Kyushu University Academic Staff Educational and Research Activities Database
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Katsuro Hayashi Last modified date:2024.04.26

Professor / Functional Materials Chemistry (Applied Fine Chemistry)
Department of Applied Chemistry
Faculty of Engineering

Graduate School
Undergraduate School
Other Organization
Administration Post
Director of the Center for Future Chemistry

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 Reseacher Profiling Tool Kyushu University Pure
Academic Degree
Ph. D (Engineering)
Country of degree conferring institution (Overseas)
Yes Doctor
Field of Specialization
Solid State Chemistry, Physical Chemistry, Ceramic Materials
ORCID(Open Researcher and Contributor ID)
Total Priod of education and research career in the foreign country
Outline Activities
Prof. Hayashi’s group covers the field of Applied Inorganic Chemistry, including synthesis of novel functional ceramic materials, and fundamental researches based on solid state chemistry and physics. They are studying not only typical metal oxide-based ceramics but also novel mixed-anion compounds with nitride, hydride, and electride. Materials functions such as ionic conduction/exchange and dielectric/conductive properties are applied to development of energy storage and electronic devices. In particular, they are interested in materials that contribute to the development of innovative energy storage devices and their composites.

Research: Electroceramics, Novel Batteries, All Solid State Battery, Solid State Chemistry, Physical Chemistry of Solids
Education: Inorganic Chemistry, Inorganic Materials Chemistry, Inorganic Solid State Chemistry, Ceramic Engineering
Research Interests
  • Development of Novel Batteries (e.g. All Solid State Batteries)
    keyword : Sodium, Solid electrolyte, Oxide-based All Solid-State Battery, Air Battery
  • Development of Mixed Anion Compounds toward New Functionalities
    keyword : Oxyhydrides, Carbonitrides, Materials Process, Analysis
  • Electronic materials based on element strategy
    keyword : transparent conductor, nanoporous, element strategy, electrode, battery
Current and Past Project
  • Development of sodium ion batteries using elements with no resource constraints with the goal of achieving high energy density and long life.
    The lithium-ion battery, which was first commercialized in Japan, has the highest energy density of any practical storage battery and is therefore indispensable for the realization of GX technology. However, they require rare and toxic elements, and the price of lithium raw materials has been fluctuating wildly due to the uneven distribution of lithium resources. High-cost cobalt, nickel, and copper are also required. As the range of storage battery applications expands and efforts to address environmental and energy issues on a global scale become more important, the development of lithium-substitute storage batteries free from geopolitical risks and resource constraints is one of the most important issues in innovative GX technology. In this R&D, we will focus on sodium, which is the same family as lithium in the periodic table and has no resource constraints, and work on materials development, battery design, mechanism analysis, and computational science research for social implementation of the next-generation storage battery "sodium ion battery" that inherits the lithium-ion battery technology originated in Japan. In particular, Professor Hayashi's group will be responsible for the development of an all-solid-state oxide storage battery that inherits the features of the sodium ion battery.

Academic Activities
1. Hiroshi Kageyama, Katsuro Hayashi, Kazuhiko Maeda, J. Paul Attfield, Zenji Hiroi, James M. Rondinelli, Kenneth R. Poeppelmeier, Expanding frontiers in materials chemistry and physics with multiple anions, Nature Communications, 9, Article No. 772, 2018.02.
2. Katsuro Hayashi, Peter V. Sushko, Yasuhiro Hashimoto, Alexander L. Shluger, Hideo Hosono, Hydride Ions in Oxide Hosts Hidden by Hydroxide Ions, Nature Communications, 6, Article No. 4515, 2014.03, The true oxidation state of formally 'H(-)' ions incorporated in an oxide host is frequently discussed in connection with chemical shifts of (1)H nuclear magnetic resonance spectroscopy, as they can exhibit values typically attributed to H(+). Here we systematically investigate the link between geometrical structure and chemical shift of H(-) ions in an oxide host, mayenite, with a combination of experimental and ab initio approaches, in an attempt to resolve this issue. We demonstrate that the electron density near the hydrogen nucleus in an OH(-) ion (formally H(+) state) exceeds that in an H(-) ion. This behaviour is the opposite to that expected from formal valences. We deduce a relationship between the chemical shift of H(-) and the distance from the H(-) ion to the coordinating electropositive cation. This relationship is pivotal for resolving H(-) species that are masked by various states of H(+) ions.
3. Katsuro Hayashi, Kazunari Shima, Fumiaki Sugiyama, A mixed aqueous/aprotic sodium/air cell using a NASICON ceramic separator, Journal of the Electrochemical Society, 10.1149/2.067309jes, 160, 9, 2013.07, An aqueous (mixed aqueous/aprotic) Na-air cell is fabricated and its discharge properties are examined experimentally. This design is attractive because Na is not only more abundant and cheaper than Li, but also potentially advantageous for enhancing cell output. The theoretical energy density of the aqueous Na-air cell exceeds that of a Li one under conditions where precipitation of hydroxides in the aqueous electrolyte is not allowed. Na 3Zr2Si2PO12 (NASICON) ceramics, which has a Na+ ion conductivity of 2 × 10-3 S · cm-1 at 50°C, is used as a solid electrolyte separator in the Na-air cell. Involvement of O2 gas in the cell reaction is verified by changing cell voltage in the presence or absence of O2 flow through the aqueous electrolyte. The Na-air cell exhibits an electrochemical discharge of ∼600 mAh· g-1 and energy density of ∼1500 Wh· kg-1 based on the weights of reacted Na and H2O. Its maximum areal output power is 11 mW· cm -2 and depends on the thickness of the NASICON ceramic separator, the concentration of NaOH in the aqueous electrolyte and the type of cathode, suggesting that cell performance can be improved by optimization of these components..
4. Katsuro Hayashi, Peter V. Sushko, David Muñoz Ramo, Alexander L. Shluger, Satoshi Watauchi, Isao Tanaka, Satoru Matsuishi, Masahiro Hirano, Hideo Hosono, Nanoporous crystal 12CaO·Al2O3
A playground for studies of ultraviolet optical absorption of negative ions, Journal of Physical Chemistry B Materials, 10.1021/jp065793b, 111, 8, 1946-1956, 2007.03, A novel nanoporous material 12CaO·Al2O3 (C12A7) offers a possibility of incorporating large concentrations (>10 21 cm-3) of a wide range of extraframework anions inside its nanopores. We have investigated, both experimentally and theoretically, optical absorption associated with several types of such anions, including F-, OH-, O-, O2-, O2 2-, and O2 2-, and assigned their optical absorption bands. It is demonstrated that the chemical identity and concentration of extraframework anions can be controlled by an appropriate treatment of "as grown" C12A7. We also show that the position of the adsorption edge is, in turn, determined by the chemical identity of the extraframework species and can be varied in the range of ∼4-6 eV. We suggest that C12A7 is a unique host material, which can be used as a playground for studying negatively charged species that are unstable in other environments..
5. Satoru Matsuishi, Yoshitake Toda, Masashi Miyakawa, Katsuro Hayashi, Toshio Kamiya, Masahiro Hirano, Isao Tanaka, Hideo Hosono, High-density electron anions in a nanoporous single crystal
[Ca24Al28O64]4+ (4e-), Science, 10.1126/science.1083842, 301, 5633, 626-629, 2003.08, We removed ∼100% of clathrated oxygen ions from the crystallographic cages in a single crystal of 12CaO·7Al2O3, leading to the formation of high-density (∼2 x 1021 cm-3) electrons highly localized in the cages. The resulting electron forms a structure that we interpret as an F+ center and migrates throughout the crystal by hopping to a neighboring cage with conductivity ∼100 siemens per centimeter, demonstrating that the encaged electron behaves as an anion. The electron anions couple antiferromagnetically with each other, forming a diamagnetic pair or singlet bipolaron. The resulting [Ca24Al28O64]4+(4e-) may be regarded as a thermally and chemically stable single crystalline "electride"..
6. Katsuro Hayashi, Satoru Matsuishi, Naoto Ueda, Masahiro Hirano, Hideo Hosono, Maximum incorporation of oxygen radicals, O- and O2
-, into 12CaO·7Al2O3 with a nanoporous structure, Chemistry of Materials, 10.1021/cm020959g, 15, 9, 1851-1854, 2003.05, The effects of oxygen partial pressure (pO2) up to 400 atm on the generation of active oxygen radicals in 12CaO·7Al2O3 (C12A7) was examined using a hot isostatic pressing technique. Concentrations of superoxide (O2
-) and oxygen anion radicals (O-), which were analyzed from a combination of electron paramagnetic spin resonance (EPR) and Raman spectroscopy, increased with pO2. The total concentration of the radicals reached 1.7 × 1021 cm3, which is comparable to the theoretical maximum, confirmed that dominant radical incorporation process is O2- (cage) + O2 (atmosphere) → O- (cage) + O2
- (cage). The radical incorporated C12A7 has a large magnetic susceptibility that obeys Curie's law down to 2.5 K without magnetic ordering, although a weak exchange interaction was suggested by the line narrowing of the EPR signal..
7. Katsuro Hayashi, Satoru Matsuishi, Toshio Kamiya, Masahiro Hirano, Hideo Hosono, Light-induced conversion of an insulating refractory oxide into a persistent electronic conductor, Nature, 10.1038/nature01053, 419, 6906, 462-465, 2002.10, Materials that are good electrical conductors are not in general optically transparent, yet a combination of high conductivity and transparency is desirable for many emerging opto-electronic applications. To this end, various transparent oxides composed of transition or post-transition metals (such as indium tin oxide) are rendered electrically conducting by ion doping. But such an approach does not work for the abundant transparent oxides of the main-group metals. Here we demonstrate a process by which the transparent insulating oxide 12CaO·7Al2O3 (refs 7-13) can be converted into an electrical conductor. H- ions are incorporated into the subnanometre-sized cages of the oxide by a thermal treatment in a hydrogen atmosphere; subsequent irradiation of the material with ultraviolet light results in a conductive state that persists after irradiation ceases. The photo-activated material exhibits moderate electrical conductivity (∼0.3 S cm-1) at room temperature, with visible light absorption losses of only one per cent for 200-nm-thick films. We suggest that this concept can be applied to other main-group metal oxides, for the direct optical writing of conducting wires in insulating transparent media and the formation of a high-density optical memory..
8. Katsuro Hayashi, Masahiro Hirano, Satoru Matsuishi, Hideo Hosono, Microporous crystal 12CaO·7Al2O3 encaging abundant O- radicals, Journal of the American Chemical Society, 10.1021/ja016112n, 124, 5, 738-739, 2002.02, Extremely high concentrations (>1020 cm-3) of active oxygenic radicals, O- and O2
-, have been created in the zeolitic crystal, 12CaO·7Al2O3 (C12A7), which can accommodate anions in its cavities. An increase in oxygen pressure and a decrease in water vapor pressure at high temperature enhance the formation of the radicals. The oxidation of Pt is observed on the surface of the material as a result of reaction with the active oxygens..
9. Katsuro Hayashi, Takahisa Yamamoto, Taketo Sakuma, Grain orientation dependence of the PTCR effect in niobium-doped barium titanate, Journal of the American Ceramic Society, 10.1111/j.1151-2916.1996.tb08780.x, 79, 6, 1669-1672, 1996.04, The positive temperature coefficient of resistivity (PTCR) effect is directly measured in single grain boundaries in 0.1-mol%-Nb-doped BaTiO3 with 1 mm coarse grains. The PTCR effect largely depends on grain boundary structure. Random grain boundaries exhibit the PTCR effect as in polycrystalline samples, but the PTCR effect does not appear in highly coherent boundaries such as small-angle boundaries, twin boundaries, and coincidence site lattice (CSL) boundaries with low ∑ values. For ∑= 3 boundaries, the resistance increase above the Curie temperature is a function of deviation angle. A small PTCR effect is observed in ∑ = 3 boundaries with a deviation angle of about 9° in contrast with ideal ∑ = 3 boundaries and boundaries with a deviation of about 4°..
1. 林 克郎, Chemistry of hydride ion and proton in anion-encaging crystals: Mayenite and apatite, Nonstoichiometric Compounds Ⅵ, 2016.09.
Membership in Academic Society
  • The American Ceramic Society
  • The Electrochemical Society of Japan
  • The Solid State Ionics Society of Japan
  • The Chemical Society of Japan
  • The Japan Society fo Applied Physics
  • The Japan Institute of Metals and Materials
  • The Ceramic Society of Japan
Educational Activities
Professor Hayashi is in charge of lectures mainly in the field of inorganic chemistry in basic education, undergraduate education, graduate education, and their international courses. Through the activities of the Japan Engineering Education Association and the Kyushu Engineering Education Association, he will also contribute to high school and university education from the perspective of Kyushu, as well as to entrance examinations and curricula in the Faculty of Engineering. As a researcher and educator, He will convey the interest and importance of inorganic materials and ceramics through lectures on traditional ceramics, cutting-edge industrial components and products, related resource and environmental issues, and solid state science combined with high school physics and chemistry in a way that is easy to understand.
Professional and Outreach Activities
Starting with activities at the Kyushu Engineering Association, we conduct educational activities that connect high schools, universities, society, and regions and the world..