JP2019084484A - Palladium core platinum shell fine particle supported with carrier, and manufacturing method therefor - Google Patents

Abstract

To find a condition for synthesizing a PdPt core-shell type fine particle and provide the PdPt core-shell type fine particle at low cost.SOLUTION: In consideration of a problem that variation of fine particles is large when a core-shell type catalyst fine particle of a carbon carrying palladium core platinum shell is synthesized at a form that palladium is carried by a carrier from synthesis of palladium of a core, ethylene glycol is used as a dispersant, and sodium tetrachloro palladium (2) acid (a palladium raw material) and a sodium hydroxide solution of product mass of 4 to 7 times of that of the palladium raw material are added to a dispersion in which the carrier is dispersed as an additive having a function of generation of hydroxide ions excluding potassium hydroxide in the dispersant to prepare a reaction raw material liquid. By adding sodium hydroxide from synthesis of palladium in coexistence with carbon, variation of fine particles disappears and fine particles with uniform properties can be manufactured at low cost.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a support-supported palladium core platinum shell fine particle and a method for producing the same, and more particularly to a core-shell type fine particle produced by using a sodium hydroxide for the support-supported palladium core before forming a platinum shell.

The terms used in this patent specification are defined as follows.
Shell: It is said that a shell structure is formed when a substance different from the substrate is arranged in the form of layered or partially layered or partially aggregated particles around the substrate with a certain fine particle as the substrate. Underlying nanoparticles are used as core particles, sometimes referred to as core-shell structure.

  A polymer electrolyte fuel cell (hereinafter referred to as PEFC) fueled by hydrogen is considered to be an environmentally friendly energy device that can be used by electric transportation vehicles. As metal catalysts such as bimetallic metal particles such as palladium-cored platinum-sur-nanoparticles as electrochemical catalysts of this PEFC show higher oxygen reduction activity than catalysts using only platinum, and It is of great interest to reduce the use of precious platinum.

  A catalyst containing metal nanoparticles using binary metal-based metal particles is dispersed in a porous carbon material having a high surface area such as activated carbon, carbon nanotubes, or graphene in order to maximize the catalytic effect and ensure conductivity. It is common to be fixed and fixed.

  In recent years, it has become clear that metal nanoparticles composed of a plurality of types of metal elements exhibit different properties as compared to nanoparticles of only one type of metal. For this reason, alloy nanoparticles obtained by alloying two types of metals, core-shell type nanoparticles obtained by coating one metal nanoparticle with another metal, and the like are actively studied, and various proposals have been made.

  It is expected that core-shell nanoparticles can be provided with different catalytic activity than nanoparticles of shell metal only if they can form a shell layer in contact with the outside uniformly. It is speculated that this is because, when the core particle becomes a base, the electronic properties of the shell layer and the geometrical arrangement of the crystal structure are modified, and the activation energy of the intended reaction is reduced more effectively. It is done.

  In addition, when the metal having catalytic activity is very expensive, the core-shell structure is economical because the expensive metal can be effectively disposed in the shell layer in contact with the reactant. In addition, by uniformly coating a chemically stable noble metal as a shell, it is possible to indirectly participate in the reaction while shielding an easily oxidizable, soluble base metal from the outside, and to exhibit new catalytic properties. Will also be possible.

  Among core-shell type metal nanoparticles for catalytic use, palladium core platinum shell particles are attracting attention. Platinum nanoparticles are known as catalysts for various chemical reactions, but cost is a problem and they have not been widely used. It has only been adopted in a limited manner in processes that can achieve sufficient productivity including costs.

  Attempts have been made to use small amounts of platinum effectively and to obtain as good catalytic performance as possible, and in recent years palladium core platinum shell metal nanoparticles to lower the cost of catalysts for fuel cells for home and automobile use Is considered to be effective.

  However, since it is very difficult to uniformly coat the shell layer in the synthesis of core-shell type metal nanoparticles, the synthesis conditions are often limited in the laboratory, and the particle diameter is reduced to a small value of single nanometer. As the observation by electron microscope and the analysis using electron beam and X-ray also become more difficult, the data for proving the core-shell structure often left uncertainty. Therefore, a process for mass-producing core-shell type metal nanoparticles having a uniform shell layer while maintaining stable quality at low cost has not been realized yet.

  Non-Patent Document 1 claims that palladium cored platinum shell particles are promising mainly for fuel cell catalyst applications.

  In Patent Documents 1 and 2, there is an underpotential deposition method in which a monoatomic layer of copper is formed on the surface of a palladium particle by adjusting the potential on the electrode and subsequently copper and platinum are substituted by adding a platinum salt. Have been described. Although this method is excellent in that it can form a shell of a single atomic layer in principle, it is based on platinum because electrons are not uniformly transmitted to the material and that the reactant is not uniformly supplied. Shell coverage may not be sufficient. In addition, although this method is suitable for the purpose of forming a small amount of core-shell particles in the laboratory and analyzing the characteristics, it is a method that still has difficulties when considering productivity and automation in mass production.

  On the other hand, a method of forming a shell by electroless plating without using an electrode has also been proposed. In Patent Document 3, the platinum shell layer is formed on palladium particles by examining the type of platinum salt, and the coverage is measured, but it is not satisfactory and it is determined whether the shell layer has a uniform thickness. Not

  When using a core-shell type metal fine particle as a catalyst, it is important to select fine particles having high conductivity and high surface area and a combination of fine particles as a carrier and distributing the fine particles at a desired density on the carrier. The particle diameter is preferably as small as possible, and in order to make the characteristics uniform, it is preferable that the particle diameters be uniform. At present, in the impregnation method currently used as a catalyst preparation method, supported particles are easily aggregated, and it is difficult to uniformly convert two or more types of metals into alloy particles or core-shell type particles. It has become.

  As a heating means for the reaction solution, the reaction solution is irradiated with microwaves. Patent Document 4 uses a semiconductor oscillator and a microwave resonance cavity, and arranges a reaction tube of a continuous flow system at the largest position of a standing wave of an electric field, thereby achieving a chemical reaction without damaging rapid heating and uniformity. Attempts have been made to carry out heating. This method combining a single mode heating method and a continuous flow system is extremely useful when the reaction is sufficiently promoted by microwave heating and completed in a short time.

By synthesizing core particles using liquid phase reduction, subsequent modifications such as shell formation can be easily performed, but when trying to increase productivity using a batch method, nucleation is caused by uneven heating and stirring. However, the particle size tends to be uneven, and other problems. Therefore, at present, most of the metal nanoparticles that are said to have uniform particle sizes are at the laboratory level, and it has been difficult to increase productivity without sacrificing quality when producing metal nanoparticles .
In particular, although palladium cored platinum shell nanoparticles are expected for catalytic applications, it is difficult to produce uniform shell layers with stable quality and cost savings.

  As a technique corresponding to this point, Patent Document 5 uses microwave heating for synthesis of palladium core particles and adjusts the shell formation reaction by adding hydroxide ions to form a uniform platinum shell layer. A technology for achieving both stable quality and improved productivity is described.

JP, 2011-218278, A JP, 2012-16684, A JP 2012-120949 A JP 2011-137226 A JP, 2015-223535, A

NEDO Achievement Report: "Development of polymer electrolyte fuel cell technology promotion technology development / basic technology development / platinum reduction technology" (2010-2012) interim report for 2010

  Although various methods have been proposed as methods for producing core-shell particles for fuel cell oxygen reduction catalysts, it is difficult for any method to continuously produce shell layers with stable quality and at low cost. is there. For example, while the method described in Patent Document 5 aims to form a uniform platinum shell layer by adjusting the shell formation reaction by adding sodium hydroxide ion, Patent Document 5 has stable quality and the like. Detailed conditions for achieving both productivity improvement are not described.

  The problems to be solved by the present invention are core-shell type fine particles of carrier-supporting palladium core platinum shell as oxygen reduction catalyst, core-shell type fine particles of carbon-supporting palladium core platinum shell (hereinafter also referred to as PdPt) particularly emphasized. As a production method, a reaction solution containing sodium hydroxide (NaOH) is circulated, and microwave irradiation is performed in the presence of a carbon support to find conditions for stably producing carbon-supported palladium core particles continuously. And, after synthesis of carbon-supported palladium core particles, an NaOH solution and a platinum raw material are added thereto to stably form a platinum shell layer in the presence of a carbon support, thereby providing high performance and high productivity PdPt core-shell type particles. It is about finding the conditions for manufacturing.

  Then, the problem to be solved by the present invention is to provide PdPt core-shell type microparticles at low cost by using the expensive precious metal raw material without waste by the above manufacturing method and reducing the extra steps.

  In order to solve the above problems and achieve the above object, the present invention has, for example, the following configuration.

  That is, in the method for producing metal fine particles according to the present invention, a reaction liquid containing a palladium precursor, a reducing agent for the precursor, and carbon as a carrier of palladium is distributed in a flow pipe disposed in a microwave irradiation space. The microwave is uniformly and intensively irradiated toward the flow pipe in the microwave irradiation space, and the reaction liquid in the flow pipe in the microwave irradiation space is circulated by the microwave irradiation. In the method for producing metal fine particles, which uniformly heats and produces metal fine particles over the entire longitudinal direction of the direction, the reaction solution contains sodium hydroxide, and the diameter of the metal fine particles is determined according to the mixing amount of sodium hydroxide. To control.

  Then, for example, the diameter of the metal fine particles is controlled by controlling the hydroxide ion concentration of the reaction liquid by the mixing amount of sodium hydroxide mixed in the reaction liquid.

  The apparatus for producing metal fine particles according to the present invention is a apparatus for producing metal fine particles including a microwave irradiation space and a microwave oscillator for irradiating the microwave irradiation space with microwaves, and the flow pipe is And a portion disposed in the portion disposed in the microwave irradiation space, wherein the reaction solution flows in the microwave irradiation space, and the microwave emitted from the microwave oscillator is In the microwave irradiation space, the reaction liquid in the flow pipe is uniformly heated over the entire length direction of the flow direction, and the reaction containing the metal precursor and the reducing agent of the metal precursor is retained. And a mixing means for mixing a sodium hydroxide solution with the reaction liquid held in the reaction liquid holding part, wherein the reaction liquid mixed in the mixing means is the flow It is circulated in the tube, characterized in that to produce the fine metal particles.

  And, for example, the mixing means is characterized in that the diameter of the metal fine particles is controlled by controlling the hydroxide ion concentration of the reaction liquid by the mixing amount of sodium hydroxide mixed in the reaction liquid.

Hereinafter, examples of the present invention will be specifically described.
In the first invention (hereinafter referred to as invention 1) made to solve the problems, an alcohol is used as a dispersion medium, and a palladium precursor (palladium raw material) is added to a dispersion in which a carrier is dispersed, and a reaction raw material liquid It is a manufacturing method of carrier-supported palladium fine particle colloid which reduces the said palladium raw material by carrying out microwave heating, and synthesizes a carrier-supported palladium fine particle, and generates hydroxide ion except potassium hydroxide in a dispersion medium It is a method for producing a carrier-supported palladium fine particle colloid characterized by adding an additive having a function.

  In a second invention (hereinafter referred to as invention 2) developed by developing invention 1, in the invention 1, the alcohol is ethylene glycol, the carrier is carbon fine particles, and the palladium precursor is tetrachloropalladium. (2) A process of producing carbon-supported palladium fine particle catalyst by microwave continuous heating method by adding sodium hydroxide which is sodium acid and 4 to 7 times the substance weight of the palladium raw material as the additive. It is a method for producing a carrier-supported palladium fine particle colloid, characterized in that the method comprises:

  A third invention (hereinafter referred to as invention 3) developed by expanding invention 1 or 2 is characterized in that a fuel cell ionomer is added to the carrier dispersion of the raw material in invention 1 or 2 It is a manufacturing method of palladium fine particle colloid.

  A fourth invention (hereinafter referred to as invention 4) developed by developing invention 3 is that, in invention 3, the ionomer to be added is a copolymer of perfluorofluorinated sulfonyl vinyl ether and tetrafluoroethylene. It is a method for producing a carrier-supported palladium fine particle colloid characterized by the above.

  A fifth invention (hereinafter referred to as invention 5) made to solve the above problems is a solution containing as a raw material a colloid produced by the method according to any of inventions 1 to 4 and containing a platinum precursor, Additives having the function of generating hydroxide ions other than potassium hydroxide in a dispersion medium to form a reaction support liquid at room temperature to form a platinum shell on a support-supported palladium core particle to form a platinum shell. It is a manufacturing method of shell particulates catalyst, and after adding the above-mentioned additive to the above-mentioned platinum precursor solution (platinum raw material), hydroxide ion concentration except free, coordination, adsorption potassium hydroxide is the above-mentioned It is a method for producing a carrier-supported palladium core platinum shell microparticle catalyst characterized in that the amount is 2 to 6 times the substance mass of the platinum raw material.

  According to a sixth invention (hereinafter referred to as invention 6) made by developing invention 5, in the invention 5, the platinum raw material is a solution containing hexachloroplatinum (4) acid ion, and the additive is sodium hydroxide After the addition of the sodium hydroxide solution, the concentration of hydroxide ions excluding free, coordinated, adsorbed potassium hydroxide is 2 to 6 times the substance mass of the platinum material. It is a manufacturing method of a carrier-supported palladium core platinum shell particulate catalyst.

  A seventh invention (hereinafter referred to as invention 7) developed by developing invention 5 is the method according to invention 5, wherein the support is carbon fine particles, and the carbon-supported palladium fine particle catalyst is produced by a microwave continuous heating method. Carrier-support comprising a step of producing a carbon-supported palladium-cored platinum-shell particulate catalyst by continuous flow method in which a step of forming fine particle colloid and a step of forming platinum shell at normal temperature are connected by a continuous flow path It is a manufacturing method of a palladium core platinum shell particulate catalyst.

  According to an eighth invention (hereinafter referred to as the eighth invention) made by developing the seventh invention, in the seventh invention, when the palladium core platinum shell fine particle catalyst is made into a dry powder, sodium ions remain in the dry powder. It is a manufacturing method of the support | carrier support palladium core platinum shell fine particle catalyst characterized by the above-mentioned.

  The ninth invention (hereinafter referred to as the ninth invention) made by developing the fifth invention is characterized in that, in any one of the fifth to eighth inventions, the fuel cell ionomer is added to the carrier dispersion of the raw material. It is a manufacturing method of the support | carrier support palladium core platinum shell fine particle catalyst made as this.

  A tenth invention (hereinafter referred to as invention 10) developed by developing invention 9 is that, in invention 9, the ionomer to be added is a copolymer of perfluorofluorinated sulfonyl vinyl ether and tetrafluoroethylene. It is a method for producing a carrier-supported palladium core platinum shell particulate catalyst characterized by the present invention.

  The eleventh invention (hereinafter referred to as the invention 11) made to solve the above-mentioned problems is manufactured by the manufacturing method according to any of the inventions 5 to 10, characterized in that it is manufactured by a carbon-supported palladium core platinum shell fine particle It is.

  The twelfth invention made to solve the above problems (hereinafter referred to as the invention 12) uses, as a catalyst, a carbon-supported palladium-cored platinum shell fine particle manufactured by the manufacturing method according to any of the inventions 5 to 10 It is a polymer electrolyte fuel cell characterized in that.

The thirteenth invention (hereinafter referred to as the invention 13) made to solve the problems referring to the examples 1 to 12 while referring to the inventions 1 to 12 is a 0.1 M aqueous solution of perchloric acid with a width of 14.5 cm. In addition to a glass 5-neck flask for measurement of convective voltammetry having a height of 12.5 cm and a volume of 300 ml or more, 3 liters / minute of nitrogen was bubbled for 30 minutes to remove oxygen as an electrolyte, and platinum was 0 On a 5 mm diameter glassy carbon rotary electrode of the glassy carbon portion coated with catalyst ink to contain .96 μg
When a durability test is performed at a temperature of 25 ° C., using a reversible hydrogen electrode as a reference electrode and applying a potential cycle of 0.6 V for 3 seconds and 1.0 V for 3 seconds with a square wave as one cycle,
An aqueous solution of 0.1 M perchloric acid is added to the flask, and 3 L / min of oxygen is bubbled for 30 minutes to use nitrogen as an electrolyte.
Under the conditions of a rotational speed of 1600 [rotation / min] of the electrode, a temperature of 25 ° C., and a scanning speed to the high potential side of 20 [mV / sec],
Using a mass activity calculation method to calculate the oxygen reduction current value at a potential of 0.9 V with the reversible hydrogen electrode as the reference electrode by using the Koutecky-Levich equation and compensating for the solution resistance,
The platinum mass activity as an oxygen reduction catalyst after 10000 potential cycles, that is, the value obtained by dividing the current value in the mass activity calculation method by the coated platinum amount of 0.96 μg can maintain 95% or more of the mass activity before the durability test It is a palladium core platinum shell particulate catalyst characterized by being.

  The fourteenth invention (hereinafter referred to as the invention 14) developed by developing the invention 13 is an invention in a support-supported palladium core platinum shell fine particle catalyst manufactured using the manufacturing method according to any of the inventions 5-10. A palladium core platinum shell particulate catalyst characterized in that a mass activity value of the palladium core platinum shell particulate catalyst calculated by the mass activity calculation method described in 13 is 300 to 400 [A / g] in initial activity. .

  If sodium hydroxide is used for the synthesis of carbon-supported palladium core particles in the core-shell type fine particles of carbon-supported palladium core platinum shell according to the method found by the present invention, the above-mentioned particles become catalyst fine particles if the hydroxide ion concentration is appropriately adjusted. In the case, it is possible to inexpensively provide core-shell type fine particles of carbon-supporting palladium-cored platinum shell having high catalytic performance and excellent durability.

It is a figure explaining the manufacturing method of the carbon support palladium core platinum shell particulates concerning the present invention. It is a figure explaining the transmission electron microscope image of the carbon support palladium core platinum shell particles as an example of an embodiment of the present invention. It is the figure which compared the oxygen reduction ability (mass activity) before and behind the durability test by the electrochemical measurement method of the carbon support palladium core platinum shell microparticles | fine-particles as an embodiment example of this invention, and platinum microparticles. It is a figure explaining transition of the maintenance ratio of mass activity to the number of electric potential cycles in the endurance test of the carbon support palladium core platinum shell particulates as an example of an embodiment of the present invention.

1: Raw material solution of palladium core particles, carbon carrier, sodium hydroxide aqueous solution dissolved and dispersed in solvent and pump for feeding it 2: Microwave cavity reaction system 3: Platinum shell layer forming solution and its delivery Liquid pump system 4: Raw material liquid for forming platinum shell layer and liquid feed pump system 5a, 5b: Process using mixer 6: Tank for platinum shell formation reaction 7: Carbon supported palladium core platinum shell catalyst 7a: carbon carrier 7b: palladium core Platinum shell catalyst 8a: Point 8b where initial activity in load response durability test is represented as 100% 8: Tank for platinum shell formation reaction 8c: load response durability test point 8 where retention rate of mass activity after 10000 cycles is represented: Line 8e connecting 8a and 8b: Line connecting 8b and 8c

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The drawings used for the description schematically show the dimensions, shapes, arrangement relationships, and the like of the respective constituent elements to the extent that the example of the present invention can be understood. Further, for convenience of the description of the present invention, the enlargement ratio may be partially changed for illustration, and may not necessarily be similar to the real thing such as the embodiment. Moreover, in each figure, the same number is attached | subjected to the same structure and duplication description is abbreviate | omitted. Furthermore, in the following description, in the range where misunderstanding does not occur, the description of the method of producing metal fine particles may also serve as the description of a metal fine particle or a device for producing metal fine particles, and vice versa.

  Particularly important issues in producing carbon-supported palladium cored platinum shell fine particles are cost reduction and quality improvement. It is desirable to have a manufacturing method that has as high catalytic performance as possible, has excellent durability, and can be manufactured inexpensively.

  Forming a shell structure on core metal particles supported on a conductive support in displacement plating and electroless plating is further difficult. Since the carrier is conductive, electrons may flow through the carrier, and the oxidation reaction and the reduction reaction may occur at separate positions, and there may also be a side reaction in which single particles of shell metal are formed on the carrier.

  The formation of core-shell metal fine particles having a uniform shell structure may require a process similar to plating, but existing plating methods can not be applied as they are. However, in order to uniformly grow the shell layer without side reactions both in particles and between particles over the entire surface of the fine particles, it is necessary that the supply and reactivity of the shell raw material be as uniform as possible.

  In order for the shell stock material supply to be uniform, it is necessary that the reaction rate not be too fast. With regard to the reactivity, it is desirable to control so that only reaction in which a platinum shell layer is formed without pinholes on the surface of a palladium core particle is advanced as much as possible and reaction does not proceed after shell layer formation is completed.

  For example, in order to suppress unnecessary side reaction pathways, it is essential that the platinum salt precipitates as a zero-valent metal only when it comes in contact with a palladium core particle or a platinum shell layer surface having the palladium core particle as a base. In other words, it is not necessary to suppress reactions that pull electrons out of surrounding chemical species to form metal nuclei or form an excess shell layer on the already existing platinum shell layer even though they are not in contact with the underlying core particles. It does not. Also, palladium (2) ions liberated into the solvent by displacement plating can not be reduced again in any form.

  In order to realize such reaction control for all palladium core particles and platinum shell raw material salts present in the reaction liquid, the method of adding many kinds of additives tends to be uneven reaction conditions. In particular, in PEFC, the adhesion of organic molecules to the catalyst surface may reduce the activity, which requires a careful washing step.

  Here, the core particles are synthesized using liquid phase reduction, which facilitates subsequent modifications such as shell formation, but when it is intended to increase productivity using a batch method, uneven heating and stirring are possible. As a result, nucleation tends to be nonuniform, and adverse effects such as non-uniform particle diameter may occur. Most of the metal nanoparticles known to have a uniform particle size are synthesized on a laboratory scale, and it is difficult to increase productivity without sacrificing quality when producing metal particles. It will be proved.

  As a means for heating the reaction liquid in the liquid phase reduction method, microwave irradiation of the reaction liquid is performed as in the invention described in Patent Document 5. That is, in this case, by using a semiconductor oscillator and a microwave resonant cavity, the reaction tube of the continuous flow system is disposed at the highest position of the standing wave of the electric field, so that the chemistry does not lose uniformity by rapid heating. It is heating for the reaction. Particularly preferred is single-mode heating, which is a method of generating a single mode of electromagnetic field in a cavity whose size and resonance frequency are matched, in which case the reaction is sufficiently promoted by microwave heating and completed in a short time. It is useful. In addition, heating and reaction non-uniformities, which are problems in batch processes, can be significantly improved.

  In the case of synthesizing a palladium core platinum shell as fine particles for catalyst, it is difficult to uniformly support the method of supporting fine particles after synthesis, and it is difficult to have a loss of precious metal fine particles, and a difficulty of removing dispersants etc. There is. In the case where the catalyst fine particles are mixed with a carrier and supported, it is difficult to adsorb and carry the catalyst fine particles on the surface of the carbon carrier, and if too much catalyst particles are added, aggregation occurs on the carbon carrier and can not be effectively used. The surface of the catalyst may be generated, or the free supported fine catalyst particles may be generated, so that the precious metal raw material may not function effectively as a catalyst. In PEFC, polymer dispersants and organic compounds that do not participate in battery reactions adsorb to the catalyst surface and block active sites, or become carbon monoxide to cause poisoning of the catalyst and cause battery failure. It is necessary to remove such substances as much as possible because it causes the problem. However, when carbon having a high surface area is used as a carrier, a compound having a hydrophobic group such as a polymer dispersant or a surfactant is easily adsorbed to the carbon carrier and difficult to remove. Complete removal requires careful washing and firing under an inert atmosphere, which increases the number of processes and costs. Therefore, if a method of supporting noble metal fine particles on a carbon support by microwave heating is used, the metal fine particle catalyst can be uniformly supported on the support, and if the conditions are adjusted, almost all noble metal raw materials can be converted as catalysts. , Very useful.

  By using a solvent that absorbs microwaves well, heating can be performed more rapidly than ordinary heating such as a heater or an oil bath, and there are advantages such as completion of the reaction in a short time and effective use of energy. From that point of view, although it is not narrowly limited to this, in one of the embodiments of the present invention, it is a typical solvent that absorbs microwaves well, and heating to near its boiling point (196 ° C.) in a short time The ethylene glycol which can be used was used.

Furthermore, in the embodiment of the present invention, metal nanoparticles are synthesized by reducing the raw material metal salt. This reaction is expressed by a chemical formula:
M ⁺ (metal ion) + e ^- (electron is supplied from the reducing agent) → M ⁰ (metal) (1)
It becomes.
Metal particles are formed by collecting several thousands of zero-valent metals in the right term of the above chemical formula.

  Although various manufacturing methods can be considered depending on what is used as the above-described metal ion raw material and reducing agent for supplying electrons, in the embodiment of the present invention, sodium tetrachloropalladate and chloride are used as metal ions. Platinum acid was used and ethylene glycol was used as a reducing agent.

Ethylene glycol has a reducing power when heated, and in the chemical formula
Ethylene glycol → e ^- + ethylene glycol oxidation products + hydrogen ions (2)
It is expressed as
By rapidly heating ethylene glycol containing a metal source salt by microwaves, a large amount of electrons can be rapidly supplied from ethylene glycol, and microparticles of small particle size can be synthesized by rapid reduction of the source metal salt. . On the other hand, moderate heating tends to moderate the nucleation and crystal growth of metal particles and to produce nano or micron particles having a large particle size.

  In the above formula (2), hydrogen ions are released along with the supply of electrons from ethylene glycol, but their accumulation reduces the reaction rate, making it difficult to form nanoparticles with a small particle size. However, by adding a compound having a function of generating hydroxide ions in the dispersion medium, it is possible to suppress an increase in hydrogen ion concentration, and it becomes possible to maintain a high reaction rate, resulting in particles Small particles of small diameter can be produced.

  Aluminum hydroxide, ammonium hydroxide, calcium hydroxide, sodium hydroxide, magnesium hydroxide, which is a hydroxide salt containing a hydroxide, as an example of a compound having a function of generating hydroxide ions in a dispersion medium Although iron hydroxide, copper hydroxide, manganese hydroxide, zinc hydroxide, lanthanum hydroxide etc. can be mentioned, this invention is not limited to these. Moreover, although carbonate etc. are mentioned as a substance which produces | generates a hydroxide ion by dissociating in a dispersion medium, This invention is not limited to these.

  In the embodiment of the present invention, palladium core particles having a small particle diameter are synthesized using microwave heating for the core, and platinum shells are reacted slowly at room temperature by using platinum platinum alone. The formation of shells of uniform thickness is formed. In these cases, it is characterized by using sodium hydroxide as an accelerator for the reduction reaction. Here, the addition of sodium hydroxide as an additive having the function of generating hydroxide ions other than potassium hydroxide in the dispersion medium makes the reduction reaction at high temperature faster and makes the reaction mild even at room temperature. Will proceed. For this reason, although the shell of uniform thickness can be formed, it becomes possible to form a shell with higher quality by using sodium hydroxide especially.

  In addition, although amines are also considered as a compound which suppresses increase of hydrogen ion concentration, since amines tend to form a complex with a palladium raw material or a platinum raw material or to be adsorbed on the surface of the produced fine particles, the reaction of these raw materials The appearance of sex and particle growth changes in a complex way. Metal hydroxides are also considered as a source of hydroxide ions, but must be sufficiently soluble in ethylene glycol. As described in detail below, the inventors of the present invention have used sodium hydroxide as a hydroxide for synthesis of palladium core particles in core-shell type catalyst fine particles of carbon-supported palladium core platinum shell as a result of many experiments. Is particularly preferable, and the condition was found.

  In the embodiment of the present invention, the above reaction is carried out in the coexistence of a carbon support. In this case, palladium particles are formed in a state of being attached to carbon, a platinum shell also grows on the surface of palladium particles on carbon, and a core-shell structure is formed on the carbon support.

  In Patent Document 5, synthesis of palladium core particles and platinum shell particles is performed in an environment in which the carbon support does not coexist, but in the presence of the carbon support, carbon aggregation, clogging of the carbon reaction tube, support on the palladium core particles Unfavorable reaction pathways can result for catalysts such as uneven distribution, formation of platinum single particles on carbon. Therefore, the production method of the present invention is known which is capable of simultaneously performing synthesis of core particles and its loading on carbon in a continuous reaction system and then forming a uniform shell layer on the core particles loaded on carbon. It was not.

  The inventors of the present invention have found that the concentration of hydroxide ions in the reaction is very important in the formation of palladium core particles. And, as a result of extensive trial and error, carbon-supported palladium-cored platinum shell fine particles having high performance by using the continuous synthesis method in which the reaction solution is irradiated with microwaves while suppressing the above-mentioned undesirable reaction path The process of obtaining the catalyst could be completed.

  The embodiment of the present invention based on the above will be specifically described below.

  FIG. 1 is a view schematically showing the configuration of a carbon-supported palladium-cored platinum shell fine particle as an embodiment of the present invention. In FIG. 1, the code | symbol 1 has shown the pump which sends the reaction raw material liquid which melt | dissolved and disperse | distributed the raw material salt of palladium core particle, an ionomer, a carbon support, the sodium hydroxide raw material in the solvent, and the reaction raw material liquid. Specifically, the reaction raw material which mixed tetrachloro palladium (2) acid sodium (Na2PdCl4), Nafion (registered trademark), Vulcan (registered trademark) XC 72, sodium hydroxide aqueous solution, and EG (ethylene glycol) The feed pump which sends a liquid to the following process is shown.

  Reference numeral 2 is a cavity for confining the electric field of microwaves, irradiating the liquid in the reaction tube and heating it. Specifically, the reaction liquid produced and sent in the above-mentioned reaction raw material preparation process is made to flow through the reaction tube passing through the inside of the microwave cavity, and the reaction raw material liquid flowing inside the reaction pipe is irradiated with microwaves It is a cavity and constitutes a microwave irradiation system.

  Reference numeral 3 indicates a platinum shell layer forming solution and its feed pump system, which is composed of a sodium hydroxide aqueous solution and a pump for feeding the same, and symbol 5a is sent by the feed pump system 3 The process of mixing the sodium hydroxide aqueous solution and the carbon support palladium nanoparticle dispersion liquid produced | generated by the microwave cavity reaction system shown with code | symbol 2 with a mixer is shown.

  Reference numeral 4 is a solution in which a raw material salt for forming a platinum shell layer is dissolved and a pump for feeding the solution. Reference numeral 5b is mixed with the platinum source solution sent by the pump 4 according to the process shown by reference numeral 5a. The process of mixing with the dispersion liquid by a mixer is shown. The code | symbol 6 has shown the tank for collect | recovering the mixture of the raw material for carbon support palladium core particle dispersion liquid and platinum shell formation, and performing platinum shell formation reaction.

  In the configuration of FIG. 1, specifically, the reaction raw material liquid is raised to 100 ° C. by the microwave irradiation in the microwave irradiation step in the cavity 2. After cooling, it proceeds to the subsequent steps and is mixed with an aqueous solution of sodium hydroxide in step 5a and further with an ethylene glycol chloroplatinate solution in step 5b, and left at room temperature for about 72 hours. The reduction reaction is allowed to proceed to prepare a carbon-supported palladium-cored platinum shell microparticle colloid.

  Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not narrowly limited thereto.

<Example>
The mixture is mixed with ethylene glycol so that Vulcan (registered trademark) XC72 is 0.1% by weight and sodium tetrachloropalladium (2) is 2 mM, and sodium tetrachloropalladate (2) is completely dissolved. Also, ultrasonic waves are applied to make Vulcan® XC 72 a uniform dispersion. Furthermore, 5 M NaOH aqueous solution is added so that it may become 4 to 7 times the substance mass of sodium tetrachloro palladium (2) acid, it mixes well, and this is made into the reaction raw material liquid. The reaction raw material liquid is sent by a pump capable of handling a carbon dispersion liquid.

  As a result of the inventors of the present invention repeating detailed experiments repeatedly, it is desirable to add sodium hydroxide 4 to 7 times the substance mass of sodium tetrachloropalladium (2) to be added to the reaction raw material liquid I clarified that. When the hydroxide ion concentration is low, nucleation is delayed, the particle size is increased, and unreacted palladium ions may remain. On the other hand, when the hydroxide ion concentration is high, the reduction rate is too fast, and an unsupported particle or aggregate of palladium nanoparticles is formed.

The reaction raw material liquid was fed at a flow rate of 6 ml / min in a PFA (Perfluoroalkoxy) reaction tube with an inner diameter of 2 mm, and heated at 100 ° C. The reaction tube was placed along the central axis of the microwave cavity having a cylindrical space with an inner diameter of 90 mm and a height of 10 cm. Heating was performed by irradiating the cavity with microwaves of a frequency at which a standing wave of TM ₀₁₀ mode is formed, and the temperature of the reaction raw material liquid was measured at a central position of the reaction tube by a radiation thermometer. The frequency at which the TM ₀₁₀ mode standing wave is formed changes depending on the temperature of the reaction raw material liquid, but the frequency of the microwave to be irradiated is adjusted so as to always coincide with the frequency. The frequency range at this time was 2.45 GHz.

  An aqueous solution of sodium hydroxide necessary for the platinum shell formation reaction was finely adjusted and added to the carbon-supported palladium core particle dispersion synthesized by the above method, using a mixer (mixer in a piping joint flow path). In the present example, a 0.5 M aqueous solution of sodium hydroxide was added so that the amount of hydroxide ions involved in the shell formation reaction was about 2 to 6 times the mass of the hexachloroplatinum (4) acid ion.

  An aqueous solution of sodium hydroxide is added to the carbon-supported palladium core particle dispersion synthesized by the above method, and then the mixture is mixed with 100 mM chloride so that the molar ratio of palladium to platinum of the liquid after mixing is 1: 1. It was mixed with a platinum acid (4) ethylene glycol solution. The mixture was collected in a collection vessel and left at room temperature for 72 hours for complete reaction.

  The hydroxide ions added in the step (liquid feed pump system) indicated by symbol 3 in FIG. 1 are rapidly neutralized with the hydrogen ions generated from the platinum source added in the step (liquid feed pump system) indicated by symbol 4 As it reacts, not all amounts of added hydroxide ions participate in the shell formation reaction. However, it is believed that free hydroxide ion still remaining after neutralization reaction, hydroxide ion forming a complex with platinum ion, and hydroxide ion adsorbed on the surface of palladium particle participate in the shell forming reaction. Be The inventors repeated detailed experiments repeatedly, and as a result, these hydroxide ion concentrations are 2 to 6 times the substance mass of hexachloroplatinum (4) acid ion which is a precursor of platinum shell formation which is a raw material It became clear that it would be desirable to be a degree. If the hydroxide concentration in the shell formation reaction is low, the reaction rate will be slow and the platinum source will be non-reacted, and if the hydroxide concentration is too high, platinum will be formed on the carbon support or palladium core surface as particles instead of shells. In addition, free particles of platinum are likely to be by-produced. When the platinum raw material salt is a salt obtained by neutralizing chloroplatinic acid, or when the palladium core particles are formed by another method, when the palladium core particles are purified before the shell formation reaction, the hydroxide ion It is necessary to adjust the concentration of sodium hydroxide added so as to fall within the range of

  In addition, in the platinum shell formation reaction, carbon supported palladium core platinum is also a method of adding a platinum shell raw material liquid and a sodium hydroxide aqueous solution to the carbon supported palladium core particle dispersion synthesized and recovered by the above method. Shell particles can be synthesized.

  In the microwave continuous synthesis method of the carbon-supported palladium core particle dispersion liquid according to the above-mentioned method, an ionomer for a fuel cell, which is a kind of polymer electrolyte, can be coexisted at an appropriate concentration. If the concentration of the fuel cell ionomer is not excessive with respect to carbon, the carbon dispersibility is improved without adversely affecting the synthesis of palladium core particles and the subsequent formation of platinum shell, and risks such as clogging of reaction tubes in continuous reaction Can be reduced. As the ionomer, a copolymer of perfluorofluorinated sulfonyl vinyl ether and tetrafluoroethylene is widely used, and the dispersibility of carbon can be improved by adding an appropriate amount of ionomer also in the above method. In this embodiment, Nafion (registered trademark) (DE 520 CS type) is used as an example of the ionomer for a fuel cell, and the raw material liquid (symbol in FIG. 1) is adjusted so that the concentration of Nafion (registered trademark) becomes 0.03%. 1).

  It is easy to make a uniform dispersion of carbon in a small amount of experiment at the laboratory level, but on a scale of several tens of liters or more, the dispersion is due to the influence of aggregation, sedimentation, unevenness of sonication, etc. It becomes difficult to maintain the uniformity of the In addition, if the flow path is blocked in the continuous reaction system, there is a possibility that the reaction tube may be ruptured due to an increase in pressure, and frequent stop and recovery of the continuous reaction system also cause the cost increase of the process. Therefore, it is very important from the viewpoints of safety and economy in continuous reaction systems that the dispersibility of carbon and the blocking of flow paths do not occur in the production of products.

  When a fuel cell ionomer is used as a dispersant for carbon, it is also important that it does not need to be completely removed by purification, calcination or the like. Polymeric dispersants such as polyvinyl pyrrolidone are widely used in the synthesis of metal particles, but while these dispersants improve the dispersibility of metal particles and carbon, they are strongly adsorbed on the particle surface, so they are completely eliminated. It has been found difficult to remove, and it is also known that the polymer dispersant remaining on the catalyst surface significantly impairs the catalyst performance. Since a fuel cell ionomer is one of the components of a cell added in the cell preparation process for transfer of protons to the catalyst surface, even if a small amount remains, it has almost no effect on fuel cell performance.

  The formed core-shell particles were purified by centrifugation, and were observed by TEM (transmission electron microscopy) and analyzed by EDS (energy dispersive X-ray analysis) using an electron microscope (JEM-2200FS manufactured by JEOL Ltd.).

Comparative Example 1
As Comparative Example 1, a commercially available carbon-supported platinum catalyst was prepared, and the catalytic activities of the oxygen reduction reaction were compared.

Comparative Example 2
As Comparative Example 2, a carbon-supported platinum catalyst was synthesized by a microwave continuous method, and the catalytic activity of the oxygen reduction reaction was compared. The preparation method is described below. Vulcan (registered trademark) XC72 as a carbon carrier and Nafion (registered trademark) (DE 520 CS) as a dispersing agent were mixed with ethylene glycol, and sufficiently irradiated with ultrasonic waves to disperse carbon well. To the dispersion are added ethylene glycol solution of hexachloroplatinum (4) and potassium hydroxide ethylene glycol solution, and finally 0.1 g / L of carbon, 0.03 g / L of Nafion (registered trademark), hexachloroplatinum (2 The raw material solution was prepared such that the concentration of the acid was 2 mM and the concentration of potassium hydroxide was 20 mM. The raw material liquid was heated so that the temperature of the raw material liquid was 85 ° C., by flowing a PFA reaction tube with an inner diameter of 2 mm disposed on the cylindrical central axis of the microwave cavity at a flow rate of 2 ml / min.

  Measurement and load of oxygen reduction catalyst activity with reference to the standard method proposed by FCCJ (Fuel Cell Commercialization Promotion Council) (The method described in "Target of solid decentralized fuel cell, proposal of research and development issues and evaluation method") A response potential cycle endurance test was conducted. The detailed method is described below.

  The catalyst fine particles obtained in the above Examples and Comparative Examples are subjected to repeated purification by centrifugation to remove ethylene glycol and water-soluble salts and the like, and finally to a carbon concentration of 0.0125% by weight, Nafion (registered A catalyst ink having a concentration of 0.0125% by weight was produced. The solvent of the catalyst ink was a mixed solvent of water and IPA (isopropanol) (3: 1 by weight). 20 μL of this catalyst ink was applied to a polished glassy carbon rotating electrode with a diameter of 5 mm, dried, and used for electrochemical measurement. The electrolyte used was 0.1 M perchloric acid, and a reversible hydrogen electrode was used as a reference electrode. In the electrolytic cell which bubbled nitrogen and expelled oxygen, the catalyst surface was cleaned by a potential scan in the range of 0.05 to 1.2 V (hereinafter, the value of potential is expressed with reference to a reversible hydrogen electrode). The electrochemically active surface area was measured from the form of adsorption and desorption peaks. Subsequently, oxygen was dissolved in the electrolytic solution by bubbling to saturate, and the rotary electrode was rotated at 1600 rpm to perform convective voltammetry to measure the oxygen reduction activity. The scanning speed was 20 mV / sec from low potential to high potential, the value of oxygen reduction current at 0.9 V was recorded, and the oxygen reduction activity of the catalyst was calculated from the Koutechy-Levich equation. The temperature of the electrolyte at the time of activity measurement was 25.degree. The oxygen reduction activity was calculated in the form of an oxygen reduction current (A) (mass activity) per weight (g) of platinum used as a raw material. The unit of mass activity is ampere per gram [A / g].

  The potential cycle in the load response durability test is saturated by bubbling nitrogen into the electrolyte solution by using 0.66V for 3 seconds and 1.0V for 3 seconds square wave using the above electrolyte and rotating electrode. A potential of 10000 cycles was applied at 25 ° C. for 5000 cycles under the above conditions, and the surface area and the oxygen reduction activity were measured by the same method as described above before and after the potential cycle.

  FIG. 2 is an image of a carbon-supported palladium-cored platinum shell fine particle catalyst observed by a transmission electron microscope. The carbon support 7a and the palladium core platinum shell catalyst fine particle 7b supported thereon constitute the carbon-supported palladium core platinum shell fine particle catalyst synthesized in the example. As exemplified by reference numeral 7b, particles of 3 to 4 nm are substantially uniformly supported on the carbon support. In addition, according to the EDS results, the distribution of palladium and platinum was uniform and consistent over a wide range, and the ratio was almost the same as the ratio of the preparation amount at the time of synthesis. From this, the synthesis method proposed by the inventors of the present invention uses precious metals without waste, and can also achieve the high surface area required for the oxygen reduction catalyst.

  FIG. 3 is a graph comparing the mass activity of the oxygen reduction catalyst before and after the durability test of the above-mentioned example and the comparative example. The results shown in FIG. 3 are the initial mass activity prior to the durability test and the mass activity after the 5000 cycle load response durability test. In Examples, the mass activity before and after the durability test is 394 [A / g], 385 [A / g], in Comparative Example 1 74 [A / g], 33 [A / g], Comparative Example 2 241 It was [A / g] and 164 [A / g]. The examples have activity several times that of commercial platinum catalysts, and it can be seen that platinum which is more expensive and rare than platinum catalysts synthesized using microwaves can be used effectively as catalysts. In addition, as a result of the load response durability test, in the examples, the decrease in activity was slight, and both of the catalyst activity and the increase in durability could be achieved. On the other hand, in the comparative example, it is considered that the elution of platinum proceeds by the potential cycle, and the decrease in mass activity is remarkable.

  FIG. 4 shows the transition of the mass activity maintenance ratio with respect to the number of potential cycles in the durability test of the carbon-supported palladium core platinum shell fine particle catalyst of the example. Here, the maintenance rate is the activity after the durability test with respect to the initial activity expressed in percentage, and is an index showing the maintenance ratio of the activity due to the increase in the number of potential cycles, where the initial activity is 100%. Assuming that the initial activity (indicated by 8a) is 100%, the activity after 5000 cycles (indicated by 8b) is 98% and the activity after 10000 cycles (indicated by 8c) is 97%. From this, it can be understood that the carbon-supported palladium-cored platinum-shell particulate catalyst of the example maintains the activity almost close to the initial activity even after 10,000 cycles of potential cycle, which is an important characteristic in practical use of fuel cells. It became clear that it was very excellent in certain durability. In the case of Comparative Example 2 in FIG. 3, the activity after 5000 cycles was 68% of the initial value.

  For example, in the durability test of the carbon-supported palladium core platinum shell fine particle catalyst of the example, a glass for convective voltammetry measurement having a capacity of 14.5 cm, height 12.5 cm, 300 ml or more of 0.1 M perchloric acid aqueous solution In addition to the five-necked flask made by bubbling nitrogen for 30 minutes by bubbling 3 L / min for 30 minutes and using oxygen as electrolyte, the diameter of 5 mm of glassy carbon part coated with catalyst ink so that 0.96 μg of platinum is contained A durability test was carried out by applying a potential cycle to a glassy carbon rotary electrode at a temperature of 25 ° C., using a reversible hydrogen electrode as a reference electrode for 3 seconds at 0.6 V and a square wave at 1.0 V for 3 seconds. Add 0.1 M aqueous solution of perchloric acid to the flask and bubble 3 liters / minute of oxygen for 30 minutes to Used as the electrolyte, and the scanning speed to the high potential side of 20 [mV / s] at a rotational speed of 1600 [rotation / min], a temperature of 25 ° C., and a rotational speed of the above-mentioned glassy carbon rotary electrode Using a mass activity calculation method in which the oxygen reduction current value at an electric potential of 0.9 V with the reversible hydrogen electrode as the reference electrode is derived from the Koutecky-Levich equation, and after 10,000 cycles as an electric potential cycle The platinum mass activity as an oxygen reduction catalyst, that is, the value obtained by dividing the current value in the above mass activity calculation method by the coated platinum amount of 0.96 μg can maintain 95% or more of the mass activity before the durability test. Was confirmed.

  The sample prepared for the durability test in the embodiment of the present invention varies depending on the preparation conditions of the material, such as the environment to be prepared. For example, an example of the sample used for the 5000 cycle test has an initial value of 388 A sample of [A / g] was tested at 382 [A / g] after the test, and an example of the sample used for the test of 10000 cycles was a sample having an initial value of 314 [A / g] after the test of 306 [A / g]. It has fallen to]. This activity reduction amount is an amount sufficiently smaller than the conventional activity reduction amount. The reduction rate based on the initial value is 1.5% in the case of the test of 5000 cycles and 2.5% in the case of the tests of 10000 cycles. On the other hand, in Comparative Example 1 of FIG. 3, the initial value was 241 [A / g] and after the test was 164 [A / g] (reduction rate: 32%) in the case of the test of 5000 cycles.

  As described above, by using sodium hydroxide as a hydroxide in the synthesis of carbon-supported palladium core particles in the core-shell type catalyst fine particles of carbon-supported palladium core platinum shell of the present invention, the catalyst performance is high, and the durability test is performed. It is possible to obtain a core-shell type catalyst fine particle of a carbon-supported palladium core platinum shell with less performance deterioration.

  Although the present invention has been described above by adding examples and comparative examples with reference to the drawings, the present invention is not narrowly limited to this, and many variations are possible based on the technical concept of the present invention. It is obvious that

  In the synthesis of the palladium core of the core-shell type fine particles of the carbon-supported palladium core platinum shell of the present invention, sodium hydroxide is used under microwave irradiation, and further sodium hydroxide is added and left for a predetermined time including the platinum source solution. The palladium core platinum shell catalyst fine particles formed and manufactured have high catalytic efficiency and excellent durability, and can be used as a catalyst for a chemical reaction or a fuel cell.

Claims (14)

  An alcohol is used as a dispersion medium, and a palladium precursor (palladium raw material) is added to a dispersion in which a carrier is dispersed to form a reaction raw material solution, and the palladium raw material is reduced by microwave heating to synthesize carrier-supported palladium fine particles. Method of producing a carrier-supporting palladium fine particle colloid, wherein an additive having a function of generating hydroxide ions other than potassium hydroxide in a dispersion medium is added, .   The alcohol is ethylene glycol, the carrier is carbon fine particles, the palladium precursor is sodium tetrachloropalladium (2), and the additive is 4 to 7 times the mass of the palladium raw material as the additive. The method for producing a carrier-supporting palladium fine particle colloid according to claim 1, comprising the steps of adding sodium hydroxide of substance amount and producing a carbon-supported palladium fine particle catalyst by a microwave continuous heating method.   The method for producing a carrier-supported palladium fine particle colloid according to claim 1 or 2, wherein an ionomer for a fuel cell is added to a carrier dispersion of a raw material.   The method for producing a carrier-supported palladium fine particle colloid according to claim 3, wherein the ionomer to be added is a copolymer of perfluorofluorinated sulfonyl vinyl ether and tetrafluoroethylene.   The addition which has a function which uses the colloid manufactured by the method of any one of Claims 1-4 as a raw material, and produces | generates the solution containing a platinum precursor, and the hydroxide ion except potassium hydroxide in a dispersion medium. Agent is added to form a platinum shell on a carrier-supporting palladium core particle by reacting as a reaction raw material solution at room temperature to form a support-supporting palladium core platinum shell fine particle catalyst, which is a platinum precursor solution (platinum raw material) Carrier-supported palladium characterized in that the concentration of hydroxide ions excluding potassium hydroxide which is free, coordinated, and adsorbed after addition of the additive is 2 to 6 times the substance mass of the platinum raw material Method of producing core platinum shell particulate catalyst.   The platinum source is a solution containing hexachloroplatinate (4) acid ion, and the additive is sodium hydroxide, and potassium hydroxide released, coordinated, and adsorbed after addition of the sodium hydroxide solution The method for producing a carrier-supported palladium core platinum shell fine particle catalyst according to claim 5, wherein the hydroxide ion concentration to be removed is 2 to 6 times the substance mass of the platinum raw material.   A continuous flow in which the carrier is carbon fine particles, a carbon-supported palladium fine particle catalyst is produced by a microwave continuous heating method, and the step of forming the carbon-supported palladium fine particle colloid and the step of platinum shell formation at normal temperature are connected by a continuous flow path The method for producing a carrier-supported palladium core platinum shell microparticle catalyst according to claim 5, comprising the step of producing a carbon-supported palladium core platinum shell microparticle catalyst by carrying out by the method.   8. The method for producing a carrier-supported palladium core platinum shell microparticle catalyst according to claim 7, wherein when the palladium core platinum shell microparticle catalyst is made into a dry powder, a sodium component remains in the dry powder.   The method for producing a carrier-supported palladium core platinum shell microparticle catalyst according to any one of claims 5 to 8, wherein an ionomer for a fuel cell is added to a carrier dispersion liquid of a raw material.   10. The method according to claim 9, wherein the ionomer added is a copolymer of perfluorofluorinated sulfonyl vinyl ether and tetrafluoroethylene.   A carbon-supported palladium-cored platinum shell fine particle produced by the method according to any one of claims 5 to 10.   A polymer electrolyte fuel cell characterized in that a carbon-supported palladium core platinum shell fine particle produced by the production method according to any one of claims 5 to 10 is used as a catalyst. Add an aqueous solution of 0.1 M perchloric acid to a glass 5-neck flask for convective voltammetric measurement with a width of 14.5 cm, a height of 12.5 cm, and a volume of 300 ml or more, and boil 3 L / min of nitrogen for 30 minutes. A glassy carbon rotary electrode of 5 mm in diameter having a glassy carbon portion coated with a catalyst ink so that 0.96 μg of platinum is contained as an electrolyte by using oxygen expelled as an electrolytic solution,
When a durability test is performed at a temperature of 25 ° C., using a reversible hydrogen electrode as a reference electrode and applying a potential cycle of 0.6 V for 3 seconds and 1.0 V for 3 seconds with a square wave as one cycle,
An aqueous solution of 0.1 M perchloric acid is added to the flask, and 3 L / min of oxygen is bubbled for 30 minutes to use nitrogen as an electrolyte.
Under the conditions of a rotational speed of 1600 [rotation / min] of the electrode, a temperature of 25 ° C., and a scanning speed to the high potential side of 20 [mV / sec],
Using a mass activity calculation method to calculate the oxygen reduction current value at a potential of 0.9 V with the reversible hydrogen electrode as the reference electrode by using the Koutecky-Levich equation and compensating for the solution resistance,
The platinum mass activity as an oxygen reduction catalyst after 10000 potential cycles, that is, the value obtained by dividing the current value in the mass activity calculation method by the coated platinum amount of 0.96 μg can maintain 95% or more of the mass activity before the durability test A palladium core platinum shell particulate catalyst characterized by having.   A carrier-supported palladium core platinum shell microparticle catalyst manufactured using the method according to any one of claims 5 to 10, wherein the mass activity value of the palladium core platinum shell microparticle catalyst calculated by the mass activity calculation method is The palladium core platinum shell particulate catalyst according to claim 13, characterized in that it has an initial activity of 300 to 400 [A / g].