JP-7855223-B2 - Composite particles and methods for producing the same

Inventors

• 衣本 太郎
• ピエール・イブス・オル

Assignees

• 国立大学法人 大分大学

Dates

Publication Date

20260508

Application Date

20220420

Claims (5)

1. A composite particle comprising a first metal oxide particle and a second metal oxide particle, The particle size of the first metal oxide particle is smaller than the particle size of the second metal oxide particle. A plurality of the first metal oxide particles, in particle shape, cover at least a portion of the surface of the second metal oxide particles to form a corona shape, and the first metal oxide particles are epitaxially grown on the surface of the second metal oxide particles. The first metal oxide particles are metal oxide particles containing bismuth, ruthenium, and oxygen, and The second metal oxide particles are metal oxide particles containing bismuth, titanium, and oxygen, and It is for catalytic use. composite particles.
2. The composite particle according to claim 1, wherein the particle diameter of the first metal oxide particle is 1/2 or less of the particle diameter of the second metal oxide particle.
3. The composite particle according to claim 1, wherein the amount of the first metal oxide particles is 5.0 to 40 parts by mass per 100 parts by mass of the second metal oxide particles.
4. A method for producing composite particles according to any one of claims 1 to 3 , comprising the following steps: (i) preparing the second metal oxide particles, and (ii) preparing a mixed solution containing a source of each element constituting the first metal oxide particles, the second metal oxide particles, and a basic compound, and epitaxially growing the first metal oxide particles on the surface of the second metal oxide particles in the mixed solution.
5. The above step (i) includes a firing step at a temperature of 200°C or higher, and the above step (ii) and the steps up to the production of the composite particles do not include a firing step at a temperature of 200°C or higher. The manufacturing method according to claim 4 .

Description

This invention relates to composite particles and a method for producing them. Electrolysis of water (also known as "water electrolysis") is a technology known for producing hydrogen by using electrical energy to break down water. For example, as disclosed in Non-Patent Document 1, typical water electrolysis methods include alkaline water electrolysis and solid polymer water electrolysis. Both methods require two catalysts: one for generating hydrogen and another for generating oxygen. In particular, the energy loss (overpotential) involved in the oxygen generation reaction (oxygen evolution reaction) is relatively large, and therefore, minimizing energy loss is crucial. Furthermore, because the electrochemical conditions at the electrodes in the oxygen evolution reaction are extremely harsh, the electrode catalyst also requires durability. In solid polymer electrolyte water electrolysis systems, iridium oxide is known as a promising material as an electrode catalyst due to its durability and catalytic activity. However, iridium is scarce, which presents a challenge in terms of increasing the cost of water electrolysis. On the other hand, in the alkaline water electrolysis method, electrode catalysts that are relatively less expensive than iridium can be used as catalysts. Regarding this, numerous electrode catalysts that can be used in alkaline water electrolysis reactions have been reported. For example, Patent Document 1 discloses an oxygen evolution and oxygen reduction catalyst characterized by having a pyrochlore-type metal oxide as its main component, which contains aluminum, bismuth, ruthenium, and oxygen, and exhibits an oxygen ratio of 6.5 to 7.3 in TPR measurements. Furthermore, Patent Document 2 discloses an air electrode for an air secondary battery comprising an air electrode mixture containing a catalytic mixed powder. Here, the catalytic mixed powder in Patent Document 2 is an aggregate of mixed particles in which catalyst particles smaller than the core particles are combined with core particles. The core particles contain Ni, and the catalyst particles are formed from a pyrochlore-type metal oxide catalyst and are present on the surface of the core particles. Furthermore, Patent Document 3 discloses a catalyst in which a catalyst made of a metal or metal oxide is formed on the surface of compound particles via epitaxial bonding. More specifically, the catalyst of Patent Document 3 is characterized by having compound particles (1) having a metastable surface (1a) which is a surface with a metastable plane orientation, and a catalyst (2) made of a metal or metal oxide being formed on the metastable surface (1a) of the compound particle (1) in a state that inherits the atomic arrangement state of the metastable plane orientation. Furthermore, Patent Document 4 discloses fine particles on which a catalytic substance is uniformly supported on the surface. More specifically, the fine particles of Patent Document 4 are characterized in that a vacuum container having a polygonal internal cross-sectional shape is rotated with a rotation axis substantially perpendicular to the cross-section, and sputtering is performed while stirring or rotating the fine particles inside the vacuum container, thereby coating the surface of the fine particles with ultrafine particles or a thin film having a particle size smaller than the fine particles, and the ultrafine particles or the thin film consists of at least one of a metal catalyst, an oxide catalyst, and a composite catalyst. Japanese Patent Publication No. 2019-195775Japanese Patent Publication No. 2021-077563Japanese Patent Publication No. 2007-105652Japanese Patent Publication No. 2005-264297 Shigenori Mitsushima, Koichi Matsuzu, "Current Status and Challenges of Water Electrolysis Technology," Hydrogen Energy System, Vol. 36, No. 1, 2011, pp. 11-16. Figure 1 is a schematic diagram illustrating the unique structure of the composite particles of the present invention.Figure 2 is a schematic diagram illustrating the core-shell structure of a conventional composite particle.Figure 3 shows the X-ray diffraction patterns of the composite particle BRO-BTO and the BTO particle.Figure 4 is a scanning electron microscope image of BTO particles.Figure 5 is a scanning electron microscope image of the composite particle BRO-BTO.Figure 6 is a scanning electron microscope image of BTO particles.Figure 7 is a scanning electron microscope image of the composite particle BRO-BTO.Figure 8 is a scanning electron microscope image of the composite particle BRO-BTO.Figure 9 shows the polarization curves for Example 1 and Comparative Example 1.Figure 10 shows the results of Example 1 and Comparative Example 1 when electrolysis was performed at 1.6V, and the results of Comparative Example 2 when electrolysis was performed at 1.7V.Figure 11 shows the results of Example 1, Comparative Example 1, and Comparative Example 2 when electrolysis was performed at 1.7V.Figure 12 is a dia