Updated on 2025/06/05

写真a

 
TSUJI YUTA
 
Organization
Faculty of Engineering Sciences Department of Advanced Analytical Science for Materials and Devices Associate Professor
Center for Polymer Interface and Molecular Adhesion Science (Concurrent)
School of Engineering (Concurrent)
Interdisciplinary Graduate School of Engineering Sciences Department of Interdisciplinary Engineering Sciences(Concurrent)
Title
Associate Professor
Contact information
メールアドレス
Tel
0925837862
Profile
(1) I am engaged in the following research activities at the Institute of Integrated Science and Technology: Theoretical studies on catalytic reactions on metal oxide surfaces. Theoretical studies on adhesive interactions at the interface between adhesive resins and inorganic/metal materials. Theoretical studies on quantum interference phenomena in molecular wires. Informatics research for catalyst discovery. Crystal structure exploration using swarm intelligence. Catalyst activity control through composite anions. Electron state studies of electrides. Research on chemical graph theory. Research on stacked aromaticity. Research on catalytic informatics. Research on perovskite solar cells. Research on hydrogenation catalysts. Research on water electrolysis catalysts Research on organometallic structures Research on self-assembled monolayers (2) I am responsible for the following subjects in the Department of Integrated Fundamental Engineering at the Faculty of Engineering: Introduction to Integrated Fundamental Engineering, co-teaching, Kyushu University, Faculty of Engineering, 2022 academic year. Integrated Fundamental Informatics II, Kyushu University, Faculty of Engineering, 2023 academic year. Introduction to Integrated Engineering I, co-teaching, Kyushu University, Faculty of Engineering, 2023 academic year. Fusion Applied Informatics A, Department of Fusion Basic Engineering, Faculty of Engineering, Kyushu University, 2024-. (3) I am responsible for the following subject in the Graduate School of Integrated Sciences and Technology: Introduction to Integrated Sciences and Technology, co-teaching, Kyushu University, Graduate School of Integrated Sciences and Technology, 2023 academic year. Material Function Design Foundation Special Lecture II e, co-teaching, Kyushu University, Graduate School of Integrated Sciences and Technology, 2024 academic year. (4) In the laboratory, I provide guidance for master's thesis research for master's degree students and doctoral thesis research for doctoral degree students.
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Research Areas

  • Nanotechnology/Materials / Inorganic/coordination chemistry

  • Nanotechnology/Materials / Functional solid state chemistry

  • Nanotechnology/Materials / Fundamental physical chemistry

  • Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Electron device and electronic equipment

Degree

  • Ph.D. in Engineering

Research History

  • Kyushu University Faculty of Engineering Sciences Associate Professor 

    2022.3 - Present

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    Country:Japan

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  • Kyushu University Institute for Materials Chemistry and Engineering Assistant Professor 

    2018.1 - 2022.2

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  • コーネル大学博士研究員(2013年5月~2016年3月)   

Research Interests・Research Keywords

  • Research theme: Theoretical study on Metal Organic Frameworks

    Keyword: Metal Organic Frameworks

    Research period: 2024.2

  • Research theme: Molecular orbital

    Keyword: Molecular orbital

    Research period: 2024

  • Research theme: Molecular electronics

    Keyword: Molecular electronics

    Research period: 2024

  • Research theme: Conductivity

    Keyword: Conductivity

    Research period: 2024

  • Research theme: Band calculation

    Keyword: Band calculation

    Research period: 2024

  • Research theme: Electride

    Keyword: Electride

    Research period: 2024

  • Research theme: First-principles calculation

    Keyword: First-principles calculation

    Research period: 2024

  • Research theme: Surface science

    Keyword: Surface science

    Research period: 2024

  • Research theme: Catalysis

    Keyword: Catalysis

    Research period: 2024

  • Research theme: Quantum chemistry

    Keyword: Quantum chemistry

    Research period: 2024

  • Research theme: Adhesion

    Keyword: Adhesion

    Research period: 2024

  • Research theme: Theoretical study on thermophysical properties of metal complexes

    Keyword: metal complexes

    Research period: 2023.7

  • Research theme: Theoretical study on copper surface adhesion

    Keyword: copper surface

    Research period: 2023.6

  • Research theme: Theoretical study on the phenomenon of fuel cell aging process

    Keyword: aging process

    Research period: 2023.6

  • Research theme: Theoretical study on water electrolysis reaction

    Keyword: water electrolysis reaction

    Research period: 2023.4

  • Research theme: Theoretical study on adhesion of graphene

    Keyword: graphene

    Research period: 2023.1

  • Research theme: Theoretical study on stacked aromaticity

    Keyword: Aromatic, pi-conjugated

    Research period: 2022.10

  • Research theme: Theoretical Study on Methane Dry Reforming

    Keyword: Dry Reforming

    Research period: 2022.7

  • Research theme: Theoretical study on self-assembled monolayers

    Keyword: self-assembled monolayers

    Research period: 2022.4

  • Research theme: Theoretical study on perovskite solar cells

    Keyword: Perovskite, solar cells

    Research period: 2022.4

  • Research theme: Theoretical study on hydrogenation catalysts

    Keyword: hydrogenation catalysts

    Research period: 2022.4

  • Research theme: Theoretical study on non-oxidative methane coupling reaction

    Keyword: non-oxidative methane coupling

    Research period: 2022.4

  • Research theme: Electronic Origin of Catalytic Activity of TiH2 for Ammonia Synthesis

    Keyword: catalysis, ammonia, titanium

    Research period: 2019.7 - 2021.1

  • Research theme: Mixed-Anion Control of C–H Bond Activation of Methane on the IrO2 Surface

    Keyword: methane, catalysis, IrO2

    Research period: 2019.4 - 2020.6

  • Research theme: Theoretical study on catalytic reactions on mixed anion compounds

    Keyword: metal oxide, mixed anion, methane, density functional theory, catalyst

    Research period: 2019.4

  • Research theme: Exploration for New Electride Materials

    Keyword: Electrides, Database, Density Functional Theory, Band Calculation

    Research period: 2018.6

  • Research theme: Crystal structure search using swarm intelligence

    Keyword: Crystal structure search, swarm intelligence, density functional theory, band calculation, electride

    Research period: 2018.5

  • Research theme: Informatics study for the search for catalysts

    Keyword: informatics, methane, density functional theory, metal surfaces

    Research period: 2018.1

  • Research theme: Theoretical study on catalytic reactions on metal oxide surfaces

    Keyword: metal oxide, methane, density functional theory, catalyst

    Research period: 2018.1

  • Research theme: Theoretical study on adhesion interaction at the interface between adhesive resin and h-BN

    Keyword: epoxy resin, h-BN, adhesion, density functional theory

    Research period: 2018.1

  • Research theme: Theoretical study on adhesion interaction at the interface between adhesive resin and metals

    Keyword: epoxy resin, gold, adhesion, density functional theory

    Research period: 2018.1

  • Research theme: Theoretical study on quantum interference in molecular wires

    Keyword: molecular wire, conductance, quantum interference, molecular electronics

    Research period: 2018.1

  • Research theme: Graph Theoretic Study on Molecular Conductance

    Keyword: Graph Theory, Conductance, Adjacency Matrix, Green's Function

    Research period: 2017.12

  • Research theme: Theoretical Study on Catalytic Reactions on Metal-Cluster/Metal Oxide Interface

    Keyword: Cerium Oxide, Ni cluster, methane, C-H activation

    Research period: 2017.11

Awards

  • 2023年度(第4回)理論化学会奨励賞

    2023.5   理論化学会   The 4th Annual (2023) Theoretical Chemistry Society Encouragement Award

  • The 4th Annual (2023) Theoretical Chemistry Society Encouragement Award

    2023.5   Japan Society of Theoretical Chemistry   化学結合のトポロジーに基づいた物性の理解

    Yuta Tsuji

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  • 第15回(2022年度)分子科学会奨励賞

    2022.9   分子科学会   The 15th Annual (2022) Molecular Science Society Encouragement Award.

  • The 15th Annual (2022) Molecular Science Society Encouragement Award.

    2022.9   Japan Society for Molecular Science   分子科学的視点に基づく表面反応の理論的研究

    Yuta Tsuji

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  • 第11回新化学技術研究奨励賞

    2022.6   新化学技術推進協会   The 11th Annual New Chemical Technology Research Encouragement Award

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Papers

  • Oxidative Addition of Methane and Reductive Elimination of Ethane and Hydrogen on Surfaces: From Pure Metals to Single Atom Alloys

    Yuta Tsuji, Masataka Yoshida, Takashi Kamachi, Kazunari Yoshizawa

    Journal of the American Chemical Society   144 ( 40 )   18650 - 18671   2022.10   ISSN:00027863 eISSN:15205126

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    Language:Others   Publishing type:Research paper (scientific journal)   Publisher:American Chemical Society  

    Oxidative addition of CH_4 to the catalyst surface produces CH_3 and H. If the CH_3 species generated on the surface couple with each other, reductive elimination of C_2H_6 may be achieved. Similarly, H’s could couple to form H_2. This is the outline of nonoxidative coupling ofmethane (NOCM). It is difficult to achieve this reaction on a typical Pt catalyst surface. This is because methane is overoxidized and coking occurs. In this study, the authors approach this problem from a molecular aspect, relying on organometallic or complex chemistry concepts. Diagrams obtained by extending the concepts of the Walsh diagram to surface reactions are used extensively. C–H bond activation, i.e., oxidative addition, and C–C and H–H bond formation, i.e., reductive elimination, on metal catalyst surfaces are thoroughly discussed from the point of view of orbital theory. The density functional theory method for structural optimization and accurate energy calculations and the extended Hückel method for detailed analysis of crystal orbital changes and interactions play complementary roles. Limitations of monometallic catalysts are noted. Therefore, a rational design of single atom alloy (SAA) catalysts is attempted. As a result, the effectiveness of the Pt_1/Au(111) SAA catalyst for NOCM is theoretically proposed. On such an SAA surface, one would expect to find a single Pt monatomic site in a sea of inert Au atoms. This is desirable for both inhibiting overoxidation and promoting reductive elimination.

    DOI: 10.1021/jacs.2c08787

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    Repository Public URL: https://hdl.handle.net/2324/7160837

  • Toward Computational Screening of Bimetallic Alloys for Methane Activation: A Case Study of MgPt Alloy Reviewed

    Masataka Yoshida, Yuta Tsuji, Shoji Iguchi, Hikari Nishiguchi, Ichiro Yamanaka, Hideki Abe, Takashi Kamachi, Kazunari Yoshizawa

    ACS Catalysis   12 ( 15 )   9458 - 9472   2022.8   ISSN:2155-5435

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    Language:Others   Publishing type:Research paper (scientific journal)   Publisher:ACS Catalysis  

    CH4 is the main component of natural gas; there is a need for heterogeneous catalysts that can directly convert it into useful substances. On active metal surfaces, e.g., Pt surfaces, CH4 is sequentially dehydrogenated to CH or C. It is very difficult to obtain useful C2 products from them. We here present a catalytic informatics strategy with DFT calculations and databases to discover bimetallic alloy catalysts for selective methane coupling, which cannot be achieved with monometal catalysts. Considering two properties required for a methane conversion catalyst, i.e., reactivity and selectivity, alloy surfaces that allow the initial C–H bond cleavage reaction of methane to proceed and that stabilize CH2 and CH3 species more than CH and C species will be suitable catalysts for direct methane conversion. An exhaustive screening of alloys satisfying such conditions is carried out using density functional theory calculations. As a result, MgPt is predicted to be one of the most useful catalysts; on its surface, the activity of Pt is moderately suppressed due to Mg, and CH3 and CH2 species get more stable than CH and C species. The calculations predict that the C–C coupling reaction with the lowest activation barrier on the MgPt surface occurs for the pair of CH3 and CH2, producing the C2H5 adsorbed species; it becomes ethane if hydrogenated and ethylene if dehydrogenated. In addition, the optimal Mg/Pt ratio for the reaction is computationally explored, and it is found that the Mg/Pt ratio of 1:1 is the best. Eventually, experimental verification is carried out by actually synthesizing an alloy satisfying this ratio; the nonoxidative coupling reaction of methane molecules is tested in the presence of the MgPt catalyst, and the formation of C2 hydrocarbons as primary products is confirmed.

    DOI: 10.1021/acscatal.2c01601

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  • Theoretical Study on the Contribution of Interfacial Functional Groups to the Adhesive Interaction between Epoxy Resins and Aluminum Surfaces Reviewed

    Shin Nakamura, Satoru Yamamoto, Yuta Tsuji, Keiji Tanaka, Kazunari Yoshizawa

    Langmuir   38 ( 21 )   6653 - 6664   2022.5   ISSN:0743-7463 eISSN:1520-5827

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    Language:Others   Publishing type:Research paper (scientific journal)   Publisher:American Chemical Society ({ACS})  

    To ensure the quality and reliability of products bonded by epoxy resin adhesives, elucidation of the microscopic adhesion mechanism is essential. The adhesive interaction and bonding strength between epoxy resins and hydroxylated γ-alumina (001) surfaces were investigated by using a combined molecular dynamics (MD) and density functional theory (DFT) study. The curing reaction of an epoxy resin consisting of diglycidyl ether of bisphenol A (DGEBA) and 4,4′-diaminodiphenyl sulfone (DDS) was simulated. The resin structure was divided into fragmentary structures to study the interaction of each functional group with the alumina surface using DFT calculations. From the characteristics of the adhesive structures and the calculated adhesion energies, it was found that the fragments forming hydrogen bonds with hydroxy groups on the alumina surface resulted in large adhesion energies. On the other hand, the fragments adsorbed on the alumina surface via dispersion interactions resulted in small adhesion energies. The adhesion forces evaluated from the Hellmann-Feynman force calculations indicated the significant contribution of the hydroxy groups and benzene ether moieties derived from DGEBA to the adhesive stress of the DGEBA/DDS epoxy resin. The direction of hydrogen bonding between the epoxy resin and the surface and the difference in geometry at the interface between the donor and acceptor of hydrogen bonding played a central role in maintaining the adhesive strength during the failure process of the adhesive interface.

    DOI: 10.1021/acs.langmuir.2c00529

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  • Topology Dictates Magnetic and Conductive Properties of a π-Stacked System: Insight into Possible Coexistence of Magnetic and Conductive Systems Reviewed

    Yuta Tsuji, Kazuki Okazawa, Keita Kurino, Kazunari Yoshizawa

    Journal of Physical Chemistry C   126 ( 6 )   3244 - 3256   2022.2   ISSN:1932-7447 eISSN:1932-7455

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    Language:Others   Publishing type:Research paper (scientific journal)   Publisher:American Chemical Society ({ACS})  

    In this paper, conductivity and magnetism in alternant hydrocarbons are discussed based on the topology of π-conjugated networks. In a molecular system with two spin centers, when the spins are separated by an odd-length walk, they interact antiferromagnetically with each other, but when they are separated by an even-length walk, they interact ferromagnetically. The conduction through the pathway connecting the two spins is expected to be effective for the former case, while ineffective for the latter case, but both show almost the same conductance in a magnetic system. This is because in the latter case, a feature in the electron transmission spectrum that causes destructive quantum interference is localized away from the Fermi level of the electrode and in a very narrow energy range, not affecting the zero-bias conductance. This tendency is further accentuated by generating weak coupling between the electrode surfaces and the spins to preserve the radical character of the molecule sandwiched between two electrodes. Although there is a challenge on how to stabilize radical molecules in a confined environment between electrodes, what is presented in this paper would give a clue on how to construct a system where magnetism and conductivity coexist.

    DOI: 10.1021/acs.jpcc.1c10502

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  • Theoretical Study on the Electronic Structure of Heavy Alkali-Metal Suboxides Reviewed

    Yuta Tsuji, Mikiya Hori, Kazunari Yoshizawa

    Inorganic chemistry   59 ( 2 )   1340 - 1354   2020.1

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    Language:English   Publishing type:Research paper (scientific journal)  

    On the metal-rich side of the phase diagrams of the Rb-O, Cs-O, and Rb-Cs-O systems, one can find a variety of stoichiometries: for example, Rb9O2, Rb6O, Cs4O, Cs7O, Cs11O3, RbCs11O3, and Rb7Cs11O3. They may be termed heavy alkali-metal suboxides. The application of the standard electron-counting scheme to these compounds suggests the presence of surplus electrons. This motivated us to carry out a theoretical study using the first-principles density functional theory (DFT) method. The structures of these compounds are based on either a formally cationic Rb9O2 or Cs11O3 cluster. The analyses of the partial charge density just below the Fermi level and the electron localization function (ELF) have revealed that there exist surplus electrons in interstitial regions of all the investigated suboxides so that the excess positive charge of the cluster can be compensated. Density of states (DOS) calculations suggest that all of the compounds are metallic. Therefore, the suboxides listed above may be regarded as a new family of metallic electrides, where coreless electrons reside in interstitial spaces and provide a conduction channel. Except for the phases of Rb9O2 and Cs11O3, the suboxide structures include both the cationic clusters and alkali-metal matrix. Several charge analyses indicate that the interstitial surplus-electron density can be assigned to the alkali-metal atoms in the metal matrix, leading to the possibility of the presence of negatively charged alkali-metal atoms, namely Rb- (rubidide) and Cs- (caeside) ions, a.k.a. alkalides. In Rb6O, Rb-, Rb0, and Rb+ are found to coexist in the same crystal structure. Similarly, in Cs7O, one can find the three types of Cs atoms. However, in Cs4O, no Cs0 state is identified. In the Rb-Cs-O ternary suboxides, Rb takes a negatively charged anion state or neutral state, while all of the Cs atoms are found to be cationic because they get involved in the Cs11O3 cluster and all the Rb atoms exist in interstitial sites. Orbital interactions between the clusters are analyzed to understand how the condensation of the clusters into the solid happens and how the electride nature ensues. These clusters are found to have some superatomic character.

    DOI: 10.1021/acs.inorgchem.9b03046

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Books

  • Comprehensive Inorganic Chemistry III (Third Edition)

    辻 雄太

    Elsevier  2023 

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    Total pages:7208  

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Presentations

  • Reactivity and Properties of Metal Clusters Invited International conference

    @Yuta Tsuji

    The 21st International Conference on Discrete Geometric Analysis for Materials Design  2021.9 

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    Event date: 2021.9

    Language:English   Presentation type:Oral presentation (general)  

    Venue:オンライン   Country:Japan  

  • 固体触媒反応の軌道理論 Invited

    @辻雄太

    凝縮系の理論化学2021  2021.3 

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    Event date: 2021.3

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:京都大学桂キャンパス   Country:Japan  

  • 量子化学計算による接着界面の理論的研究 Invited

    @辻雄太

    日本接着学会西部支部若手主催講演会  2021.1 

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    Event date: 2021.1

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:オンライン   Country:Japan  

  • 複合アニオンによる活性化エネルギー制御 Invited

    @辻雄太

    第二回複合アニオンウェブセミナー  2020.7 

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    Event date: 2020.7

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:オンライン   Country:Japan  

  • 新規エレクトライド物質の探索 Invited

    @辻雄太

    2019年度DV-Xα研究協会特別講演会  2019.12 

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    Event date: 2019.12

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:九州大学先導物質化学研究所   Country:Japan  

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MISC

  • Correction to: Ready-to-transfer two-dimensional materials using tunable adhesive force tapes (Nature Electronics, (2024), 7, 2, (119-130), 10.1038/s41928-024-01121-3)

    Nakatani M., Fukamachi S., Solís-Fernández P., Honda S., Kawahara K., Tsuji Y., Sumiya Y., Kuroki M., Li K., Liu Q., Lin Y.C., Uchida A., Oyama S., Ji H.G., Okada K., Suenaga K., Kawano Y., Yoshizawa K., Yasui A., Ago H.

    Nature Electronics   7 ( 4 )   2024.4

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    Publisher:Nature Electronics  

    Correction to: Nature Electronicshttps://doi.org/10.1038/s41928-024-01121-3, published online 9 February 2024. In the version of this article initially published, the label in Fig. 2f now reading “Ra = 1.4 nm” appeared as “Ra = 0.14 nm” and is now amended in the HTML and PDF versions of the article.

    DOI: 10.1038/s41928-024-01170-8

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  • 化学結合のトポロジーに基づいた物性の理解 : 奨励賞 受賞寄稿—Understanding of Physical Properties Based on the Topology of Chemical Bonds

    辻 雄太

    フロンティア : 理論化学会誌 = Frontier : journal of the Japan Society of Theoretical Chemistry   6 ( 1 )   巻頭1p,10 - 18   2024.1   ISSN:2758-4496

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    Language:Japanese   Publisher:[岡崎] : 理論化学会 = Japan Society of Theoretical Chemistry  

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    Other Link: https://ndlsearch.ndl.go.jp/books/R000000004-I033611278

  • Pathways to a Theoretical Approach to Exospheric-type Supra Ceramics

    辻雄太, 岩井宏樹

    セラミックス   59 ( 7 )   2024   ISSN:0009-031X

  • Concepts of Computational Approach to Explore Heterogeneous Catalysts for Direct Methane Conversion

    Yuta Tsuji, Masataka Yoshida, Kazunari Yoshizawa, Takashi Kamachi

    ChemCatChem   2023.5

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    Language:Others  

    DOI: 10.1002/cctc.202201488

  • 第5章第1節 メタン選択酸化の計算科学最前線

    塩田淑仁, 辻雄太, 吉澤一成

    メタンと二酸化炭素 ~ その触媒的化学変換技術の現状と展望 ~   2023.3

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    Language:Japanese  

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Industrial property rights

Patent   Number of applications: 1   Number of registrations: 0
Utility model   Number of applications: 0   Number of registrations: 0
Design   Number of applications: 0   Number of registrations: 0
Trademark   Number of applications: 0   Number of registrations: 0

Professional Memberships

  • The Catalysis Society of Japan

    2022.11 - Present

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  • The Adhesion Society of Japan

    2022.11 - Present

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  • The Chemical Society of Japan

  • Japan Society for Molecular Science

  • Society of Computer Chemistry,Japan

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Committee Memberships

  • 触媒学会西日本支部   Organizer   Domestic

    2024.5 - 2025.5   

  • 理論化学会   Organizer   Domestic

    2023.10 - 2025.9   

  • 日本化学会九州支部   日本化学会九州支部会計幹事  

    2023.4 - 2024.3   

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    Committee type:Academic society

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  • 日本接着学会   日本接着学会若手交流会幹事  

    2022.11 - Present   

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    Committee type:Academic society

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  • 日本接着学会   若手会委員   Domestic

    2022.10 - Present   

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Academic Activities

  • 座長

    第17回分子科学討論会2023  ( Japan ) 2023.9

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    Type:Competition, symposium, etc. 

  • Screening of academic papers

    Role(s): Peer review

    2023

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    Type:Peer review 

    Number of peer-reviewed articles in foreign language journals:120

  • 実行委員

    第45回ケモインフォマティクス討論会  ( Japan ) 2022.11

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    Type:Competition, symposium, etc. 

  • Screening of academic papers

    Role(s): Peer review

    2022

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    Type:Peer review 

    Number of peer-reviewed articles in foreign language journals:35

    Number of peer-reviewed articles in Japanese journals:2

  • 実行委員

    触媒インフォマティクス研究会2021  ( Japan ) 2021.10

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Other

  • We performed first-principles calculations to elucidate the mechanism of a tape that can transfer bimetallic materials and whose adhesiveness is greatly affected by UV light.

    2024.4

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    Graphene and other two-dimensional (2D) materials can be used to create electronic and optoelectronic devices. However, their development has been limited by the lack of effective large-area transfer processes. Here we report a transfer method that uses functional tapes with adhesive forces controlled by ultraviolet light. The adhesion of the tape is optimized for the transfer of monolayer graphene, providing a yield of over 99%. Once detached from the growth substrate, the graphene/tape stack enables easy transfer of graphene to the desired target substrate. The method can be used to transfer other 2D materials, including bilayer graphene, transition metal dichalcogenides, hexagonal boron nitride and stacked heterostructures. The solvent-free nature of the final release step facilitates transfer to various target substrates including flexible polymers, paper and three-dimensional surfaces. The tape/2D material stacks can also be cut into desired sizes and shapes, allowing site-selective device fabrication with reduced loss of 2D materials.

  • In this study, the adhesive interaction between gold and epoxy resin is theoretically investigated. These materials are important components of various electronic devices. The objectives of this study are (1) to elucidate a realistic adhesion mechanism between gold surfaces and epoxy resin, and (2) to obtain device design guidelines to achieve excellent adhesion and reduce adhesive breakdown, which causes device failure. Die pad surfaces used for chip mounting in microelectronics are usually formed by electrolytic plating technology. Ionic gold solutions such as K[Au(CN)2] are used in this technique. Our previous combined theoretical and experimental studies have shown that the counter anion of gold cations, CN-, has a high affinity for gold and tends to remain on the gold surface produced by plating. However, the content of cyano groups on the plated gold surface is still unknown. Therefore, we constructed a gold surface embedded with cyano groups with varying coverage by simulation. Ab initio density functional theory calculations were used to investigate the effect of different cyano group coverage on the adhesive strength. It was found that as the number of cyano groups on the surface increased, the direct interaction between the gold surface and the epoxy resin was prevented, but the hydroxyl and amino groups in the epoxy resin and hardener formed more hydrogen bonds with the cyano groups adsorbed on the surface. As a result, surfaces with intermediate cyano group coverage (approximately 33%) were found to provide the highest adhesive strength. The findings of this study are of great importance for industrial applications.

    2021.3

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    In this study, the adhesive interaction between gold and epoxy resin is theoretically investigated. These materials make up crucial components of a wide range of electronic devices. The objectives of the study are (1) to elucidate the bonding mechanism between epoxy resin and a realistic gold surface, and (2) to obtain a device-design guideline for superior adhesion, thus reducing the bonding breakage that may potentially cause device failure. Die pad surfaces used in chip attachment methods for microelectronics are usually fabricated using an electrolytic plating technique. This technique involves ionic gold solutions like K[Au(CN)2]. The combined theoretical and experimental studies previously carried out by the authors have revealed that the CN– counteranion of the gold cation has a high affinity for gold and is likely to remain on the realistic gold surface generated by plating. However, the cyano group content on the surface of the plated gold is still unknown. Therefore, gold surfaces embedded with cyano groups with various coverages are constructed. The effect of the varying coverage of the cyano groups on the adhesion strength is inspected using first-principles density functional theory calculations. As the number of cyano groups on the surface increases, the direct interaction between the gold surface and the epoxy resin is hindered, but the hydroxy and amino groups in the epoxy resin and hardener form more hydrogen bonds with the cyano groups adsorbed on the surface. It is found that the surface with intermediate cyano coverage (about 33%) yields the highest adhesive strength.

  • In this paper, the nature of the lowest-energy electrons is detailed. The orbital occupied by such electrons can be termed the lowest occupied molecular orbital (LOMO). There is a good correspondence between the Hückel method in chemistry and graph theory in mathematics; the molecular orbital, which chemists view as the distribution of an electron with a specific energy, is to mathematicians an algebraic entity, an eigenvector. The mathematical counterpart of LOMO is known as eigenvector centrality, a centrality measure characterizing nodes in networks. It may be instrumental in solving some problems in chemistry, and also it has implications for the challenge facing humanity today. This paper starts with a demonstration of the transmission of infectious disease in social networks, although it is unusual for a chemistry paper but may be a suitable example for understanding what the centrality (LOMO) is all about. The converged distribution of infected patients on the network coincides with the distribution of the LOMO of a molecule that shares the same network structure or topology. This is because the mathematical structures behind graph theory and quantum mechanics are common. Furthermore, the LOMO coefficient can be regarded as a manifestation of the centrality of atoms in an atomic assembly, indicating which atom plays the most important role in the assembly or which one has the greatest influence on the network of these atoms. Therefore, it is proposed that one can predict the binding energy of a metal atom to its cluster based on its LOMO coefficient. A possible improvement of the descriptor using a more sophisticated centrality measure is also discussed.

    2021.1

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    In this paper, the nature of the lowest-energy electrons is detailed. The orbital occupied by such electrons can be termed the lowest occupied molecular orbital (LOMO). There is a good correspondence between the Hückel method in chemistry and graph theory in mathematics; the molecular orbital, which chemists view as the distribution of an electron with a specific energy, is to mathematicians an algebraic entity, an eigenvector. The mathematical counterpart of LOMO is known as eigenvector centrality, a centrality measure characterizing nodes in networks. It may be instrumental in solving some problems in chemistry, and also it has implications for the challenge facing humanity today. This paper starts with a demonstration of the transmission of infectious disease in social networks, although it is unusual for a chemistry paper but may be a suitable example for understanding what the centrality (LOMO) is all about. The converged distribution of infected patients on the network coincides with the distribution of the LOMO of a molecule that shares the same network structure or topology. This is because the mathematical structures behind graph theory and quantum mechanics are common. Furthermore, the LOMO coefficient can be regarded as a manifestation of the centrality of atoms in an atomic assembly, indicating which atom plays the most important role in the assembly or which one has the greatest influence on the network of these atoms. Therefore, it is proposed that one can predict the binding energy of a metal atom to its cluster based on its LOMO coefficient. A possible improvement of the descriptor using a more sophisticated centrality measure is also discussed.

  • On the metal-rich side of the phase diagram of the Rb-O, Cs-O, and Rb-Cs-O systems, various stoichiometries can be found. For example, Rb9O2, Rb6O, Cs4O, Cs7O, Cs11O3, RbCs11O3, and Rb7Cs11O3. These are called heavy alkali metal oxides. In these compounds, the presence of surplus electrons is suggested. The first-principles density functional theory (DFT) method is used for the theoretical study. The structures of these compounds are based on cationic Rb9O2 or Cs11O3 clusters. The partial charge density and electron localization function (ELF) below the Fermi level are analyzed, and it is found that there are excess electrons in the crystalline pore region of all nitrides to compensate for the excess positive charge in the clusters. Density of state (DOS) calculations suggest that all compounds are metallic; with the exception of the phases of Rb9O2 and Cs11O3, the structures of the nitrides contain both cationic clusters and alkaline metal matrices. Several charge analyses have shown that surplus electron density can be assigned to alkali metal atoms in the metal matrix, leading to the possible presence of negatively charged alkali metal atoms, i.e., Rb- and Cs- ions (alkaloids); in Rb6O, Rb-, Rb0, and Rb+ have been found to coexist in the same crystal structure. Similarly, there are three types of Cs in Cs7O; in the Rb-Cs-O ternary oxide, Rb takes a negatively charged anionic or neutral state, but all Cs atoms are involved in the Cs11O3 cluster and are all cationic. The orbital interactions between the clusters are analyzed to determine how the condensation of the clusters into solids occurs and how the electrical properties of the clusters arise. These clusters have been found to have super-atomic properties.

    2020.1

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    On the metal-rich side of the phase diagrams of the Rb–O, Cs–O, and Rb–Cs–O systems, one can find a variety of stoichiometries: for example, Rb9O2, Rb6O, Cs4O, Cs7O, Cs11O3, RbCs11O3, and Rb7Cs11O3. They may be termed heavy alkali-metal suboxides. The application of the standard electron-counting scheme to these compounds suggests the presence of surplus electrons. This motivated us to carry out a theoretical study using the first-principles density functional theory (DFT) method. The structures of these compounds are based on either a formally cationic Rb9O2 or Cs11O3 cluster. The analyses of the partial charge density just below the Fermi level and the electron localization function (ELF) have revealed that there exist surplus electrons in interstitial regions of all the investigated suboxides so that the excess positive charge of the cluster can be compensated. Density of states (DOS) calculations suggest that all of the compounds are metallic. Therefore, the suboxides listed above may be regarded as a new family of metallic electrides, where coreless electrons reside in interstitial spaces and provide a conduction channel. Except for the phases of Rb9O2 and Cs11O3, the suboxide structures include both the cationic clusters and alkali-metal matrix. Several charge analyses indicate that the interstitial surplus-electron density can be assigned to the alkali-metal atoms in the metal matrix, leading to the possibility of the presence of negatively charged alkali-metal atoms, namely Rb– (rubidide) and Cs– (caeside) ions, a.k.a. alkalides. In Rb6O, Rb–, Rb0, and Rb+ are found to coexist in the same crystal structure. Similarly, in Cs7O, one can find the three types of Cs atoms. However, in Cs4O, no Cs0 state is identified. In the Rb–Cs–O ternary suboxides, Rb takes a negatively charged anion state or neutral state, while all of the Cs atoms are found to be cationic because they get involved in the Cs11O3 cluster and all the Rb atoms exist in interstitial sites. Orbital interactions between the clusters are analyzed to understand how the condensation of the clusters into the solid happens and how the electride nature ensues. These clusters are found to have some superatomic character.

  • Group 14 lithium compounds are called lithium tetrelides. Among them, Li17Tt4 (Tt = Si, Ge, Sn, Pb), which has the highest proportion of lithium, had extra electrons, which became clear from density functional calculation. Since the surplus electrons leave the nucleus and exist between the lattices, the electrons themselves are considered to be a kind of electronide (electride) that behaves as an anion. Analysis of the density of states and electron density revealed that the surplus electron wave function orbitally interacted with the surrounding ion wave function, and a novel coupling mode was found.

    2019.5

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    The lithium-richest phase in the binary Li-Tt system (Tt = Si, Ge, Sn, and Pb) has a stoichiometry of Li17Tt4. In the beginning of this paper, the structural complexity of Li17Tt4 is gradually stripped away using the concept of the M26 cluster found in γ-brass structures and a Tt-centered polyhedral representation. By means of the first-principles electronic structure calculations, which are followed by the analyses of the electron localization function (ELF), Bader charges, and spin density, we observe non-nuclear maxima of the ELF, electron density, and spin density. Since the electron densities off the atoms are confined in crystalline voids, separated from each other, and behaving as an anion, Li17Tt4 can be identified as a potential zero-dimensional electride. This finding agrees with a simple Zintl picture, which suggests a valence electron count of [(Li+)17(Tt4−)4·e−]. Detailed analyses on the band structures, the projected density of states, and crystal orbitals at the Γ point in the reciprocal space hint at the potential of forming a bond between the non-nuclear electron density and the neighboring atoms. Signatures of bonding and anti-bonding orbital interactions can be witnessed.

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Research Projects

  • ベイズ的機械学習を用いた高エントロピー酸化物触媒の最適化

    Grant number:25H01541  2025.4 - 2027.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Transformative Research Areas (A)

    辻 雄太

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    Grant type:Scientific research funding

  • 革新的水電解触媒の設計に向けたスケーリング則の軌道論的起源の解明

    Grant number:25K00065  2025.2 - 2028.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    辻 雄太

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    Grant type:Scientific research funding

    CiNii Research

  • 燃料電池等利用の飛躍的拡大に向けた共通課題解決型産学官連携研究開発事業/共通課題解決型基盤技術開発/固体高分子形燃料電池生産時のエージングプロセスの現象解明

    2023.6 - 2025.3

    日本 

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    Authorship:Coinvestigator(s) 

    Immediately after assembly, fuel cell (FC) stacks are dry and have inadequate proton passage, and the catalyst surfaces are covered with oxides and contaminants that reduce activity. Therefore, stacks cannot be shipped directly. Prior to shipment, the stacks are subjected to power generation testing equipment to increase their power output, whereby the water produced creates proton pathways and simultaneously removes contaminants from the catalyst surfaces. This process increases the output of the stack to a level where it can be shipped.

    The wetting process of this aging process will be elucidated by synchrotron X-ray imaging in combination with operando infrared spectroscopy, operando high-resolution X-ray absorption spectroscopy, and ab initio calculations of catalyst surface phenomena. By integrating these advanced measurement techniques with electrochemical measurement results, it will be possible to understand the phenomena of the aging process and take measures to address the needs of industry.

    FC-Cubic, which has been studying the aging process in collaboration with Toyota Motor Corporation, Honda Motor Company, Panasonic Corporation, Toshiba Energy Systems, and Toyota Central R&D Labs, will serve as the point of contact for this project. FC-Cubic is a research institute that combines academia and industry to conduct fundamental research on fuel cell development and is responsible for fundamental research on the aging process. The information obtained will help improve the aging process.

  • 燃料電池等利用の飛躍的拡大に向けた共通課題解決型産学官連携研究開発事業/共通課題解決型基盤技術開発/固体高分子形燃料電池生産時のエージングプロセスの現象解明

    2023 - 2024

    NEDO

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    Authorship:Coinvestigator(s)  Grant type:Contract research

  • 木下基礎科学研究基金助成事業/第一原理計算を用いた水電解のための電極触媒の理論的研究

    2023

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    Grant type:Donation

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Educational Activities

  • (1) I am responsible for the following subjects in the Department of Integrated Fundamental Engineering at the Faculty of Engineering:

    Introduction to Integrated Fundamental Engineering, co-teaching, Kyushu University, Department of Integrated Fundamental Engineering, 2022 academic year.
    Integrated Fundamental Informatics II, Kyushu University, Department of Integrated Fundamental Engineering, 2023 academic year.
    Introduction to Integrated Engineering I, co-teaching, Kyushu University, Department of Integrated Fundamental Engineering, 2023 academic year.
    Fusion Applied Informatics A, Department of Fusion Basic Engineering, Faculty of Engineering, Kyushu University, 2024-.
    (2) I am responsible for the following subject in the Graduate School of Integrated Sciences and Technology:
    Introduction to Integrated Sciences and Technology, co-teaching, Kyushu University, Graduate School of Integrated Sciences and Technology, 2023 academic year.
    Material Function Design Foundation Special Lecture II e, co-teaching, Kyushu University, Graduate School of Integrated Sciences and Technology, 2024 academic year.
    (3) In the laboratory, I provide guidance for master's thesis research for master's degree students and doctoral thesis research for doctoral degree students.

Class subject

  • 総合理工学修士実験

    2023.4 - 2024.3   Full year

  • 総合理工学修士演習

    2023.4 - 2024.3   Full year

  • 総合理工学修士演習

    2023.4 - 2024.3   Full year

  • 融合基礎情報学Ⅱ

    2023.4 - 2023.9   First semester

  • 総合理工学要論 id-ej(日本語)

    2023.4 - 2023.9   First semester

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FD Participation

  • 2021.1   Role:Participation   Title:先導物質化学研究所 2021年度第一回FD

    Organizer:[Undergraduate school/graduate school/graduate faculty]

  • 2021.1   Role:Participation   Title:先導物質化学研究所 2020年度第一回FD

    Organizer:[Undergraduate school/graduate school/graduate faculty]

  • 2020.1   Role:Participation   Title:先導物質化学研究所 2019年度第二回FD

    Organizer:[Undergraduate school/graduate school/graduate faculty]

  • 2019.5   Role:Participation   Title:先導物質化学研究所 2019年度第一回FD

    Organizer:[Undergraduate school/graduate school/graduate faculty]

  • 2019.1   Role:Moderator   Title:平成30年度第2回先導研FD研修会

    Organizer:[Undergraduate school/graduate school/graduate faculty]

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Visiting, concurrent, or part-time lecturers at other universities, institutions, etc.

  • 2024  福岡工業大学・生命環境化学科  Classification:Part-time lecturer  Domestic/International Classification:Japan 

    Semester, Day Time or Duration:前期、4月から9月まで

  • 2023  福岡工業大学・生命環境化学科  Classification:Part-time lecturer  Domestic/International Classification:Japan 

    Semester, Day Time or Duration:前期、4月から9月まで

  • 2022  福岡工業大学・生命環境化学科  Classification:Part-time lecturer  Domestic/International Classification:Japan 

    Semester, Day Time or Duration:前期、4月から9月まで

  • 2021  福岡工業大学・生命環境化学科  Classification:Part-time lecturer  Domestic/International Classification:Japan 

    Semester, Day Time or Duration:前期、4月から9月まで

  • 2020  福岡工業大学・生命環境化学科  Classification:Part-time lecturer  Domestic/International Classification:Japan 

    Semester, Day Time or Duration:前期、4月から9月まで

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Other educational activity and Special note

  • 2024  Special Affairs  We designed and implemented a class in which students could learn the basics of deep learning by writing and running their own programs using Google Colaboratory and Jupyter Notebook.

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    We designed and implemented a class in which students could learn the basics of deep learning by writing and running their own programs using Google Colaboratory and Jupyter Notebook.

  • 2023  Special Affairs  I designed and conducted a class where students could learn the fundamentals of data analysis and machine learning by writing their own programs and running them using tools like Google Colaboratory and Jupyter Notebook.

     詳細を見る

    I designed and conducted a class where students could learn the fundamentals of data analysis and machine learning by writing their own programs and running them using tools like Google Colaboratory and Jupyter Notebook.

Outline of Social Contribution and International Cooperation activities

  • Outreach activities include lectures for high school students, introduction of research through open campuses, and joint research with business and industry, as well as technical guidance and lectures.

Social Activities

  • 九州大学オープンキャンパスにて研究内容の紹介を行った。

    九州大学  九州大学伊都キャンパス  2023.8

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    Audience:General, Scientific, Company, Civic organization, Governmental agency

    Type:Other

  • 「計算科学および情報科学を活用した触媒材料探索」というタイトルで新化学技術推進協会  先端化学・材料技術部会 コンピュータケミストリ分科会 勉強会にて企業の研究者向けに講演を行いました。

    新化学技術推進協会  新化学技術推進協会  2023.5

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    Audience:General, Scientific, Company, Civic organization, Governmental agency

    Type:Seminar, workshop

  • 筑紫地区オープンキャンパスにて研究内容の紹介を行った。

    九州大学筑紫キャンパス  九州大学筑紫キャンパス  2023.5

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    Audience:General, Scientific, Company, Civic organization, Governmental agency

    Type:Other

  • 筑紫地区オープンキャンパスにて研究内容の紹介を行った。

    九州大学筑紫キャンパス  九州大学筑紫キャンパス  2022.5

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    Audience:General, Scientific, Company, Civic organization, Governmental agency

    Type:Other

  • 「量子力学を使った材料研究の最前線」という題目で 平成29年度第3回グローバルリーダー育成塾(福岡,2017年8月)にて大分県の高校生に対して大学での最先端の研究について紹介した

    大分県教育委員会グローバルリーダー育成塾  2017.8

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    Audience:Infants, Schoolchildren, Junior students, High school students

    Type:Seminar, workshop

Travel Abroad

  • 2017.3

    Staying countory name 1:United States   Staying institution name 1:サンノゼ州立大学

  • 2017.2

    Staying countory name 1:United States   Staying institution name 1:サンノゼ州立大学

  • 2015.8

    Staying countory name 1:Denmark   Staying institution name 1:コペンハーゲン大学

  • 2015.7

    Staying countory name 1:Denmark   Staying institution name 1:コペンハーゲン大学

  • 2013.5 - 2016.3

    Staying countory name 1:United States   Staying institution name 1:コーネル大学