electrolyte solutions, including dye-sensitized solar cells, require high corrosion resistance, low resistivity, and high catalytic activity. Platinum with properties is used by laminating with a single layer or other metals.

  However, since platinum is extremely expensive, an electrode with a small amount of platinum used is required for dye-sensitized solar cells and the like. However, a new electrode having high corrosion resistance, low resistivity, and catalytic activity is required. Development is awaited. In addition, by using a laminated structure of platinum and other metals as the electrode, the electrode used in combination with platinum is expensive because the amount of platinum used is reduced. Development is desired.

  The present invention has been made in view of the above prior art, and as an electrode used in various electrode materials, for example, electrolysis of dye-sensitized solar cells, fuel cells and electrolyte solutions, it has high corrosion resistance and low resistance. It is an object to provide an inexpensive laminated electrode having resistivity and catalytic characteristics.

The present invention
(1) has a metal thin film made of at least one metal selected from the group consisting of chromium and titanium is formed on the base plate, and a dispersion layer obtained by dispersing platinum particles on the metal thin film, the metal thin film the thickness is 300Nm～1myuemu, the thickness of the dispersion layer is 3 nm to 10 nm, layered electrode wherein the average particle size of the platinum particles in the dispersion layer is 10nm or less (hereinafter, one of the present invention Called embodiment ),
(2) platinum chromium formed on the base plate, a metal thin film made of at least one metal selected from the group consisting of aluminum and copper, titanium thin film formed on the metal thin film, and on the titanium thin It has a dispersion layer in which particles are dispersed, the thickness of the metal thin film is 300 nm to 1 μm, the thickness of the titanium thin film is 100 nm to 300 nm, the thickness of the dispersion layer is 3 nm to 10 nm, and platinum in the dispersion layer A laminated electrode having an average particle diameter of 10 nm or less (hereinafter, referred to as another embodiment of the present invention )
About.

It is a schematic sectional drawing of the laminated electrode which concerns on one reference example relevant to this invention. It is a schematic sectional drawing of the laminated electrode which concerns on one Embodiment of this invention . It is a schematic sectional drawing of the laminated electrode which concerns on the other reference example relevant to this invention. It is a schematic sectional drawing of the laminated electrode which concerns on other embodiment of this invention . It is a schematic sectional drawing of the counter electrode of the conventional dye-sensitized solar cell.

1 Substrate 2 Metal thin film 3 Platinum thin film 4 Platinum dispersion layer 5 Metal thin film 6 Titanium thin film

The substrate used in the present invention is not particularly limited, and examples thereof include a substrate made of a material such as glass .

One reference example (hereinafter referred to as one reference example) related to the present invention is a metal thin film made of at least one metal selected from the group consisting of chromium and titanium formed on a substrate, and on the metal thin film. It is a laminated electrode having a platinum thin film formed. Since one reference example has such a laminated structure, it has high corrosion resistance, low resistivity, and catalytic properties.

A metal thin film made of at least one metal selected from the group consisting of chromium and titanium is formed on the substrate. The resistivity of these metals is 5 to 13 × 10 ⁻⁸ Ωm, which is almost equal to the resistance value of platinum (11 × 10 ⁻⁸ Ωm), so these metals are equivalent to platinum. It has the conductivity of. In addition, these metals have excellent corrosion resistance against acidic solutions, basic solutions, metal salt solutions, organic solvents, etc., and have almost the same resistivity and corrosion resistance as platinum, so they are low in efficiency and excellent in corrosion resistance. ing.

  The metal thin film can be formed on the substrate by, for example, a sputtering method. The thickness of the formed metal thin film is preferably 300 nm to 1 μm, more preferably 500 to 900 nm, from the viewpoint of securing a low resistivity.

  A platinum thin film is formed on the formed metal thin film. The platinum thin film can be formed on the metal thin film by, for example, a sputtering method. The thickness of the platinum thin film to be formed is preferably 10 to 50 nm, more preferably 10 to 30 nm, from the viewpoint of enhancing economic efficiency and sufficiently exhibiting catalytic activity.

One embodiment of the present invention is a laminated electrode in which a dispersion layer in which platinum particles are dispersed is formed on a metal thin film instead of the platinum thin film used in one reference example . In this dispersion layer, platinum particles are individually separated and dispersed in an island shape on the metal thin film, so that a high catalytic action is exhibited. Therefore, one embodiment of the present invention has an advantage that the consumption of platinum can be further reduced as compared with one reference example .

  The average particle diameter of the platinum particles is preferably 10 nm or less, more preferably 5 to 10 nm, from the viewpoint of efficiently functioning the catalytic action that promotes the transfer of electrons at the electrode.

  The dispersion layer in which the platinum particles are dispersed is preferably formed so that the platinum particles occupy 20% or more of the area of the metal thin film from the viewpoint of sufficiently exhibiting the catalytic action. From the viewpoint of reducing the amount of platinum used, it is preferable to occupy 80% or less.

The dispersion layer in which the platinum particles are dispersed can be formed, for example, by controlling the film forming time to be short by sputtering or the like. The thickness of the formed dispersion layer is preferably from 3 to 10 nm, more preferably from 5 to 8 nm, from the viewpoint of allowing the catalytic function to function efficiently and from the viewpoint of suppressing the amount used thereof to the necessary minimum amount. Further, the density of the platinum particles in the dispersion layer is preferably 1.7 × 10 ^{−6 to} 6.7 × 10 ⁻⁶ g from the viewpoint of allowing the catalytic function to function efficiently and the amount used thereof being kept to the minimum necessary amount. / Cm ³ , more preferably 2.5 × 10 ^{−6 to} 5.0 × 10 ⁻⁶ g / cm ³ .

Another reference example related to the present invention (hereinafter referred to as another reference example) is a metal thin film made of at least one metal selected from the group consisting of chromium, aluminum and copper formed on a substrate, the metal A laminated electrode having a titanium thin film formed on the thin film and a platinum thin film formed on the titanium thin film.

As a result of intensive research on electrode materials that enable cost reduction, the present inventors have found that laminated electrodes of other reference examples are excellent in high corrosion resistance, low resistivity, and high catalytic action. .

  A metal thin film made of at least one metal selected from the group consisting of chromium, aluminum and copper is formed on the substrate.

  The metal thin film can be formed on the substrate by, for example, a sputtering method. The thickness of the formed metal thin film is preferably 300 nm to 1 μm, more preferably 500 to 900 nm, from the viewpoint of securing a low resistivity.

  A titanium thin film is formed on the formed metal thin film. The titanium thin film can be formed on the metal thin film by, for example, a sputtering method. The thickness of the titanium thin film to be formed is preferably 100 to 300 nm, more preferably 150 to 250 nm, from the viewpoint of imparting corrosion resistance and improving economy.

  Next, a platinum thin film is formed on the formed titanium thin film. The platinum thin film can be formed on the titanium thin film by, for example, sputtering. The thickness of the formed platinum thin film is preferably 10 to 50 nm, more preferably 10 to 30 nm, from the viewpoint of imparting corrosion resistance and improving economy.

Another embodiment of the present invention is a laminated electrode in which a dispersion layer in which platinum particles are dispersed is formed on a metal thin film instead of the platinum thin film used in other reference examples .

  The average particle diameter of the platinum particles is preferably 10 nm or less, more preferably 5 to 10 nm, from the viewpoint of efficiently functioning the catalytic action that promotes the transfer of electrons at the electrode.

  The dispersion layer in which the platinum particles are dispersed is preferably formed so that the platinum particles occupy 20% or more of the area of the metal thin film from the viewpoint of sufficiently exhibiting the catalytic action. From the viewpoint of reducing the amount of platinum used, it is preferable to occupy 80% or less.

The dispersion layer in which the platinum particles are dispersed can be formed, for example, by controlling the film forming time to be short by sputtering or the like. The thickness of the formed dispersion layer is preferably from 3 to 10 nm, more preferably from 5 to 8 nm, from the viewpoint of allowing the catalytic function to function efficiently and from the viewpoint of suppressing the amount used thereof to the necessary minimum amount. Further, the density of the platinum particles in the dispersion layer is preferably 1.7 × 10 ^{−6 to} 6.7 × 10 ⁻⁶ g from the viewpoint of allowing the catalytic function to function efficiently and the amount used thereof being kept to the minimum necessary amount. / Cm ³ , more preferably 2.5 × 10 ^{−6 to} 5.0 × 10 ⁻⁶ g / cm ³ .

  Next, the laminated electrode of the present invention will be described with reference to the drawings.

Figure 1 is a schematic cross-sectional view of a stacked electrodes one reference example. The laminated electrode shown in FIG. 1 was formed on a surface of the metal thin film 2 and a metal thin film 2 made of at least one metal selected from the group consisting of chromium and titanium formed on the substrate 1. The platinum thin film 3 is used.

FIG. 2 is a schematic cross-sectional view showing one embodiment of the laminated electrode of one embodiment of the present invention . 2 includes a metal thin film 2 made of at least one metal selected from the group consisting of chromium and titanium formed on the substrate 1, and platinum particles formed on the metal thin film 2. Is formed by a dispersion layer 4 in which is dispersed.

Figure 3 is a schematic cross-sectional view of a stacked electrodes of another reference example. The laminated electrode shown in FIG. 3 includes a metal thin film 5 made of at least one metal selected from the group consisting of chromium, aluminum and copper formed on the substrate 1 and titanium formed on the metal film. The thin film 6 is composed of a platinum thin film 3 formed on the titanium thin film 6.

FIG. 4 is a schematic cross-sectional view showing one embodiment of a laminated electrode according to another embodiment of the present invention . The laminated electrode shown in FIG. 4 includes a metal thin film 5 made of at least one metal selected from the group consisting of chromium, aluminum and copper formed on the substrate 1, and titanium formed on the metal film. The thin film 6 is composed of a dispersion layer 4 in which platinum particles formed on the titanium thin film 6 are dispersed.

The stacked electrodes of one embodiment and other embodiments of the present invention both use much less platinum than the conventional platinum electrode 1 and platinum film 3 shown in FIG. Therefore, it can be suitably used for a dye-sensitized solar cell, a fuel cell, an electrode for electrolysis of an electrolyte, and the like as an inexpensive electrode instead of a platinum electrode.

  Next, the present invention will be described in more detail based on examples. However, the present invention is not limited to such examples.

Example 1
A chromium thin film having a thickness of 700 nm was formed on a glass substrate (Corning, product number: Corning # 1737) by a sputtering method. The chromium thin film was formed by sputtering using an RF magnetron sputtering apparatus (manufactured by Anerva Co., Ltd.) under the conditions of an RF power of 200 W, an argon gas pressure of 0.2 Pa, and a film forming time of 60 minutes.

Next, a platinum thin film having a thickness of 10 nm was formed on the formed chromium thin film by a sputtering method to obtain a laminated electrode of one reference example . The chromium thin film was formed by sputtering using an RF magnetron sputtering apparatus (manufactured by Anerva Co., Ltd.) under the conditions of an RF power of 200 W, an argon gas pressure of 0.2 Pa, and a film forming time of 1 minute and 20 seconds.

Example 2
In the same manner as in Example 1, a 700 nm thick chromium thin film was formed on a glass substrate by sputtering.

Next, by forming a dispersion layer (thickness 5 nm) of platinum particles having an average particle diameter of 8 nm on the formed chromium thin film by a sputtering method, a multilayer electrode of one embodiment of the present invention was obtained. . The chromium thin film was formed by sputtering using an RF magnetron sputtering apparatus (manufactured by Anerva Co., Ltd.) under the conditions of RF power of 200 W, argon gas pressure of 0.2 Pa, and film formation time of 40 seconds.

Example 3
A copper thin film having a thickness of 800 nm was formed on the same type of glass substrate as used in Example 1 by sputtering. The copper thin film was formed by sputtering using an RF magnetron sputtering apparatus (manufactured by Anerva Co., Ltd.) under the conditions of an RF power of 300 W, an argon gas pressure of 0.2 Pa, and a film forming time of 80 minutes.

  Next, a titanium thin film having a thickness of 200 nm was formed on the formed copper thin film by sputtering. The titanium thin film was formed using an RF magnetron sputtering apparatus (manufactured by Anerva Co., Ltd.) under the conditions of an RF power of 200 W, an argon gas pressure of 0.2 Pa, and a film forming time of 30 minutes.

Next, a 20-nm-thick platinum thin film was formed on the formed titanium thin film by a sputtering method to obtain a laminated electrode of another reference example . The platinum thin film was formed using an RF magnetron sputtering apparatus (manufactured by Anerva Co., Ltd.) under the conditions of RF power of 200 W, argon gas pressure of 0.2 Pa, and film formation time of 2 minutes and 40 seconds.

Example 4
On the same type of glass substrate as used in Example 1, a copper thin film having a thickness of 800 nm was formed by a sputtering method in the same manner as in Example 3.

  Next, a titanium thin film having a thickness of 200 nm was formed on the formed copper thin film by a sputtering method in the same manner as in Example 3.

Next, a multilayer electrode of another embodiment of the present invention was obtained by forming a dispersion layer (thickness 5 nm) of platinum particles having an average particle diameter of 6 nm on the formed titanium thin film by sputtering. . The platinum thin film was formed using an RF magnetron sputtering apparatus (manufactured by Anerva Co., Ltd.) under the conditions of an RF power of 200 W, an argon gas pressure of 0.2 Pa, and a film forming time of 40 seconds.

Comparative Example 1
A conventional laminated electrode was obtained by forming a platinum thin film having a thickness of 20 nm on a glass substrate of the same type as the glass substrate used in Example 1 by sputtering. The platinum thin film was formed by sputtering using an RF magnetron sputtering apparatus (manufactured by Anerva Co., Ltd.) under the conditions of RF power of 200 W, argon gas pressure of 0.2 Pa, and film formation time of 2 minutes and 40 minutes.

Comparative Example 2
By performing the same operation as in Comparative Example 1 except that the film forming conditions for forming the platinum thin film in Comparative Example 1 were changed to RF power 200 W, argon gas pressure 0.2 Pa, and film forming time 80 minutes. A conventional laminated electrode having a platinum thin film thickness of 600 nm was obtained.

Comparative Example 3
A conventional laminated electrode was obtained by forming a 700 nm-thick chromium thin film on a glass substrate of the same type as the glass substrate used in Example 1 by sputtering. The chromium thin film was formed by sputtering using an RF magnetron sputtering apparatus (manufactured by Anerva Co., Ltd.) under the conditions of an RF power of 200 W, an argon gas pressure of 0.2 Pa, and a film forming time of 60 minutes.

Comparative Example 4
A conventional laminated electrode was obtained by forming a copper thin film having a thickness of 800 nm on a glass substrate of the same type as the glass substrate used in Example 1 by sputtering. The copper thin film was formed by sputtering using an RF magnetron sputtering apparatus (manufactured by Anerva Co., Ltd.) under the conditions of an RF power of 200 W, an argon gas pressure of 0.2 Pa, and a film forming time of 80 minutes.

  In addition, the film thickness of the thin film of each metal was computed by observation with an electron microscope and the film forming speed of the thin film.

  Next, the physical properties of the laminated electrodes obtained in each Example and each Comparative Example were evaluated based on the following methods. The results are shown in Table 1.

[Method for evaluating physical properties]
(1) Surface resistance of the surface on which the thin film of the laminated electrode was formed The surface resistance of the surface on which the thin film of the laminated electrode was formed was measured by a four-terminal method using a sheet resistance measuring instrument [manufactured by Mitsubishi Chemical Corporation].

(2) Corrosion resistance Dye-sensitized solar cell electrolyte solution (0.1 mol / L lithium iodide, 0.05 mol / L iodine, 0.6 mol / L dimethylpropylimidazolium iodide and 0.5 mol / L In the methoxyacetonitrile solution containing butylpyridine), the laminated electrodes obtained in each Example or each Comparative Example were immersed for 1 week, and then the surface on which the thin film was formed was observed with an electron microscope to examine the corrosion status. Evaluation based on the evaluation criteria.

〔Evaluation criteria〕
○: Almost no change and corrosion is less than 10% of the immersion surface.
Δ: Corrosion has progressed to 10% or more and less than 80% of the immersion surface.
X: Corrosion proceeds at 80% or more of the immersion surface.

(3) Photoelectric conversion efficiency An FTO transparent conductive film (film thickness: 600 nm) and a titanium oxide film (film thickness: 15 μm) are sequentially stacked on the same type of glass substrate as used in Example 1, and the oxidation. A working electrode was prepared by supporting a ruthenium dye [manufactured by Solaronix, product number: N719] on a titanium film.

The obtained working electrode and the laminated electrode obtained in each example or each comparative example were bonded as a counter electrode, and 0.5 mL of an electrolyte solution having the same composition as the electrolyte solution used for examining the corrosion resistance was bonded thereto. Injection was performed from the mating surfaces, and the working electrode and the laminated electrode were sandwiched between electrode clips without leakage due to surface tension, and a dye-sensitized solar cell having an effective area of the photoelectrode portion of 0.25 cm ² was produced.

  The photoelectric conversion efficiency of the obtained dye-sensitized solar cell was evaluated under light irradiation of AM1.5 using a solar simulator [manufactured by Eihiro Seiki Co., Ltd.].

  From the results shown in Table 1, the laminated electrodes obtained in each Example were obtained even though the film thickness of platinum was 1/30 or less of the conventional platinum single layer electrode obtained in Comparative Example 2. It can be seen that the platinum single layer electrode obtained in Comparative Example 2 has substantially the same sheet resistance, corrosion resistance, and photoelectric conversion efficiency.

  Therefore, it can be seen that the laminated electrodes obtained in the respective examples can be sufficiently substituted even if the amount of platinum used is smaller than that of the conventional platinum single layer electrode.

  According to the present invention, as an electrode used in various electrode materials, for example, electrolysis of dye-sensitized solar cells, fuel cells and electrolyte solutions, it has high corrosion resistance, low resistivity and catalytic properties, and is inexpensive. A laminated electrode is provided.

Claims (2)

A dye sensitizer having a metal thin film made of at least one metal selected from the group consisting of chromium and titanium formed on a substrate, and a dispersion layer formed by separating platinum particles on the metal thin film in an island shape A laminated electrode used as a counter electrode of a solar cell ,
The thickness of the said metal thin film is 300 nm-1 micrometer, The thickness of the said dispersion layer is 3 nm-10 nm, The average particle diameter of the platinum particle in the said dispersion layer is 10 nm or less, The laminated electrode characterized by the above-mentioned. A metal thin film made of at least one metal selected from the group consisting of chromium, aluminum and copper formed on the substrate, a titanium thin film formed on the metal thin film, and platinum particles on the titanium thin film as islands A laminated electrode used for a counter electrode of a dye-sensitized solar cell having a dispersed layer formed separately ,
The thickness of the metal thin film is 300 nm to 1 μm, the thickness of the titanium thin film is 100 nm to 300 nm, the thickness of the dispersion layer is 3 nm to 10 nm, and the average particle diameter of platinum particles in the dispersion layer is A laminated electrode having a thickness of 10 nm or less.

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