HYDRAZINE OXIDATION CATALYST ELECTRODE AND METHOD FOR MANUFACTURING SAME

Abstract

To provide a catalyst electrode for hydrazine oxidation that shows photocatalysis and catalysis for the oxidation of hydrazine and can oxidize hydrazine both under light irradiation and at a dark place and a method for producing the same.SOLUTION: A catalyst electrode for hydrazine oxidation 10 includes an electrode substrate 12 having an n-type organic semiconductor layer 14 and a p-type organic semiconductor layer 16 laminated thereon in this order, where the p-type organic semiconductor layer 16 has a silver-containing catalytic promoter 18 supported thereon. The catalyst electrode for hydrazine oxidation shows photocatalysis and catalysis for the oxidation of hydrazine and can oxidize hydrazine both under light irradiation and at a dark place. The catalyst electrode for hydrazine oxidation can be produced by a lamination step of laminating an n-type organic semiconductor layer and a p-type organic semiconductor layer on an electrode substrate in this order and a silver-supporting step of allowing the p-type organic semiconductor layer to support silver thereon.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a catalytic electrode for hydrazine oxidation and a method for producing the same. [Background technology]

[0002] Hydrogen is expected to be a clean energy source that does not emit carbon dioxide when burned. However, hydrogen is a gas at room temperature and pressure, making it difficult to store and transport. Therefore, technology is being developed to convert hydrogen into hydrogen compounds called hydrogen carriers, store and transport them efficiently, and extract hydrogen from the hydrogen carriers when it is used.

[0003] Hydrazine (N2H4) is a liquid at room temperature and has a high hydrogen content, so it has attracted attention as a hydrogen carrier. It has been reported that hydrazine can be decomposed into nitrogen and hydrogen by a photocatalytic reaction (Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] T. Abe et al., RSC Advances, 2015, 5, 46325-46329. Summary of the Invention [Problem to be solved by the invention]

[0005] The photocatalytic electrode described in Non-Patent Document 1 has a structure in which an n-type organic semiconductor layer and a p-type organic semiconductor layer are laminated on an electrode substrate. This photocatalytic electrode can oxidize hydrazine by photocatalysis under light irradiation. In addition, it can generate hydrogen by directing electrons released with the oxidation of hydrazine to a counter electrode. This method is expected to be a clean hydrogen production method because it can generate hydrogen from hydrazine using sunlight, which is a renewable energy source.

[0006] However, the photocatalytic electrode of Non-Patent Document 1 does not work in the dark because it oxidizes hydrazine by photocatalysis. Therefore, it cannot be used in situations where light does not reach, such as at night. Therefore, the object of the present invention is to provide a catalytic electrode for hydrazine oxidation that exhibits photocatalytic and catalytic actions on the oxidation of hydrazine and can oxidize hydrazine both under light irradiation and in the dark, and a method for producing the same. [Means for solving the problem]

[0007] As a result of intensive research by the present inventors to solve the above problems, they found that in a catalyst electrode in which an n-type organic semiconductor and a p-type organic semiconductor are laminated on an electrode substrate, when a silver compound is supported as a co-catalyst on the surface of the p-type organic semiconductor, hydrazine can be oxidized both under light irradiation and in the dark. Based on this finding, they further researched and completed the present invention. That is, the above problems are solved by the invention having the following configuration.

[0008] [1] On top of the electrode substrate Made of perylene derivatives n-type organic semiconductor layer and Made of metal phthalocyanine A catalyst electrode in which p-type organic semiconductor layers are laminated in this order, and a co-catalyst containing silver is supported on the p-type organic semiconductor layer. It is also used to burn hydrazine or decompose it into hydrogen and nitrogen under light irradiation and in the dark. Catalytic electrode for hydrazine oxidation. [2] On top of the electrode substrate Made of perylene derivatives n-type organic semiconductor layer and Made of metal phthalocyanine A catalyst electrode in which p-type organic semiconductor layers are laminated in this order, and a co-catalyst containing a silver compound is supported on the p-type organic semiconductor layer. It is also used to burn hydrazine or decompose it into hydrogen and nitrogen under light irradiation and in the dark. Catalytic electrode for hydrazine oxidation. [3] The catalyst electrode for hydrazine oxidation according to [1] or [2], characterized in that an adsorbent for adsorbing hydrazine is supported on the surface of the p-type organic semiconductor layer and / or the co-catalyst. [4] A method for producing a catalytic electrode for hydrazine oxidation, which is used for burning hydrazine or decomposing hydrazine into hydrogen and nitrogen under light irradiation and in a dark place, comprising the steps of: On top of the electrode substrate Made of perylene derivatives n-type organic semiconductor layer and Made of metal phthalocyanineA method for producing a catalyst electrode for hydrazine oxidation, comprising: a lamination step of laminating a p-type organic semiconductor layer in this order; and a silver supporting step of supporting silver on the p-type organic semiconductor layer. [5] The method for producing a catalyst electrode for hydrazine oxidation according to [4], characterized in that the silver loading step includes a silver compound loading step of loading a silver compound on the p-type organic semiconductor layer, and a silver production step of producing silver from the loaded silver compound. [6] The method for producing a catalyst electrode for hydrazine oxidation according to [5], wherein the silver production step includes a step of contacting the silver compound with a reducing agent. Effect of the Invention

[0009] According to the present invention, it is possible to provide a catalytic electrode for hydrazine oxidation, which exhibits photocatalytic and catalytic actions on the oxidation of hydrazine and is capable of oxidizing hydrazine both under light irradiation and in the dark, and a method for producing the same. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing the configuration of a catalytic electrode for hydrazine oxidation of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing an example of the configuration of a two-chamber electrolytic cell. [Diagram 3] 1 is an X-ray diffraction pattern of the catalytic electrode of Example 1. [Figure 4] 1 is an X-ray diffraction pattern of the catalytic electrode of Example 1 after it is used for hydrazine oxidation in the dark. [Diagram 5] 1 shows an X-ray diffraction pattern of the catalytic electrode of Example 1 after it was used for hydrazine oxidation under light irradiation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention provides a catalytic electrode for hydrazine oxidation, which exhibits photocatalytic and catalytic actions for the oxidation of hydrazine and can oxidize hydrazine both under light irradiation and in the dark, and a method for producing the same. In this specification, the action of exhibiting photocatalytic and catalytic actions and catalyzing the same oxidation reaction both under light irradiation and in the dark is also referred to as dual catalysis. Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] <Catalytic electrode> As shown in Fig. 1(a), the catalytic electrode 10 for hydrazine oxidation of the present invention is a catalytic electrode 10 in which an n-type organic semiconductor layer 14 and a p-type organic semiconductor layer 16 are laminated in this order on an electrode substrate 12, and a co-catalyst 18 containing silver (Ag) is supported on the p-type organic semiconductor layer 16. As shown in Fig. 1(b), an adsorbent 19 for adsorbing hydrazine may be further supported on the surface of the p-type organic semiconductor layer 16 and / or the co-catalyst 18.

[0013] (electrode base material) The electrode substrate 12 is made of a material having electrical conductivity. Examples of the material include a conductive transparent glass substrate, a metal substrate, and a carbon-based substrate. Specific examples of the material include a conductive transparent glass substrate coated with indium-tin oxide (ITO), fluorine-doped tin oxide (FTO), or the like, and a carbon-based substrate such as graphite, diamond, or glassy carbon. The resistance value of the electrode substrate 12 is, for example, 5 to 100 Ω / cm. 2 , preferably 8 to 20 Ω / cm 2 The electrode substrate 12 may have a variety of shapes, but is preferably a plate-like substrate having a large electrode surface area in order to increase the efficiency of light irradiation.

[0014] (n-type / p-type organic semiconductor layer) An n-type organic semiconductor layer 14 and a p-type organic semiconductor layer 16 are laminated in this order on the surface of the electrode substrate 12. The n-type organic semiconductor layer 14 is composed of an n-type organic semiconductor material. The p-type organic semiconductor layer 16 is composed of a p-type organic semiconductor material. The n-type organic semiconductor layer has a thickness of about 50 to 800 nm, preferably about 100 to 650 nm. The p-type organic semiconductor layer 16 has a thickness of about 20 to 500 nm, preferably about 30 to 350 nm. A pn ​​junction is formed at the interface between the n-type organic semiconductor layer 14 and the p-type organic semiconductor layer 16.

[0015] The n-type organic semiconductor material is not particularly limited, and may be a perylene derivative, a naphthalene derivative, a fullerene, a carbon nanotube, a graphene, etc. Here, perylene derivatives, naphthalene derivatives, fullerene or fullerenes, graphene or graphenes refer to compounds having the basic skeleton of perylene, naphthalene, fullerene, and graphene, respectively.

[0016] Particularly suitable n-type organic semiconductor materials are hexa-perihexabenzocoronene, 3,4,9,10-perylenetetracarboxyl-bisbenzimidazole or fullerenes (C 60 etc.), and carbon nanotubes.

[0017] The p-type organic semiconductor material is not particularly limited, but a macrocyclic ligand compound or its metal complex can be used. The macrocyclic ligand compound is an organic compound containing an atom having an unpaired electron on a ring that can be a ligand of a metal, and examples of the macrocyclic ligand compound include phthalocyanine derivatives, naphthalocyanine derivatives, and porphyrin derivatives. Here, the phthalocyanine derivatives, naphthalocyanine derivatives, and porphyrin derivatives refer to compounds having the basic skeletons of phthalocyanine, naphthalocyanine, and porphyrin, respectively. The metal complex is a metal complex in which a metal ion is bonded to a coordination group of the macrocyclic ligand compound. Examples of the metal ion include ions of Co, Pt, Os, Mn, Ir, Fe, Rh, Cu, Zn, Ni, Pb, Pd, or Ru.

[0018] Other examples of p-type organic semiconductor materials include conductive polymers, such as polythiophene derivatives, polyphenylenevinylene derivatives, and polyfluorene copolymers.

[0019] Preferable examples of the p-type organic semiconductor material include phthalocyanine derivatives, naphthalocyanine derivatives, and porphyrin derivatives. In particular, metal-free phthalocyanine, iron phthalocyanine, zinc phthalocyanine, copper phthalocyanine, lead phthalocyanine, chloroaluminum phthalocyanine, and cobalt phthalocyanine are preferable.

[0020] (Co-catalyst) A co-catalyst 18 is supported on the p-type organic semiconductor layer 16. The co-catalyst 18 contains silver (Ag). The co-catalyst 18 may have various shapes, such as a layer shape or a particulate shape. From the viewpoint of increasing the surface area, a particulate or porous shape is preferable. In addition, the co-catalyst 18 does not need to completely cover the surface of the p-type organic semiconductor layer 16, and it is sufficient that the co-catalyst 18 is supported so as to cover only a portion of the surface. The amount of the promoter 18 supported is not particularly limited and can be selected from various amounts. For example, the amount of the promoter 18 supported on the surface of the p-type semiconductor layer 16 is 0.3 mg / cm. 2 When the amount of the supported catalyst is about 100%, sufficient activity is obtained, which is preferable.

[0021] (Adsorbent) The surface of the p-type organic semiconductor layer 16 and / or the co-catalyst 18 may support an adsorbent 19 having hydrazine adsorption ability. By supporting the adsorbent 19, the hydrazine concentration on the surface of the co-catalyst 18 can be increased, and the efficiency of the hydrazine oxidation reaction can be improved. The material of the adsorbent is not particularly limited, and examples thereof include materials with high adsorption ability such as activated carbon, activated alumina, molecular sieve, silica gel, and clay, and polymeric materials that can be made into thin films such as ion exchange resins, chitosan, polypropylene, and organic gels. Among these, ion exchange resins are particularly suitable because they easily adsorb hydrazine. Specifically, examples thereof include perfluorosulfonic acid / PTFE (polytetrafluoroethylene) copolymers and perfluorocarboxylic acid / PTFE copolymers.

[0022] The form of the adsorbent 19 is not particularly limited, and may be layered or granular. The adsorbent 19 is preferably in contact with the co-catalyst 18, but may be disposed in the vicinity. The form and arrangement of the adsorbent 19 may be selected in various ways as long as they do not impede electron transfer between the co-catalyst 18 and the p-type organic semiconductor layer 16.

[0023] <Oxidation of hydrazine> The catalytic electrode for hydrazine oxidation of the present invention oxidizes hydrazine through the same reaction (N2H4→N2+4H) by both photocatalysis and catalysis. + +4e - ) can be achieved. Therefore, according to the present invention, it becomes possible to oxidize hydrazine both under light irradiation and in the dark. Furthermore, under light irradiation, the photocatalytic action promotes the oxidation of hydrazine due to the action of the co-catalyst, so that hydrazine can be oxidized more effectively than with a conventional photocatalytic electrode that does not exhibit dual catalysis.

[0024] There is no particular limitation on the atmosphere in which the hydrazine oxidation catalyst electrode of the present invention is used, and it can be preferably used in the gas phase or liquid phase. Particularly preferably, in an electrolytic cell in which a working electrode and a counter electrode are installed, the hydrazine oxidation catalyst electrode of the present invention is used as the working electrode, and is immersed in a hydrazine solution in the electrolytic cell, and the working electrode is placed under light irradiation or in a dark place to oxidize hydrazine in the liquid phase. As the electrolytic cell, various types such as a single-chamber electrolytic cell or a two-chamber electrolytic cell can be selected. In addition, there is no particular limitation on the electrolysis method, and either constant current electrolysis or constant voltage electrolysis may be selected.

[0025] 2 is a schematic diagram showing an example of a configuration in which the catalytic electrode 10 for hydrazine oxidation of the present invention is used in a two-chamber electrolytic cell 20. The two-chamber electrolytic cell 20 is composed of an anode chamber 22 and a cathode chamber 24 separated by a salt bridge 26. The anode chamber 22 is composed of a working electrode 30 immersed in a hydrazine solution 38. The catalytic electrode 10 for hydrazine oxidation of the present invention is used as the working electrode 30. The cathode chamber 24 is composed of a counter electrode 34 immersed in an aqueous electrolyte solution 32. In the cathode chamber 24, a reference electrode 36 is appropriately placed by immersing it in the aqueous electrolyte solution 32 according to the electrolysis method. The electrode substrate 12, counter electrode 34, and reference electrode 36 of the working electrode 30 are connected to a power supply 40 by a conductor 42.

[0026] There is no particular limit to the concentration of hydrazine in the hydrazine solution 38, but the pH is preferably 0 or more. There is no particular limit to the solvent of the hydrazine solution 38 as long as hydrazine is soluble in the solvent, and water is usually used. The counter electrode 34 can be selected from various types according to the reduction reaction of the counter electrode 34. For example, when hydrogen ions are reduced at the counter electrode 34 to generate hydrogen, a precious metal electrode such as a platinum electrode or a gold electrode is used. The electrolyte aqueous solution 32 is preferably an acidic aqueous solution containing an acid such as phosphoric acid or sulfuric acid. A phosphoric acid aqueous solution is particularly preferred. The electrolyte aqueous solution 32 preferably has a pH of 5 or less, and more preferably a pH of 2 or less.

[0027] The power supply unit 40 is composed of a potentiostat, a function generator, a coulomb meter, and the like. Although there is no particular limitation on the light source (not shown) that irradiates the working electrode 30 with light, since the catalytic electrode of the present invention absorbs light having a wavelength of near infrared or less to exhibit photocatalytic activity, it is preferable to use a light source that includes light having a wavelength of about 1200 nm or less. As the light source, for example, sunlight, a halogen lamp, a xenon lamp, a mercury lamp, a fluorescent lamp, an LED, or the like can be suitably used.

[0028] In the above-mentioned configuration, the catalytic electrode 10 (30) for hydrazine oxidation of the present invention can oxidize hydrazine in the hydrazine solution 38 regardless of the presence or absence of light irradiation. There is no particular need to apply a potential to the working electrode in order to oxidize hydrazine, but a potential may be applied appropriately by the power supply device 40. Electrons released from hydrazine as it is oxidized are transported to the counter electrode 34. By configuring the counter electrode 34 to generate hydrogen, hydrazine can be decomposed into nitrogen and hydrogen (N2H4→N2+2H2) in the entire system. In this way, by using the catalytic electrode for hydrazine oxidation of the present invention, it is possible to produce hydrogen from hydrazine as a hydrogen carrier both under light irradiation and in the dark.

[0029] The catalytic electrode for hydrazine oxidation of the present invention can also be used for the purpose of burning hydrazine. In the above-mentioned two-chamber electrolytic cell 20, the counter electrode 34 is placed in an oxygen atmosphere, and oxygen reduction is induced at the counter electrode 34, thereby causing a combustion reaction of hydrazine (N2H4+O2→N2+2H2O) in the entire system. This is nothing other than a fuel cell using hydrazine as fuel, and the energy generated by the combustion reaction can be extracted as electrical energy. In addition, the reaction rate under light irradiation is faster than in the dark. In this way, the catalytic electrode of the present invention can be suitably used for the combustion reaction of hydrazine.

[0030] The mechanism by which the catalytic electrode of the present invention exhibits dual catalysis with respect to the oxidation of hydrazine is presumed to be as follows, taking into account the examples. (Oxidation by photocatalysis) When the catalyst electrode of the present invention is irradiated with light, excited electrons and holes are generated by the light absorption of the n-type / p-type organic semiconductor layer. The holes move to silver (co-catalyst) via the upper end of the valence band of the p-type organic semiconductor layer, and induce the oxidation of hydrazine on the surface of the co-catalyst. (Catalytic oxidation) In the dark, silver acts as a conventional catalyst (thermal catalyst) and induces the oxidation of hydrazine, which releases electrons. The excited electrons and the electrons released from hydrazine are transported to the counter electrode via a conductor, where they are consumed to induce reactions such as hydrogen production and oxygen reduction.

[0031] <Method of manufacturing catalytic electrode for hydrazine oxidation> A suitable method for producing the hydrazine oxidation catalyst electrode of the present invention includes a lamination step of laminating an n-type organic semiconductor layer and a p-type organic semiconductor layer in this order on an electrode substrate, and a silver supporting step of supporting silver on the p-type organic semiconductor layer. The method will be described in detail below.

[0032] (Lamination process) In the lamination step, first, an n-type organic semiconductor layer containing an n-type organic semiconductor material is laminated on an electrode substrate, and then a p-type organic semiconductor layer containing a p-type organic semiconductor material is laminated on the n-type organic semiconductor layer. As described above, perylene derivatives, naphthalene derivatives, fullerenes, carbon nanotubes, graphenes, etc. can be used as n-type organic semiconductor materials. As described above, phthalocyanine derivatives, naphthalocyanine derivatives, porphyrin derivatives, metal phthalocyanines, etc. can be used as p-type organic semiconductor materials. A material that forms a good pn junction between the n-type organic semiconductor layer and the p-type organic semiconductor layer is used. Both the n-type and p-type organic semiconductor layers can be laminated by known methods, such as vacuum deposition, sputtering, electrochemical coating (electrodeposition), coating, etc. Among these, the vacuum deposition method is preferred for uniform coating.

[0033] (Silver loading process) In the next silver supporting step, silver is supported on the p-type organic semiconductor layer to obtain the catalyst electrode for hydrazine oxidation of the present invention. The silver to be supported is in the form of powder or lump obtained by a known method. The method of supporting silver is a sputtering method, coating, or the like. For example, when coating, powdered silver is dispersed in water or alcohol, and the dispersion is coated on the p-type organic semiconductor layer and dried to support the silver. In this way, the catalyst electrode for hydrazine oxidation of the present invention is obtained.

[0034] In the silver supporting step, an adsorbent may be further supported. As described above, examples of materials used for the adsorbent include materials with high adsorption capacity such as activated carbon, activated alumina, molecular sieves, silica gel, and clay, and polymeric materials that can be made into thin films such as ion exchange resins, chitosan, polypropylene, and organic gels. In particular, ion exchange resins such as perfluorosulfonic acid / PTFE copolymers and perfluorocarboxylic acid / PTFE copolymers can be preferably used. The adsorbent may be supported, for example, by preparing a dispersion in which the adsorbent is dispersed in water or alcohol after supporting silver, applying the dispersion on the p-type organic semiconductor layer, and drying it. Alternatively, the adsorbent may be added to the silver dispersion, and the resulting dispersion may be applied on the p-type organic semiconductor layer and dried to support the adsorbent and silver at the same time.

[0035] The silver supporting step may be configured to include a silver compound supporting step of supporting a silver compound on the p-type organic semiconductor layer, and a silver generating step of generating silver from the supported silver compound, as shown below. This method is for obtaining the hydrazine oxidation catalyst electrode of the present invention by supporting a silver compound, which is a precursor of silver, on the p-type organic semiconductor layer, and then generating silver from the silver compound.

[0036] (Silver compound supporting process) In the silver compound supporting step, first, a silver compound is supported on the p-type organic semiconductor layer of the catalyst electrode obtained by the lamination step described above. The silver compound is a silver (I) compound that can generate silver by performing a treatment such as heating or reduction, and examples thereof include silver oxide (Ag2O), silver salts such as silver oxalate, silver nitrate, and silver acetate, silver halides such as silver chloride and silver bromide, and organic silver compounds such as silver neodecanoate, silver octylate, and silver salicylate. These can be obtained by known synthesis methods. Methods for supporting the silver compound include coating, sputtering, electrochemical coating (electrodeposition), and the like. For example, in the case of coating, a dispersion liquid in which a powdered silver compound is dispersed in water or alcohol, or a solution of the silver compound is coated on the p-type organic semiconductor layer and dried to support the silver compound.

[0037] In the silver compound supporting step, an adsorbent similar to that described in the silver supporting step can be further supported. The adsorbent is supported, for example, by dispersing the adsorbent in water or alcohol after supporting the silver compound, applying the dispersion onto the p-type organic semiconductor layer and drying it. Alternatively, the adsorbent may be added to the dispersion (or solution) of the silver compound described above, and the resulting mixture is applied onto the p-type organic semiconductor layer and dried, thereby supporting the adsorbent simultaneously with the silver compound.

[0038] The catalytic electrode carrying the silver compound obtained here will be described in detail in the section on other embodiments of the catalytic electrode.

[0039] (Silver production process) In the next silver generation step, silver is generated from the silver compound supported on the p-type organic semiconductor layer. Various methods such as reduction treatment, heat treatment, and exposure treatment can be used to generate silver depending on the properties of the silver compound used. The reduction process involves contacting the silver compound supported on the catalytic electrode with a reducing agent to produce silver. Examples of the reducing agent that can be used include hydrazine, carbon monoxide, and hydrogen. As a specific method, for example, the reduction process is performed by immersing the catalytic electrode supporting silver oxide in a liquid containing a reducing agent. This reduces the silver oxide to produce silver. The hydrazine solution in which the catalytic electrode is immersed may be a solution containing the hydrazine to be oxidized (e.g., hydrazine as a hydrogen carrier). This allows the silver compound to be reduced to silver by an in-situ reaction without the need for a separate reducing agent, and the catalytic electrode for hydrazine oxidation of the present invention can be obtained, followed by the oxidation of hydrazine and the production of hydrogen.

[0040] The heat treatment is a process in which a catalyst electrode carrying a silver compound such as silver oxide, silver salt, or organic silver compound is heated to thermally decompose the silver compound to generate silver. The heating temperature may be selected according to the type of silver compound used, and is not particularly limited. The exposure treatment is a process in which a catalyst electrode carrying a photosensitive silver compound such as silver halide is irradiated with light to decompose the silver compound to generate silver. For example, visible light, ultraviolet light, and X-rays can be appropriately used for the exposure treatment.

[0041] Through the above silver production process, silver is produced from the silver compound and supported on the p-type organic semiconductor layer, thereby obtaining the catalytic electrode for hydrazine oxidation of the present invention.

[0042] <Other aspects of catalytic electrode for hydrazine oxidation> A catalytic electrode for hydrazine oxidation according to another embodiment of the present invention is a catalytic electrode in which an n-type organic semiconductor layer and a p-type organic semiconductor layer are laminated in this order on an electrode substrate, and a co-catalyst containing a silver compound is supported on the p-type organic semiconductor layer. This catalytic electrode is a catalytic electrode obtained by the above-mentioned silver compound supporting step. When this catalytic electrode is immersed in a hydrazine solution for hydrazine oxidation in an electrolytic cell such as that shown in Fig. 2, silver is produced from the silver compound by the reduction of hydrazine. In this way, an electrode that exhibits photocatalytic and catalytic effects on the oxidation of hydrazine by an in-situ reaction is obtained. Therefore, the catalytic electrode for hydrazine oxidation of the present invention, which supports a promoter containing a silver compound such as silver oxide that can be reduced to silver by hydrazine, can also be used substantially preferably for hydrazine oxidation. EXAMPLES

[0043] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0044] <Creating a catalytic electrode> Example 1 The catalytic electrode of Example 1 was prepared as follows. An electrode substrate was a conductive transparent glass substrate (hereinafter referred to as "ITO substrate") coated with indium-tin oxide (ITO) (manufactured by Asahi Glass Co., Ltd., resistance 8 Ω / cm 2 ) was used. The ITO substrate was cut to 1.5 cm x 1 cm, and a conductive wire was attached to a 0.5 cm x 1 cm section using a silver-containing epoxy adhesive (Fujikura Chemical Industries, Ltd., D-500). Furthermore, the silver part (the surface of the hardened adhesive) was covered with an epoxy adhesive to insulate it from contact with the electrolyte aqueous solution.

[0045] An n-type organic semiconductor layer and a p-type organic semiconductor layer were laminated by vacuum deposition on an ITO substrate with a conductive wire attached. The n-type organic semiconductor material was a perylene derivative, 3,4,9,10-perylenetetracarboxyl-bisbenzimidazole (hereinafter referred to as "PTCBI"), and the p-type organic semiconductor material was a metal phthalocyanine, cobalt phthalocyanine (hereinafter referred to as "CoPc"). The ITO substrate with the conductive wire attached was placed in a vacuum deposition apparatus (ULVAC Kiko Co., Ltd., VPC-260) and the vacuum level was set to approximately 1.0 x 10 -3 PTCBI was deposited on the ITO-coated side of the ITO substrate to a thickness of about 220 nm under conditions of 0.03 nm / s and 0.02 Pa. Next, a vacuum of about 1.0×10 was applied to the deposited PTCBI. -3 CoPc was deposited to a thickness of about 70 nm at 100 Pa and a deposition rate of 0.03 nm / s. The resulting catalyst electrode is called "ITO / PTCBI / CoPc."

[0046] Next, silver oxide (Ag2O) was supported on ITO / PTCBI / CoPc. Silver oxide was synthesized according to the description in the literature (X. Xu et al., Applied catalysis B: Environmental, 2015, 176-177, 637). 13.0 mg of silver oxide was suspended in a mixture of 200 μL of alcohol solution (manufactured by Aldrich) containing 5 wt% of commercially available Nafion (registered trademark) and 800 μL of methanol. 23 μL of this suspension was dropped onto ITO / PTCBI / CoPc and dried at 70 ° C for 30 minutes. The obtained catalyst electrode was designated as Example 1.

[0047] Before using the catalytic electrode of Example 1 for the oxidation of hydrazine, it was evaluated using an X-ray diffraction apparatus (Rigaku Corporation, SmartLab 9 kW, radiation source: CuKα), and a peak attributed to silver oxide (AgO) was confirmed in the X-ray diffraction pattern (FIG. 3).

[0048] Comparative Example 1 A catalytic electrode of Comparative Example 1 was prepared in the same manner as in Example 1, except that silver oxide was not used.

[0049] <Evaluation of hydrazine oxidation ability> (Evaluation method) The hydrazine oxidation ability of the catalytic electrodes of Example 1 and Comparative Example 1 was evaluated using a two-chamber electrolytic cell. The two-chamber electrolytic cell used had the configuration shown in FIG. 2. First, a salt bridge was created in the following manner. 1.3 g of agar and 4.74 g of potassium nitrate were added to approximately 10 mL of distilled water, dissolved in a warm bath, and poured into the bridged portion of the two-chamber cell and cooled to solidify. Next, the catalytic electrode of Example 1 or Comparative Example 1 was placed in the anode chamber as a working electrode, and a platinum wire and a reference electrode (silver-silver chloride electrode) were placed in the cathode chamber as a counter electrode. As an aqueous electrolyte solution, a 5 mmol / L aqueous hydrazine solution (pH=11) was placed in the anode chamber (working electrode side), and an aqueous phosphoric acid solution (pH=0) was placed in the cathode chamber (counter electrode side). The counter electrode, reference electrode, and working electrode were connected to a potentiostat (HA-301, manufactured by Hokuto Denko Corporation). Furthermore, a function generator (HB-104, manufactured by Hokuto Denko Corporation) and a coulomb meter (HF-201, manufactured by Hokuto Denko Corporation) were connected to the potentiostat. In the two-chamber electrolytic cell with the above configuration, electrolysis was performed under conditions in which the gas atmosphere in the anode and cathode chambers, the light irradiation conditions, and the applied potential were changed. During electrolysis, the amount of nitrogen, which is a product of hydrazine decomposition, was measured using a gas chromatograph (GL Sciences, GC-3200; carrier gas, Ar; column, molecular sieve 5Å). Under conditions in which hydrogen was generated at the counter electrode, the amount of hydrogen generated was also measured.

[0050] (Hydrazine decomposition reaction) The hydrazine oxidation capability was evaluated by placing the anode and cathode chambers under an inert atmosphere. Under these conditions, hydrazine oxidation occurs at the working electrode and hydrogen generation occurs at the counter electrode, and hydrazine is decomposed into nitrogen and hydrogen (N2H4→N2+2H2) in the entire system. First, argon gas was passed through the anode and cathode chambers for 30 minutes to remove the dissolved oxygen in the electrolyte solution. A light intensity of 100 mW / cm was applied to the uncoated side of the ITO substrate of the catalyst electrode. 2 Electrolysis was performed for 3 hours while applying a potential of +0.3 V (vs. Ag / AgCl) to the sample. Electrolysis was also performed in the dark (without light irradiation).

[0051] Table 1 shows the results of measuring the amounts of nitrogen and hydrogen produced when the catalytic electrode of Example 1 or Comparative Example 1 was used as the working electrode. [Table 1]

[0052] When the catalytic electrode of Example 1 was used, the generation of nitrogen and hydrogen, which is a reduction product, associated with the oxidation of hydrazine was confirmed both under light irradiation and in the dark. The amount of nitrogen and hydrogen generated was greater under light irradiation than in the dark. From this result, it was found that the catalytic electrode of Example 1 exhibited dual catalysis and could oxidize hydrazine by both photocatalysis and catalysis. When the catalytic electrode of Comparative Example 1 was used, it was confirmed that nitrogen and hydrogen, which are reduction products, were generated as a result of the oxidation of hydrazine under light irradiation. However, in the dark, the oxidation of hydrazine was not induced, and the generation of nitrogen was not confirmed. From this result, it was confirmed that the catalytic electrode of Comparative Example 1 exhibits a photocatalytic effect on the oxidation of hydrazine, but does not exhibit any catalytic effect in the dark.

[0053] The catalytic electrode of Example 1 was used for electrolysis for 3 hours in the dark or under light irradiation, and was then evaluated again by X-ray diffraction. The X-ray diffraction patterns are shown in Figure 4 (in the dark) and Figure 5 (under light irradiation). In both Figures 4 and 5, no peaks attributed to silver oxide (Ag2O) were observed, but peaks attributed to silver (Ag) were observed. From this result, it was found that the silver oxide supported on the catalytic electrode of Example 1 was reduced to silver by contact with hydrazine, regardless of the presence or absence of light irradiation.

[0054] From the above results, it was found that in a catalytic electrode in which an n-type organic semiconductor layer and a p-type organic semiconductor layer are laminated in this order on an electrode substrate, the supported silver acts as a promoter for the oxidation of hydrazine and contributes to the occurrence of dual catalysis. In addition, a catalytic electrode supporting silver oxide can also be obtained by an in-situ reaction, and therefore it can be said to be a catalytic electrode that essentially exhibits dual catalysis for the oxidation of hydrazine.

[0055] (Hydrazine combustion reaction) Next, the oxidation ability of hydrazine was evaluated by placing the anode chamber under an inert gas atmosphere and the cathode chamber under an oxygen atmosphere. Under these conditions, oxidation of hydrazine occurs at the working electrode and oxygen reduction occurs at the counter electrode, and the hydrazine combustion reaction (N2H4+O2→N2+2H2O) occurs in the entire system. Argon gas was passed through the anode chamber for 30 minutes to remove the dissolved oxygen in the electrolyte solution. The cathode chamber was not passed through with argon gas, and was kept under an oxygen atmosphere (atmospheric conditions). A light intensity of 100 mW / cm was applied to the uncoated side of the ITO substrate of the catalyst electrode. 2 The reaction was carried out for 3 hours without applying a potential between the working electrode and the counter electrode. In the dark (without light irradiation), the reaction was carried out for 10 hours. After the reaction, the amount of nitrogen generated in the anode chamber was measured, and the nitrogen generation rate was calculated.

[0056] Table 2 shows the measurement results of the nitrogen production rate when the catalytic electrode of Example 1 was used as the working electrode. [Table 2]

[0057] When the catalytic electrode of Example 1 was used, the generation of nitrogen accompanying the oxidation of hydrazine was confirmed both under light irradiation and in the dark. The rate of nitrogen generation was higher under light irradiation than in the dark. From this result, it was confirmed that the catalytic electrode of Example 1 exhibited dual catalysis even under conditions aimed at the combustion of hydrazine, and was capable of oxidizing hydrazine by both photocatalysis and catalysis.

[0058] As described above, according to the present invention, it is possible to provide a catalytic electrode for hydrazine oxidation, which exhibits photocatalytic and catalytic actions on the oxidation of hydrazine and can oxidize hydrazine both under light irradiation and in the dark, and a method for producing the same. Furthermore, the catalytic electrode for hydrazine oxidation of the present invention can oxidize hydrazine more effectively than a conventional photocatalytic electrode that does not exhibit dual catalysis, since the photocatalytic action promotes the oxidation of hydrazine under light irradiation due to the action of a co-catalyst. Therefore, the catalytic electrode for hydrazine oxidation of the present invention can be effectively used in various industrial fields that require the oxidation of hydrazine, such as hydrogen production by decomposition of hydrazine and electric energy production by combustion of hydrazine. [Explanation of symbols]

[0059] 10. Catalytic electrode for hydrazine oxidation 12 Electrode base material 14 n-type organic semiconductor layer 16 p-type organic semiconductor layer 18 Cocatalyst 19 Adsorbents

Claims

1. A catalytic electrode for hydrazine oxidation used when burning hydrazine or decomposing hydrazine into hydrogen and nitrogen under light irradiation and in a dark place, the catalytic electrode comprising an n-type organic semiconductor layer made of a perylene derivative and a p-type organic semiconductor layer made of a metal phthalocyanine laminated in this order on an electrode substrate, the p-type organic semiconductor layer supporting a co-catalyst containing silver.

2. A catalytic electrode for hydrazine oxidation used when burning hydrazine or decomposing hydrazine into hydrogen and nitrogen under light irradiation and in a dark place, the catalytic electrode comprising an n-type organic semiconductor layer made of a perylene derivative and a p-type organic semiconductor layer made of a metal phthalocyanine laminated in this order on an electrode substrate, the p-type organic semiconductor layer supporting a promoter containing a silver compound.

3. 3. The catalyst electrode for hydrazine oxidation according to claim 1, wherein an adsorbent for adsorbing hydrazine is supported on the surface of the p-type organic semiconductor layer and / or the co-catalyst.

4. A method for manufacturing a catalytic electrode for hydrazine oxidation used in burning hydrazine or decomposing hydrazine into hydrogen and nitrogen under light irradiation and in a dark place, the method comprising: a lamination step of laminating an n-type organic semiconductor layer made of a perylene derivative and a p-type organic semiconductor layer made of a metal phthalocyanine in that order on an electrode substrate; and a silver loading step of loading silver on the p-type organic semiconductor layer.

5. 5. The method for producing a catalyst electrode for hydrazine oxidation according to claim 4, wherein the silver supporting step comprises a silver compound supporting step of supporting a silver compound on the p-type organic semiconductor layer, and a silver generating step of generating silver from the supported silver compound.

6. 6. The method for producing a catalyst electrode for hydrazine oxidation according to claim 5, wherein the silver producing step includes a step of contacting the silver compound with a reducing agent.

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