Supported metal catalysts, electrochemical cells

Abstract

The present invention provides a supported metal catalyst which has enhanced electrical conductivity.　The present invention provides a supported metal catalyst which is provided with a carrier powder and metal fine particles that are supported by the carrier powder, wherein: the carrier powder is an assembly of carrier fine particles; each of the carrier fine particles has a chain part that is configured by fusion bonding a plurality of crystallites in the form of a chain; the carrier fine particles are configured from a metal oxide; the metal oxide is doped with a dopant element; and the atomic ratio of titanium to the total of titanium and tin is from 0.30 to 0.80.

Description

[Technical field]

[0001] The present invention relates to a supported metal catalyst and an electrochemical cell. The supported metal catalyst of the present invention can be used, for example, as a catalyst for an electrochemical reaction in an electrochemical cell. The electrochemical cell means a cell that generates an electrochemical reaction, and examples thereof include a fuel cell that generates electricity using fuel such as hydrogen or methanol through an electrochemical reaction, a hydrogen purification booster that produces high-pressure, high-purity purified hydrogen gas from a hydrogen-containing gas through an electrochemical reaction, a redox flow battery that performs charging and discharging through a redox reaction, and a water electrolysis cell that decomposes water into hydrogen and oxygen through an electrochemical reaction. [Background technology]

[0002] Patent Document 1 discloses that a supported metal catalyst, in which a metal catalyst is supported on a support made of titanium oxide doped with a different metal, is used in the catalyst layer of the anode electrode of a fuel cell. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2016 / 203679 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the internal resistance of the fuel cell of Patent Document 1 cannot be said to be sufficiently small, and it is desirable to increase the electrical conductivity of the supported metal catalyst.

[0005] The present invention has been made in view of the above circumstances, and aims to provide a supported metal catalyst having enhanced electrical conductivity. [Means for solving the problem]

[0006] According to the present invention, there is provided a supported metal catalyst comprising a support powder and metal particles supported on the support powder, wherein the support powder is an aggregate of support particles, the support particles have a chain-like portion formed by a plurality of crystallites fused and bonded in a chain shape, the support particles are composed of a metal oxide, the metal oxide is doped with a doping element, and the atomic ratio of titanium to the sum of titanium and tin is 0.30 to 0.80.

[0007] As a result of investigations, the inventors found that the electrical conductivity is particularly high when the atomic ratio of titanium to the total of titanium and tin in the metal oxide constituting the support fine particles is 0.30 to 0.80, leading to the completion of the present invention. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a model diagram of the catalyst structure of a supported metal catalyst 100. [Diagram 2] 2 is a diagram of carrier particles 150 extracted from FIG. [Diagram 3] FIG. 2 is a diagram showing the state of branches 160 of the carrier particles 150 in FIG. [Figure 4] FIG. 2 is a diagram showing gas diffusion paths in FIG. [Diagram 5] An example of the distribution of voids 110 contained in the carrier powder is shown. [Figure 6] 1 is an example of a TEM image of a supported metal catalyst 100. [Figure 7] A model diagram of a fuel cell is shown. [Figure 8] 1 is a cross-sectional view through the center of a burner 2 of a production apparatus 1 for producing a carrier powder. [Figure 9] FIG. 9 is an enlarged view of a region X in FIG. [Figure 10] 9 is a cross-sectional view taken along line AA in FIG. 8. [Figure 11] FIG. 11 is an enlarged view of an area Y in FIG. [Figure 12] 1 shows a flow of a process for supporting and reducing metal fine particles 130. [Figure 13]1 is a graph showing the measurement results of electrical conductivity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Various characteristic features shown in the following embodiment can be combined with each other. Also, each characteristic feature can be an invention independently.

[0010] 1-1. Supported metal catalyst 100 As shown in Figures 1 to 4, the supported metal catalyst 100 comprises a support powder which is an aggregate of support particles 150 having a chain-like portion formed by fusion-bonding a plurality of crystallites 120 into a chain shape, and metal particles 130 supported on the support powder.

[0011] The electrical conductivity of the supported metal catalyst 100 is preferably 0.02 S / cm or more, and more preferably 0.03 S / cm or more. The electrical conductivity is, for example, 0.02 to 1000 S / cm, specifically, for example, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 1, 10, 100, or 1000 S / cm, and may be within a range between any two of the numerical values ​​exemplified here.

[0012] Each component will be described below.

[0013] 1-1. Carrier microparticles 150 and carrier powder As shown in Fig. 1, the support fine particle 150 has a three-dimensional void 110 surrounded by its branches 160 and holes present between the multiple branches. The branches 160 are portions where a chain-like portion formed by fusion-bonding multiple crystallites 120 constituting the support fine particle 150 branches off as branches. A gas diffusion path that diffuses oxygen as an oxidant and / or hydrogen as a fuel and transports them onto the supported metal catalyst 100 is formed by the three-dimensional configuration of the support fine particle 150 described above.

[0014] As shown in Figs. 1 to 3 as examples of the structural model of the supported metal catalyst, the support fine particle 150 has a total of four holes, including a first hole surrounded by points (branching points, hereinafter sometimes simply referred to as branches) b1, b2, b5, b4, and b1 where branches are connected to each other, a second hole surrounded by branching points b1, b2, b3, and b1, a third hole surrounded by branching points b2, b3, b6, b7, b5, and b2, and a fourth hole surrounded by branching points b1, b3, b6, b7, b5, b4, and b1. Here, if the surface surrounded by the branching points of each hole (first to fourth hole) is the hole surface, the void 110 is a three-dimensional space surrounded by these four hole surfaces. The support fine particle 150 has a plurality of holes surrounded by a plurality of branching points where a plurality of branches are connected to each other in this way. And the three-dimensional space (void) surrounded by a plurality of holes is continuously provided. Therefore, this gap becomes a gas diffusion path (gas diffusion path) for oxygen, hydrogen, etc. Fig. 4 is a diagram showing the gas diffusion path in Fig. 1. Fig. 4 shows an example of a gas diffusion path (gas diffusion path) of a gap 110. A flow (gas diffusion path) 170 of an oxidant (gas), a fuel gas, etc. can flow in a desired direction through the gap 110 as shown in Fig. 4. In other words, this gap 110 becomes a gas diffusion path.

[0015] A simple configuration of the carrier fine particles 150 may simply include one hole (for example, a first hole surrounded by branch points b1, b2, b5, b4, and b1). In this case, the carrier fine particles 150 will have a void 110 equal to the thickness of the crystallite grain of the crystallite 120. An even simpler configuration may be one in which the carrier fine particles 150 have one or more branches. Even in this case, the carrier fine particles 150 cannot come into close contact with each other due to the presence of branches, and voids 110 can be provided between them.

[0016] The above-mentioned hole may be rephrased as a closed curve (closed loop). Alternatively, it may be rephrased as having a void 110 surrounded by a closed surface including the above-mentioned multiple branch points (for example, branch points b1 to b7). The branch points b1 to b7 may be regarded as the center of gravity of the metal oxide crystallites constituting the carrier microparticles 150, in which the branches are connected to each other, or may be any one point on the crystallite.

[0017] The carrier fine particle 150 has a branch 160 consisting of a chain-like portion formed by fusing and bonding a plurality of crystallites 120 in a chain shape, and has the property of conducting electrons itself. As shown in Figures 1 to 4, the carrier fine particle 150 has a plurality of branches 160, and the branches are in a network state via branch points (b1 to b7) where the branches are connected to each other, and the branches have an electrically conductive property between them. Therefore, the branch 160 of the carrier fine particle 150 shown by the dotted line from point P0 in Figure 1 itself constitutes an electron conduction path (electron conduction path) 140.

[0018] The size of the crystallite 120 is preferably 1 to 100 nm, more preferably 5 to 40 nm. Specifically, the size is, for example, 1, 5, 10, 15, 20, 25, 30, 35, 40, 50, or 100 nm, and may be within a range between any two of the values ​​exemplified here. The size of the crystallite 120 (crystallite diameter) can be calculated based on the Scherrer formula from the half-width of the peak in the XRD pattern.

[0019] The aggregate of the carrier fine particles 150 is in a powder form. Such an aggregate is called a "carrier powder."

[0020] The average particle size of the carrier fine particles 150 in the carrier powder is 0.1 μm to 4 μm, and preferably 0.5 μm to 2 μm. The average particle size of the carrier fine particles 150 can be measured by a laser diffraction / scattering type particle size distribution measuring device.

[0021] The specific surface area of ​​the carrier powder is 12m 2 / g or more is preferable, and 25m 2 / g or more is more preferable. The specific surface area is, for example, 12 to 100 m 2 / g, specifically, for example, 12, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100m 2 / g and may be within the range between any two of the values ​​exemplified herein.

[0022] An example of the distribution of voids 110 contained in the support powder is shown in Figure 5. The distribution of voids 110 can be obtained by measuring the volume of the three-dimensional voids in the support powder using a mercury porosimeter. Figure 5 shows the cumulative distribution of the value (sphere equivalent diameter by mercury intrusion method) obtained by calculating the volume per void from the measured volume value and the number of voids and converting it into the diameter of a sphere having the same volume as the calculated volume. As shown in Figure 5, it is preferable that the support powder has voids (primary pores) of 11 nm or less and voids (secondary pores) larger than 11 nm. This ensures a gas diffusion path.

[0023] The carrier powder preferably has a porosity of 50% or more, more preferably 60% or more. The porosity is, for example, 50 to 80%, specifically, for example, 50, 55, 60, 65, 70, 75, or 80%, and may be within a range between any two of the values ​​exemplified here. The porosity can be determined by the ratio of the bulk density of the carrier powder molded with a uniaxial pressure molding machine (molded body size: 5 mm x 5 mm x 30 mm, molding pressure 2 MPa or less) to the true density of the carrier powder, mercury intrusion porosimetry, or FIB-SEM.

[0024] The carrier powder preferably has an angle of repose of 50 degrees or less, more preferably 45 degrees or less. In this case, the carrier powder has the same fluidity as wheat flour and is easy to handle. The angle of repose is, for example, 20 to 50 degrees, specifically, for example, 20, 25, 30, 35, 40, 45, or 50 degrees, and may be within a range between any two of the values ​​exemplified here. The angle of repose can be determined by a falling volume method.

[0025] The carrier fine particles 150 are composed of a metal oxide. The metal oxide is doped with a doping element. The doping element is an element with a different valence from titanium and tin. As the doping element, at least one is selected from rare earth elements such as yttrium, group 5 elements such as niobium and tantalum, group 6 elements such as tungsten, and group 15 elements such as antimony. By doping with such an element, it is possible to impart electrical conductivity to the carrier fine particles. Among such elements, group 5 elements such as niobium and tantalum, or group 6 elements such as tungsten are preferred, and tantalum, niobium, antimony, or tungsten are particularly preferred. Tantalum and tungsten are particularly preferred because they have a large solid solubility limit.

[0026] The atomic ratio of the doping element to the total metal contained in the metal oxide is preferably 0.05 to 0.30. In this case, the electrical conductivity of the supported metal catalyst 100 is particularly high. Specifically, this atomic ratio is, for example, 0.05, 0.10, 0.15, 0.20, 0.25, or 0.30, and may be within a range between any two of the numerical values ​​exemplified here.

[0027] The metal oxide is preferably a composite oxide of titanium and tin, and the atomic ratio of titanium to the total of titanium and tin is 0.30 to 0.80, and preferably 0.40 to 0.80. In this case, the electrical conductivity of the supported metal catalyst 100 is high. Specifically, this atomic ratio is, for example, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, or 0.80, and may be within a range between any two of the numerical values ​​exemplified here.

[0028] 1-2. Metal fine particles 130 The metal fine particles 130 are fine particles of a metal or alloy that can function as a catalyst. The metal fine particles 130 preferably contain platinum, and more preferably are platinum. The average particle diameter of the numerous metal fine particles 130 supported on the carrier powder is 3 to 10 nm. Specifically, the average particle diameter may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 nm, and may be within a range between any two of the numerical values ​​exemplified here. If the average particle diameter of the metal fine particles 130 is less than 3 nm, they will dissolve as the electrode reaction progresses, and if it is greater than 10 nm, the electrochemically active surface area will be small, and the desired electrode performance will not be obtained. The metal microparticles 130 are particles with higher contrast than the crystallites among particles dispersed on the surface of the crystallites (120) having a crystallite size of 1 to 100 nm among particles photographed in a TEM transmission image of the supported metal catalyst 100 as shown in Fig. 6. The size of the metal microparticles can be calculated by measuring the diameters of the circumscribed circles of all the metal microparticles 130 photographed and calculating the arithmetic average.

[0029] The metal microparticle 130 preferably includes a core and a skin layer that covers the core. The core preferably includes an alloy of a precious metal and a transition metal. The skin layer preferably includes a precious metal. The precious metal is preferably platinum, and the transition element is preferably cobalt (Co) or nickel (Ni), with cobalt being particularly preferred.

[0030] It is preferable that titanium is dissolved in the metal microparticles 130, and it is preferable that more titanium is dissolved in the core than in the skin layer. In this way, the activity of the core is improved by dissolving a large amount of titanium in the core.

[0031] The amount of the metal particles 130 supported is preferably 1 to 50 mass %, and more preferably 5 to 25 mass %. Specific examples of the amount supported are 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 mass %, and may be within a range between any two of the numerical values ​​exemplified here.

[0032] The electrochemically active surface area of ​​the supported metal catalyst 100 is 20 m 2 / g or more. This surface area is, for example, 20 to 200 m 2 / g, specifically, for example, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200m 2 / g and may be within a range between any two of the numerical values ​​exemplified herein. The electrochemically active surface area can be determined by the rotating ring-disk electrode method or cyclic voltammetry of a membrane electrode assembly (sweep rate 0.1 V / sec or less).

[0033] 2. Fuel Cell 200 A model diagram of a fuel cell of the present invention is shown in Fig. 7. In Fig. 7, a fuel cell 200 is configured such that a catalyst layer 220A and a gas diffusion layer 210A on the anode 201 side face a catalyst layer 220K and a gas diffusion layer 210K on the cathode 202 side, with an electrolyte membrane 230 sandwiched between them. The anode gas diffusion layer 210A, the anode catalyst layer 220A, the electrolyte membrane 230, the cathode catalyst layer 220K, and the cathode gas diffusion layer 210K are arranged in this order. By connecting a load 203 between the anode 201 and the cathode 202 of the fuel cell 20, power is output to the load 203.

[0034] At least one of the anode side catalyst layer 220A and the cathode side catalyst layer 220K is preferably formed of the supported metal catalyst 100, and it is more preferable that the anode side catalyst layer 220A is formed of the supported metal catalyst 100. The supported metal catalyst 100 has a higher electrical resistance in an oxygen atmosphere than in a hydrogen atmosphere. For this reason, when the supported metal catalyst 100 is used in the anode side catalyst layer 220A, the occurrence of an oxygen reduction reaction in the anode side catalyst layer 220A during start-up and stop of the fuel cell is suppressed, and even if the support of the cathode side catalyst layer 220K is carbon, the corrosion reaction is suppressed, and the deterioration of the power generation performance of the fuel cell is suppressed.

[0035] Examples of catalysts other than the supported metal catalyst 100 include the catalyst disclosed in Patent Document 1, catalysts in which metal particles are supported on a support of a ceramic other than the metal oxide of the present invention (e.g., tin oxide, titanium oxide), and catalysts in which metal particles are supported on a carbon support.

[0036] 3. Manufacturing method of carrier powder First, a manufacturing apparatus 1 that can be used to manufacture a carrier powder will be described with reference to Figures 8 to 11. The manufacturing apparatus 1 includes a burner 2, a raw material supply unit 3, a reaction tube 4, a recovery vessel 5, and a gas storage unit 6. The raw material supply unit 3 includes an outer tube 13 and a raw material flow tube 23.

[0037] The burner 2 is cylindrical, and the raw material supply unit 3 is disposed inside the burner 2. Burner gas 2a flows between the burner 2 and the outer cylinder 13. The burner gas 2a is used to form a flame 7 at the tip of the burner 2 by ignition. A high-temperature region of 1000°C or more is formed by the flame 7. The burner gas 2a preferably contains a combustible gas such as propane, methane, acetylene, hydrogen, or nitrous oxide. In one example, a mixed gas of oxygen and propane can be used as the burner gas 2a. The temperature of the high-temperature region is, for example, 1000 to 2000°C, specifically, for example, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, or 2000°C, and may be within a range between any two of the numerical values ​​exemplified here.

[0038] A raw material solution 23a for producing a carrier powder flows through the raw material flow tube 23. The raw material solution 23a contains a titanium compound and a tin compound. Examples of the titanium compound and the tin compound include fatty acid titanium and fatty acid tin. The carbon number of the fatty acid is, for example, 2 to 20, preferably 4 to 15, and more preferably 6 to 12. The fatty acid is preferably octylic acid.

[0039] The raw material solution 23a may contain a metal compound for doping the carrier fine particles 150. Examples of the metal compound include fatty acid metal (Nb, Ta, W, etc.) salts. The number of carbon atoms in the fatty acid is, for example, 2 to 20, preferably 4 to 15, and more preferably 6 to 12. Examples of fatty acid metal salts include niobium octylate, tantalum octylate, antimony octylate, and tungsten octylate.

[0040] In the raw material solution 23a, the titanium compound and the tin compound are preferably dissolved or dispersed in a non-aqueous solvent. Examples of the non-aqueous solvent include organic solvents such as turpentine. If the raw material solution 23a contains moisture, the fatty acid titanium and fatty acid tin may be hydrolyzed and deteriorated.

[0041] A mist-forming gas 13a used to turn the raw solution 23a into mist flows between the outer cylinder 13 and the raw material flow cylinder 23. When the mist-forming gas 13a and the raw material solution 23a are ejected together from the tip of the raw material supply unit 3, the raw material solution 23a is turned into mist. The mist 23b of the raw material solution 23a is sprayed into the flame 7, and the titanium compound and the tin compound in the raw material solution 23a undergo a thermal decomposition reaction in the flame 7 to generate a carrier powder that is an aggregate of carrier fine particles 150 having a chain-like portion formed by fusion-bonding the crystallites 120 into a chain-like portion. The mist-forming gas 13a is, for example, oxygen.

[0042] The reaction tube 4 is provided between the collector 5 and the gas storage section 6. A flame 7 is formed in the reaction tube 4. The collector 5 is provided with a filter 5a and a gas exhaust section 5b. Negative pressure is applied to the gas exhaust section 5b. Therefore, an airflow toward the gas exhaust section 5b is generated in the collector 5 and the reaction tube 4.

[0043] The gas storage section 6 is cylindrical and includes a cooling gas inlet 6a and a slit 6b. A cooling gas 6g is introduced into the gas storage section 6 from the cooling gas inlet 6a. Since the cooling gas inlet 6a is oriented in a direction along the tangent of the inner peripheral wall 6c of the gas storage section 6, the cooling gas 6g introduced into the gas storage section 6 through the cooling gas inlet 6a swirls along the inner peripheral wall 6c. A burner insertion hole 6d is provided in the center of the gas storage section 6. The burner 2 is inserted into the burner insertion hole 6d. The slit 6b is provided at a position adjacent to the burner insertion hole 6d so as to surround the burner insertion hole 6d. Therefore, when the burner 2 is inserted into the burner insertion hole 6d, the slit 6b is provided so as to surround the burner 2. The cooling gas 6g in the gas storage section 6 is driven by the negative pressure applied to the gas outlet 5b and discharged from the slit 6b toward the reaction tube 4. The cooling gas 6g may be any gas capable of cooling the generated metal oxide, and is preferably an inert gas, such as air. The flow rate of the cooling gas 6g is preferably at least twice the flow rate of the burner gas 2a. The upper limit of the flow rate of the cooling gas 6g is not particularly specified, but is, for example, 1000 times the flow rate of the burner gas 2a. The flow rate of the cooling gas 6g / flow rate of the burner gas 2a is, for example, 2 to 1000, and specifically, for example, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, 200, 500, 1000, and may be within a range between any two of the numerical values ​​exemplified here. In this embodiment, negative pressure is applied to the gas discharge part 5b to cause the cooling gas 6g to flow, but positive pressure may be applied to the cooling gas introduction part 6a to cause the cooling gas 6g to flow.

[0044] After the carrier particles 150 leave the flame 7, they are immediately cooled by the cooling gas 6g, so that the structure having the chain-like parts is maintained. The cooled carrier particles 150 are captured and collected by the filter 5a. The captured carrier particles 150 may be heat-treated at 400 to 1000°C to adjust the crystallite size to a desired size.

[0045] In the present invention, the carrier powder, which is an aggregate of carrier fine particles 150, can be produced by using a production device 1 to form a high-temperature region of 1000°C or higher at the tip of a burner 2 with a flame 7, and supplying a cooling gas 6g to the periphery of the high-temperature region through a slit 6b while causing a thermal decomposition reaction of a titanium compound and a tin compound in the high-temperature region. The high-temperature region may be formed by a means other than the flame 7, such as plasma.

[0046] 4. Method for producing the supported metal catalyst 100 The method for producing the supported metal catalyst 100 includes a supporting step and a reducing step.

[0047] <Supporting process> In the supporting step, the metal fine particles 130 are supported on the support powder. This supporting can be performed using a technique such as a reverse micelle method, a colloid method, an impregnation method, etc. In the colloid method, the supporting step includes an adsorption step and a heat treatment step.

[0048] In the adsorption step, metal colloid particles are adsorbed onto the carrier powder. More specifically, a dispersion liquid is prepared by dispersing metal colloid particles synthesized by a colloid method in an aqueous solution, and the metal colloid particles are added to and mixed with the dispersion liquid, thereby adsorbing the colloid particles onto the surface of the carrier powder. The carrier powder with the colloid particles adsorbed thereon can be separated from the dispersion medium through filtration and drying. The metal of the metal colloid particles includes platinum.

[0049] In the heat treatment step, after the adsorption step, heat treatment is performed at 100 to 400° C. to convert the metal colloid particles into metal microparticles 130. The temperature of this heat treatment is specifically, for example, 100, 150, 200, 250, 300, 350, or 400° C., and may be within a range between any two of the numerical values ​​exemplified here.

[0050] The heat treatment time is, for example, 0.1 to 20 hours, and preferably 0.5 to 5 hours. Specifically, the time is, for example, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, or 20 hours, and may be within a range between any two of the values ​​exemplified here.

[0051] The heat treatment can be carried out in an atmosphere of an inert gas such as nitrogen or an atmosphere of an inert gas containing 1 to 4% hydrogen.

[0052] <Reduction process> In the reduction step, after the heat treatment step, a reduction treatment is performed on the metal microparticles 130. The reduction treatment can be performed by performing a heat treatment in a reducing atmosphere containing a reducing gas such as hydrogen.

[0053] The temperature of this heat treatment is, for example, 70 to 300° C., and preferably 100 to 200° C. Specifically, the temperature is, for example, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 250, or 300° C., and may be within a range between any two of the numerical values ​​exemplified here.

[0054] The heat treatment time is, for example, 0.01 to 20 hours, and preferably 0.1 to 5 hours. Specifically, the time is, for example, 0.01, 0.05, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, or 20 hours, and may be within a range between any two of the values ​​exemplified here.

[0055] When the reducing gas is hydrogen, the concentration is, for example, 0.1 to 100% by volume, preferably 0.2 to 10% by volume, and more preferably 0.5 to 3% by volume. Specifically, the concentration is, for example, 0.1, 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 10, or 100% by volume, and may be within a range between any two of the values ​​exemplified here.

[0056] The metal particles 130 after the heat treatment in the supporting step may be in an oxidized state, in which case the metal particles 130 may not exhibit catalytic activity. In this case, the catalytic activity of the metal particles 130 can be increased by reducing the metal particles 130. EXAMPLES

[0057] A supported metal catalyst was produced by the method described below, and various evaluations were carried out.

[0058] 1. Preparation of Supported Metal Catalyst 100 <Example 1> (Manufacture of carrier powder) The carrier powder was manufactured using the manufacturing apparatus 1 shown in FIG. 8 to FIG. 11. A gas mixture of oxygen 5 L / min and propane gas 1 L / min was used as the burner gas 2a, and this gas was ignited to form a flame (chemical flame) 7 of 1600°C or higher at the tip of the burner 2. The raw material solution 23a was a mixture of titanium octylate, tin octylate, and tantalum octylate in a molar ratio of 0.40:0.60:0.10 mixed with mineral split turpentine and dissolved therein. Oxygen was used as the mist-forming gas 13a. The mist-forming gas 13a at 9 L / min and the raw material solution 23a at 3 g / min were mixed, sprayed from the tip of the raw material supply unit 3, which is a spray nozzle (atomizer), to the center of the flame, and burned to generate the carrier powder, which is an aggregate of the carrier fine particles 150. At that time, the gas exhaust section 5b was made negative pressure, and air was sucked from the slit 6b at a flow rate of 170 L / min, and the generated carrier powder was collected in the collector 5 (with filter 5a). The raw material supply section 3 has a double tube structure (total length 322.3 mm), and oxygen gas is supplied from the outer tube 13, and the raw material solution 23a is supplied to the raw material circulation tube 23, which has a fluid nozzle and an air nozzle at the tip, where the raw material solution 23a is made into a mist 23b. The amount of carrier powder collected was 10 g or more after 60 minutes of operation.

[0059] (Supporting and reducing metal particles (Pt) 130) Following the procedure of FIG. 12, metal particles 130 were supported on the carrier powder.

[0060] First, 0.57 mL of an aqueous solution of chloroplatinic acid hexahydrate was dissolved in 38 mL of ultrapure water, and 1.76 g of sodium carbonate was added thereto and stirred (Step S1 in FIG. 12).

[0061] The solution was diluted with 150 ml of water, and the pH of the solution was adjusted to 5 using NaOH. Then, 25 ml of hydrogen peroxide was added, and the pH was readjusted to 5 with NaOH (Step S2 in FIG. 12).

[0062] A dispersion of 0.50 g of carrier powder dispersed in 15 mL of ultrapure water was added to the dispersion (step S3 in FIG. 12), and the mixture was stirred at 90° C. for 3 hours (step S4 in FIG. 12). After cooling to room temperature, the mixture was filtered and washed with ultrapure water and alcohol, dried overnight at 80° C., and then heat-treated in nitrogen at 400° C. for 2 hours to support the metal particles 130 on the carrier powder, and then heat-treated in 1% hydrogen at 150° C. for 2 hours to reduce the metal particles 130 (step S5 in FIG. 12). Through the above steps, a supported metal catalyst 100 in which the metal particles 130 are supported on the carrier powder was obtained.

[0063] <Examples 2 to 5 and Comparative Examples 1 to 4> A supported metal catalyst 100 was produced in the same manner as in Example 1, except that the molar ratio of titanium octoate, tin octoate, and tantalum octoate was changed as shown in Table 1. [Table 1]

[0064] 2. Measurement of electrical conductivity For the examples and comparative examples, the electrical conductivity of the support powder before supporting the metal fine particles 130 and the electrical conductivity of the supported metal catalyst 100 after supporting the metal fine particles 130 were measured. The results are shown in Table 1 and FIG.

[0065] 13, the supported metal catalyst 100 of the example had higher electrical conductivity than the supported metal catalyst 100 of the comparative example. Also, in the supported metal catalyst 100, the Ti / (Ti+Sn) atomic ratio had a larger effect on electrical conductivity than in the support powder.

[0066] The method for measuring the electrical conductivity is as follows. Eight samples of supported metal catalyst or support powder (hereinafter referred to as "target samples"), which had been precisely weighed out to the same amount using a precision electronic balance, were filled into eight sample folders (diameter 3 mm, depth 5 mm) in the measurement jig. The measurement jig filled with the target samples was set in the pressure device, and the target samples were compressed with a force of 1.1 kN. Using electrodes set in the compression tool of the pressure device, the resistance value of the target sample when compressed was measured using the DC two-terminal method, and the length when compressed was also measured at the same time. This operation was performed on four or more target samples of different weights, and the relationship between the length (x-axis) and resistance value (y-axis) of the target sample when compressed was determined, and extrapolated in the y-axis direction to determine the value of the y-intercept. The resistivity of the target sample was determined from the value of the y-intercept and the length and cross-sectional area of ​​the compact, and the electrical conductivity, which is its reciprocal, was calculated. [Explanation of symbols]

[0067] 1: manufacturing equipment, 2: burner, 2a: burner gas, 3: raw material supply section, 4: reaction tube, 5: recovery vessel, 5a: filter, 5b: gas exhaust section, 6: gas storage section, 6a: cooling gas inlet section, 6b: slit, 6c: inner peripheral wall, 6d: burner insertion hole, 6g: cooling gas, 7: flame, 13: outer tube, 13a: mist gas, 20: fuel cell, 23: raw material flow tube, 23a: raw material Feed solution, 23b: mist, 100: supported metal catalyst, 110: voids, 120: crystallites, 130: metal particles, 150: carrier particles, 160: branches, 200: fuel cell, 201: anode, 202: cathode, 203: load, 210A: anode side gas diffusion layer, 210K: cathode side gas diffusion layer, 220A: anode side catalyst layer, 220K: cathode side catalyst layer

Claims

1. A supported metal catalyst comprising a support powder and metal fine particles supported on the support powder, The carrier powder is an aggregate of carrier fine particles, The carrier fine particles have a chain-like portion formed by fusing and bonding a plurality of crystallites into a chain, The carrier fine particles are composed of a metal oxide, the metal oxide is a composite oxide of titanium and tin, and has a first atomic ratio of 0.30 to 0.80; the first atomic ratio is an atomic ratio of titanium to a sum of titanium and tin; The metal oxide is doped with a doping element having a different valence from titanium and tin, the doping element is tantalum, niobium, antimony or tungsten; the second atomic ratio is 0.05 to 0.30; The second atomic ratio is an atomic ratio of the doping element to the total metal contained in the metal oxide. Supported metal catalysts.

2. 2. The supported metal catalyst of claim 1, The supported metal catalyst, wherein the first atomic ratio is from 0.40 to 0.

80.

3. The supported metal catalyst according to claim 1 or 2, The supported metal catalyst, wherein the metal particles include platinum.

4. An electrochemical cell comprising the supported metal catalyst of claim 3.

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