WO2014069208A1 - Catalyseur au platine à structure cœur-écorce, son procédé de fabrication et pile à combustible l'utilisant - Google Patents

Catalyseur au platine à structure cœur-écorce, son procédé de fabrication et pile à combustible l'utilisant Download PDF

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WO2014069208A1
WO2014069208A1 PCT/JP2013/077617 JP2013077617W WO2014069208A1 WO 2014069208 A1 WO2014069208 A1 WO 2014069208A1 JP 2013077617 W JP2013077617 W JP 2013077617W WO 2014069208 A1 WO2014069208 A1 WO 2014069208A1
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platinum
core
shell
catalyst
ruthenium
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Japanese (ja)
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稔 稲葉
大門　英夫
健仁 西川
雄太 池畑
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学校法人同志社
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/48—Silver or gold
    • B01J23/52—Gold
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
    • B01J23/8926—Copper and noble metals
    • B01J35/397—
    • B01J35/40—
    • B01J35/50—
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/03—Precipitation; Co-precipitation
    • B01J37/031—Precipitation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/03—Precipitation; Co-precipitation
    • B01J37/031—Precipitation
    • B01J37/035—Precipitation on carriers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/054—Nanosized particles
    • B22F1/0549—Hollow particles, including tubes and shells
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/17—Metallic particles coated with metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C5/00—Alloys based on noble metals
    • C22C5/02—Alloys based on gold
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C5/00—Alloys based on noble metals
    • C22C5/04—Alloys based on a platinum group metal
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8647—Inert electrodes with catalytic activity, e.g. for fuel cells consisting of more than one material, e.g. consisting of composites
    • H01M4/8657—Inert electrodes with catalytic activity, e.g. for fuel cells consisting of more than one material, e.g. consisting of composites layered
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/9041—Metals or alloys
    • H01M4/905—Metals or alloys specially used in fuel cell operating at high temperature, e.g. SOFC
    • H01M4/9058—Metals or alloys specially used in fuel cell operating at high temperature, e.g. SOFC of noble metals or noble-metal based alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
    • H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/1007—Fuel cells with solid electrolytes with both reactants being gaseous or vaporised
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a platinum core-shell catalyst suitable for use as a catalyst for oxygen reduction reaction in a fuel cell, a method for producing the same, and a fuel cell using the catalyst.
  • a polymer electrolyte fuel cell is a clean energy device that generates only water by causing an oxidation reaction of hydrogen on the anode side and a reduction reaction of oxygen on the cathode side.
  • a catalyst using platinum (Pt) as a catalyst on the cathode side is known.
  • a catalyst using platinum, which is a noble metal has high catalytic activity and high electrical conductivity, and has an advantage that it is less susceptible to corrosion and poisoning due to the state of the surrounding environment and substances present in the surrounding environment.
  • Patent Document 1 Japanese Patent Application Laid-Open No. 2012-41581 discloses core particles made of ruthenium having a face-centered cubic crystal structure as core-shell fine particles that reduce the amount of platinum used and improve catalytic activity, A core-shell fine particle having a shell made of platinum having a face-centered cubic crystal structure formed on the surface is disclosed.
  • the main object of the present invention is to increase the catalyst efficiency of platinum by improving the surface density of platinum atoms on the surface of the catalyst fine particles, thereby reducing the amount used, and the center of the surface where the surface density of platinum atoms in the shell is maximized.
  • the inventors have found that a cubic crystal structure is used.
  • gold is known as a core metal for the platinum shell.
  • Gold is a precious metal, has a lower ionization tendency than platinum, is stable against oxidation, and has a much larger amount of resources than platinum, and thus is expected as one of core metals.
  • Patent Document 2 Japanese Patent Laid-Open No. 2011-212666 discloses a method for producing a platinum surface catalyst layer on the surface of a gold core particle without using a reducing agent.
  • a gold layer is immersed in a solution containing divalent or tetravalent platinum ions to deposit a platinum layer directly on the gold core.
  • a catalyst having a gold core / platinum shell can be obtained by a simple method.
  • the durability and catalytic efficiency of the catalyst are not examined.
  • Patent Document 3 Japanese Patent Laid-Open No. 2010-92725 discloses a catalyst in which a shell of Pt or an alloy thereof is formed on the surface of core particles made of Au or an alloy thereof.
  • Au having a large lattice constant is used as a core
  • Pt having a small lattice constant is used as a shell.
  • the core or shell may be an alloy of Au or Pt.
  • a base metal such as Fe and Co and a noble metal such as Ag, Ru, Pd and Ir can be added to Pt of the shell by 40 atomic% or less.
  • the Au core particle size is 1 to 10 nm and the Pt shell thickness is 2 nm or less.
  • the lattice constant referred to in this document is a lattice constant in a single crystal, and an interatomic distance in an actual nanoparticle is not considered.
  • Non-Patent Document 1 when the Pt monolayer catalyst constructed on Au single crystal is compared with the Pt monolayer catalyst constructed on Au nanoparticles having a particle size of 3 nm, the latter oxygen reduction activity is observed. It has been reported to be about 2.5 times better.
  • the Pt monolayer has acquired an electronic state (binding force with oxygen species) suitable for the oxygen reduction reaction and exhibits high oxygen reduction activity.
  • an object of the present invention is to provide a platinum core-shell catalyst having gold core particles having excellent durability and catalytic efficiency.
  • the inventors have the property that platinum dissolves in gold, so that the platinum atoms on the surface of the catalyst particles become a gold core as the potential cycle is repeated. Considering that the catalytic activity decreases due to the decrease in platinum atoms on the surface of the catalyst particles due to the solid solution, investigations have been conducted.
  • the inventors focused on the thermodynamic properties of the shell component and the core component in the study to solve the above-mentioned problems, and from a thermodynamic point of view, a state in which solid solution burying of platinum atoms in the gold core is difficult to occur.
  • iridium (Ir) or ruthenium (Ru) which is an element having a property that is difficult to mix with gold compared to platinum and easy to mix with platinum compared to gold.
  • the inventors have found that a platinum core-shell catalyst having excellent durability and catalytic efficiency can be obtained, and have completed the present invention.
  • the present invention has a core particle containing gold and a shell containing platinum and iridium and / or ruthenium formed on the surface of the core and having a diameter of 1.6 to 6.8 nm.
  • the present invention relates to a platinum core-shell catalyst for a fuel cell.
  • the core particles preferably have a particle size of 1.0 to 5.0 nm and a shell thickness of 0.3 to 0.9 nm.
  • the platinum core-shell catalyst of the present invention since the platinum shell is formed on the surface of the gold core particle, all or most of the platinum atoms are present on the surface of the catalyst particle and can exhibit catalytic activity. That is, the utilization efficiency of platinum atoms as a catalyst is extremely high.
  • the shell contains iridium (Ir) and / or ruthenium (Ru) in addition to platinum. With this configuration, the platinum core-shell catalyst having excellent durability is obtained by suppressing the solid-solution burying of platinum shell atoms in the gold core. Furthermore, since the particle size of the catalyst is as small as 1.6 to 6.8 nm, the surface area per catalyst weight is increased, and the amount of gold used is also reduced. Furthermore, since the maximum amount of platinum that can be dissolved in the gold core is determined by the volume of the gold core, the loss of platinum due to the solid solution can be kept small by using a gold core having a small particle diameter.
  • the core particle size is in the range of 1.0 to 5.0 nm and the shell thickness is in the range of 0.3 to 0.9 nm
  • the shell is substantially changed from a monolayer (monoatomic layer) to a triatomic layer, and a gold core.
  • the particles are small enough.
  • a more suitable platinum core-shell catalyst can be obtained.
  • the platinum core-shell catalyst of the present invention can simultaneously provide high mass activity based on high platinum utilization efficiency and high durability based on a structure in which the platinum shell is prevented from dissolving in the gold core. .
  • the composition of the catalyst is set from a thermodynamic viewpoint, specifically, by adding a specific type of metal to the shell component, the solidification of platinum in the shell to the core is performed.
  • Deterring sunk invasion is an unprecedented new idea.
  • the catalyst of the present invention set based on this idea is a novel catalyst having a gold core having a particle size in a specific range and a platinum shell containing iridium and / or ruthenium, In comparison, even if the covering ratio of the shell is low, the catalyst activity retention rate is extremely excellent.
  • the ratio of iridium and / or ruthenium to platinum is preferably 0.1 to 50% at.%, And more preferably 5 to 30% at.%. With this ratio, iridium and / or ruthenium effectively suppresses the solid solution of platinum in the gold core and does not inhibit the platinum atom coverage and catalytic activity in the shell. And a catalyst having high durability can be obtained.
  • platinum and iridium and / or ruthenium may be mixed in the same layer, and iridium and / or ruthenium may be interposed between the platinum shell and the gold core particle.
  • the catalyst in which platinum and iridium and / or ruthenium are mixed in the same layer can be manufactured by a simple manufacturing process because the shell can be formed in one step. There is an advantage of being.
  • the catalyst in which iridium and / or ruthenium is interposed between the platinum shell and the gold core particle surface has iridium and / or ruthenium between the platinum shell and the gold core particle. Since it also functions as a barrier, the effect of suppressing the solid solution burying of platinum becomes higher, and at the same time, the surface of the core can be covered only with platinum, so that higher catalytic efficiency can be obtained.
  • the platinum core-shell catalyst of the present invention is preferably supported on a carrier made of a carbonaceous material.
  • a metal oxide carrier such as tin oxide (SnOx) or titanium oxide (TiOx) having high oxidation resistance, or a carrier obtained by mixing these metal oxides with a carbonaceous material. May be used.
  • the platinum core-shell catalyst of the present invention can be suitably used as a catalyst for oxidation-reduction reactions in fuel cells.
  • the present invention also includes (1) a step of forming a monoatomic layer made of copper on the surface of a gold core particle supported on a carbonaceous support, and (2) a monoatomic layer made of copper obtained in step (1). And replacing the layer with platinum and iridium and / or ruthenium.
  • gold core particles supported on a carbonaceous support are put into an acidic aqueous solution containing Cu ions in which a solid made of copper is immersed, and inert gas such as argon or nitrogen gas is used.
  • step (2) removes the solid made of copper from the aqueous solution, and then introduces a substance that gives platinum ions and iridium and / or ruthenium ions;
  • the step comprises replacing the copper on the product surface obtained in 1) with platinum and ruthenium and / or iridium.
  • a platinum core-shell catalyst having a desired particle size and shell composition is formed by forming a shell containing platinum, iridium and ruthenium in a desired ratio on the surface of a gold core particle having a desired particle size.
  • a step (1) the method using an acidic aqueous solution containing Cu ions in which a solid made of copper is immersed is more precise than the conventional UPD method, and precise potential control using an external power source and a counter electrode or reference No need for poles, etc., and since the process and equipment are simple, mass production is possible and the practical use value is extremely high.
  • the ratio of iridium and / or ruthenium to platinum is preferably 0.1 to 50% at.%, More preferably 5 to 30% at.%. Is more preferable.
  • the present invention is a method in which a compound that gives platinum ions and a compound that gives iridium and / or ruthenium ions are simultaneously added, so that platinum and iridium and / or ruthenium are mixed in the same layer. Is preferably formed. According to this method, a shell containing platinum and iridium and / or ruthenium can be easily formed on the surface of the gold core particle in one step.
  • the platinum core-shell catalyst produced by each of the above methods can be suitably used as a catalyst for an oxidation-reduction reaction in a fuel cell.
  • the platinum core-shell catalyst of the present invention contains iridium and / or ruthenium in addition to platinum in the shell, and iridium or ruthenium is present in the vicinity of the platinum atom. This suppresses the solid dissolution of platinum atoms in the gold core. That is, the durability of the catalyst is excellent, and the catalytic activity can be maintained for a long time.
  • the platinum core-shell catalyst of the present invention has iridium or ruthenium in the shell, and the gold core has a small particle size even when the platinum coverage is low and the solid solution in the gold core particles tends to be large. Therefore, it is possible to maintain good durability and high catalyst efficiency with less solid solution of platinum in the gold core.
  • the present invention effectively suppresses solid solution of platinum in the core and improves the durability of the catalyst by a simple measure of adding iridium or ruthenium as a shell component of a platinum shell / gold core catalyst having a known configuration.
  • the main purpose is to improve the utilization efficiency of the platinum catalyst by improving the catalytic activity of platinum or by producing a platinum layer by a more efficient method.
  • the present invention has improved durability in a simple manner in addition to the utilization efficiency of the catalyst.
  • the present invention has an effect that not only the amount of platinum used during the production of the catalyst can be reduced, but also the amount of platinum used can be reduced by enhancing its durability. Since the platinum core-shell catalyst of the present invention can be used as a catalyst for a fuel cell, the cost of the fuel cell can be drastically reduced.
  • the core of the platinum core-shell catalyst of the present invention is a gold-containing nanoparticle, and a known gold nanoparticle can be used, or can be produced by a known gold nanoparticle production method.
  • the gold core particles may contain other elements other than gold, such as platinum.
  • other substances may be included as long as the effects of the present invention are not affected. For example, a residue or part of an additive (reducing agent, fine particle agent, etc.) used in the manufacturing process is included. You may go out.
  • the size of the gold core particle is 1.0 to 5.0 nm. It is substantially difficult to synthesize Au core particles having a particle size of less than 1.0 mm.
  • the particle size exceeds 5.0 nm, the number of Pt atoms for forming a Pt shell increases, and the amount of gold used for obtaining a unit area also increases, which raises the problem of an increase in catalyst cost.
  • the particle size is 5.0 nm or less, a large surface area can be obtained per unit weight of the catalyst, and the amount of gold and platinum required per unit area of the catalyst can be reduced.
  • gold is even more expensive than platinum, but the combined material cost of the core material (gold) and shell material (platinum) is the current when the particle size of the gold core is around 2.5 mm.
  • the material cost is higher than the current platinum catalyst. For this reason, there is an advantage in using a smaller-sized gold core particle.
  • the particle size of the gold core particle is the average particle size obtained from a transmission electron microscope (TEM) image or the Scherrer equation applied to the X-ray diffraction peak of the (220) plane of Au. This means the value calculated by
  • the shell of the platinum core-shell catalyst of the present invention contains platinum and iridium and / or ruthenium. Specifically, a shell containing platinum and iridium may be formed on the surface of the gold core particle, or a shell containing platinum and ruthenium may be formed on the surface of the gold core particle. In addition to platinum, iridium and / or ruthenium, other atoms and / or molecules may be contained within a range satisfying a desired catalytic activity. For example, noble metals such as gold and silver, platinum compounds added in the manufacturing process, and residues of organic compounds may be included.
  • the ratio of iridium and / or ruthenium to platinum is preferably 0.1 to 50 at.%, More preferably 5 to 30 at.%.
  • iridium or ruthenium may be contained at a minimum level capable of suppressing the solid solution of platinum in the gold core, and is appropriate so as not to hinder the coverage of platinum atoms in the shell and the catalytic activity of platinum. Selected.
  • the average thickness of the platinum shell is preferably a monoatomic layer to a triatomic layer (about 0.3 nm to 0.9 nm), and more preferably a monoatomic layer to a diatomic layer (about 0.3 nm to 0.6 nm).
  • platinum atoms that exhibit activity as an oxygen reduction catalyst are only platinum atoms located in the outermost layer (outermost surface) of the shell, there is no particular advantage in increasing the thickness of the shell.
  • Iridium and / or ruthenium may be mixed with platinum to constitute the surface layer of the catalyst, or may be interposed between the gold core and the platinum shell.
  • platinum core-shell catalyst of the present invention contains iridium and / or ruthenium in the platinum shell, platinum is prevented from being solid-solution-embedded in the gold core particles.
  • Table 1 shows heats of mixing ⁇ H (kJ / mol) when platinum (Pt), gold (Au), iridium (Ir), and ruthenium (Ru) are mixed at a ratio of 50:50.
  • the smaller the value the more stable the mixture of the A component and the B component.
  • the heat of mixing iridium and ruthenium with respect to platinum is +1 kJ / mol and -1 kJ / mol, respectively, which is smaller than the heat of mixing gold and platinum (+7 kJ / mol).
  • the heat of mixing of iridium and ruthenium with gold is + 19 + kJ / mol and +22 kJ / mol, respectively, which is larger than the heat of mixing of gold and platinum (+7 kJ / mol). That is, iridium and ruthenium are easier to mix with platinum than gold, and iridium and ruthenium are harder to mix with gold than platinum.
  • the platinum core-shell catalyst of the present invention is preferably dispersed and supported on the surface of a carrier made of a carbonaceous material.
  • the carbonaceous material include carbon black, ketjen black, acetylene black, and carbon nanotube.
  • metal oxide carriers such as tin oxide (SnOx) and titanium oxide (TiOx) having high oxidation resistance may be used.
  • SiOx tin oxide
  • TiOx titanium oxide
  • the support preferably has a specific surface area of about 10 to 1000 m 2 / g. It is considered that the platinum core-shell catalyst is supported on the surface of the support mainly by electrostatic interaction. A chemical bond can also be formed between the platinum core-shell catalyst and the support in order to more firmly support it and reduce the dropping of the catalyst from the support surface.
  • the coverage of the gold core particle surface with platinum and ruthenium and / or iridium can be 50-100%, preferably 60-100%, more preferably 70-100%. Since the amount of platinum solid solution in the gold core is determined by the volume of the gold core particle, if the gold core particle has the same particle size, the higher the platinum coverage, the lower the proportion of platinum lost due to solid solution in gold (that is, When the platinum coverage is low, the proportion of platinum lost by solid solution in gold is high (that is, the durability as a catalyst is low).
  • the gold core particle having the same particle size has a platinum shell amount of about 1/2 to 1/4 of that of a conventional platinum core-shell catalyst (a catalyst having a shell made only of platinum).
  • a conventional platinum core-shell catalyst a catalyst having a shell made only of platinum.
  • durability equivalent to that of the conventional platinum core-shell catalyst see Examples. That is, although the catalyst of the present invention has a low surface coverage of platinum (the number of platinum atoms on the surface), it does not easily cause solid solution in gold. This is presumably because the presence of iridium and / or ruthenium suppresses solid solution of platinum. This is an effect peculiar to the present invention different from the conventional platinum core-shell catalyst.
  • the method for producing the platinum core-shell catalyst of the present invention is not particularly limited.
  • the copper monoatomic layer obtained in step (1) can be preferably produced by a method including a step of replacing platinum with iridium and / or ruthenium.
  • Gold core particles supported on a carbonaceous carrier can be synthesized by a known synthesis method. For example, tetrachloroauric acid (HAuCl 4 ) or the like is added to alkanethiol as a protective agent in an aqueous solution, an organic solution, or a mixed solution thereof, and then reduced to form gold nanoparticles. There is a method of obtaining gold core particles supported on a carbonaceous support by adsorbing to a carbonaceous support via alkanethiol chemisorbed on the carbon, and subsequently removing a part of the thiol group and hydrocarbon chain by heat treatment. .
  • a known method can be used to form a monoatomic layer made of copper on the surface of the gold core particle.
  • the UPD method disclosed in Non-Patent Document 1 can be followed, or the method can be changed as appropriate.
  • an improved Cu-UPD method that does not require precise potential control using an external power source and a counter electrode or a reference electrode.
  • gold core particles supported on a carbonaceous support are put into an acidic aqueous solution containing Cu ions in which a solid made of copper is immersed, and an inert gas atmosphere such as argon or nitrogen is used.
  • an inert gas atmosphere such as argon or nitrogen is used.
  • a monoatomic film made of copper is formed on the surface of the gold core by stirring in the medium.
  • the copper monoatomic film is not necessarily a uniform film composed of a monoatomic film on the entire surface, but includes a film in which two or more atoms overlap each other.
  • the solid made of copper used in the improved Cu-UPD method is an object that at least has a surface made of copper and is ionized to produce copper ions (Cu 2+ ) when contacted with gold nanoparticles.
  • a copper mesh, a copper wire, a copper grain, a copper plate, a copper lump, etc. are mentioned.
  • CuSO 4 , CuCl 2 , Cu (CH 3 COO) 2 , Cu (NO 3 ) 2 and the like can be cited as substances that give Cu ions used in acidic aqueous solutions containing Cu ions. By doing so, Cu ions are dissociated.
  • the Cu ion concentration is not particularly limited, but can be, for example, 0.1 mM to 100 mM, and is preferably about 1 mM to 50 mM from the viewpoint of the reaction rate and the stability of the reaction solution.
  • the acid that gives the acidic solution is not particularly limited as long as it can dissolve copper, and examples thereof include nitric acid, sulfuric acid, hydrochloric acid, perchloric acid, and the like.
  • the concentration can be set to 10 mM to 1 M. From the viewpoint of controlling the speed and the potential of the copper solid, it can be set to about 20 mm to 0.5 mm.
  • Gold core particles supported on a carbonaceous support are introduced into an acidic solution containing the above Cu ions immersed in the above copper solid, and stirred, for example, at 0 to 45 ° C. for 1 to 50 hours under an inert gas flow. By doing so, a copper monoatomic film is formed on the gold core surface.
  • the copper on the product surface obtained is replaced with platinum and ruthenium and / or iridium.
  • This step can be performed by a displacement plating method used in a known UPD method or the like.
  • platinum ions include platinum salts (K 2 PtCl 4 , K 2 PtBr 4 ), and examples of substances that give ruthenium ions and / or iridium ions include ruthenium chloride, ruthenium nitrate, and iridium chloride. And iridium nitrate.
  • the step of replacing the monoatomic film made of copper with platinum and ruthenium and / or iridium is performed by removing the copper solid from the above-described acidic solution containing Cu ions soaked in the copper solid,
  • a compound containing ruthenium and / or iridium can be added to the aqueous solution simultaneously or sequentially and stirred. That is, for example, a platinum compound and an iridium and / or ruthenium ion compound may be simultaneously introduced to form a shell in which platinum and iridium and / or ruthenium are mixed in the same layer.
  • the addition of the platinum compound and the iridium and / or ruthenium ion compound is preferably carried out with as little time as possible after removing the copper solid.
  • the reaction time and temperature can be appropriately selected.
  • the reaction time is 0 to 45 ° C. for 1 minute to 50 hours (preferably 1 minute to 1 hour). It is.
  • the gold core particles having a shell containing platinum and iridium and / or ruthenium obtained by the above method are washed, dried and the like as required by a known method, and the platinum core-shell catalyst for fuel cells of the present invention Is obtained.
  • the production method of the present invention can include separation, purification, washing steps and the like as necessary.
  • Example 1 Preparation of iridium-containing platinum shell / gold core catalyst
  • i Preparation of Au / C core 7.619 ⁇ 10 ⁇ 4 mol of HAuCl 4 was dissolved in 80 ml of pure water.
  • a separatory funnel Using a separatory funnel, a toluene solution of 625 mg of tetraoctylammonium bromide as a phase transfer agent and an aqueous HAuCl 4 solution were mixed and allowed to stand to move [AuCl 4 ] ⁇ to the toluene phase. The aqueous phase was removed and the toluene phase was transferred to an Erlenmeyer flask and placed in a thermostatic bath at 30 ° C.
  • the solution was transferred to a separatory funnel to remove the aqueous phase, the Au colloid solution was transferred to a round bottom flask, and toluene was distilled off using an evaporator. 30 ml of n-hexane was added to the round bottom flask after the toluene was distilled off, and the Au colloid was redispersed by irradiation with ultrasonic waves for 30 minutes. Thereafter, 80 ml of ethanol was added to increase the polarity of the solvent to precipitate Au colloid. Using a centrifuge, Au colloid was precipitated and separated by treatment at 12000 rpm for 15 minutes.
  • the supernatant was removed and the Au colloid was redispersed in n-hexane. Then, n-hexane was distilled off using an evaporator, 10 ml of n-hexane was added, and ultrasonic waves were irradiated for 30 minutes. Thereafter, 80 ml of ethanol was added to precipitate Au colloid. The colloidal Au was washed by repeating this operation four times. The washed Au colloid was dispersed in 30 ml of n-hexane.
  • 350 mg of carbon support (Ketjen black EC 300 J, specific surface area 800 m 2 / g) is ultrasonically dispersed in 350 ml of n-hexane for 1 hour, then added with Au colloid n-hexane dispersion, and then for another 30 minutes Ultrasonic irradiation was performed. Thereafter, the solution was stirred for a whole day and night using a magnetic stirrer at room temperature to support Au colloid on the carbon support. The carbon-supported Au core (Au / C core) was filtered off with suction by stirring the n-hexane solution stirred overnight, and dried in an oven at 60 ° C. for 6 hours in the atmosphere to obtain an Au / C core.
  • carbon support Karljen black EC 300 J, specific surface area 800 m 2 / g
  • FIG. 2 shows the structure of the rotating ring disk electrode. A catalyst was applied and supported on the disk portion, and the working electrode was rotated to generate a constant convection in the electrolyte, thereby controlling mass transfer.
  • Example 2 Preparation of ruthenium-containing platinum shell / gold core catalyst
  • i Preparation of PtRu / Au / C catalyst Au / C core after the same heat treatment as used in Example 1 (support rate 28.4 wt.%, 200 mg (particle size 2.8 nm) was dispersed in a 300 ml aqueous solution containing 50 mM H 2 SO 4 and 10 mM CuSO 4 .
  • Ar was flowed at a flow rate of 100 ml / min., And the Cu mesh was allowed to coexist in the aqueous solution, and then stirred at 30 ° C. for 10 hours to form a Cu shell on the surface of the Au core particles.
  • Table 2 summarizes the results of composition analysis of the catalysts of Examples 1 and 2 and Comparative Example 1 using a fluorescent X-ray analyzer (SEA1200VX, manufactured by SII).
  • the catalyst of Example 1 contains iridium (Ir), and the catalyst of Example 2 contains ruthenium (Ru). Was confirmed.
  • FIG. 3 shows changes in the electrochemical surface area of Example 1 and Comparative Example 1 accompanying the durability test.
  • the horizontal axis indicates the number of potential cycles, and the vertical axis indicates the surface area retention rate (%) with the electrochemical surface area before the cycle test as 100%.
  • Example 1 showed an electrochemical surface area retention substantially equivalent to that of Comparative Example 1.
  • the catalyst of Example 1 has a smaller number of platinum shell atoms than Comparative Example 1 (about 1/4).
  • the platinum shell coverage number of atoms
  • the proportion of platinum lost from the surface as a solid solution embedded in the gold core is relatively high, and the durability is reduced.
  • the catalyst of Example 1 of the present invention has the same durability as that of Comparative Example 1 even if the number of platinum shell atoms is about 1/4 that of the Pt / Au / C catalyst of Comparative Example 1. That is, the result of FIG. 3 shows that the durability of platinum atoms existing on the catalyst surface of Example 1 is dramatically improved in the durability test of 10,000 cycles. This is probably because the solid solution of platinum was suppressed by the presence of iridium, thereby improving the durability of the catalyst.
  • FIG. 4 shows the durability test of Example 2, Comparative Example 1 and the reference platinum fine particle catalyst (platinum fine particle catalyst supported on a carbonaceous carrier, not a core shell, particle size 2.8 nm, loading rate 48 wt.%).
  • the change of the electrochemical surface area accompanying with is shown.
  • the horizontal axis indicates the number of potential cycles, and the vertical axis indicates the surface area retention rate (%) with the electrochemical surface area before the cycle test as 100%.
  • Example 2 showed a higher electrochemical surface area retention than Comparative Example 1 and Reference Example.
  • the catalyst of Example 2 of the present invention has high durability exceeding that of the conventional platinum catalyst even though the number of platinum shell atoms is about half that of the Pt / Au / C catalyst of Comparative Example 1. . That is, the results of FIG. 4 show that the durability of platinum atoms existing on the catalyst surface of Example 2 is dramatically improved in the 10,000 cycles durability test. This is probably because the presence of ruthenium suppresses the solid dissolution of platinum and improves the durability of the catalyst.

Abstract

La présente invention a pour objet un catalyseur au platine à structure cœur-écorce qui a une durabilité et un rendement catalytique supérieurs et qui comprend des particules de cœur comprenant de l'or et ayant un diamètre extrêmement petit (inférieur ou égal à 5 nm). Le catalyseur au platine à structure cœur-écorce selon la présente invention pour des piles à combustible est caractérisé en ce que sa taille des particules est de 1,6-6,8 nm et en ce qu'il comprend des particules de cœur qui comprennent de l'or et une écorce formée sur la surface du cœur et comprenant du platine et de l'iridium et/ou du ruthénium.
PCT/JP2013/077617 2012-10-29 2013-10-10 Catalyseur au platine à structure cœur-écorce, son procédé de fabrication et pile à combustible l'utilisant WO2014069208A1 (fr)

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WO2017150010A1 (fr) * 2016-02-29 2017-09-08 エヌ・イー ケムキャット株式会社 Catalyseur destiné à une électrode, composition destinée à former une électrode à diffusion de gaz, électrode à diffusion de gaz, ensemble électrode à membrane, et empilement de piles a combustible
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JP2019519080A (ja) * 2016-06-30 2019-07-04 フオルクスワーゲン・アクチエンゲゼルシヤフトＶｏｌｋｓｗａｇｅｎ Ａｋｔｉｅｎｇｅｓｅｌｌｓｃｈａｆｔ 燃料電池用の担持触媒材料を製造する方法

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WO2017150009A1 (fr) * 2016-02-29 2017-09-08 エヌ・イー ケムキャット株式会社 Catalyseur pour électrode, composition pour former une électrode à diffusion de gaz, électrode à diffusion de gaz, ensemble d'électrode à membrane, et empilage de piles à combustible
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