JP2008077999A - Catalyst used for electrochemical electrode and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst used for an electrochemical electrode having such structure that noble metal nanoparticles are carried on an inorganic oxide conductive carrier which is a substitute for carbon and to provide the manufacturing method of the catalyst. <P>SOLUTION: The catalyst used for the electrochemical electrode (an oxidation reduction electrode) is formed by carrying platinum nanoparticles on a titanium oxide (TiO<SB>x</SB>) nanostructure formed by dendritically aggregating titanium oxide nanoparticles having a nanometer size. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a catalyst used for an electrochemical electrode used in batteries, sensors, etc. using oxidation / reduction reactions, and more particularly to an electrochemical electrode composed of titanium oxide nanostructures and platinum nanoparticles. The present invention relates to a catalyst and a method for producing the same.

Catalysts with a structure in which a catalytic noble metal is supported on a carrier having a large specific surface area (over 10 m ² / g) are used for chemical synthesis of compounds and hazardous substances present in exhaust gas from internal combustion engines. As well as electrochemical electrodes typified by fuel cells. The noble metal material having a catalytic action needs to be present on the surface of the support with high dispersibility as nanoparticles having a particle size of about 1 to 10 nm in order to develop high catalytic activity.

  In a catalyst used for an electrochemical electrode such as a fuel cell, a carbon material having high electrical conductivity is generally used as a noble metal support. On the other hand, in combustion catalysts used for automobile exhaust gas purification, oxides such as aluminum oxide, zeolite, and titanium oxide are used as a carrier.

  As a method for producing a catalyst having a structure in which a noble metal is supported on a support, for example, in the case of a platinum-supported electrode catalyst, carbon black previously calcined is added to an aqueous solution such as chloroplatinic acid, suspended, and then evaporated to dryness. Examples thereof include those that are washed with water and washed to deposit platinum fine particles on the surface of carbon black.

Moreover, after impregnating and coating a powdered carbon carrier or oxide carrier with a noble metal precursor, a structure in which noble metal particles are deposited on the powdered carrier by firing at 1000 ° C. or higher after a drying process A method of forming is disclosed. (See Patent Document 1)
Furthermore, a method of impregnating a porous material made of a heat-resistant polymer or an inorganic oxide with a noble metal precursor solution and chemically reducing and precipitating is also disclosed. (See Patent Document 2)
In addition, after chemically synthesizing the composite oxide as the support precursor, after forming the support through the drying and firing steps, contacting the aqueous solution of the noble metal precursor, drying, and then heat-treating in a reducing atmosphere Is also disclosed. (See Patent Document 3)
As a technique for using a nanostructure as a catalyst used for an electrochemical electrode, a manganese oxide nanostructure used for an oxygen reduction electrochemical electrode and a method for producing the same are disclosed. (See Patent Document 4)
There have been reports on the generation of hydrogen peroxide which causes corrosion in electrochemical electrodes combining platinum and carbon. (See Non-Patent Document 1)
JP 2003-24798 A JP-A-2005-139376 JP 2006-35127 A Japanese Patent No. 3785543 JP 2006-210135 A Electrochemical and Solid-State Letters, 7 (12) A474-A476 (2004).

  A catalyst used for an electrochemical electrode typified by a fuel cell generally has a structure in which a catalyst material made of noble metal particles is supported on a conductive carrier made of a carbon material as described above in order to extract electricity to an external circuit. Is. However, as shown in Non-Patent Document 1, when a combination of platinum and carbon is used as a catalyst, the corrosion factor of the membrane-electrode assembly (MEA), which is the main component of the fuel cell, The resulting hydrogen peroxide will reduce the life of the fuel cell. It has been reported that the generation of hydrogen peroxide does not occur with platinum alone.

  Further, the catalyst in which the precious metal disclosed in Patent Documents 1 to 3 described above is supported on a single inorganic oxide is used for a chemical reaction or gas reforming at a high temperature. Large specific surface area and thermal and chemical stability. In general, however, inorganic oxides have low electrical conductivity and are not suitable for use in electrochemical electrodes.

  Furthermore, the use of the manganese oxide nanostructure disclosed in Patent Document 4 described above for an oxygen reduction electrode of a fuel cell or the like is stable when the electrolyte is alkaline or neutral. In the polymer electrolyte fuel cell (PEFC) in which the acid is acidic, there is a problem that manganese oxide is eluted in the electrolyte, which is not suitable for an acidic electrolyte.

  The present invention has been made in view of such a point, and provides a catalyst used for an electrochemical electrode having a structure in which noble metal nanoparticles are supported on an inorganic oxide conductive support instead of carbon, and a method for producing the same. With the goal.

  As a result of intensive studies to solve the above problems, the present inventor has found that the above object can be achieved by using a conductive titanium oxide nanostructure as a carrier, and to complete the present invention. It came.

  In order to solve the above problems, the catalyst used in the electrochemical electrode of the present invention is formed by supporting platinum nanoparticles on a titanium oxide nanostructure in which nanometer-sized titanium oxide nanoparticles are aggregated in a dendritic shape. It is structured.

  The method for producing a catalyst for use in the electrochemical electrode of the present invention includes a step of producing titanium oxide nanoparticles, and the titanium oxide nanoparticles are deposited in a substantially vertical direction on a conductive substrate. The manufacturing method of the catalyst used for the electrochemical electrode which has the process of forming the titanium oxide nanostructure which titanium oxide aggregated in dendritic form, and carrying | supporting a platinum nanoparticle on the said titanium oxide nanostructure It is.

  With the above configuration, the present invention can provide a catalyst used for an electrochemical electrode having a structure in which noble metal nanoparticles are supported on an inorganic oxide conductive support instead of carbon, and a method for producing the catalyst.

More specifically, the invention according to claim 1 of the present invention is an electric device in which platinum nanoparticles are supported on a titanium oxide nanostructure in which nanometer-sized titanium oxide nanoparticles are aggregated in a dendritic shape. It is a catalyst used for chemical electrodes. By using a nanostructure in which nanoparticles are agglomerated in a dendritic form as a support, the surface area can be dramatically increased, and excellent catalytic performance not found in catalysts using bulk materials can be achieved. By using TiO _x (x <2) having electrical conductivity instead of titanium dioxide which is an insulator, it is possible to facilitate the transfer of electrons between the reactant and the catalyst and to activate the catalytic ability. Furthermore, by supporting platinum nanoparticles on the surface of the titanium oxide nanostructure, generation of hydrogen peroxide can be suppressed, and it can be expected to improve the life of MEA.

  Here, in the invention described in claim 1, it is desirable that the titanium oxide nanostructure includes titanium monoxide nanoparticles.

The invention according to claim 3 of the present invention is an electrochemical electrode in which platinum nanoparticles are supported on a titanium oxide (TiO _x ) nanostructure in which nanometer-sized titanium oxide nanoparticles are aggregated in a dendritic shape. A method for producing a catalyst for use in manufacturing a titanium oxide nanoparticle, and depositing the titanium oxide nanoparticle by arranging the titanium oxide nanoparticle in a substantially vertical direction on a conductive substrate. This is a method for producing a catalyst for use in an electrochemical electrode, comprising a step of forming a dendritic titanium oxide nanostructure and a step of supporting platinum nanoparticles on the titanium oxide nanostructure. According to this method, a catalyst used for an electrochemical electrode in which platinum nanoparticles are supported on a titanium oxide (TiO _x ) nanostructure in which nanometer-sized titanium oxide nanoparticles are aggregated in a dendritic form can be easily obtained. Can be made.

  Here, when forming the titanium oxide nanostructure, it is desirable to provide a step of promoting oxidation of the titanium oxide to form titanium oxide nanoparticles having different valences.

  Furthermore, it is desirable that the raw material of the titanium oxide nanoparticles is a titanium monoxide sintered body.

  In addition, a laser ablation method is suitable for forming the titanium oxide nanostructure, and a sputtering method is suitable for the step of supporting the platinum nanoparticles.

According to the present invention, a catalyst used for an electrochemical electrode in which platinum nanoparticles are supported on a titanium oxide (TiO _x ) nanostructure in which nanometer-sized titanium oxide nanoparticles are aggregated in a dendritic manner. Thus, a catalyst used for an electrochemical electrode having a large surface area and exhibiting excellent catalytic activity can be provided.

  In addition, the method for producing a catalyst for use in the electrochemical electrode of the present invention can directly form a titanium oxide nanostructure carrying platinum nanoparticles on a conductive substrate. A method for producing a catalyst used for an electrochemical electrode that can be easily immobilized can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
In the present embodiment, a catalyst used for an electrochemical electrode in which platinum nanoparticles are supported on a titanium oxide (TiO _x ) nanostructure in which nanometer-sized titanium oxide nanoparticles are aggregated in a dendritic manner will be described. To do.

  The catalyst used for the electrochemical electrode in the present embodiment is composed of a support made of a titanium oxide nanostructure in which titanium oxide nanoparticles are aggregated in a dendritic shape, and platinum nanoparticles supported on the surface of the support. . The titanium oxide nanoparticles are the smallest structural unit in the form of particles, and particles having high crystallinity in which the crystal lattice can be clearly confirmed are particularly preferable. The average particle diameter of the titanium oxide nanoparticles is not limited, but is usually preferably in the range of 1 nm to 50 nm, and more preferably in the range of 2 nm to 20 nm. Furthermore, although the average particle diameter of the platinum nanoparticles is not limited, it is usually usually preferably in the range of 1 nm to 50 nm, more preferably in the range of 2 nm to 10 nm.

The oxidation state of the titanium oxide nanoparticles constituting the titanium oxide nanostructure is not limited. However, since titanium oxide exhibits conductivity in a state where oxygen vacancies are generated, _x of TiO _x is preferably less than 2. is there. In particular, since titanium monoxide (TiO) has metallic conductivity, the titanium oxide nanostructure preferably includes titanium monoxide nanoparticles.

  As a catalyst for an electrochemical electrode having the above structure, FIG. 1 shows a scanning electron micrograph of a nanostructured catalyst in which platinum nanoparticles are supported on a titanium oxide nanostructure in which titanium oxide nanoparticles are aggregated in a dendritic shape. Show. As is clear from the planar image of FIG. 1, the nanostructured catalyst forms a very porous structure useful as a catalyst. Furthermore, it can be seen from the cross-sectional image of FIG. 1 that the nanostructured catalyst has a so-called dendritic structure with a very high porosity of about 2 μm arranged in a substantially vertical direction.

Furthermore, the catalyst is a highly crystalline nano-sized nanocrystal having a size of about 2 to 10 nm on which the crystal lattice can be clearly confirmed, as is clear from the cross-sectional transmission electron microscope observation photograph in the vicinity of the surface in FIG. It can be seen that particles are present. From the electron diffraction measurement, it was confirmed that the surface nanoparticles were platinum (Pt). Furthermore, when an electron beam with a diameter of 1 nm was irradiated and evaluated by energy dispersive X-ray analysis (EDX), the uppermost nanoparticles were observed to have characteristic X-rays of Pt. However, when EDX analysis was performed by irradiating an electron beam with a diameter of about 100 nm, not only Pt but also characteristic X-rays of titanium (Ti) and oxygen (O) were observed, and the nanostructure was formed on the surface of TiO _x with Pt nanoparticles. Was shown to be a supported structure. On the other hand, it can be seen from the cross-sectional transmission electron microscope observation photograph near the center of the dendritic aggregate in FIG. 2B that nanoparticles having a particle size of about 2 nm are present with good dispersibility. The dispersed nanoparticles of about 2 nm were confirmed to be highly crystalline Pt nanoparticles by electron diffraction measurement. From XDX analysis using an electron beam with a diameter of 1 nm, characteristic X-rays of Pt, Ti, and O were observed. This is evidence that three types of elements exist in the thickness direction of the sample subjected to cross-sectional observation, and this indicates that Pt nanoparticles are supported on the surface of TiO _x . Furthermore, it was found from the electron diffraction results of nanoparticles having a diameter of about 5 to 10 nm that highly crystalline TiO nanoparticles were present.

From the above analysis results, the catalyst is supported on the surface of TiO _x nanostructures in which highly crystalline Pt nanoparticles having a particle size of about 2 to 10 nm are aggregated in a dendritic form with titanium oxide nanoparticles containing TiO. Structure.

By supporting platinum nanoparticles on TiO _x nanostructures in which nanometer-level titanium oxide nanoparticles are agglomerated in a dendritic manner as described above, the surface area is dramatically increased and bulk materials are used. In addition to exhibiting excellent catalytic performance not found in conventional catalysts, it is possible to exchange electrons between reactants and catalysts by using TiO _x (x <2) that has electrical conductivity instead of titanium dioxide as an insulator. And the catalytic ability can be activated.

  Furthermore, by supporting platinum nanoparticles on the surface of the titanium oxide nanostructure, generation of hydrogen peroxide can be suppressed, and it can be expected to improve the life of the MEA.

(Embodiment 2)
In the present embodiment, a catalyst used for an electrochemical electrode in which platinum nanoparticles are supported on a titanium oxide (TiO _x ) nanostructure in which nanometer-sized titanium oxide nanoparticles are aggregated in a dendritic manner. The method will be described in detail.

Method for producing a catalyst for use in the electrochemical electrode of the present embodiment, TiO a step of preparing a TiO _x nanoparticles, by depositing arranged in a substantially vertical direction a TiO _x nanoparticles on a conductive substrate _{The method} includes a step of forming a TiO _x nanostructure in which _x nanoparticles are aggregated in a tree shape, and a step of supporting platinum (Pt) nanoparticles on the TiO _x nanostructure. Furthermore, it is possible to provide a step of controlling the oxidation number of TiO _x by promoting the oxidation of the surface of the produced TiO _x nanoparticles.

According to this method, a catalyst used for an electrochemical electrode in which platinum nanoparticles are supported on a titanium oxide (TiO _x ) nanostructure in which nanometer-sized titanium oxide nanoparticles are aggregated in a dendritic form can be easily obtained. Can be made.
Hereinafter, each step will be described.

(1) Step of preparing a TiO _x nanoparticles and, TiO _x nanostructures TiO _x nanoparticles by depositing by arranging a TiO _x nanoparticles substantially vertically on a conductive substrate are aggregated into dendritic Step of Forming Body In the present embodiment, as a step of producing TiO _x nanoparticles, a method of applying energy to a solid material to desorb constituent materials and then rapidly cooling to form nanoparticles is used. Specifically, a gas evaporation method, a laser ablation method, a sputtering method, or the like may be used.

The TiO _x nanoparticles produced by the above process are deposited on a conductive substrate. Here, by controlling the atmospheric gas species and atmospheric pressure, the aggregation state of the nanoparticles is changed, and the structure (dendritic aggregation structure) in the deposition direction of the nanocrystals is controlled to be substantially vertical on the conductive substrate. It can be deposited in an orientation.

(2) carrying the Pt nanoparticles of Pt nanoparticles on TiO _x nano structures formed in step step (1) carrying on TiO _x nanostructures. As a process of supporting the Pt nanoparticles, a method of supporting Pt by depositing the solid material after applying energy to the solid material to desorb it is used. Specifically, a sputtering method, a laser ablation method, or the like may be used. Alternatively, the TiO _x nanostructure may be brought into contact with an aqueous solution in which a platinum precursor (compound such as chloroplatinic acid) is dissolved, dried, and then subjected to a reduction treatment to carry Pt nanoparticles.

More specifically, the surface of the TiO _x nanostructure in which the highly crystalline Pt nanoparticles having a particle size of about 2 to 10 nm shown in Embodiment 1 are aggregated in a dendritic form with titanium oxide nanoparticles containing TiO. A method for producing a catalyst used for an electrochemical electrode having a structure supported on the substrate will be described in detail.

Here, TiO _x nanoparticles are produced using a laser ablation method. Note that the laser ablation method is a method of irradiating a target material with laser light having a high energy density (pulse energy: about 1.0 J / cm 2 or more) to melt and desorb an irradiated target material surface.

First, after the inside of the nanoparticle production apparatus is evacuated to a final vacuum of about 10 ⁻⁷ Pa, an atmosphere gas (He) at a constant flow rate (about 0.5 SLM) is introduced via a mass flow controller. Here, the atmospheric gas pressure in the nanoparticle production apparatus is set to one pressure value in the range of about 100 to 1000 Pa by interlocking with the operation of the gas exhaust system mainly including the scroll pump or the helical groove pump. In this state, the surface of a titanium monoxide (TiO) sintered body target installed in the nanoparticle production apparatus is focused and irradiated with pulsed laser light. Here, an ArF excimer laser (wavelength: 193 nm) is used. At this time, a laser ablation phenomenon occurs on the surface of the TiO target, and ions of Ti, O, TiO _x or neutral particles (atoms, molecules, clusters) are desorbed, and the molecular and cluster levels are mainly large in the target normal direction. Keep going and inject. The desorbed material collides with the atmospheric gas atoms, thereby making the flight direction messed up and dissipating kinetic energy into the atmosphere, promoting association and aggregation in the gas phase, and forming nanoparticles. The produced TiO _x nanoparticles are deposited on a conductive substrate disposed facing the TiO target to form a TiO _x nanostructure.

In the above, as the atmosphere gas, although using He gas, Ar, Kr, Xe, may be another inert gas such as N _2. In this case, what is necessary is just to set a pressure so that gas density may become equivalent to the case of He gas. For example, when Ar (gas density: 1.78 g / l) is used as the atmospheric gas, the pressure may be set to about 0.1 times based on He (gas density: 0.18 g / l).

Furthermore, by adding oxygen (O ₂ ) gas at a rate of 0.1% to the atmospheric gas and introducing it, the oxidation of the surface of the TiO _x nanoparticles can be promoted and the oxidation number of TiO _x can be controlled. In this case, the atmospheric gas pressure may be 99.3% when only He is used as the atmospheric gas. The proportion of O ₂ gas added to the atmospheric gas is not limited to 0.1%.

Next, Pt nanoparticles are supported on the TiO _x nanostructure formed in the above process. Here, Pt is supported using a sputtering method. After evacuating the inside of the sputtering apparatus to an ultimate vacuum of about 10 ⁻⁴ Pa, Ar gas is introduced at a constant flow rate (about 10 sccm) via a mass flow controller, and the atmospheric gas pressure of the sputtering apparatus is about 0.5 Pa. Differential exhaust is performed so that a constant pressure of Next, an RF voltage is applied to a Pt target in the sputtering apparatus, and Pt is deposited on the TiO _x nanostructure by sputtering for a predetermined time with an RF power of 100 W.

As described above, according to the method for producing a catalyst used for the electrochemical electrode of the present embodiment, a titanium oxide (TiO _x ) nanostructure in which nanometer-sized titanium oxide nanoparticles are aggregated in a dendritic shape. A catalyst used for an electrochemical electrode having platinum nanoparticles supported thereon can be easily produced.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

(Example 1)
Preparation of platinum nanoparticle-supported titanium oxide nanostructure catalyst (test electrode 1)
A platinum nanoparticle-supported titanium oxide nanostructure catalyst was produced using the production method shown in the second embodiment.

First, a TiO _x nanostructure was deposited on carbon paper (TGP-H-120 manufactured by Toray Industries, Inc., thickness 0.37 mm mm, porosity 78%) having a size of 18 × 18 mm as a conductive substrate. Specifically, He gas is introduced as an atmospheric gas at a flow rate of 0.5 SLM, the atmospheric gas pressure is 667 Pa, a TiO sintered body (purity: 99.9%) is used as a target, and TiO _x nanoparticles are formed by laser ablation. Fabrication and deposition were performed in an 8 × 8 mm region for 100 seconds to obtain a titanium oxide (TiO _x ) nanostructure in which nanometer-sized titanium oxide nanoparticles were aggregated in a dendritic shape.

  Next, Pt is deposited in an 8 × 8 mm region for 50 seconds by sputtering (RF output: 100 W, target substrate 70 mm, film formation rate 0.1 nm / second), and the platinum nanoparticle-supported titanium oxide nanostructure catalyst is formed. A test electrode 1 fixed on carbon paper was obtained. The amount of Pt supported was about 7 μg.

FIG. 3 shows a scanning electron micrograph of the test electrode 1. A structure in which platinum nanoparticles were supported on a titanium oxide (TiO _x ) nanostructure in which nanometer-sized titanium oxide nanoparticles were aggregated in a dendritic shape was obtained.

(Example 2)
Preparation of platinum nanoparticle-supported titanium oxide nanostructure catalyst (test electrode 2)
A platinum nanoparticle-supported titanium oxide nanostructure catalyst was produced using the production method shown in the second embodiment.

First, a TiO _x nanostructure was deposited on carbon paper (TGP-H-120 manufactured by Toray Industries, Inc., thickness 0.37 mm mm, porosity 78%) having a size of 18 × 18 mm as a conductive substrate. Specifically, 0.1% O ₂ gas is added to He gas as the atmospheric gas and introduced at a flow rate of 0.5 SLM, and the TiO sintered body (purity: 99.9%) is set at an atmospheric gas pressure of 662 Pa. Titanium oxide (TiO _x ) nanostructures in which nanometer-sized titanium oxide nanoparticles are agglomerated in a dendritic manner by preparing and depositing TiO _x nanoparticles as a target by laser ablation for 100 seconds in an 8 x 8 mm region Got.

  Next, Pt is deposited in an 8 × 8 mm region for 50 seconds by sputtering (RF output: 100 W, target substrate 70 mm, film formation rate 0.1 nm / second), and the platinum nanoparticle-supported titanium oxide nanostructure catalyst is formed. A test electrode 2 fixed on carbon paper was obtained. The amount of Pt supported was about 7 μg.

FIG. 4 shows a scanning electron micrograph of the test electrode 2. A structure in which platinum nanoparticles were supported on a titanium oxide (TiO _x ) nanostructure in which nanometer-sized titanium oxide nanoparticles were aggregated in a dendritic shape was obtained.

(Comparative example)
Preparation of Comparative Electrode The carbon paper alone (Comparative Electrode 1) was prepared as a comparative electrode for comparison of catalytic activity. In addition, a comparative electrode 2 in which TiO _x nanostructures were deposited on carbon paper was prepared in the same manner as in Example 2 that did not carry Pt nanoparticles.

  Furthermore, a comparative electrode 3 was prepared in which a manganese oxide nanostructure was deposited on carbon paper under the same production conditions as in Example 2 except that the target was a manganese monoxide sintered body.

(Example 3)
Evaluation of Oxygen Reduction Activity of Test Electrode A three-electrode cell having the configuration shown in FIG. 5 was constructed, and oxygen reduction characteristics at the test electrode were evaluated by current-voltage characteristics. In FIG. 5, 1 is an air electrode, 1a is a test electrode or a comparison electrode, 1b is a fluororesin porous sheet, 1c is an electrode lead, 2 is a counter electrode, 3 is a reference electrode, 4 is an electrolyte, and 5 is an air electrode. This is a glass cell having an opening with a diameter of 8 mm. As shown in FIG. 5, the air electrode 1 is exposed to the atmosphere on the surface of the fluororesin porous sheet 1 b and the other surface is in contact with the electrolyte solution 4 (that is, the test electrode). Alternatively, they are arranged so as to be in contact with the reference electrode 1a). As the electrolytic solution 4, a 0.1 N sulfuric acid (H 2 SO 4) aqueous solution having a pH of 2 was used. The counter electrode 2 was platinum, and the reference electrode 3 was an Ag / AgCl (saturated KCl) electrode. The test electrode or comparative electrode 1a and the fluororesin porous sheet 1b were brought into close contact with each other.

  FIG. 6 shows a comparison of current-voltage characteristics when the test electrodes 1 and 2 and the comparison electrodes 1 and 2 are the air electrode 1. Further, during the measurement, the applied voltage was maintained for at least 10 seconds and then measured. It was found that the test electrodes 1 and 2 can obtain a current about 100 times larger than the comparative electrodes 1 and 2 under the same overvoltage (0.3 V).

  On the other hand, in the comparative electrode 3 using the manganese oxide nanostructure, manganese oxide was eluted in the sulfuric acid electrolyte during measurement, and oxygen reduction activity evaluation could not be performed. Unlike Patent Document 4, it was found that manganese oxide nanostructures are not suitable for acidic electrolytes.

  The catalyst used for the electrochemical electrode according to the present invention has excellent catalytic activity and is useful for electrodes such as fuel cells, gas sensors and the like. Further, it can be widely applied to uses such as electrochemical electrodes using a catalyst carrier having conductivity instead of a carbon support having poor corrosion resistance.

Catalyst for use in an electrochemical electrode in which platinum nanoparticles are supported on a titanium oxide (TiO _x ) nanostructure in which nanometer-sized titanium oxide nanoparticles are aggregated in a dendritic form in Embodiment 1 of the present invention Scanning electron micrograph of Catalyst for use in an electrochemical electrode in which platinum nanoparticles are supported on a titanium oxide (TiO _x ) nanostructure in which nanometer-sized titanium oxide nanoparticles are aggregated in a dendritic form in Embodiment 1 of the present invention Transmission electron microscope observation photograph Scanning electron micrograph of test electrode 1 in Example 1 of the present invention Scanning electron micrograph of test electrode 1 in Example 2 of the present invention Cross-sectional schematic diagram of a triode electrode cell in the measurement of the embodiment of the present invention The graph which shows the current-voltage (electromotive force) characteristic with respect to the oxygen reduction reaction in the test electrodes 1 and 2, and a comparison electrode

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air electrode 1a Air electrode mixture 1b Fluororesin porous sheet 1c Electrode lead 2 Counter electrode 3 Reference electrode 4 Electrolytic solution 5 Glass cell

Claims (7)

A catalyst used for an electrochemical electrode in which platinum nanoparticles are supported on a titanium oxide (TiO _x , x <2) nanostructure in which nanometer-sized titanium oxide nanoparticles are aggregated in a tree shape.   The catalyst used for an electrochemical electrode according to claim 1, comprising titanium monoxide nanoparticles as nanometer-sized titanium oxide nanoparticles.   A method for producing a catalyst for use in an electrochemical electrode in which platinum nanoparticles are supported on a titanium oxide nanostructure obtained by agglomerating nanometer-sized titanium oxide nanoparticles in a dendritic form, comprising: A step of forming, and a step of forming a titanium oxide nanostructure in which the titanium oxide is aggregated in a dendritic form by depositing the titanium oxide nanoparticles arranged in a substantially vertical direction on a conductive substrate; and The manufacturing method of the catalyst used for the electrochemical electrode which has the process of carry | supporting a platinum nanoparticle on the said titanium oxide nanostructure.   The manufacturing method of the catalyst used for the electrochemical electrode of Claim 3 which comprises the process of promoting the oxidation of the said titanium oxide produced, and setting it as the titanium oxide nanoparticle from which a valence differs.   The method for producing a catalyst for use in an electrochemical electrode according to claim 4, wherein the raw material of the titanium oxide nanoparticles is a titanium monoxide sintered body.   The method for producing a catalyst for use in an electrochemical electrode according to any one of claims 3 to 5, wherein the titanium oxide nanostructure in which the titanium oxide nanoparticles are aggregated in a dendritic manner is produced by a laser ablation method.   The method for producing a catalyst for use in an electrochemical electrode according to any one of claims 3 to 6, wherein the platinum nanoparticles are supported by a sputtering method.

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