WO2023276457A1 - Method for manufacturing electrode catalyst for fuel cell - Google Patents

Method for manufacturing electrode catalyst for fuel cell Download PDF

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WO2023276457A1
WO2023276457A1 PCT/JP2022/020068 JP2022020068W WO2023276457A1 WO 2023276457 A1 WO2023276457 A1 WO 2023276457A1 JP 2022020068 W JP2022020068 W JP 2022020068W WO 2023276457 A1 WO2023276457 A1 WO 2023276457A1
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platinum
platinum complex
carbon black
nitric acid
catalyst
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PCT/JP2022/020068
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French (fr)
Japanese (ja)
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克彦 山下
一則 古閑
直也 青木
愛美 岡部
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石福金属興業株式会社
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Priority to CN202280002917.8A priority Critical patent/CN115867380A/en
Priority to KR1020227035903A priority patent/KR20230006469A/en
Publication of WO2023276457A1 publication Critical patent/WO2023276457A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
    • H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
    • 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
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/18—Carbon
    • 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
    • B01J23/42—Platinum
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • 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
    • B01J37/04—Mixing
    • 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
    • B01J37/08—Heat treatment
    • 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
    • B01J37/08—Heat treatment
    • B01J37/082—Decomposition and pyrolysis
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • 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 fuel cell electrode catalyst.
  • Platinum catalysts are used in applications such as catalysts for purifying exhaust gas from internal combustion engines and electrode catalysts for fuel cells.
  • a platinum catalyst is generally dispersed and supported on a carrier such as carbon, alumina or silica-alumina.
  • a platinum catalyst is produced by immersing a catalyst carrier in a solution of a platinum compound to reduce and support the catalyst.
  • a dinitrodiammine platinum complex or compound Pt(NO 2 ) 2 (NH 3 ) 2 ) is generally used because it does not contain chlorine and increases the activity of a platinum catalyst supported on a carrier.
  • Patent Document 1 an aqueous solution of dinitrodiammineplatinum nitrate is added to a carbon carrier, stirred, heated and dried to obtain a carbon carrier on which a platinum compound is supported. a heat treatment below the self-decomposition temperature of the catalyst, and contacting the carbon support with a reducing gas to reduce the platinum compound.
  • Patent Document 2 describes a dinitrodiammineplatinum nitrate solution characterized by a platinum concentration of 1 g/L and an absorbance at 420 nm of 1.5 to 3, and a carrier immersed in the dinitrodiammineplatinum nitrate solution.
  • a method for producing a platinum catalyst for an exhaust gas catalyst is described in which the platinum component is adsorbed on the carrier, the platinum component is adsorbed on the carrier surface, dried, calcined and reduced.
  • platinum is supported by conventional methods such as permeation of a nitric acid aqueous solution of dinitrodiammineplatinum into a porous substrate, drying by evaporation of the solvent, thermal decomposition or reduction.
  • the platinum derived from the platinum complex that is not adsorbed is also supported, which may result in coarsening and uneven distribution of the platinum particles.
  • a lower temperature is also preferable for the thermal decomposition temperature of the platinum complex.
  • the adsorption rate of the platinum complex to the carbon support is high, and the platinum complex adsorbed on the carbon support is thermally decomposed at a lower thermal decomposition temperature, and the fine platinum particles are supported on the carbon powder in a highly dispersed manner. ing.
  • Aspect 1 Dinitrodiammineplatinum complex or compound is dissolved in an aqueous nitric acid solution to a concentration of 100 ⁇ 20 g/L in terms of platinum and 220 ⁇ 40 g/L in nitric acid concentration, and heated at 100 to 110° C. for 18 to 24 hours.
  • an aqueous nitric acid solution containing a platinum complex in which the dinitrodiammine platinum is modified or denatured A step of mixing an aqueous dispersion of carrier carbon black and the platinum complex-containing nitric acid aqueous solution to adsorb the platinum complex on the surface of the carbon black to obtain a carbon black-containing liquid in which the platinum complex is adsorbed; A step of filtering the carbon black-containing liquid, washing and drying the filtered carbon black having the platinum complex adsorbed thereon, and obtaining a powder having the platinum complex adsorbed on the surface of the carbon black; A thermal decomposition step of the platinum complex by thermally decomposing the carbon black powder to which the platinum complex is adsorbed at 280 ° C.
  • a method for producing a platinum-supported carbon catalyst comprising: Aspect 2: The modified or denatured platinum complex-containing nitric acid aqueous solution is L * a * b * of the aqueous solution when the aqueous solution is diluted with pure water so that the platinum concentration becomes 1 wt% *chroma a * in the color system A method for producing a platinum-supported carbon catalyst according to aspect 1, wherein is 28 to 35. Aspect 3: The method for producing a platinum-supported carbon catalyst according to aspect 1 or 2, wherein the drying is performed at a temperature of 180°C to 230°C.
  • Aspect 4 In the thermal decomposition step, the powder having the platinum complex adsorbed on the surface of the carbon black is deposited in an appropriate container to a layer thickness (deposition thickness) in the range of 0.1 mm to 30 mm, and an inert gas or The method for producing a platinum-supported carbon catalyst according to any one of aspects 1 to 3, wherein the platinum complex is thermally decomposed at 280°C to 400°C in a nitrogen gas atmosphere.
  • Aspect 5 The method for producing a platinum-supported carbon catalyst according to any one of aspects 1 to 4, wherein the amount of platinum supported in the platinum-supported carbon catalyst is adjusted to 5 wt% to 20 wt% relative to the total weight of the catalyst. .
  • the adsorption rate of the platinum complex to carbon black is high, and the platinum complex adsorbed to carbon black can be thermally decomposed at a relatively low temperature, so even if the production amount is increased, uniform and fine platinum particles are highly dispersed. It is possible to produce a platinum-supported carbon catalyst supported on.
  • Example 1 is a graphical representation of the results of differential scanning calorimetry-mass spectrometry (DSC-Mass) performed on a dried sample of carbon black with adsorbed platinum complexes according to the present invention. Graphic representation of the results of similar measurements on dried samples under different conditions than in FIG. TEM image of catalyst particles of Example 3
  • the dinitrodiammine platinum complex or compound is added to the nitric acid aqueous solution so that the concentration is 100 ⁇ 20 g / L in terms of platinum and the nitric acid concentration is 220 ⁇ 40 g / L.
  • the ratio of platinum to nitric acid in the aqueous nitric acid solution is adjusted to approximately 1:2.2 on a weight basis.
  • the nitric acid aqueous solution thus prepared is heated at 100 to 110° C., preferably 101 to 107° C., more preferably 103 to 105° C., for 18 to 24 hours, preferably 19 to 22 hours, more preferably 20 to 21 hours. Heating causes a change in the color saturation of the solution prior to heat treatment.
  • the terms "platinum complex or compound” and “complex” are used interchangeably.
  • the change in chroma is L * a * b * in the aqueous solution when the nitric acid aqueous solution containing the platinum complex after the heating step is diluted with pure water so that the platinum concentration becomes 1 wt%. may be 28-35 , preferably 29-34, more preferably 30-33.
  • the chroma a * of the corresponding aqueous solution before said heat treatment is not limited, but can generally be between -3 and -1.
  • the temperature for drying the carbon black to which the platinum complex is adsorbed is not limited, but is generally 50 ° C. to 250 ° C., preferably 80 ° C. to 250 ° C., more preferably 180 °C to 230 °C.
  • the drying time can be determined as appropriate by referring to, for example, the results of DSC - Mass shown in FIG. 1 or FIG. , under the above temperature, 10 hours to 72 hours, preferably 12 hours to 60 hours, more preferably 14 hours to 48 hours.
  • the thermal decomposition step of the platinum complex can be generally carried out at 280 to 400°C, preferably 290 to 350°C, more preferably 300 to 320°C.
  • the thermal decomposition time is generally 0.25 hours to 3 hours, preferably 0.5 hours to 2 hours, more preferably 0.75 hours to 1.5 hours at the above heating temperature.
  • the pyrolysis process uses, but is not limited to, a vat with a flat bottom and a depth exceeding 30 mm, which is the normally assumed layer thickness (deposition thickness). You may Such a bat can be, for example, but not limited to, a carbon or titanium container measuring 250 mm x 250 mm x 50 mm deep or 325 mm x 530 mm x 60 mm deep.
  • the amount of platinum supported in the platinum-supported carbon catalyst is adjusted to 5 wt% to 20 wt%, 7.5 to 15 wt%, more preferably 8 to 13 wt%, based on the total weight of the catalyst. good too.
  • a dinitrodiammineplatinum complex or compound is dissolved in an aqueous nitric acid solution, and the solution is heated at a predetermined temperature for a predetermined time to obtain a modified or denatured nitric acid aqueous solution containing a dinitrodiammineplatinum complex. be done. This will cause the solution to ripen.
  • the platinum complex or compound is easily adsorbed to carbon black in an aqueous solution, and even if it is highly efficient and the production amount is increased, or the production scale is expanded, uniform and fine platinum particles are highly dispersed. It is understood that supported platinum on carbon catalysts can be produced.
  • the process or treatment of dissolving dinitrodiammineplatinum in an aqueous nitric acid solution to a platinum equivalent of 100 ⁇ 20 g/L and a nitric acid concentration of 220 ⁇ 40g/L is the same as the dinitrodiammineplatinum nitric acid in Patent Documents 1 and 2 above.
  • the ratio of platinum to nitric acid in the aqueous solution is 1:0.7 to 1 on a weight basis.
  • the heat treatment of the nitric acid aqueous solution is performed at 100 to 110.degree.
  • the reaction in which the valence of platinum in the solution increases from divalent to tetravalent progresses, and at the same time the ligand coordinated to the platinum complex changes, and the adsorption of the platinum complex to carbon black increases.
  • the reaction proceeds with the heating time, if the heating time is shorter than 18 hours, the adsorption rate of the platinum complex decreases. On the other hand, if the heating time is longer than 24 hours, platinum precipitates are likely to be generated, which is not preferable. Therefore, generally, heating for 18-24 hours can adsorb 90% or more of the platinum complex and does not produce a precipitate of platinum.
  • the chroma is measured with a transmissive color measuring instrument (TZ6000) manufactured by Nippon Denshoku Industries Co., Ltd.
  • absorbance at 420 nm may be measured.
  • Absorbance at 420 nm can be measured using V-750 manufactured by JASCO Corporation by placing a sample adjusted with pure water to a concentration of 1 g/L in a quartz cell.
  • the absorbance at 420 nm of the sample with a chroma a * value of 30 was 1.06, and that of the sample with a chroma a * value of 35 was 1.07.
  • the alkali consumption of these samples was determined by the known method described in Patent Document 1, the alkali consumption was 1.2 g for each 1 g of platinum.
  • the platinum complex in order to prevent excessive deterioration of the platinum complex, as a result of aging at a relatively high nitric acid concentration (high alkali consumption) with respect to 1 g of platinum, the platinum complex has a small absorbance at 420 nm. ing.
  • the present invention includes a step of mixing a dispersion of carbon black in water with an aqueous nitric acid solution containing a platinum complex after the heating step to adsorb the platinum complex to the carbon powder.
  • the carbon black used in the present invention is not particularly limited as long as it has a functional group on its surface and is used for supporting platinum in the production of an electrode catalyst. Specific examples include carbon black such as furnace black, channel black, and acetylene black.
  • the water used here can be ion-exchanged pure water.
  • Adsorption of the platinum complex in the aqueous solution is carried out by dispersing carbon black in pure water, adding an aqueous nitric acid solution containing the platinum complex after the heating step to the dispersion, and stirring for several hours to mix.
  • An acidic solution may be added to the carbon black dispersion to make it acidic, and then the aqueous solution of the platinum complex after the heating step may be mixed.
  • the acid nitric acid which leaves little residue on the catalyst is preferable.
  • the adsorption of the platinum complex to carbon black reaches equilibrium in about one hour, it is desirable to set the adsorption time to about several hours.
  • the platinum complex By adsorbing the platinum complex in an aqueous solution after the heating step having the characteristics described above, the platinum complex is highly dispersed and easily supported on the carbon black, and the desired catalyst particle size is uniform even if the production amount is increased.
  • a carbon catalyst supporting platinum can be produced.
  • another supporting method after mixing carbon powder with a solution containing a platinum complex, there is also a method of supporting the platinum complex on the carbon support by evaporating the solvent by evaporation to dryness. Since it is necessary to evaporate a large amount of solvent due to the fact that it tends to aggregate and become large, and that it tends to be unevenly distributed, it is necessary to evaporate a large amount of solvent, which incurs energy costs. is not preferred.
  • the platinum complex is adsorbed to the functional group on the surface of the carbon black, and the platinum complex that is not adsorbed is removed by filtration and washing, so that the coarsening and uneven distribution of the platinum particles can be suppressed. You can easily increase the amount.
  • the amount of platinum supported in the platinum-supported carbon catalyst can generally be from 5 wt% to 20 wt% based on the total weight of the catalyst. Specifically, the amount of carbon powder is adjusted with respect to the amount of dinitrodiammineplatinum nitric acid solution.
  • the present invention includes a step of obtaining a powder in which a platinum complex is adsorbed on carbon black by filtering, washing, and drying.
  • the filtration method used in the present invention is not particularly limited, and various means can be used. Specifically, it can be carried out using a belt filter, a drum filter, a centrifuge, a vacuum filter, a pressure filter, a filter press, or the like.
  • the dryer used in the present invention is not particularly limited, and various dryers can be used for drying. Specific examples include hot air dryers, vacuum dryers, inert ovens, and the like.
  • Drying can generally be carried out at 50°C to 250°C. Moisture is removed by the treatment, and some NOx components are also removed. For example, sample 1 after vacuum-drying the powder in which the platinum complex was adsorbed on the surface of carbon black at 100 ° C. for 19 hours, sample 2 after vacuum-drying at 100 ° C. for 19 hours and further vacuum-drying at 190 ° C. for 14 hours. Scanning calorimetry-mass spectrometry (DSC-Mass) was performed. STA 440F3 (manufactured by Netch Japan Co., Ltd.) was used as the DSC analyzer.
  • the drying temperature it is preferable to set the drying temperature to 180° C. to 230° C. to reduce the amount of heat generated during thermal decomposition.
  • the present invention includes a thermal decomposition step of thermally decomposing the powder having the platinum complex adsorbed on the carbon support generally at 280° C. to 400° C. in an inert gas or nitrogen gas atmosphere.
  • a powder having a platinum-containing complex supported on the surface of carbon black is generally heated to a relatively low temperature of 280° C. to 400° C. in an inert gas or nitrogen gas atmosphere. It is characterized by adopting a process of thermally decomposing at Moreover, by this process, a platinum-supported electrode catalyst with a small catalyst particle size of about 2 to 5 nm can be produced without using a reducing agent. A temperature of 280° C. or less is not preferable because thermal decomposition is insufficient. On the other hand, if the temperature is 400° C. or higher, the catalyst particles aggregate and become coarse, which is not preferable. In addition, from the fact that the decomposition peak of the platinum complex and the detection peak of CO 2 are almost the same from FIG. It is assumed that the platinum complex can be thermally decomposed at the temperature.
  • the thermal decomposition reaction of the platinum complex becomes significant from around 280.degree. Therefore, thermal decomposition can be accelerated by thermally decomposing at 280° C. or higher. On the other hand, if the thermal decomposition proceeds too rapidly, heat generation may cause problems such as agglomeration of the catalyst particles, which is not preferable.
  • the thermal decomposition temperature is generally 280°C to 400°C, preferably 290°C to 350°C. More preferably, it is 300°C to 320°C.
  • a container suitable for the pyrolysis step is a rectangular flat container (bat) made of carbon, and a layer thickness (deposition thickness) of 0.1 mm to 0.1 mm of powder in which a platinum complex is adsorbed on the surface of carbon black. It is deposited in a range of 30 mm and thermally decomposed at the above heating temperature in an inert gas or nitrogen gas atmosphere.
  • the catalyst particle size can be adjusted to a target size within 2 nm to 5 nm. If the layer thickness is higher than 30 mm, the catalyst particle size will be larger than 5 nm.
  • Dinitrodiammineplatinum was dissolved in an aqueous nitric acid solution to a concentration of 100 g/L in terms of platinum and a nitric acid concentration of 180 g/L.
  • the solution was heated with stirring at about 104° C. for 20 hours.
  • solution S1 was obtained.
  • this solution S1 was adjusted for each example.
  • Example 1 ⁇ Preparation of supported catalyst> (Example 1) 9.0 g of Vulcan XC-72R (manufactured by CABOT) was dispersed in 700 mL of pure water. Next, 4.9 g of nitric acid was added to this dispersion to acidify it. An amount of solution S1 corresponding to 1.0 g of platinum was added to the resulting acidic dispersion and then stirred for 4 hours. The dispersion was filtered to obtain a filter cake. After washing it with pure water, it was dried at 60° C. for 19 hours. Thus, a powder in which the platinum complex was adsorbed on the carbon support was obtained. This powder is hereinafter referred to as "powder P1".
  • the powder P1 was pulverized into powder, placed in a container so that the thickness (deposition thickness) of the powder P1 was 0.1 mm, and subjected to heat treatment at 310° C. for 1 hour under nitrogen gas flow. .
  • Example 1 A supported catalyst was produced as described above. Hereinafter, this will be referred to as "Example 1".
  • Example 2 1800 g of Vulcan XC-72R (manufactured by CABOT) was dispersed in 140 L of pure water. Next, 975 g of nitric acid was added to this dispersion to acidify it. A quantity of solution S1 corresponding to 208 g of platinum was added to the resulting acidic dispersion and then stirred for 4 hours. The dispersion was filtered to obtain a filter cake. After washing this with pure water, it was subjected to vacuum drying at 100° C. for 19 hours. Thus, a powder in which the platinum complex was adsorbed on the carbon support was obtained. This powder is hereinafter referred to as "powder P2".
  • Example 2 A supported catalyst was produced as described above. Hereinafter, this will be referred to as "Example 2".
  • Example 3 A supported catalyst was prepared in the same manner as in Example 2, except that the thickness of the powder during the pyrolysis process was 4 mm. Hereinafter, this will be referred to as "Example 3".
  • Example 4 A supported catalyst was prepared in the same manner as in Example 2, except that the thickness of the powder during the pyrolysis process was 6 mm. Hereinafter, this will be referred to as "Example 4".
  • Example 5 A supported catalyst was produced in the same manner as in Example 2, except that the vacuum drying was carried out at 200° C. for 46 hours and the powder thickness (deposition thickness) during the pyrolysis step was 7 mm. Hereinafter, this will be referred to as "Example 5".
  • Example 6 A supported catalyst was produced in the same manner as in Example 2, except that the vacuum drying was carried out at 200° C. for 46 hours and the powder thickness (deposition thickness) during the pyrolysis step was 10 mm. Hereinafter, this will be referred to as "Example 6".
  • Example 7 A supported catalyst was produced in the same manner as in Example 2, except that the thickness of the powder during the pyrolysis step was 4 mm and the temperature was 330°C. Hereinafter, this will be referred to as "Example 7".
  • Comparative example 1 A powder having a platinum complex adsorbed on a carbon support was produced in the same manner as in Example 1, except that the solution S1 was changed to the solution S2. Hereinafter, this is called “comparative example 1".
  • Table 1 below shows the average particle size and standard deviation of platinum in the platinum-supported carbon catalysts of Examples 1 to 7 and Comparative Examples 1 and 2.
  • chroma a* of dinitrodiammineplatinum nitric acid solution The chroma a * in the L * a * b * color system was measured for the platinum complex contained in each of the solutions S1 to S2. This measurement was performed as follows using a transmission color measuring instrument (TZ6000) manufactured by Nippon Denshoku Industries Co., Ltd.
  • the solution S1 was diluted with pure water so that the platinum concentration was 1 wt %, and used as a sample for measurement.
  • the light source was D65
  • the field of view was 2 degrees
  • the sample was placed in a quartz cell with a physical length of 10 mm
  • the L * a * b * values of transmitted light were measured.
  • the chroma a * of the platinum solution S1 used in Examples 1 to 7 was 30.
  • the platinum solution S2 used in Comparative Examples 1 and 2 had a saturation a * of 7.
  • the platinum particle size is larger than the desired particle size, which is not preferable.
  • the catalysts according to Examples 1 to 7 have high platinum adsorption rates. Further, by changing the layer thickness, the catalyst particle diameter can be adjusted to a specific size within 2 to 5 nm. In other words, these results suggest that a highly dispersed platinum catalyst can be efficiently produced by producing a catalyst by this production method.
  • the metal surface area (metal dispersity) of the catalyst particles of Example 3 was measured by the CO adsorption method. Specifically, using a metal dispersion measuring device (BEL-METAL-3 manufactured by Bell Japan), 25 mg of catalyst particles were pretreated at 130 ° C. with helium, hydrogen, and helium in this order, and then heated to 50 ° C. The amount of adsorbed CO was calculated from the number of pulses until the amount of CO in the exhaust gas became constant, and the metal surface area of the catalyst particles was obtained.
  • the metal surface area of Example 3 was 118 m 2 /g, which is higher than the level generally required.
  • Example 3 A TEM image of Example 3 is shown in FIG. From the TEM image, it can be seen that catalyst particles of about 3 nm are supported in a highly dispersed manner.
  • Example 3 In order to evaluate the performance as a fuel cell electrode catalyst, the oxygen reduction reaction (ORR) activity of Example 3 was evaluated by the rotating electrode method using a BAS potentiogalvanostat.
  • a catalyst ink was prepared by dispersing Example 3 and the perfluorosulfonic acid dispersion in a mixed solvent of 2-propanol and water. The prepared catalyst ink was applied to glassy carbon (diameter 6 mm) so that the amount of platinum was 18 ⁇ g/cm 2 to prepare an electrode for measurement.
  • the prepared measurement electrode is immersed in nitrogen gas-saturated 25 ° C., 0.1 mol / L perchloric acid, a reversible hydrogen electrode (RHE) is used as the reference electrode, a platinum wire is used as the counter electrode, and the potential range is 0.05 V ⁇
  • RHE reversible hydrogen electrode
  • a platinum wire is used as the counter electrode
  • the potential range is 0.05 V ⁇
  • a cyclic voltammogram was measured at 1.2 V (vs. RHE) and a potential sweep rate of 50 mV/sec.
  • ECSA electrochemically active surface area
  • the potential is 0.05 V to 1.2 V (vs.RHE) and the potential sweep rate is 10 mV/sec.
  • Polarization curves were measured. From the obtained polarization curve, the oxygen reduction current value (I) of 0.9 V and the oxygen reduction current value (Id) of 0.4 V as the diffusion limit current value are calculated by the following formula, the activation excluding the diffusion effect of oxygen
  • the specific activity was calculated by dividing this activation current value (Ik) by ECSA, and the mass activity was calculated by dividing the platinum weight on the glassy carbon electrode.
  • the ECSA of Catalyst C3 was 67.8 m 2 /g, and the specific activity and mass activity were 173 ⁇ A/cm 2 and 118 A/g, respectively, indicating catalytic performance above the generally required level. Therefore, the catalyst produced by this production method can be used as an electrode catalyst for fuel cells.
  • the catalyst produced by the production method of the present invention exhibits catalytic performance at or above the generally required level, it can be used, for example, in the production and use of fuel cell electrodes.

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Abstract

[Problem] To provide a method for manufacturing a highly active platinum-carrying carbon catalyst, which is an electrode catalyst for a fuel cell. [Solution] A method for manufacturing a platinum-carrying carbon catalyst, comprising: a step for dissolving a dinitrodiammine platinum complex or compound in a nitric acid aqueous solution so as to achieve a concentration of 100±20 g/L in terms of platinum and a nitric acid concentration of 220±40 g/L, and heating the solution for 18-24 hours at 100-110ºC, thereby obtaining a platinum complex-containing nitric acid aqueous solution in which dinitrodiammine platinum has been changed or modified; and a step for, by using the aqueous solution, causing the platinum complex to be adsorbed to the surface of carbon black, then cleaning the carbon black which is selectively separated and to which the platinum complex has been adsorbed, drying the carbon black, and thermally decomposing the carbon black.

Description

燃料電池用電極触媒の製造方法METHOD FOR MANUFACTURING FUEL CELL ELECTROCATALYST
本発明は、燃料電池用電極触媒の製造方法に関する。 The present invention relates to a method for producing a fuel cell electrode catalyst.
内燃機関からの排気ガスを浄化する触媒や燃料電池用電極触媒等の用途で、白金触媒が使用されている。白金触媒は、白金をカーボン、アルミナ、シリカ－アルミナ等の担体に分散担持させるのが一般的である。例えば、白金触媒は、白金属化合物溶液中に触媒用担体を浸漬して還元担持することによって製造される。中でもジニトロジアンミン白金錯体又は化合物（Ｐｔ（ＮＯ２）２（ＮＨ３）２）は、塩素を含まず、担体に担持した白金触媒の活性が高くなることより一般的に利用されている。 Platinum catalysts are used in applications such as catalysts for purifying exhaust gas from internal combustion engines and electrode catalysts for fuel cells. A platinum catalyst is generally dispersed and supported on a carrier such as carbon, alumina or silica-alumina. For example, a platinum catalyst is produced by immersing a catalyst carrier in a solution of a platinum compound to reduce and support the catalyst. Among them, a dinitrodiammine platinum complex or compound (Pt(NO 2 ) 2 (NH 3 ) 2 ) is generally used because it does not contain chlorine and increases the activity of a platinum catalyst supported on a carrier.
特許文献１には、炭素担体に、ジニトロジアンミン白金硝酸水溶液を加え、撹拌、加熱、乾燥させて、白金化合物を担持させた炭素担体を得た後、不活性ガス中、１００℃以上、白金化合物の自己分解温度未満で加熱処理し、その炭素担体を還元ガスと接触させて、白金化合物を還元する還元工程と、を含む燃料電池用電極触媒の製造方法が記載されている。 In Patent Document 1, an aqueous solution of dinitrodiammineplatinum nitrate is added to a carbon carrier, stirred, heated and dried to obtain a carbon carrier on which a platinum compound is supported. a heat treatment below the self-decomposition temperature of the catalyst, and contacting the carbon support with a reducing gas to reduce the platinum compound.
特許文献２には、１ｇ／Ｌの白金濃度で、４２０ｎｍにおける吸光度が１．５～３であることを特徴とするジニトロジアンミン白金硝酸溶液、および、そのジニトロジアンミン白金硝酸溶液中に、担体を浸漬して白金成分を担体上に吸着させ、白金成分を担体表面に吸着させ、乾燥、焼成、還元することによって排気ガス触媒用白金触媒を製造する方法が記載されている。 Patent Document 2 describes a dinitrodiammineplatinum nitrate solution characterized by a platinum concentration of 1 g/L and an absorbance at 420 nm of 1.5 to 3, and a carrier immersed in the dinitrodiammineplatinum nitrate solution. A method for producing a platinum catalyst for an exhaust gas catalyst is described in which the platinum component is adsorbed on the carrier, the platinum component is adsorbed on the carrier surface, dried, calcined and reduced.
特開２０１０－１６７３５３JP 2010-167353 特開２００５－３０６７００JP 2005-306700
燃料電池触媒においては、２～５ｎｍの微細白金粒子を高分散に担持した白金担持カーボン粉末が要望されている。 In fuel cell catalysts, carbon powder supporting platinum on which fine platinum particles of 2 to 5 nm are supported in a highly dispersed manner is desired.
上記２～５ｎｍの微細白金粒子を高分散に担持するためには、従来手法の、ジニトロジアンミン白金の硝酸水溶液の多孔質基体への浸透、溶媒の蒸発乾燥、熱分解または還元により白金の担持を行うと、吸着していない白金錯体由来の白金をも担持するため、白金粒子の粗大化や偏在化が生じてしまうことがある。また、水溶液中でのカーボン担体への白金錯体の吸着反応のみを利用する場合、白金錯体のカーボン担体への吸着性を向上させる必要がある。白金錯体の熱分解温度についてもより低温が好ましい。
すなわち、白金錯体のカーボン担体への吸着率が高く、より低い熱分解温度でカーボン担体に吸着した白金錯体が熱分解し、微細な白金粒子をカーボン粉末に高分散に担持させることが課題となっている。 In order to support the above fine platinum particles of 2 to 5 nm in a highly dispersed manner, platinum is supported by conventional methods such as permeation of a nitric acid aqueous solution of dinitrodiammineplatinum into a porous substrate, drying by evaporation of the solvent, thermal decomposition or reduction. When this is done, the platinum derived from the platinum complex that is not adsorbed is also supported, which may result in coarsening and uneven distribution of the platinum particles. Moreover, when only the adsorption reaction of the platinum complex to the carbon support in the aqueous solution is used, it is necessary to improve the adsorption of the platinum complex to the carbon support. A lower temperature is also preferable for the thermal decomposition temperature of the platinum complex.
That is, the adsorption rate of the platinum complex to the carbon support is high, and the platinum complex adsorbed on the carbon support is thermally decomposed at a lower thermal decomposition temperature, and the fine platinum particles are supported on the carbon powder in a highly dispersed manner. ing.
ジニトロジアンミン白金錯体又は化合物含有硝酸水溶液における白金と硝酸の比率を、重量基準で、例えば１：２．２とし、そのジニトロジアンミン白金錯体又は化合物含有硝酸水溶液を一定の条件下で加熱すると従来技術文献に開示されたものとは異なる特性を有する又は状態のジニトロジアンミン白金錯体又は化合物含有硝酸水溶液が得られ、このような状態の前記水溶液を用いて白金錯体をカーボンブラックへ吸着させ、濾過、洗浄、乾燥させた後、熱分解することにより、白金錯体のカーボンブラックへの吸着率が高く均一で微細な白金粒子を高分散に担持できることが、いまや、見出された。
したがって、限定されるものでないが、本発明として、次の特徴又は態様の発明が提供される。
態様１：　ジニトロジアンミン白金錯体又は化合物を硝酸水溶液に、白金換算で１００±２０ｇ／Ｌ、硝酸濃度で２２０±４０ｇ／Ｌになるように溶解させ、１００～１１０℃で１８～２４時間加熱することで前記ジニトロジアンミン白金を改変又は変成した白金錯体含有硝酸水溶液を得る工程と、
担体カーボンブラックの水分散液と前記白金錯体含有硝酸水溶液を混合し、前記白金錯体を前記カーボンブラックの表面上に吸着させて前記白金錯体が吸着したカーボンブラック含有液を得る工程と、
前記カーボンブラック含有液を濾過し、濾別された前記白金錯体が吸着したカーボンブラックを洗浄し、乾燥させて、前記カーボンブラックの表面上に前記白金錯体が吸着した粉末を得る工程と、
前記白金錯体が吸着したカーボンブラック粉末を不活性ガスまたは窒素ガス雰囲気中、２８０℃～４００℃で熱分解することによる白金錯体の熱分解工程と、
を含むことを特徴とする白金担持カーボン触媒の製造方法。
態様２：　改変又は変成した前記白金錯体含有硝酸水溶液は、当該水溶液を１ｗｔ％の白金濃度となるように純水で希釈した場合の水溶液のＬ＊ａ＊ｂ＊表色系における彩度a＊が２８～３５であることを特徴とする態様１の白金担持カーボン触媒の製造方法。
態様３：　前記乾燥は、１８０℃～２３０℃の温度下で行われることを特徴とする態様１又は２の白金担持カーボン触媒の製造方法。
態様４：　前記熱分解工程は、前記カーボンブラックの表面上に白金錯体が吸着した粉末を、適当な容器に、層厚（堆積厚）０．１ｍｍ～３０ｍｍの範囲に堆積させ、不活性ガスまたは窒素ガス雰囲気中、２８０℃～４００℃で前記白金錯体を熱分解することを特徴とする態様１～３のいずれかの白金担持カーボン触媒の製造方法。
態様５：　白金担持カーボン触媒中の白金担持量は、前記触媒の総重量当たり、５ｗｔ％～２０ｗｔ％に調整されることを特徴とする態様１～４のいずれかの白金担持カーボン触媒の製造方法。 When the ratio of platinum and nitric acid in the nitric acid aqueous solution containing the dinitrodiammine platinum complex or the compound is set to, for example, 1:2.2 on a weight basis and the dinitrodiammine platinum complex or the compound-containing nitric acid aqueous solution is heated under certain conditions, prior art documents An aqueous nitric acid solution containing a dinitrodiammineplatinum complex or compound having properties or states different from those disclosed in is obtained, and the aqueous solution in such a state is used to adsorb the platinum complex to carbon black, filtered, washed, It has now been found that by drying and then thermally decomposing, the adsorption rate of the platinum complex to carbon black is high, and uniform and fine platinum particles can be supported in a highly dispersed manner.
Accordingly, the invention provides, but is not limited to, the following features or aspects.
Aspect 1: Dinitrodiammineplatinum complex or compound is dissolved in an aqueous nitric acid solution to a concentration of 100±20 g/L in terms of platinum and 220±40 g/L in nitric acid concentration, and heated at 100 to 110° C. for 18 to 24 hours. obtaining an aqueous nitric acid solution containing a platinum complex in which the dinitrodiammine platinum is modified or denatured;
A step of mixing an aqueous dispersion of carrier carbon black and the platinum complex-containing nitric acid aqueous solution to adsorb the platinum complex on the surface of the carbon black to obtain a carbon black-containing liquid in which the platinum complex is adsorbed;
A step of filtering the carbon black-containing liquid, washing and drying the filtered carbon black having the platinum complex adsorbed thereon, and obtaining a powder having the platinum complex adsorbed on the surface of the carbon black;
A thermal decomposition step of the platinum complex by thermally decomposing the carbon black powder to which the platinum complex is adsorbed at 280 ° C. to 400 ° C. in an inert gas or nitrogen gas atmosphere;
A method for producing a platinum-supported carbon catalyst, comprising:
Aspect 2: The modified or denatured platinum complex-containing nitric acid aqueous solution is L * a * b * of the aqueous solution when the aqueous solution is diluted with pure water so that the platinum concentration becomes 1 wt% *chroma a * in the color system A method for producing a platinum-supported carbon catalyst according to aspect 1, wherein is 28 to 35.
Aspect 3: The method for producing a platinum-supported carbon catalyst according to aspect 1 or 2, wherein the drying is performed at a temperature of 180°C to 230°C.
Aspect 4: In the thermal decomposition step, the powder having the platinum complex adsorbed on the surface of the carbon black is deposited in an appropriate container to a layer thickness (deposition thickness) in the range of 0.1 mm to 30 mm, and an inert gas or The method for producing a platinum-supported carbon catalyst according to any one of aspects 1 to 3, wherein the platinum complex is thermally decomposed at 280°C to 400°C in a nitrogen gas atmosphere.
Aspect 5: The method for producing a platinum-supported carbon catalyst according to any one of aspects 1 to 4, wherein the amount of platinum supported in the platinum-supported carbon catalyst is adjusted to 5 wt% to 20 wt% relative to the total weight of the catalyst. .
本発明に従うと、白金錯体のカーボンブラックへの吸着率が高く、カーボンブラックに吸着した白金錯体を比較的低温で熱分解できるので、製造量を多くしても均一で微細な白金粒子を高分散に担持した白金担持カーボン触媒を製造することができる。 According to the present invention, the adsorption rate of the platinum complex to carbon black is high, and the platinum complex adsorbed to carbon black can be thermally decomposed at a relatively low temperature, so even if the production amount is increased, uniform and fine platinum particles are highly dispersed. It is possible to produce a platinum-supported carbon catalyst supported on.
本発明にしたがう白金錯体が吸着したカーボンブラックの乾燥後の一サンプルについて示走査熱量測定－質量分析（ＤＳＣ－Ｍａｓｓ）を行った結果のグラフ表示。1 is a graphical representation of the results of differential scanning calorimetry-mass spectrometry (DSC-Mass) performed on a dried sample of carbon black with adsorbed platinum complexes according to the present invention. 図１と異なる条件下での乾燥後のサンプルについて同様の測定を行った結果のグラフ表示。Graphic representation of the results of similar measurements on dried samples under different conditions than in FIG. 実施例３の触媒粒子のＴＥＭ像TEM image of catalyst particles of Example 3
発明の詳細な説明Detailed description of the invention
本明細書で使用する用語は、特記しない限り、当該技術分野で常用されている意味を有するものとして使用している。
さらに、以下、本発明について、具体的に説明する。
態様１における、改変又は変成した白金錯体含有硝酸水溶液を得る工程では、ジニトロジアンミン白金錯体又は化合物を硝酸水溶液に、白金換算で１００±２０ｇ／Ｌ、硝酸濃度で２２０±４０ｇ／Ｌになるように溶解させ、１００～１１０℃で１８～２４時間加熱することにより、当該硝酸水溶液における白金と硝酸の比率は、重量基準で、ほぼ１：２．２に調整される。こうして調整された硝酸水溶液は、１００～１１０℃、好ましくは、１０１～１０７℃、より好ましくは、１０３～１０５℃で、１８～２４時間、好ましくは、１９～２２時間、より好ましくは２０～２１加熱することで、加熱処理前の溶液の彩度に変化がもたらされる。本明細書において、「白金錯体又は化合物」にいう、錯体と化合物は互換可能な用語として使用している。
本発明に従う、彩度の変化は、前記加熱工程後の白金錯体を含む硝酸水溶液を１ｗｔ％の白金濃度となるように純水で希釈した場合の水溶液における、Ｌ＊ａ＊ｂ＊表色系における彩度a＊が２８～３５、好ましくは、２９～３４、より好ましくは３０～３３、となるようにしてもよい。前記加熱処理前の相当する水溶液の彩度a＊は、限定されるものでないが、一般的に、－３～－１であることができる。 Terms used herein have their meanings commonly used in the art unless otherwise specified.
Further, the present invention will be specifically described below.
In the step of obtaining the modified or denatured platinum complex-containing nitric acid aqueous solution in aspect 1, the dinitrodiammine platinum complex or compound is added to the nitric acid aqueous solution so that the concentration is 100 ± 20 g / L in terms of platinum and the nitric acid concentration is 220 ± 40 g / L. By dissolving and heating at 100-110° C. for 18-24 hours, the ratio of platinum to nitric acid in the aqueous nitric acid solution is adjusted to approximately 1:2.2 on a weight basis. The nitric acid aqueous solution thus prepared is heated at 100 to 110° C., preferably 101 to 107° C., more preferably 103 to 105° C., for 18 to 24 hours, preferably 19 to 22 hours, more preferably 20 to 21 hours. Heating causes a change in the color saturation of the solution prior to heat treatment. As used herein, the terms "platinum complex or compound" and "complex" are used interchangeably.
According to the present invention, the change in chroma is L * a * b * in the aqueous solution when the nitric acid aqueous solution containing the platinum complex after the heating step is diluted with pure water so that the platinum concentration becomes 1 wt%. may be 28-35 , preferably 29-34, more preferably 30-33. The chroma a * of the corresponding aqueous solution before said heat treatment is not limited, but can generally be between -3 and -1.
態様１の発明において、白金錯体が吸着したカーボンブラックを乾燥するための温度は、限定されるものでないが、一般的には５０℃～２５０℃、好ましくは８０℃～２５０℃、より好ましくは１８０℃～２３０℃としてもよい。乾燥時間は、例えば、図１又は図２に示されるＤＳＣ－Ｍａｓｓの結果を参照に、サンプルから適度に水分、ＮＯ、ＣＯ２が除かれる挙動等を参照し適宜決定することができるが、一般に、上記温度下で、１０時間～７２時間、好ましくは１２時間～６０時間、より好ましくは１４時間～４８時間であることができる。
また、前記白金錯体の熱分解工程は、一般的には、２８０～４００℃、好ましくは２９０℃～３５０℃、より好ましくは３００℃～３２０℃で行うことができる。加熱分解時間は、一般に、上記加熱温度下で、０．２５時間～３時間、好ましくは０．５時間～２時間、より好ましくは０．７５時間～１．５時間とすることができる。
当該熱分解工程は、適当な容器は、限定されるものではないが、底面が平らであり、かつ、通常想定されている層厚（堆積厚）である３０ｍｍを超える深さを有するバットを使用してもよい。かようなバットは、限定されるものでないが、例えば、２５０ｍｍ×２５０ｍｍ×深さ５０ｍｍ又は３２５ｍｍ×５３０ｍｍ×深さ６０ｍｍのカーボン製又はチタン製容器であることができる。 In the invention of aspect 1, the temperature for drying the carbon black to which the platinum complex is adsorbed is not limited, but is generally 50 ° C. to 250 ° C., preferably 80 ° C. to 250 ° C., more preferably 180 °C to 230 °C. The drying time can be determined as appropriate by referring to, for example, the results of DSC - Mass shown in FIG. 1 or FIG. , under the above temperature, 10 hours to 72 hours, preferably 12 hours to 60 hours, more preferably 14 hours to 48 hours.
Further, the thermal decomposition step of the platinum complex can be generally carried out at 280 to 400°C, preferably 290 to 350°C, more preferably 300 to 320°C. The thermal decomposition time is generally 0.25 hours to 3 hours, preferably 0.5 hours to 2 hours, more preferably 0.75 hours to 1.5 hours at the above heating temperature.
The pyrolysis process uses, but is not limited to, a vat with a flat bottom and a depth exceeding 30 mm, which is the normally assumed layer thickness (deposition thickness). You may Such a bat can be, for example, but not limited to, a carbon or titanium container measuring 250 mm x 250 mm x 50 mm deep or 325 mm x 530 mm x 60 mm deep.
態様１の発明において、白金担持カーボン触媒中の白金担持量は、当該触媒の総重量当たり、５ｗｔ％～２０ｗｔ％、７．５～１５ｗｔ％、より好ましくは８～１３ｗｔ％に調整するようにしてもよい。 In the invention of aspect 1, the amount of platinum supported in the platinum-supported carbon catalyst is adjusted to 5 wt% to 20 wt%, 7.5 to 15 wt%, more preferably 8 to 13 wt%, based on the total weight of the catalyst. good too.
本発明が採用する特徴のある工程又は処理について、以下、さらに具体的に説明するが、本発明の範囲は、これらの説明又は理論に拘束されるものでない。 The characteristic steps or processes adopted by the present invention are described in more detail below, but the scope of the present invention is not bound by these descriptions or theories.
＜ジニトロジアンミン白金硝酸水溶液の加熱処理＞
本発明に従えば、上述のとおり、ジニトロジアンミン白金錯体又は化合物を硝酸水溶液に溶解させ、当該溶解液を所定の温度で所定時間加熱することで改変又は変成したジニトロジアンミン白金錯体含有硝酸水溶液が得られる。これは、当該溶解液に熟成させることになる。これにより、白金錯体又は化合物が水溶液中でカーボンブラックに吸着されやすくなり、高効率で且つ製造量を多くしても、又製造スケールを拡大しても、均一で微細な白金粒子を高分散に担持した白金担持カーボン触媒を製造することができるものと理解される。 <Heat treatment of dinitrodiammineplatinum nitric acid aqueous solution>
According to the present invention, as described above, a dinitrodiammineplatinum complex or compound is dissolved in an aqueous nitric acid solution, and the solution is heated at a predetermined temperature for a predetermined time to obtain a modified or denatured nitric acid aqueous solution containing a dinitrodiammineplatinum complex. be done. This will cause the solution to ripen. As a result, the platinum complex or compound is easily adsorbed to carbon black in an aqueous solution, and even if it is highly efficient and the production amount is increased, or the production scale is expanded, uniform and fine platinum particles are highly dispersed. It is understood that supported platinum on carbon catalysts can be produced.
ジニトロジアンミン白金を硝酸水溶液に、白金換算で１００±２０ｇ／Ｌ、硝酸濃度で２２０±４０ｇ／Ｌになるように溶解させる工程又は処理は、前記の特許文献１及び特許文献２におけるジニトロジアンミン白金硝酸水溶液における白金と硝酸の比率が重量基準で、１：０．７～１であるのと大きく異なり、ジニトロジアンミン白金硝酸水溶液における白金と硝酸の比率を、ほぼ１：２．２としている。そして、前記硝酸水溶液の加熱処理は、１００～１１０℃で行う。当該処理段階において、溶液中の白金の価数が２価から４価へと増大する反応が進行すると同時に白金錯体に配位する配位子が変化し、白金錯体のカーボンブラックへの吸着性が改善する。当該反応は加熱時間とともに進行するため、加熱時間が１８時間よりも短いと白金錯体の吸着率が低下する。一方、加熱時間が２４時間よりも長くなると白金の沈殿が生成されやすくなり好ましくない。したがって、一般的に、１８～２４時間加熱することで白金錯体の９０％以上を吸着でき、かつ白金の沈殿を生成しない。 The process or treatment of dissolving dinitrodiammineplatinum in an aqueous nitric acid solution to a platinum equivalent of 100±20 g/L and a nitric acid concentration of 220±40g/L is the same as the dinitrodiammineplatinum nitric acid in Patent Documents 1 and 2 above. The ratio of platinum to nitric acid in the aqueous solution is 1:0.7 to 1 on a weight basis. The heat treatment of the nitric acid aqueous solution is performed at 100 to 110.degree. In the treatment step, the reaction in which the valence of platinum in the solution increases from divalent to tetravalent progresses, and at the same time the ligand coordinated to the platinum complex changes, and the adsorption of the platinum complex to carbon black increases. Improve. Since the reaction proceeds with the heating time, if the heating time is shorter than 18 hours, the adsorption rate of the platinum complex decreases. On the other hand, if the heating time is longer than 24 hours, platinum precipitates are likely to be generated, which is not preferable. Therefore, generally, heating for 18-24 hours can adsorb 90% or more of the platinum complex and does not produce a precipitate of platinum.
本発明によれば、上述したように、加熱工程後の白金錯体を含む硝酸水溶液を１ｗｔ％の白金濃度となるように純水で希釈した場合の水溶液における、Ｌ＊ａ＊ｂ＊表色系における彩度a＊は一般的に２８～３５である。加熱工程後の白金錯体を含む硝酸水溶液がそのような特性を有するか又は状態にあれば、次工程において白金錯体の９０％以上を担体に吸着でき、かつ白金の沈殿を生成しない。そのため、彩度a＊の確認を行い、加熱処理時間を微調整しながら生産することが望ましい。なお、彩度は、日本電色工業株式会社製の透過色測定器(ＴＺ６０００)で測定される。 According to the present invention, as described above, the L * a * b * color system in the aqueous solution when the nitric acid aqueous solution containing the platinum complex after the heating step is diluted with pure water so that the platinum concentration becomes 1 wt%. The saturation a * at is typically 28-35. If the nitric acid aqueous solution containing the platinum complex after the heating step has such properties or is in such a state, 90% or more of the platinum complex can be adsorbed on the carrier in the next step, and no platinum precipitates. Therefore, it is desirable to check the saturation a * and fine-tune the heat treatment time during production. The chroma is measured with a transmissive color measuring instrument (TZ6000) manufactured by Nippon Denshoku Industries Co., Ltd.
また、彩度a＊の他の指標として、４２０ｎｍにおける吸光度の測定を行ってもよい。４２０ｎｍにおける吸光度の測定は、日本分光製のＶ-７５０を用いて、１ｇ/Ｌ濃度になるように純水を用いて調整した試料を石英セル中に入れ行うことができる。彩度a＊の値が３０のサンプルの４２０ｎｍにおける吸光度は、１．０６であり、彩度a＊の値が３５のサンプルは、１．０７であった。また、これらのサンプルのアルカリ消費量を特許文献１記載の公知の方法で求めたところ、白金量１ｇに対してアルカリ消費量は共に１．２ｇであった。本発明では、過度な白金錯体の変質を防止するために、白金量１ｇに対し比較的高い硝酸濃度（高アルカリ消費量）で熟成を行った結果、４２０ｎｍにおける吸光度が小さい形の白金錯体となっている。 Also, as another index of chroma a * , absorbance at 420 nm may be measured. Absorbance at 420 nm can be measured using V-750 manufactured by JASCO Corporation by placing a sample adjusted with pure water to a concentration of 1 g/L in a quartz cell. The absorbance at 420 nm of the sample with a chroma a * value of 30 was 1.06, and that of the sample with a chroma a * value of 35 was 1.07. Further, when the alkali consumption of these samples was determined by the known method described in Patent Document 1, the alkali consumption was 1.2 g for each 1 g of platinum. In the present invention, in order to prevent excessive deterioration of the platinum complex, as a result of aging at a relatively high nitric acid concentration (high alkali consumption) with respect to 1 g of platinum, the platinum complex has a small absorbance at 420 nm. ing.
＜前記加熱処理以外の処理＞
また、本発明は、カーボンブラックを水に分散させた分散液に前記加熱工程後の白金錯体を含む硝酸水溶液を混合し、前記白金錯体を前記カーボン粉末に吸着させる工程を含む。 <Treatments other than the heat treatment>
Further, the present invention includes a step of mixing a dispersion of carbon black in water with an aqueous nitric acid solution containing a platinum complex after the heating step to adsorb the platinum complex to the carbon powder.
本発明で用いるカーボンブラックは特に限定されるものではなく、電極触媒の製造において白金を担持させるために用いられる表面に官能基を有するカーボンブラックであればよい。具体的には、ファーネスブラック、チャンネルブラック、アセチレンブラック等のカーボンブラックが挙げられる。なお、ここで用いる水はイオン交換した純水とすることができる。 The carbon black used in the present invention is not particularly limited as long as it has a functional group on its surface and is used for supporting platinum in the production of an electrode catalyst. Specific examples include carbon black such as furnace black, channel black, and acetylene black. The water used here can be ion-exchanged pure water.
白金錯体の水溶液中での吸着は、純水中にカーボンブラックを分散させた後、この分散液に加熱工程後の白金錯体を含む硝酸水溶液を加えて数時間撹拌して混合することで行う。カーボンブラックの分散液に酸性の溶液を添加して酸性とした後に加熱工程後の白金錯体の水溶液を混合してもよい。この際、酸としては触媒への残留の少ない硝酸が好ましい。また、白金錯体のカーボンブラックへの吸着は１時間程度で平衡となるため、吸着時間は数時間程度とすることが望ましい。 Adsorption of the platinum complex in the aqueous solution is carried out by dispersing carbon black in pure water, adding an aqueous nitric acid solution containing the platinum complex after the heating step to the dispersion, and stirring for several hours to mix. An acidic solution may be added to the carbon black dispersion to make it acidic, and then the aqueous solution of the platinum complex after the heating step may be mixed. At this time, as the acid, nitric acid which leaves little residue on the catalyst is preferable. Moreover, since the adsorption of the platinum complex to carbon black reaches equilibrium in about one hour, it is desirable to set the adsorption time to about several hours.
上記記載の特徴を有する加熱工程後に、水溶液中で白金錯体を吸着させることにより、白金錯体がカーボンブラックに高分散で担持されやすくなり、製造量を多くしても均一な所望の触媒粒径の白金を担持させたカーボン触媒を製造することができる。また、他の担持方法として、白金錯体を含む溶液にカーボン粉末を混合した後、蒸発乾固により、溶媒を蒸発させることで白金錯体を前記カーボン担体上に担持する手法もあるが、白金粒子が凝集し大きくなり易い点、偏在化が進みやすい点、等のため、大量の溶媒を蒸発する必要がありエネルギーコストがかかるので、特に製造量を多くするか又はスケールアップを図る場合の製造方法としては好ましくない。
すなわち、本発明の製造方法では、白金錯体をカーボンブラック表面の官能基に吸着させ、吸着していない白金錯体を濾過、洗浄で除去するので、白金粒子の粗大化や偏在化を抑制でき、製造量を容易に増やすことができる。 By adsorbing the platinum complex in an aqueous solution after the heating step having the characteristics described above, the platinum complex is highly dispersed and easily supported on the carbon black, and the desired catalyst particle size is uniform even if the production amount is increased. A carbon catalyst supporting platinum can be produced. Further, as another supporting method, after mixing carbon powder with a solution containing a platinum complex, there is also a method of supporting the platinum complex on the carbon support by evaporating the solvent by evaporation to dryness. Since it is necessary to evaporate a large amount of solvent due to the fact that it tends to aggregate and become large, and that it tends to be unevenly distributed, it is necessary to evaporate a large amount of solvent, which incurs energy costs. is not preferred.
That is, in the production method of the present invention, the platinum complex is adsorbed to the functional group on the surface of the carbon black, and the platinum complex that is not adsorbed is removed by filtration and washing, so that the coarsening and uneven distribution of the platinum particles can be suppressed. You can easily increase the amount.
白金担持カーボン触媒中の白金担持量は、一般的に、当該触媒の総重量当たり５ｗｔ％～２０ｗｔ％とすることができる。具体的には、ジニトロジアンミン白金硝酸溶液の量に対して、カーボン粉末量を調整することで行う。 The amount of platinum supported in the platinum-supported carbon catalyst can generally be from 5 wt% to 20 wt% based on the total weight of the catalyst. Specifically, the amount of carbon powder is adjusted with respect to the amount of dinitrodiammineplatinum nitric acid solution.
また、本発明は、濾過、洗浄、乾燥させて、カーボンブラックに白金錯体が吸着した粉末を得る工程を含む。 Moreover, the present invention includes a step of obtaining a powder in which a platinum complex is adsorbed on carbon black by filtering, washing, and drying.
本発明で用いる濾過方法としては特に限定されるものではなく、種々の手段によって行うことができる。具体的には、ベルトフィルター、ドラムフィルター、遠心分離機、真空濾過器、加圧濾過器、フィルタープレスなどを用いて行うことができる。 The filtration method used in the present invention is not particularly limited, and various means can be used. Specifically, it can be carried out using a belt filter, a drum filter, a centrifuge, a vacuum filter, a pressure filter, a filter press, or the like.
本発明で用いる洗浄方法としては、上記濾過で得られた濾過ケーキに純水を加圧しながら均一に通過させることで行った。 As a washing method used in the present invention, pure water was uniformly passed through the filter cake obtained by the above filtration while pressurizing it.
本発明で用いる乾燥器としては特に限定されるものではなく、さまざまな乾燥器を用いて乾燥を行うことができる。具体的には、熱風乾燥器、真空乾燥器、イナートオーブンなどが挙げられる。 The dryer used in the present invention is not particularly limited, and various dryers can be used for drying. Specific examples include hot air dryers, vacuum dryers, inert ovens, and the like.
乾燥は、上述したように、一般的に、５０℃～２５０℃で行うことができる。当該処理により、水分が除かれると共に、一部のＮＯｘ成分も除去される。例えば、カーボンブラックの表面に白金錯体が吸着した粉末を１００℃で１９時間真空乾燥した後のサンプル１、１００℃で１９時間真空乾燥後さらに１９０℃で１４時間真空乾燥した後のサンプル２の示差走査熱量測定－質量分析（ＤＳＣ－Ｍａｓｓ）を行った。ＤＳＣ分析計は、ＳＴＡ ４４０Ｆ３（ネッチ・ジャパン株式会社製）を用いた。前記ＤＳＣ分析計にはガスクロマトグラフ質量分析計ＪＭＳ－Ｑ１５００ＧＣ（日本電子株式会社製）が接続され、ＤＳＣ分析計で発生したガス成分のマススペクトルを測定した。試料約１０ｍｇを試料台にのせた後、ヘリウム雰囲気において、２０℃／分の昇温速度で５００℃まで昇温し、ＤＳＣ及びｍ／ｅ＝１８（Ｈ２Ｏ）、３０（ＮＯ）、４４（ＣＯ２）成分のシグナル強度を測定した。得られた結果の一例を図１、図２に示した。図１、図２から高温での乾燥処理を行うことで、水分の除去に加えて一部のＮＯｘ成分が除去され、それにともなってＤＳＣの発熱ピークが小さくなることが示唆される。熱分解時に発熱量が大きくなりすぎると触媒粒子の凝集などの不具合を生じる恐れがあり好ましくないため、乾燥温度を１８０℃～２３０℃とし、熱分解時の発熱量を小さくすることが好ましい。 Drying, as described above, can generally be carried out at 50°C to 250°C. Moisture is removed by the treatment, and some NOx components are also removed. For example, sample 1 after vacuum-drying the powder in which the platinum complex was adsorbed on the surface of carbon black at 100 ° C. for 19 hours, sample 2 after vacuum-drying at 100 ° C. for 19 hours and further vacuum-drying at 190 ° C. for 14 hours. Scanning calorimetry-mass spectrometry (DSC-Mass) was performed. STA 440F3 (manufactured by Netch Japan Co., Ltd.) was used as the DSC analyzer. A gas chromatograph mass spectrometer JMS-Q1500GC (manufactured by JEOL Ltd.) was connected to the DSC analyzer, and the mass spectrum of gas components generated by the DSC analyzer was measured. After placing about 10 mg of the sample on the sample stage, the temperature was raised to 500°C at a rate of 20°C/min in a helium atmosphere, and DSC and m/e = 18 (H 2 O), 30 (NO), 44 The signal intensity of the (CO 2 ) component was measured. An example of the obtained results is shown in FIGS. From FIGS. 1 and 2, it is suggested that the high-temperature drying treatment removes some of the NOx components in addition to the removal of moisture, and accordingly reduces the exothermic peak of the DSC. If the amount of heat generated during thermal decomposition becomes too large, problems such as aggregation of the catalyst particles may occur, which is not preferable. Therefore, it is preferable to set the drying temperature to 180° C. to 230° C. to reduce the amount of heat generated during thermal decomposition.
また、高温での乾燥を行う場合は、真空乾燥器、イナートオーブン等を使用し、酸素が存在しない条件下で乾燥を行うことが望ましい。また、発生したＮＯｘガスが直ちに除去できる真空度、不活性ガスまたは窒素ガスのガス流通下とすることがさらに望ましい。 When drying at a high temperature, it is desirable to use a vacuum dryer, an inert oven, or the like, and dry under oxygen-free conditions. Further, it is more desirable to set the vacuum to be able to immediately remove the generated NOx gas, and to be under the flow of an inert gas or nitrogen gas.
また、本発明は、上述したとおり、不活性ガスまたは窒素ガス雰囲気中、一般的に、２８０℃～４００℃で前記カーボン担体上に白金錯体が吸着した粉末を熱分解する熱分解工程を含む。 In addition, as described above, the present invention includes a thermal decomposition step of thermally decomposing the powder having the platinum complex adsorbed on the carbon support generally at 280° C. to 400° C. in an inert gas or nitrogen gas atmosphere.
本発明の電極触媒の製造方法は、カーボンブラックの表面上に白金を含んだ錯体が担持された粉末を不活性ガスまたは窒素ガス雰囲気中、一般的に、２８０℃～４００℃という比較的低い温度で熱分解する工程を採用することに特徴がある。また、この工程により、還元剤を使用することなく２～５ｎｍ程度の小さい触媒粒径の白金担持電極触媒を製造することができる。２８０℃以下では、熱分解が不十分であり好ましくない。また、４００℃以上では、触媒粒子が凝集により粗大化し好ましくない。
なお、図１より白金錯体の分解ピークとＣＯ２の検出ピークがほぼ一致していることより、白金錯体が吸着しているカーボンブラックの官能基の分解時に発生するエネルギーを利用し、比較的低い温度で白金錯体が熱分解できると考える。 In the method for producing an electrode catalyst of the present invention, a powder having a platinum-containing complex supported on the surface of carbon black is generally heated to a relatively low temperature of 280° C. to 400° C. in an inert gas or nitrogen gas atmosphere. It is characterized by adopting a process of thermally decomposing at Moreover, by this process, a platinum-supported electrode catalyst with a small catalyst particle size of about 2 to 5 nm can be produced without using a reducing agent. A temperature of 280° C. or less is not preferable because thermal decomposition is insufficient. On the other hand, if the temperature is 400° C. or higher, the catalyst particles aggregate and become coarse, which is not preferable.
In addition, from the fact that the decomposition peak of the platinum complex and the detection peak of CO 2 are almost the same from FIG. It is assumed that the platinum complex can be thermally decomposed at the temperature.
上記図１、図２に例示したＤＳＣピークから、白金錯体の熱分解反応は２８０℃付近から顕著になることが分かる。従って、２８０℃以上で熱分解することで、熱分解を促進することができる。一方、あまりにも熱分解を急激に進めすぎると発熱によって触媒粒子の凝集などの不具合を生じる恐れがあり好ましくない。以上の点から、上述したとおり、熱分解温度は、一般的には２８０℃～４００℃とし、２９０℃～３５０℃とすることが好ましく。より好ましくは、３００℃～３２０℃である。 From the DSC peaks exemplified in FIGS. 1 and 2 above, it can be seen that the thermal decomposition reaction of the platinum complex becomes significant from around 280.degree. Therefore, thermal decomposition can be accelerated by thermally decomposing at 280° C. or higher. On the other hand, if the thermal decomposition proceeds too rapidly, heat generation may cause problems such as agglomeration of the catalyst particles, which is not preferable. From the above points, as described above, the thermal decomposition temperature is generally 280°C to 400°C, preferably 290°C to 350°C. More preferably, it is 300°C to 320°C.
また、他の方法として、水素を還元剤として使用し気相還元する方法や、エタノールを還元剤として使用し、事前に液相還元する方法などが報告されているが、還元反応の制御が難しいため触媒粒子の凝集を招き易い点、還元剤が触媒へ残留する点、工程が増える点等から特に製造量を多くした製造方法としては好ましくない。 In addition, as other methods, a method of gas phase reduction using hydrogen as a reducing agent and a method of prior liquid phase reduction using ethanol as a reducing agent have been reported, but control of the reduction reaction is difficult. Therefore, it is not preferable as a production method that requires a particularly large production volume because it tends to cause agglomeration of the catalyst particles, the reducing agent remains in the catalyst, and the number of steps increases.
熱分解工程については上述したが、さらに説明すると、カーボン担体上に白金錯体が吸着した粉末を、容器に、層厚（堆積厚）０．１ｍｍ～３０ｍｍの範囲に堆積させ、不活性ガスまたは窒素ガス雰囲気中、２８０℃～４００℃で熱分解することができる。熱分解工程に適する容器は、より具体的には、カーボン製の角型の平たい容器（バット）に、カーボンブラックの表面上に白金錯体が吸着した粉末を層厚（堆積厚）０．１ｍｍ～３０ｍｍの範囲に堆積させ、不活性ガスまたは窒素ガス雰囲気中、前記加熱温度下で熱分解する。 The pyrolysis step has been described above, but to explain further, the powder with the platinum complex adsorbed on the carbon support is deposited in a container in a layer thickness (deposition thickness) range of 0.1 mm to 30 mm, and an inert gas or nitrogen It can be thermally decomposed at 280°C to 400°C in a gas atmosphere. More specifically, a container suitable for the pyrolysis step is a rectangular flat container (bat) made of carbon, and a layer thickness (deposition thickness) of 0.1 mm to 0.1 mm of powder in which a platinum complex is adsorbed on the surface of carbon black. It is deposited in a range of 30 mm and thermally decomposed at the above heating temperature in an inert gas or nitrogen gas atmosphere.
後に示す表１の実施例２ないし実施例４で示すように同じ温度で熱分解した場合であっても、層厚を高くすると、触媒粒径は大きくなる。この傾向を利用することで、触媒粒径を２ｎｍ～５ｎｍの中の狙った大きさに調整することができる。層厚を３０ｍｍより高くすると、触媒粒径は５ｎｍよりも大きくなる。 As shown in Examples 2 to 4 in Table 1 below, even when pyrolysis is performed at the same temperature, increasing the layer thickness increases the catalyst particle size. By utilizing this tendency, the catalyst particle size can be adjusted to a target size within 2 nm to 5 nm. If the layer thickness is higher than 30 mm, the catalyst particle size will be larger than 5 nm.
また、後に示す表１の実施例５ないし実施例６において、２００℃で４６時間真空乾燥した粉末を熱分解した際も、触媒粒径は、層厚を高くすると大きくなる傾向にある。一方、層厚と触媒粒径の関係は、表１の実施例２ないし実施例４とは異なっている。これは、前記のとおり高温での乾燥処理を行うことで、触媒中の水分の除去に加えて触媒中のＮＯｘ成分の一部が除去された結果、熱分解の反応が温和となったためであると考えられる。また、ＮＯｘ成分の一部が除去される効果を利用することで、不活性ガス雰囲気中での熱分解において、一度により多くの粉末を処理することが可能となる。 Further, in Examples 5 and 6 in Table 1 shown later, when the powder vacuum-dried at 200° C. for 46 hours was thermally decomposed, the catalyst particle size tended to increase as the layer thickness increased. On the other hand, the relationship between layer thickness and catalyst particle size is different from that of Examples 2 to 4 in Table 1. This is because, as a result of removing some of the NOx components in the catalyst in addition to removing the moisture in the catalyst by performing the drying treatment at a high temperature as described above, the thermal decomposition reaction was mild. it is conceivable that. Moreover, by utilizing the effect of removing a part of the NOx component, it becomes possible to process more powder at one time in thermal decomposition in an inert gas atmosphere.
以下、本発明の具体的な実施態様について説明するが、本発明は、それらに限定されるものではない。 Specific embodiments of the present invention will be described below, but the present invention is not limited to them.
＜ジニトロジアンミン白金硝酸溶液の調製＞
（溶液Ｓ１の調製）
１ｗｔ％の白金濃度及び透過色測定の彩度a＊が３０～３５であるジニトロジアンミン白金硝酸溶液Ｓ１を、以下のようにして調製した。 <Preparation of dinitrodiammineplatinum nitric acid solution>
(Preparation of solution S1)
A dinitrodiammineplatinum nitrate solution S1 having a platinum concentration of 1 wt % and a chroma a* of 30 to 35 in transmission color measurement was prepared as follows.
ジニトロジアンミン白金を硝酸水溶液に、白金換算で１００ｇ／Ｌ、硝酸濃度で１８０ｇ／Ｌになるように、溶解させた。この溶液を攪拌しながら、約１０４℃で２０時間に亘って加熱した。このようにして、溶液Ｓ１を得た。なお、この溶液Ｓ１は実施例毎に調整した。 Dinitrodiammineplatinum was dissolved in an aqueous nitric acid solution to a concentration of 100 g/L in terms of platinum and a nitric acid concentration of 180 g/L. The solution was heated with stirring at about 104° C. for 20 hours. Thus, solution S1 was obtained. In addition, this solution S1 was adjusted for each example.
（溶液Ｓ２の調製）
ジニトロジアンミン白金を硝酸水溶液に、白金換算で１００ｇ／Ｌ、硝酸濃度で１８０ｇ／Ｌになるように、溶解させた。この溶液を攪拌しながら、約１０４℃で４時間に亘って加熱した。このようにして、溶液Ｓ２を得た。 (Preparation of solution S2)
Dinitrodiammineplatinum was dissolved in an aqueous nitric acid solution to a concentration of 100 g/L in terms of platinum and a nitric acid concentration of 180 g/L. The solution was heated with stirring at about 104° C. for 4 hours. Thus, solution S2 was obtained.
＜担持触媒の調製＞
（実施例１）
９．０ｇのＶｕｌｃａｎ ＸＣ－７２Ｒ（ＣＡＢＯＴ製）を、純水７００ｍＬ中に分散させた。次に、この分散液に硝酸を４．９ｇ添加し、酸性とした。得られた酸性の分散液に、１．０ｇの白金に相当する量の溶液Ｓ１を添加し、その後４時間に亘って撹拌した。該分散液を濾過して、濾過ケーキを得た。これを純水で洗浄した後、６０℃で１９時間に亘って、乾燥に供した。このようにして、カーボン担体上に白金錯体が吸着した粉末を得た。以下、この粉末を「粉末Ｐ１」と呼ぶ。 <Preparation of supported catalyst>
(Example 1)
9.0 g of Vulcan XC-72R (manufactured by CABOT) was dispersed in 700 mL of pure water. Next, 4.9 g of nitric acid was added to this dispersion to acidify it. An amount of solution S1 corresponding to 1.0 g of platinum was added to the resulting acidic dispersion and then stirred for 4 hours. The dispersion was filtered to obtain a filter cake. After washing it with pure water, it was dried at 60° C. for 19 hours. Thus, a powder in which the platinum complex was adsorbed on the carbon support was obtained. This powder is hereinafter referred to as "powder P1".
次いで、粉末Ｐ１を、粉末状に粉砕した後、粉末Ｐ１の厚さ（堆積厚）が０．１ｍｍとなるように容器に入れ、窒素ガス流通下、３１０℃で１時間に亘る熱処理に供した。 Next, the powder P1 was pulverized into powder, placed in a container so that the thickness (deposition thickness) of the powder P1 was 0.1 mm, and subjected to heat treatment at 310° C. for 1 hour under nitrogen gas flow. .
以上のようにして、担持触媒を製造した。以下、これを「実施例１」と呼ぶ。 A supported catalyst was produced as described above. Hereinafter, this will be referred to as "Example 1".
（実施例２）
１８００ｇのＶｕｌｃａｎ ＸＣ－７２Ｒ（ＣＡＢＯＴ製）を、純水１４０Ｌ中に分散させた。次に、この分散液に硝酸を９７５ｇ添加し、酸性とした。得られた酸性の分散液に、２０８ｇの白金に相当する量の溶液Ｓ１を添加し、その後４時間に亘って撹拌した。該分散液を濾過して、濾過ケーキを得た。これを純水で洗浄した後、１００℃で１９時間に亘って、真空乾燥に供した。このようにして、カーボン担体上に白金錯体が吸着した粉末を得た。以下、この粉末を「粉末Ｐ２」と呼ぶ。 (Example 2)
1800 g of Vulcan XC-72R (manufactured by CABOT) was dispersed in 140 L of pure water. Next, 975 g of nitric acid was added to this dispersion to acidify it. A quantity of solution S1 corresponding to 208 g of platinum was added to the resulting acidic dispersion and then stirred for 4 hours. The dispersion was filtered to obtain a filter cake. After washing this with pure water, it was subjected to vacuum drying at 100° C. for 19 hours. Thus, a powder in which the platinum complex was adsorbed on the carbon support was obtained. This powder is hereinafter referred to as "powder P2".
次いで、粉末Ｐ２を、粉末状に粉砕した後、粉末Ｐ２の厚さ（堆積厚）が０．７ｍｍとなるように容器に入れ（堆積させ）、窒素雰囲気中、３１０℃で１時間に亘る熱処理に供した。 Next, after pulverizing the powder P2 into a powder form, it is placed (deposited) in a container so that the thickness (deposition thickness) of the powder P2 is 0.7 mm, and heat treatment is performed at 310 ° C. for 1 hour in a nitrogen atmosphere. served to
以上のようにして、担持触媒を製造した。以下、これを「実施例２」と呼ぶ。 A supported catalyst was produced as described above. Hereinafter, this will be referred to as "Example 2".
（実施例３）
熱分解工程時の粉末の厚さを４ｍｍとしたことを除いては、実施例２と同様にして、担持触媒を製造した。以下、これを「実施例３」と呼ぶ。 (Example 3)
A supported catalyst was prepared in the same manner as in Example 2, except that the thickness of the powder during the pyrolysis process was 4 mm. Hereinafter, this will be referred to as "Example 3".
（実施例４）
熱分解工程時の粉末の厚さを６ｍｍとしたことを除いては、実施例２と同様にして、担持触媒を製造した。以下、これを「実施例４」と呼ぶ。 (Example 4)
A supported catalyst was prepared in the same manner as in Example 2, except that the thickness of the powder during the pyrolysis process was 6 mm. Hereinafter, this will be referred to as "Example 4".
（実施例５）
真空乾燥を２００℃で４６時間としたことと、熱分解工程時の粉末の厚さ（堆積厚）を７ｍｍとしたことを除いては、実施例２と同様にして、担持触媒を製造した。以下、これを「実施例５」と呼ぶ。 (Example 5)
A supported catalyst was produced in the same manner as in Example 2, except that the vacuum drying was carried out at 200° C. for 46 hours and the powder thickness (deposition thickness) during the pyrolysis step was 7 mm. Hereinafter, this will be referred to as "Example 5".
（実施例６）
真空乾燥を２００℃で４６時間としたことと、熱分解工程時の粉末の厚さ（堆積厚）を１０ｍｍとしたことを除いては、実施例２と同様にして、担持触媒を製造した。以下、これを「実施例６」と呼ぶ。 (Example 6)
A supported catalyst was produced in the same manner as in Example 2, except that the vacuum drying was carried out at 200° C. for 46 hours and the powder thickness (deposition thickness) during the pyrolysis step was 10 mm. Hereinafter, this will be referred to as "Example 6".
（実施例７）
熱分解工程時の粉末の厚さを４ｍｍとしたこと、温度を３３０℃としたことを除いては、実施例２と同様にして、担持触媒を製造した。以下、これを「実施例７」と呼ぶ。 (Example 7)
A supported catalyst was produced in the same manner as in Example 2, except that the thickness of the powder during the pyrolysis step was 4 mm and the temperature was 330°C. Hereinafter, this will be referred to as "Example 7".
（比較例１）
溶液Ｓ１を溶液Ｓ２に変えたことを除いては、実施例１と同様にして、カーボン担体上に白金錯体が吸着した粉末を製造した。以下、これを「比較例１」と呼ぶ。 (Comparative example 1)
A powder having a platinum complex adsorbed on a carbon support was produced in the same manner as in Example 1, except that the solution S1 was changed to the solution S2. Hereinafter, this is called "comparative example 1".
（比較例２）
２．７ｇのＶｕｌｃａｎ ＸＣ－７２Ｒ（ＣＡＢＯＴ製）を、純水２１０ｍＬ中に分散させた。得られた分散液に、０．３ｇの白金に相当触媒する量の溶液Ｓ１を添加し、その後、撹拌しながら６０℃で蒸発乾固した。次いで、粉末状に粉砕した後、粉末Ｐ１の厚さ（堆積厚）が０．１ｍｍとなるように容器に入れ、窒素ガス流通下、４５０℃で１時間に亘る熱処理に供した。以上のようにして製造触媒を「比較例２」と呼ぶ。なお、吸着していない白金錯体も含めて全て熱分解させるため、４５０℃とした。 (Comparative example 2)
2.7 g of Vulcan XC-72R (manufactured by CABOT) was dispersed in 210 mL of pure water. A catalytic amount of solution S1 corresponding to 0.3 g of platinum was added to the resulting dispersion, which was then evaporated to dryness at 60° C. with stirring. After pulverizing into powder, the powder P1 was placed in a container so that the thickness (deposition thickness) of the powder P1 was 0.1 mm, and subjected to heat treatment at 450° C. for 1 hour under nitrogen gas flow. The catalyst thus produced is called "Comparative Example 2". In addition, the temperature was set to 450° C. in order to thermally decompose all the platinum complexes including the unadsorbed platinum complex.
下記表１に、実施例１～７と比較例１～２の白金担持カーボン触媒の白金の平均粒子径と標準偏差を示す。 Table 1 below shows the average particle size and standard deviation of platinum in the platinum-supported carbon catalysts of Examples 1 to 7 and Comparative Examples 1 and 2.
　　表１
Figure JPOXMLDOC01-appb-I000001
Table 1
Figure JPOXMLDOC01-appb-I000001
＜ジニトロジアンミン白金硝酸溶液の彩度a＊の測定＞
溶液Ｓ１乃至Ｓ２の各々が含んでいる白金錯体について、Ｌ＊ａ＊ｂ＊表色系における彩度a＊の測定を行った。この測定は、日本電色工業株式会社製の透過色測定器（ＴＺ６０００）を用いて、以下のようにして行った。 <Measurement of chroma a* of dinitrodiammineplatinum nitric acid solution>
The chroma a * in the L * a * b * color system was measured for the platinum complex contained in each of the solutions S1 to S2. This measurement was performed as follows using a transmission color measuring instrument (TZ6000) manufactured by Nippon Denshoku Industries Co., Ltd.
まず、溶液Ｓ１を、白金濃度で１ｗｔ％となるように純水を用いて希釈し、測定用試料とした。光源はＤ６５、視野は２度とし、試料を物理長１０ｍｍの石英セル中に入れ、透過光のＬ＊ａ＊ｂ＊の値を測定した。 First, the solution S1 was diluted with pure water so that the platinum concentration was 1 wt %, and used as a sample for measurement. The light source was D65, the field of view was 2 degrees, the sample was placed in a quartz cell with a physical length of 10 mm, and the L * a * b * values of transmitted light were measured.
表１に示す通り、実施例１～実施例７に使用した白金溶液Ｓ１の彩度a＊は、３０であった。他方、比較例１、比較例２に使用した白金溶液Ｓ２の彩度a＊は７であった。 As shown in Table 1, the chroma a * of the platinum solution S1 used in Examples 1 to 7 was 30. On the other hand, the platinum solution S2 used in Comparative Examples 1 and 2 had a saturation a * of 7.
上記表１の比較例１では、白金吸着率が低く、好ましくない。 In Comparative Example 1 in Table 1 above, the platinum adsorption rate is low, which is not preferable.
比較例２では、所望の粒径より大きい白金粒径となっており、好ましくない。 In Comparative Example 2, the platinum particle size is larger than the desired particle size, which is not preferable.
上記表１から分かるように、実施例１～実施例７に係る触媒は、高い白金吸着率となっている。また、層厚を変更することで、触媒粒子径は２～５ｎｍの中の特定の大きさに調整出来ている。即ち、これらの結果から、本製造方法で触媒を製造することにより、効率的に高分散形の白金触媒を製造できることができることが示唆された。 As can be seen from Table 1 above, the catalysts according to Examples 1 to 7 have high platinum adsorption rates. Further, by changing the layer thickness, the catalyst particle diameter can be adjusted to a specific size within 2 to 5 nm. In other words, these results suggest that a highly dispersed platinum catalyst can be efficiently produced by producing a catalyst by this production method.
＜触媒粒子の金属表面積の測定＞
実施例３の触媒粒子の金属表面積（金属分散度）は、ＣＯ吸着法によって測定した。具体的には、金属分散度測定装置（ＢＥＬ－ＭＥＴＡＬ－３　日本ベル製）を用い、２５ｍｇの触媒粒子を１３０℃でヘリウム、水素、ヘリウムの順に流通ガスで前処理を施した後、５０℃でヘリウムをキャリアガスとしてＣＯをパルス状に供給し、排出ガス中のＣＯ量が一定になるまでのパルス数から吸着ＣＯ量を計算して、触媒粒子の金属表面積を求めた。実施例３の金属表面積は１１８ｍ２/ｇであり、一般的に求められる水準以上の金属表面積を有していた。 <Measurement of metal surface area of catalyst particles>
The metal surface area (metal dispersity) of the catalyst particles of Example 3 was measured by the CO adsorption method. Specifically, using a metal dispersion measuring device (BEL-METAL-3 manufactured by Bell Japan), 25 mg of catalyst particles were pretreated at 130 ° C. with helium, hydrogen, and helium in this order, and then heated to 50 ° C. The amount of adsorbed CO was calculated from the number of pulses until the amount of CO in the exhaust gas became constant, and the metal surface area of the catalyst particles was obtained. The metal surface area of Example 3 was 118 m 2 /g, which is higher than the level generally required.
＜ＴＥＭ像＞
実施例３のＴＥＭ像を図３に示す。ＴＥＭ像から、３ｎｍ程度の触媒粒子が高分散に担持されていることが分かる。 <TEM image>
A TEM image of Example 3 is shown in FIG. From the TEM image, it can be seen that catalyst particles of about 3 nm are supported in a highly dispersed manner.
＜電気化学的評価＞
燃料電池用電極触媒としての性能を評価するために、実施例３の酸素還元反応（ＯＲＲ）活性を、ビー・エー・エス製ポテンショガルバノスタットを用いて回転電極法によって評価した。実施例３及びパーフルオロスルホン酸分散液を２－プロパノール及び水の混合溶媒に分散させて、触媒インクを調製した。前記調整した触媒インクをガラス状カーボン（直径６ｍｍ）に、白金量が１８μｇ/ｃｍ２になるように塗布し、測定用電極を作製した。作製した測定用電極を窒素ガス飽和した２５℃、０．１ｍｏｌ/Ｌ過塩素酸に浸漬し、参照電極に可逆水素電極（ＲＨＥ）、対極に白金線を使用し、電位範囲を０．０５Ｖ～１．２Ｖ（ｖｓ．ＲＨＥ）、電位掃引速度５０ｍＶ/ｓｅｃでサイクリックボルタモグラムを測定した。得られたサイクリックボルタモグラムの水素脱離波から、ＥＣＳＡ（電気化学的活性表面積）を算出した。その後、セル内に酸素ガスを導入し、酸素ガス飽和雰囲気下で、測定用電極を１６００ｒｐｍで回転させながら、電位を０．０５Ｖ～１．２Ｖ（ｖｓ．ＲＨＥ）、電位掃引速度１０ｍＶ/ｓｅｃで分極曲線を測定した。得られた分極曲線から、０．９Ｖの酸素還元電流値（I）および拡散限界電流値として０．４Ｖの酸素還元電流値(Id)から、下式にて酸素の拡散影響を排除した活性化支配電流値（Ik）を算出した。
Ik=(Id・I)/(Id-I)
この活性化支配電流値（Ik）をＥＣＳＡで除することで比活性を、前記ガラス状カーボン電極上の白金重量で除することで質量活性を算出した。触媒Ｃ３のＥＣＳＡは６７．８ｍ２/ｇであり、比活性及び質量活性はそれぞれ１７３μＡ/ｃｍ２、１１８Ａ/ｇであり、一般的に求められる水準以上の触媒性能を示した。従って、本製造方法で製造した触媒は、燃料電池用電極触媒として使用できる。 <Electrochemical evaluation>
In order to evaluate the performance as a fuel cell electrode catalyst, the oxygen reduction reaction (ORR) activity of Example 3 was evaluated by the rotating electrode method using a BAS potentiogalvanostat. A catalyst ink was prepared by dispersing Example 3 and the perfluorosulfonic acid dispersion in a mixed solvent of 2-propanol and water. The prepared catalyst ink was applied to glassy carbon (diameter 6 mm) so that the amount of platinum was 18 μg/cm 2 to prepare an electrode for measurement. The prepared measurement electrode is immersed in nitrogen gas-saturated 25 ° C., 0.1 mol / L perchloric acid, a reversible hydrogen electrode (RHE) is used as the reference electrode, a platinum wire is used as the counter electrode, and the potential range is 0.05 V ~ A cyclic voltammogram was measured at 1.2 V (vs. RHE) and a potential sweep rate of 50 mV/sec. ECSA (electrochemically active surface area) was calculated from the hydrogen desorption wave of the obtained cyclic voltammogram. After that, oxygen gas is introduced into the cell, and in an atmosphere saturated with oxygen gas, while rotating the measuring electrode at 1600 rpm, the potential is 0.05 V to 1.2 V (vs.RHE) and the potential sweep rate is 10 mV/sec. Polarization curves were measured. From the obtained polarization curve, the oxygen reduction current value (I) of 0.9 V and the oxygen reduction current value (Id) of 0.4 V as the diffusion limit current value are calculated by the following formula, the activation excluding the diffusion effect of oxygen The dominant current value (Ik) was calculated.
Ik=(Id・I)/(Id−I)
The specific activity was calculated by dividing this activation current value (Ik) by ECSA, and the mass activity was calculated by dividing the platinum weight on the glassy carbon electrode. The ECSA of Catalyst C3 was 67.8 m 2 /g, and the specific activity and mass activity were 173 μA/cm 2 and 118 A/g, respectively, indicating catalytic performance above the generally required level. Therefore, the catalyst produced by this production method can be used as an electrode catalyst for fuel cells.
本発明の製造方法で製造した触媒は、般的に求められる水準以上の触媒性能を示すので、例えば、燃料電池用電極の製造、使用業において利用可能である。 Since the catalyst produced by the production method of the present invention exhibits catalytic performance at or above the generally required level, it can be used, for example, in the production and use of fuel cell electrodes.

Claims (5)

  1. ジニトロジアンミン白金錯体又は化合物を硝酸水溶液に、白金換算で１００±２０ｇ／Ｌ、硝酸濃度で２２０±４０ｇ／Ｌになるように溶解させ、１００～１１０℃で１８～２４時間加熱することで前記ジニトロジアンミン白金を改変又は変成した白金錯体含有硝酸水溶液を得る工程と、
    担体カーボンブラックの水分散液と前記白金錯体含有硝酸水溶液を混合し、前記白金錯体を前記カーボンブラックの表面上に吸着させて前記白金錯体が吸着したカーボンブラック含有液を得る工程と、
    前記カーボンブラック含有液を濾過し、濾別された前記白金錯体が吸着したカーボンブラックを洗浄し、乾燥させて、前記カーボンブラックの表面上に前記白金錯体が吸着した粉末を得る工程と、
    前記白金錯体が吸着したカーボンブラック粉末を不活性ガスまたは窒素ガス雰囲気中、２８０℃～４００℃で熱分解することによる白金錯体の熱分解工程と、
    を含むことを特徴とする白金担持カーボン触媒の製造方法。     A dinitrodiammine platinum complex or compound is dissolved in an aqueous nitric acid solution to a platinum conversion of 100 ± 20 g / L and a nitric acid concentration of 220 ± 40 g / L, and the dinitro is heated at 100 to 110 ° C. for 18 to 24 hours. obtaining a platinum complex-containing nitric acid aqueous solution in which diammine platinum is modified or denatured;
    A step of mixing an aqueous dispersion of carrier carbon black and the platinum complex-containing nitric acid aqueous solution to adsorb the platinum complex on the surface of the carbon black to obtain a carbon black-containing liquid in which the platinum complex is adsorbed;
    A step of filtering the carbon black-containing liquid, washing and drying the filtered carbon black having the platinum complex adsorbed thereon, and obtaining a powder having the platinum complex adsorbed on the surface of the carbon black;
    A thermal decomposition step of the platinum complex by thermally decomposing the carbon black powder to which the platinum complex is adsorbed at 280 ° C. to 400 ° C. in an inert gas or nitrogen gas atmosphere;
    A method for producing a platinum-supported carbon catalyst, comprising:
  2. 改変又は変成した前記白金錯体含有硝酸水溶液は、当該水溶液を１ｗｔ％の白金濃度となるように純水で希釈した場合の水溶液のＬ＊ａ＊ｂ＊表色系における彩度a＊が２８～３５であることを特徴とする請求項１記載の白金担持カーボン触媒の製造方法。 The modified or denatured platinum complex-containing nitric acid aqueous solution has an L * a * b * saturation a * in the color system of the aqueous solution when the aqueous solution is diluted with pure water to a platinum concentration of 1 wt%. 35, the method for producing a platinum-supported carbon catalyst according to claim 1.
  3. 前記乾燥は、１８０℃～２３０℃の温度下で行われることを特徴とする請求項２記載の白金担持カーボン触媒の製造方法。 The method for producing a platinum-supported carbon catalyst according to claim 2, wherein the drying is performed at a temperature of 180°C to 230°C.
  4. 前記熱分解工程は、前記カーボンブラックの表面上に白金錯体が吸着した粉末を、適当な容器に、層厚（堆積厚）０．１ｍｍ～３０ｍｍの範囲に堆積させ、不活性ガスまたは窒素ガス雰囲気中、２８０℃～４００℃で前記白金錯体を熱分解することを特徴とする請求項２記載の白金担持カーボン触媒の製造方法。 In the thermal decomposition step, the powder having the platinum complex adsorbed on the surface of the carbon black is deposited in an appropriate container to a layer thickness (deposition thickness) in the range of 0.1 mm to 30 mm, and an inert gas or nitrogen gas atmosphere The method for producing a platinum-supported carbon catalyst according to claim 2, wherein the platinum complex is thermally decomposed at a temperature of 280°C to 400°C.
  5. 白金担持カーボン触媒中の白金担持量は、前記触媒の総重量当たり、５ｗｔ％～２０ｗｔ％に調整されることを特徴とする請求項１～４のいずれか一項記載の白金担持カーボン触媒の製造方法。 Manufacture of the platinum-supported carbon catalyst according to any one of claims 1 to 4, wherein the amount of platinum supported in the platinum-supported carbon catalyst is adjusted to 5 wt% to 20 wt% relative to the total weight of the catalyst. Method.
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