WO2015151578A1 - Procédé de fabrication d'un catalyseur de type noyau-enveloppe - Google Patents

Procédé de fabrication d'un catalyseur de type noyau-enveloppe Download PDF

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WO2015151578A1
WO2015151578A1 PCT/JP2015/053234 JP2015053234W WO2015151578A1 WO 2015151578 A1 WO2015151578 A1 WO 2015151578A1 JP 2015053234 W JP2015053234 W JP 2015053234W WO 2015151578 A1 WO2015151578 A1 WO 2015151578A1
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palladium
copper
core
platinum
containing particles
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PCT/JP2015/053234
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English (en)
Japanese (ja)
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紘子 木村
典之 喜多尾
誠 安達
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トヨタ自動車株式会社
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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
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/44—Palladium
    • B01J35/33—
    • B01J35/393—
    • B01J35/397—
    • 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
    • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
    • B01J37/0018—Addition of a binding agent or of material, later completely removed among others as result of heat treatment, leaching or washing,(e.g. forming of pores; protective layer, desintegrating by heat)
    • 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
    • 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
    • B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
    • B01J37/348—Electrochemical processes, e.g. electrochemical deposition or anodisation
    • 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
    • H01M2008/1095—Fuel cells with polymeric electrolytes
    • 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

Definitions

  • the present invention relates to a method for producing a core-shell catalyst.
  • Fuel cells convert chemical energy directly into electrical energy by supplying fuel and oxidant to two electrically connected electrodes and causing the fuel to oxidize electrochemically. Therefore, since the fuel cell is not subject to the Carnot cycle, it exhibits high energy conversion efficiency.
  • a fuel cell is usually configured by laminating a plurality of single cells having a basic structure of a membrane electrode assembly in which an electrolyte membrane is sandwiched between a pair of electrodes.
  • Patent Document 1 describes a method for producing a core-shell catalyst by displacement plating using copper underpotential deposition (Cu-UPD).
  • Cu-UPD is a phenomenon in which a copper monoatomic layer in a metallic state is formed on a surface of a dissimilar metal having a strong binding force with copper at a potential nobler than the redox potential of copper.
  • a core with a copper atomic layer formed by Cu-UPD on the surface is immersed in a solution containing shell metal ions, and the core is covered with the shell by replacing the copper with the shell metal by utilizing the difference in ionization tendency.
  • the core-shell catalyst can be produced.
  • the core-shell catalyst obtained by the conventional production method has a problem that the catalyst activity per unit surface area of platinum (hereinafter referred to as specific activity) is low.
  • the present invention has been accomplished in view of the above circumstances, and an object of the present invention is to provide a method for producing a core-shell catalyst having high specific activity.
  • a method for producing a core-shell catalyst of the present invention is a method for producing a core-shell catalyst comprising: a core containing palladium; and a shell containing platinum and covering the core,
  • Preparing palladium-containing particles In the copper ion-containing electrolyte, by applying a potential nobler than the copper redox potential to the palladium-containing particles, a copper deposition step of depositing copper on the surface of the palladium-containing particles, After the copper deposition step, the copper deposited on the surface of the palladium-containing particles is contacted with a platinum ion-containing solution, thereby replacing the copper deposited on the surface of the palladium-containing particles with platinum. And a substitution step to be formed.
  • the palladium-containing particles are supported on a carrier.
  • a method for producing a core-shell catalyst with high specific activity can be provided.
  • FIG. 4 is a diagram showing an XRD measurement result of palladium particles used in Example 1.
  • FIG. 4 is a diagram showing an XRD measurement result of palladium particles used in Example 2. It is a figure which shows the XRD measurement result of the palladium particle
  • a method for producing a core-shell catalyst of the present invention is a method for producing a core-shell catalyst comprising: a core containing palladium; and a shell containing platinum and covering the core,
  • Preparing palladium-containing particles In the copper ion-containing electrolyte, by applying a potential nobler than the copper redox potential to the palladium-containing particles, a copper deposition step of depositing copper on the surface of the palladium-containing particles, After the copper deposition step, the copper deposited on the surface of the palladium-containing particles is contacted with a platinum ion-containing solution, thereby replacing the copper deposited on the surface of the palladium-containing particles with platinum. And a substitution step to be formed.
  • Non-Patent Document 1 the activity of palladium particles (hereinafter sometimes referred to as Pt / Pd) in which a single-layer platinum shell is formed varies depending on the crystal plane, and the order of activity is Pt / Pd (100) ⁇ Pt / Pd (111) to Pt / Pd (110) are reported. Furthermore, Non-Patent Documents 2 to 3 report that Pt / Pd (111) is more active than Pt (111).
  • the specific activity of the core-shell catalyst increases, that is, the larger the crystallite size of the palladium-containing particles, the more stable the surface energy (111) It is expected that the specific activity of the core-shell catalyst will increase because of the higher surface ratio.
  • the present inventors have found that the specific activity of the core-shell catalyst is lowered unless the crystallite size of the palladium-containing particles is within the range of 5 to 8.5 nm, and completed the present invention. .
  • the crystallite size of the palladium-containing particles is smaller than 5 nm, the proportion of atoms with a small number of coordinations appearing on the surface of the palladium-containing particles is small, and the interaction with the platinum shell is difficult to express. Inferred. Further, it is presumed that the ratio of the terrace portion of the crystal plane appearing on the surface of the palladium-containing particles is reduced, platinum atoms cannot be stably present, and it is difficult to form a uniform platinum shell on the surface of the palladium-containing particles.
  • the potential energy of the adsorption state of copper and platinum on the surface of the palladium particles becomes high at a negative value, so that three-dimensional platinum growth on the surface of the palladium particles occurs. It is assumed that this is because it becomes easy and it is difficult to form a uniform platinum shell.
  • the potential energy of the adsorption state of copper and platinum on the surface of palladium particles is a value obtained when the structure of palladium is assumed to be a cubic octahedron by the first principle calculation program Interface (manufactured by Toyota Central R & D Co., Ltd.). Adopted.
  • FIG. 1A is a TEM photograph of the core-shell catalyst
  • FIG. 1B is a diagram showing the Pt / Pd atomic concentration ratio obtained by observing the core-shell catalyst shown in FIG. 1A in the arrow direction.
  • the produced core-shell catalyst has a high platinum concentration on the catalyst surface and a long distance, so it is confirmed that three-dimensional growth of platinum occurs on the surface of the palladium core. did it.
  • the shell covers the core not only in a form in which the entire surface of the core is covered by the shell, but also a part of the surface of the core is covered by the shell, and a part of the surface of the core is exposed.
  • the form which is included is also included.
  • the shell may be a monoatomic layer or a polyatomic layer in which two or more atoms are stacked, but from the viewpoint of improving specific activity, the shell is preferably a monoatomic layer.
  • FIG. 2 is a flowchart showing an example of a method for producing the core-shell catalyst of the present invention.
  • the manufacturing method of the core-shell catalyst shown in FIG. 2 includes (1) a preparation step, (2) a copper deposition step, (3) a replacement step, (4) a washing step, and (5) a drying step.
  • the method for producing a core-shell catalyst of the present invention has at least (1) a preparation step, (2) a copper deposition step, and (3) a substitution step, and if necessary, after the substitution step, (4) a washing step, (5) It has a drying process.
  • each process is demonstrated in order.
  • the palladium-containing particles used in the present invention are not particularly limited as long as the crystallite size is 5 to 8.5 nm, and preferably 5.7 to 7.5 nm.
  • the crystallite size in the present invention can be determined by X-ray diffraction (XRD).
  • XRD X-ray diffraction
  • D (K ⁇ ) / ( ⁇ cos ⁇ )
  • the meaning of each symbol is as follows.
  • D Crystallite size (nm)
  • K Scherrer constant
  • ⁇ Measurement X-ray wavelength (nm)
  • ⁇ Half width (rad)
  • rad Bragg angle (rad) of diffraction line
  • the palladium-containing particles at least one particle selected from palladium particles and palladium alloy particles can be used.
  • the palladium alloy include an alloy of palladium and a metal material selected from the group consisting of iridium, ruthenium, rhodium, iron, cobalt, nickel, copper, silver, and gold.
  • the metal other than palladium constituting the palladium alloy is 1 Two or more species may be used.
  • the palladium alloy preferably has a palladium content of 80% by mass or more when the mass of the entire alloy is 100% by mass. This is because a uniform platinum-containing shell can be formed when the palladium content is 80 mass% or more.
  • the average particle size of the palladium-containing particles is not particularly limited, but is preferably 8 nm or less.
  • the average particle diameter of the palladium-containing particles exceeds 8 nm, the surface area per mass of platinum becomes small, and a lot of platinum is required to obtain the necessary activity, which is costly. If the average particle size of the palladium-containing particles is too small, the palladium itself is easily dissolved and the durability of the catalyst is lowered. Therefore, the average particle size of the palladium-containing particles is preferably 3 nm or more.
  • the calculation method of the average particle diameter of the particles used in the present invention is as follows.
  • TEM scanning electron microscope
  • the palladium-containing particles are preferably supported on a carrier.
  • carrier When using the core-shell catalyst of this invention for the electrode catalyst layer of a fuel cell, it is preferable to use an electroconductive support
  • Specific examples of materials that can be used as a carrier for supporting palladium-containing particles include Ketjen Black (trade name: manufactured by Ketjen Black International), Vulcan (trade name: manufactured by Cabot), and Nolit (trade name: Norit).
  • a commercially available product can be used as the palladium-containing particle carrier supported on the carrier, or it can be synthesized.
  • a conventionally used method can be employed as a method of supporting the palladium-containing particles on the carrier. For example, there may be mentioned a method in which palladium-containing particles are mixed with a carrier dispersion in which a carrier is dispersed, filtered, washed, redispersed in ethanol or the like and then dried with a vacuum pump or the like.
  • the firing method can be the same as the firing method in the method for controlling the crystallite size described later.
  • Examples of the method for controlling the crystallite size include a method of firing palladium-containing particles, a method of subjecting palladium-containing particles to potential cycle treatment, and the like.
  • Examples of the method of firing the palladium-containing particles include a method of firing the palladium-containing particles at 300 to 500 ° C. for 1 to 6 hours in an inert gas atmosphere such as argon gas and nitrogen gas. If the firing temperature is less than 300 ° C, the crystallite size may not increase, and if the firing temperature exceeds 500 ° C, the crystallite size may become too large.
  • the potential cycle treatment can be performed, for example, by applying a predetermined potential to the palladium-containing particles in an electrolytic solution containing palladium-containing particles.
  • the method of applying a potential to the palladium-containing particles and the potential control device can be the same as the method and device performed in the copper deposition step described later.
  • the electrolytic solution that can be used for the potential cycle treatment is not particularly limited, and examples thereof include an acid solution.
  • an acid that can be used for the potential cycle treatment specifically, an acid similar to the acid that can be used for the copper ion-containing electrolyte described later can be used.
  • a copper ion containing electrolyte solution to the electrolyte solution used for the potential cycle process.
  • a copper precipitation step may be performed by adding an aqueous copper sulfate solution to the sulfuric acid after use.
  • the counter anion in the electrolytic solution used in the potential cycle treatment and the counter anion in the copper ion-containing electrolytic solution used in the copper deposition step may be the same or different.
  • the potential cycle treatment removes oxygen in the electrolyte solution as much as possible from the viewpoint of being able to quickly remove oxides on the surface of the palladium-containing particles.
  • Nitrogen is preferably bubbled into the electrolytic solution.
  • Examples of the potential application signal pattern in the potential cycle process include a rectangular wave, a triangular wave, and a trapezoidal wave.
  • the potential range is not particularly limited, but is preferably 0.05 to 1.2 V (vs. RHE).
  • the number of potential cycles is not particularly limited when the potential application signal pattern is a triangular wave, but is preferably 10 to 6000 cycles, and the potential sweep rate can be set to 5 to 100 mV / second, for example.
  • the crystallite size of the palladium-containing particles can be controlled by subjecting the palladium-containing particles to potential cycle treatment for the following reason.
  • palladium ions are usually exchanged between the palladium-containing particles via the electrolytic solution. Therefore, dissolution and reprecipitation of palladium occur in the electrolytic solution.
  • so-called Ostwald ripening occurs in which the palladium-containing particles having a relatively small particle size are dissolved, and the dissolved palladium ions are reprecipitated on the surface of the palladium-containing particles having a relatively large particle size. It is inferred that by repeating dissolution and reprecipitation of palladium, the irregular arrangement of atoms becomes regular and the crystallite size of the palladium-containing particles increases.
  • Copper deposition step In the copper deposition step, copper is deposited on the surface of the palladium-containing particles by applying a potential higher than the redox potential of copper to the palladium-containing particles in the copper ion-containing electrolyte. It is a process.
  • FIG. 3 is a perspective view schematically showing an example of a synthesis apparatus that can be used in the method for producing a core-shell catalyst of the present invention.
  • a synthesis apparatus 20 shown in FIG. 3 includes a reaction vessel 1, a reference electrode 4, a counter electrode 5, a counter electrode compartment 6, and a stirrer 7.
  • the reaction vessel 1 is made of Ti and functions as a working electrode.
  • the surface of the reaction vessel 1 is coated with Ru 2 O to give corrosion resistance.
  • the reaction vessel 1 contains palladium-containing particles 2 having a crystallite size of 5 to 8.5 nm and an electrolytic solution 3 containing copper ions.
  • the palladium-containing particles 2 and the electrolytic solution 3 accommodated in the reaction vessel 1 can be stirred with the stirring bar 7.
  • the reference electrode 4 and the counter electrode 5 are suspended by a platinum wire 8 and are disposed so as to be sufficiently immersed in the electrolytic solution 3.
  • the reaction vessel 1, the reference electrode 4 and the counter electrode 5 which are also working electrodes are electrically connected to a potential control device (for example, a potentiostat or the like, not shown) so that the potential of the working electrode can be controlled.
  • the reference electrode 4 and the counter electrode 5 are connected to a potential control device via a platinum wire 8.
  • the counter electrode 5 is immersed in the electrolytic solution 3 while being accommodated in a glass counter electrode compartment 6.
  • the counter electrode compartment 6 is formed of a porous glass frit at the bottom, and the contact property between the counter electrode 5 and the electrolytic solution 3 is ensured.
  • the copper ion-containing electrolytic solution is not particularly limited as long as it can deposit copper on the surface of the palladium-containing particles by Cu-UPD.
  • the copper ion-containing electrolytic solution is usually composed of a predetermined amount of copper salt dissolved in a solvent, but is not particularly limited to this configuration, and some or all of the copper ions are dissociated and exist in the liquid. Any electrolyte solution may be used.
  • the solvent used for the copper ion-containing electrolytic solution include water and organic solvents, but water is preferable from the viewpoint of not preventing the precipitation of copper on the surface of the palladium-containing particles.
  • the copper salt used in the copper ion-containing electrolyte include copper sulfate, copper nitrate, copper chloride, copper chlorite, copper perchlorate, and copper oxalate.
  • the copper ion concentration is not particularly limited, but is preferably 10 to 1000 mM.
  • the copper ion-containing electrolytic solution may contain, for example, an acid or the like.
  • the acid that can be added to the electrolytic solution containing copper ions include sulfuric acid, nitric acid, hydrochloric acid, chlorous acid, perchloric acid, and oxalic acid.
  • the counter anion in the copper ion-containing electrolyte and the counter anion in the acid may be the same or different.
  • an inert gas is bubbled in advance in the electrolytic solution. This is because the oxidation of the palladium-containing particles is suppressed and uniform coating with the platinum-containing shell becomes possible. Nitrogen gas, argon gas, etc. can be used as the inert gas.
  • the palladium-containing particles may be immersed and dispersed in the electrolytic solution by adding to the electrolytic solution in a powder state.
  • the palladium-containing particles are previously dispersed in a solvent to prepare a palladium-containing particle dispersion. You may immerse and disperse
  • the solvent used in the palladium-containing particle dispersion the same solvents as those used in the above-described copper ion-containing electrolytic solution can be used.
  • the palladium-containing particle dispersion may contain the acid that can be added to the copper ion-containing electrolyte.
  • the palladium-containing particles may be fixed on the conductive base material or the working electrode, and the palladium-containing particle fixing surface of the conductive base material or the working electrode may be immersed in the electrolytic solution.
  • a palladium-containing particle paste is prepared using an electrolyte resin (for example, Nafion (registered trademark)) and a solvent such as water or alcohol, and the conductive substrate or the action. The method of apply
  • the method for applying a potential to the palladium-containing particles is not particularly limited, and a general method can be adopted.
  • the working electrode for example, a metal material such as titanium, platinum mesh, platinum plate, or gold plate, a conductive carbon material such as glassy carbon, carbon plate, or the like that can ensure conductivity can be used.
  • the reaction vessel may be formed of the above conductive material and function as a working electrode.
  • reaction vessel made of a metal material When using a reaction vessel made of a metal material as a working electrode, it is preferable to coat the inner wall of the reaction vessel with RuO 2 from the viewpoint of suppressing corrosion.
  • a carbon material reaction vessel When a carbon material reaction vessel is used as a working electrode, it can be used as it is without coating.
  • the counter electrode for example, a platinum mesh plated with platinum black and conductive carbon fiber can be used.
  • a reversible hydrogen electrode (RHE), a silver-silver chloride electrode, a silver-silver chloride-potassium chloride electrode, or the like can be used.
  • RHE reversible hydrogen electrode
  • a silver-silver chloride electrode As the reference electrode, a reversible hydrogen electrode (RHE), a silver-silver chloride electrode, a silver-silver chloride-potassium chloride electrode, or the like can be used.
  • the potential to be applied is not particularly limited as long as it is a potential at which copper can be deposited on the surface of the palladium-containing particles, that is, a potential nobler than the oxidation-reduction potential of copper, but for example, 0.35 to 0.7 V It is preferably within the range of (vs. RHE), particularly preferably 0.4 V (vs. RHE).
  • the time for applying the potential is not particularly limited, but is preferably 60 minutes or more, and more preferably until the reaction current becomes steady and approaches zero.
  • the application of the potential may be performed by sweeping the potential in a range including the potential range. Specifically, the potential range to be swept is preferably 0.3 to 0.8 V (vs. RHE).
  • the number of potential sweep cycles is not particularly limited, but is preferably 1 to 10,000 cycles.
  • the potential sweep rate is, for example, 0.01 to 100 mV / sec.
  • the copper precipitation step is preferably performed in an inert gas atmosphere such as a nitrogen atmosphere from the viewpoint of preventing oxidation of the surface of the palladium-containing particles and preventing oxidation of copper.
  • the copper ion-containing electrolyte is appropriately stirred as necessary.
  • each of the palladium-containing particles is mixed with the reaction vessel that is the working electrode by stirring the electrolytic solution.
  • the surface can be contacted and a potential can be uniformly applied to each palladium-containing particle.
  • stirring may be performed continuously or intermittently during the copper deposition step.
  • substitution step is a step of bringing the copper deposited on the surface of the palladium-containing particles into contact with the copper deposited on the surface of the palladium-containing particles by bringing a platinum ion-containing solution into contact therewith.
  • copper and platinum can be substituted due to the difference in ionization tendency by bringing the platinum ion-containing solution into contact with copper deposited on the surface of the palladium-containing particles.
  • the shell in the present invention includes platinum and a platinum alloy.
  • the platinum alloy include an alloy with a metal material selected from the group consisting of iridium, ruthenium, rhodium, nickel and gold.
  • the metal other than platinum constituting the platinum alloy may be one kind or two or more kinds.
  • the platinum alloy preferably has a platinum content of 90% by mass or more when the mass of the entire alloy is 100% by mass. This is because if the platinum content is less than 90% by mass, sufficient catalytic activity and durability cannot be obtained.
  • the platinum salt used in the platinum ion-containing solution for example, K 2 PtCl 4 , K 2 PtCl 6 or the like can be used, and an ammonia complex such as ([PtCl 4 ] [Pt (NH 3 ) 4 ]) can be used. It can also be used.
  • the platinum ion concentration in the platinum ion-containing solution is not particularly limited, but is preferably 0.01 to 100 mM.
  • the solvent that can be used in the platinum ion-containing solution can be the same as the solvent used in the electrolytic solution containing copper ions described above. Further, the platinum ion-containing solution may contain, for example, an acid or the like in addition to the solvent and the platinum salt.
  • the acid include sulfuric acid, nitric acid, hydrochloric acid, chlorous acid, perchloric acid, and oxalic acid.
  • the platinum ion-containing solution is sufficiently stirred in advance, and nitrogen is preferably bubbled into the solution in advance from the viewpoint of preventing oxidation of the palladium-containing particles and preventing oxidation of copper.
  • the replacement time is not particularly limited, but it is preferable to ensure 10 minutes or more. As the platinum ion-containing solution is added, the potential of the reaction solution increases. Therefore, it is more preferable to substitute until the monitor potential does not change.
  • a platinum ion containing solution to the electrolyte solution used for the copper precipitation process.
  • the potential control is stopped, and the platinum-containing solution is added to the copper ion-containing electrolyte used in the copper deposition step, so that the palladium-containing particles on which the copper is deposited are brought into contact with the platinum ion-containing solution. You may let them.
  • the washing process is a process of washing the core-shell catalyst after the replacement process.
  • the washing of the core-shell catalyst is not particularly limited as long as it can remove impurities without impairing the core-shell structure of the produced core-shell catalyst.
  • a method of suction filtration using water, perchloric acid, dilute sulfuric acid, dilute nitric acid or the like can be mentioned.
  • the drying step is a step of drying the obtained core-shell catalyst after the substitution step.
  • the drying of the core-shell catalyst is not particularly limited as long as it can remove the solvent and the like, and examples thereof include a method of maintaining a temperature of 50 to 100 ° C. for 6 to 12 hours in an inert gas atmosphere.
  • the core-shell catalyst may be pulverized as necessary.
  • the pulverization method is not particularly limited as long as it is a method capable of pulverizing solids. Examples of the pulverization include pulverization using an inert gas atmosphere or mortar in the atmosphere, and mechanical milling such as a ball mill, a turbo mill, and a jet mill.
  • Example 1 [Preparation process] A Ti cylindrical container having a diameter of 15 cm and having a surface coated with RuO 2 was used as a reaction container. This reaction vessel was also functioned as a working electrode. As a counter electrode, a platinum mesh plated with platinum black was prepared. The counter electrode was placed in a compartment with a frit glass on the bottom and placed in a reaction vessel with a polyethylene float. An Ag / AgCl / KCl (3M) electrode (manufactured by Cypress Systems) was used as a reference electrode. 0.055 L of 0.05 M sulfuric acid was placed in a reaction vessel serving as a working electrode. The sulfuric acid was previously bubbled with nitrogen.
  • a potentiostat as a potential control device from the outside so that the potential could be controlled.
  • Pd / C palladium-supported carbon
  • the potential of the Ag / AgCl / KCl (3M) electrode is described in terms of RHE.
  • a part of Pd / C was collected, 10% by mass of silicon powder (NIST640b) was added, mixed in an agate mortar, and XRD measurement was performed on palladium particles.
  • the XRD measurement results are shown in FIG.
  • the XRD measurement conditions are as follows.
  • Example 2 A core-shell catalyst was produced in the same manner as in Example 1 except that CV was carried out at a potential cycle number of 2500 in the preparation step, and palladium particles having an average particle size of 5.4 nm and a crystallite size of 7.5 nm were prepared.
  • the XRD measurement result of the palladium particles in Example 2 is shown in FIG.
  • Comparative Example 1 A core-shell catalyst was produced in the same manner as in Example 1 except that CV was not performed in the preparation step and palladium particles having an average particle size of 2.8 nm and a crystallite size of 4.7 nm were prepared.
  • the XRD measurement result of the palladium particles in Comparative Example 1 is shown in FIG.
  • Comparative Example 2 The same as in Example 1 except that CV was not performed in the preparation step, and calcined in an inert atmosphere at 600 ° C. for 1 hour to prepare palladium particles having an average particle size of 8.1 nm and a crystallite size of 9.9 nm. Thus, a core-shell catalyst was produced.
  • the XRD measurement result of the palladium particles in Comparative Example 2 is shown in FIG.
  • Electrolyte 0.1M perchloric acid aqueous solution (Oxygen saturated in advance by bubbling oxygen gas at 30mL / min for 30 minutes or more)
  • -Atmosphere oxygen atmosphere-Sweep speed: 10 mV / sec-Potential sweep range: 0.1 to 1.05 V (vs. RHE)
  • Rotation speed 1600 rpm
  • the catalytic activity (MA) per unit mass of platinum in each core-shell catalyst was measured.
  • the catalytic activity per unit mass of platinum in the core-shell catalyst is determined by using an oxygen reduction wave obtained by ORR measurement with a current value of 0.9 V (vs.
  • the core-shell catalysts obtained in Examples 1-2 and Comparative Examples 1-2 were subjected to cyclic voltammetry (CV) measurement, and the electrochemical surface area (ECSA) of the core-shell catalyst was calculated.
  • a catalyst ink was prepared by the same method as the mass activity evaluation, and the catalyst ink was applied to a glassy carbon electrode (RDE) and dried, and CV measurement was performed. CV measurement conditions are shown below.
  • Electrolyte 0.1M perchloric acid aqueous solution (Ar gas was bubbled at 30 mL / min for 30 minutes or more in advance and saturated with Ar) -Atmosphere: Ar atmosphere-Sweep speed: 50 mV / sec-Potential sweep range: 0.05 to 1.2 V (vs. RHE) From the obtained cyclic voltammogram, the charge amount (C) of the hydrogen desorption peak was integrated. Further, the mass (g) of platinum was calculated from the concentration and coating amount of the catalyst ink applied to the glassy carbon electrode.
  • the core-shell catalyst of Comparative Example 1 using palladium particles having a crystallite size of less than 5 nm and Comparative Example 2 using palladium particles having a crystallite size exceeding 8.5 nm has a specific activity lower than 4 A / m 2. I understand that.
  • reaction vessel palladium-containing particles 3 electrolyte 4 reference electrode 5 counter electrode 6 counter electrode compartment 7 stirrer (stirrer) 8 Platinum wire 20 Synthesizer

Abstract

L'invention concerne un procédé de fabrication d'un catalyseur de type noyau-enveloppe présentant une activité spécifique élevée. Le procédé de fabrication d'un catalyseur de type noyau-enveloppe doté d'un noyau qui comprend du palladium et d'une enveloppe qui comprend du platine et qui recouvre le noyau se caractérise en ce qu'il comprend : une étape de préparation de grains contenant du palladium qui ont un pic à 2θ = 40° ± 1° dans les résultats de mesure de diffraction de rayons X et qui ont une taille de grain cristallin, déterminée par la demi-largeur au pic à 2θ = 40° ± 1° par le procédé de Scherrer, qui est de 5 à 8,5 nm ; une étape de précipitation de cuivre consistant à appliquer un potentiel électrique plus noble que le potentiel d'oxydoréduction du cuivre aux grains contenant du palladium dans un électrolyte contenant des ions cuivre pour ainsi précipiter le cuivre sur la surface des grains contenant du palladium ; et une étape de substitution consistant à amener une solution contenant des ions platine en contact avec le cuivre précipité sur la surface des grains contenant du palladium après l'étape de précipitation de cuivre pour ainsi remplacer par le platine le cuivre précipité sur la surface des grains contenant du palladium et former ainsi une enveloppe.
PCT/JP2015/053234 2014-04-02 2015-02-05 Procédé de fabrication d'un catalyseur de type noyau-enveloppe WO2015151578A1 (fr)

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