|発明の名称 （英語）||Electrode catalyst|
|発明の概要（英語）||An electrode catalyst of the present invention contains an electrically conductive material carrying a metal or a metal oxide, and has an electrical conductivity at 30°C of 1 × 10-13 Scm-1 or more.|
Efficient use of biomass resources composed of carbon derived from carbon dioxide in the atmosphere is considered to be an effective way of reducing consumption of petroleum resources. In recent years, the production of bioalcohols such as ethanol and ethylene glycol which are used as fuels and raw materials has been industrialized. In the current industrial process, bioethanol is produced by alcoholic fermentation with enzymes using sugar or the like as a raw material, but this process has a problem of low carbon yield. On the other hand, a method of producing an alcohol by hydrogenation from a carboxylic acid abundantly contained in biomass has been attracting attention (for example, refer to Patent Document 1). Further, if energy can be extracted from the alcohol produced from the biomass as a raw material, a carbon neutral cycle can be realized using alcohol as an energy carrier.
Much research has been conducted on techniques regarding fuel cells for converting alcohols into carboxylic acids. In particular, Pt-Pd based catalysts have been attracting attention as electrode catalysts.
As a methanol oxidation catalyst, an alloy obtained by adding Pd to Pt has been known. A rule of thumb known as Vegard's Law has been known as an index for the structures of alloys. The rule of thumb is that the lattice constant of an alloy is an arithmetic mean of the lattice constants of component metals. For example, the lattice constant of PtxPd100-x, a(Pt(100-n)Pdn, 0 < n < 100), can be expressed by the following formula (1).
A method for producing Pt-Pd/C nanoparticles by a polyol method using ethylene glycol as a solvent and a reducing agent has been known (for example, refer to Non-Patent Document 1). In this production method, trisodium citrate serving as a complexing agent and a stabilizing agent, electrically conductive carbon black serving as a carrier, and palladium acetylacetonate [Pd(acac)2] and platinum acetylacetonate [Pt(acac)2] were dissolved in ethylene glycol which was also a reducing agent, and the resulting mixture was heated to reflux at 175°C for 6 hours to carry out a reduction reaction. After the completion of the reaction, the product is cooled to room temperature and then washed, and dried at 75°C for 12 hours to produce a sample. Pt-Pd in the obtained sample is in the form of nanoparticles having a diameter of about 4.7 nm to 5.2 nm. The nanoparticles have larger lattice constants obtained from the powder XRD pattern than those estimated from Vegard's law.
Further, a method for producing Pt3Pd1/C and Pt1Pd1/C using a carbon suspension obtained by suspending carbon black pretreated with 1M hydrochloric acid and 2M nitric acid in ethylene glycol has been known (for example, refer to Non-Patent Document 2). In this production method, carbon black pretreated with aqua regia is suspended in ethylene glycol to prepare a carbon suspension. While performing ultrasonic treatment, an aqueous solution obtained by dissolving H2PtCl6·6H2O and PdCl2 is added dropwise to the carbon suspension, and the mixed solution of the carbon suspension and the above aqueous solution is stirred. Then, an aqueous NaOH solution is added to the above mixed solution to adjust the pH of the mixed solution to 12 to 13. The pH-adjusted mixed solution is heated at 130°C for 3 hours to reduce metal ions, thereby obtaining Pt3Pd1/C and Pt1Pd1/C. The obtained Pt3Pd1/C and Pt1Pd1/C are washed with distilled water and dried under reduced pressure at 70°C for 8 hours when chloride ions are no longer detected in the AgNO3 solution (1 mol/L). The average primary particle size of Pt3Pd1/C obtained from a low resolution transmission electron microscope (TEM) image is 2.8 nm, and the average primary particle size of Pt1Pd1/C is 3.6 nm. The lattice constant obtained from the powder XRD pattern of Pt3Pd1/C is 3.916 × 10-10 m, and the lattice constant obtained from the powder XRD pattern of Pt1Pd1/C is 3.910 × 10-10 m. As described above, the lattice constant obtained from the Pt3Pd1/C powder XRD pattern and the lattice constant obtained from the Pt1Pd1/C powder XRD pattern are larger than the lattice constants estimated from Vegard's law.
[Patent Document 1] International Patent Publication No. 2017/154743
[Non-Patent Document 1] W. Wang et al., Electrochemistry Communications, 10, 1396-1399 (2008)
[Non-Patent Document 2] H. Li et al., J. Phys. Chem. C, 111, 5605-5617 (2007)
1. An electrode catalyst comprising an electrically conductive material carrying a metal or a metal oxide, and having an electrical conductivity at 30°C of 1 × 10-13 Scm-1 or more.
2. The electrode catalyst according to Claim 1, wherein said metal is a transition metal and said metal oxide is a transition metal oxide.
3. The electrode catalyst according to Claim 1 or 2, wherein said metal comprises any one or two or more members selected from the group consisting of Pd, Pt, Au, Ir, Ru, Rh, and Ag.
4. The electrode catalyst according to any one of Claims 1 to 3, comprising an alloy containing any one or two or more members selected from the group consisting of Pd, Pt, Ru, and Ir, and having an electrical conductivity at 30°C of 1 × 10-13 Scm-1 or more.
5. The electrode catalyst according to Claim 3 or 4, wherein said Pd and Pd are in a solid solution state.
6. The electrode catalyst according to Claim 4, wherein said alloy follows Vegard's law.
7. A method for producing a carrier-supported metal alloy which is a method for producing an alloy of an electrode catalyst comprising an electrically conductive material carrying a metal or a metal oxide, and having an electrical conductivity at 30°C of 1 × 10-13 Scm-1 or more, the method comprising:
(a) a step of dissolving one or two metal reagents in a solvent;
(b) a step of bringing an electrically conductive material into contact;
(c) a step of reacting said metal reagent with said electrically conductive material, and then reducing a product obtained by the reaction with a metal hydride reagent; and
(d) a step of treating the product reduced by said metal hydride reagent at 20°C to 500°C in the presence of hydrogen.
8. A method for producing ketones and carboxylic acids,
the method comprising a step of using an alcohol as a raw material and using an electrode catalyst comprising an electrically conductive material carrying a metal or a metal oxide and having an electrical conductivity at 30°C of 1 × 10-13 Scm-1 or more to carry out an electrochemical oxidation reaction of said alcohol.
9. A fuel cell comprising an anode, a cathode and an electrolyte,
the fuel cell that comprises an electrode catalyst on a surface or inside of the anode, or on the electrolyte side of the anode, and
directly generates electricity when alcohols are brought into contact with said electrode catalyst and electrochemically oxidized to produce ketones or carboxylic acids.
10. An energy recovery system for recovering surplus electric power energy, the system comprising:
(a) a container for storing carboxylic acids;
(b) a means for reducing carboxylic acids to alcohols using surplus electric power;
(c) a means for storing the obtained alcohols; and
(d) a means for oxidizing said alcohols to produce said carboxylic acids and generating electric power.
Contracting States: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
Extension States: BA ME
|参考情報 （研究プロジェクト等）||CREST Creation of Innovative Core Technology for Manufacture and Use of Energy Carriers from Renewable Energy AREA|
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