KEIO RESEARCHERS INFORMATION SYSTEM

Academic Degrees 【 Display / hide 】

Academic Degrees 【 Display / hide 】

• 博士（理学）, The University of Tokyo, Coursework, 2024.03

Papers 【 Display / hide 】

Papers 【 Display / hide 】

• Role of Quasi-One-Dimensional B Chains in the Catalytic Properties of CuB/Cu(111)

  Nakashima T., Tsujikawa Y., Kondo T., Koitaya T., Matsuda I., Ando Y.

  Journal of Physical Chemistry C 130 ( 15 ) 5411 - 5417 2026.04

  ISSN  19327447

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  The electron deficiency of boron leads to rich polymorphism and a high degree of freedom in material design. This research focuses on the newly reported CuB/Cu(111) surface and elucidates its catalytic properties. To assess its catalytic activity, this research investigates elementary steps relevant to CO<inf>2</inf> hydrogenation─specifically hydrogen, oxygen, and formate adsorption on this surface─by using a combination of first-principles calculations (OpenMX) and machine learning potentials (Matlantis). Our calculations verify five key points: (i) charge transfer occurs from copper atoms to boron chains, (ii) hydrogen atoms are observed to be adsorbed along the boron chain, (iii) hydrogen hopping between boron-tops shows three-center two-electron bonding in the transition state, (iv) surface oxidation can disrupt the boron chains, and (v) boron chains promote the adsorption of formate. In conclusion, the unique boron chains in CuB/Cu(111) can play a key role in the catalytic reactivity of this surface.

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• Adhesion between a borophane sheet and a metal substrate by interface bonding

  Yamaguchi K., Yin H., Niibe M., Tang J., Miyamoto M., Tsujikawa Y., Sakurai H., Murano Y., Ozawa K., Horio M., Yamaura J.i., Kondo T., Matsuda I.

  Applied Surface Science Advances 31 2026.01

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  Boron deposited on transition metal substrates has been actively investigated as a system that exhibits a wide range of surface structures. However, the specific case of nickel substrates remains largely unexplored. Nickel boride is used as a tribological material with excellent wear resistance and as a catalyst for hydrogenation, and its synthesis methods, structure, and functionality are being vigorously investigated. In this study, borophane, a two-dimensional material composed of hydrogen and boron, was heated to 300 °C in contact with a nickel substrate. We found that, compared with that annealed at 100 °C, annealed at 300 °C had a color that shifted toward longer wavelengths, and no longer dissolved in the synthesis solvent. However, x-ray diffraction and Fourier-transform infrared spectroscopy revealed no significant differences between the borophane samples annealed at 100 and 300 °C. X-ray absorption spectroscopy and x-ray photoelectron spectroscopy revealed that the surface oxide of nickel was reduced by borophane, resulting in the formation of nickel boride. Furthermore, thermal desorption spectroscopy showed that hydrogen desorbed from borophane upon contact with nickel, revealing that the borophane–nickel interface consisted of nickel boride and boron oxide layers. These findings provide insight into the surface science of boron on transition metal substrates and for the development of functional materials using these systems.

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• Discovery of bicyclic borane molecule B14H26

  Zhang X., Fujino T., Ando Y., Tsujikawa Y., Wang T., Nakashima T., Sakurai H., Yamaguchi K., Horio M., Mori H., Yoshinobu J., Kondo T., Matsuda I.

  Communications Chemistry 8 ( 1 )  2025.12

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  The discovery of fullerene following the synthesis of graphene marked a paradigm shift in chemistry. Here, we report the discovery of biycycloborane, arising from the synthesis of borophane (hydrogen boride). Uniquely, this synthesis method involves a decomposition mechanism rather than traditional atom-by-atom assembly, marking an unique approach to constructing complex borane structures. The mass spectrometry unveiled that the stable molecule has a mass of 178 in atomic mass unit with a stoichiometry of B<inf>14</inf>H<inf>26</inf>. Optical spectra and simulations further evidenced its bicyclic structure, featuring fulvene-like heptagons or octagons. This borane molecule, analogous to cyclic hydrocarbons, adopts a unit configuration with a three-center two-electron (3c-2e) bonding, akin to diborane. The B<inf>14</inf>H<inf>26</inf> molecule has been historically anticipated as a distant descendant of the dodecahedron borane, but it was born from the hydrogen boride sheet with a non-symmorphic symmetry. The discovery of biycycloborane expands the frontiers of boron chemistry, promising advancements in boron-based nanomaterials and beyond.

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• Electronic structure of the YCrB4 crystal surface, studied by micro-focused photoemission spectroscopy

  Zhang X., Tsujikawa Y., Miyamoto M., Yamaguchi K., Niibe M., Nishio-Hamane D., Yuan M., Ozawa K., Horio M., Yubuta K., Kondo T., Matsuda I.

  Physical Review Materials 9 ( 9 )  2025.09

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  We have performed a comprehensive electronic characterization of the needle-like single crystal YCrB4 metal boride, prepared by cleavage, characterized using angle-resolved photoemission spectroscopy with a microfocused beam. Our findings reveal the three-dimensional (3D) band structure of YCrB4, with band dispersions closely aligning with the first-principles calculations, confirming it is a topologically trivial insulator with a narrow band gap. Furthermore, a new metallic surface band was observed after cleavage, likely due to a space charge layer of the electron accumulation type. This study highlights the pivotal role of surface phenomena in shaping the electronic structure of YCrB4 and provides insights into the interplay between bulk and surface states, offering a path for exploring its potential applications in surface-sensitive technologies.

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• Evaluating chemical states in a single microcrystal of chromium boride with the micro-focused ion and quantum beams

  Guan Y., Zhang X., Miyamoto M., Tsujikawa Y., Yubuta K., Horio M., Isshiki H., Yamaura J.i., Abukawa T., Komori F., Matsuda I.

  Solid State Sciences 161 2025.03

  ISSN  12932558

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  We present a series of procedures that prepared and analyzed chromium borides (Cr-B) microcrystals using a combination of micro-focused ion and quantum beam techniques. The chemical state analyses were carried out using micro-photoemission spectroscopy and structural analyses were performed using micro-reflection high-energy electron diffraction and single-crystal X-ray diffraction. This approach successfully identified the existence of CrB<inf>2</inf> and Cr<inf>2</inf>B<inf>3</inf> phases in a Cr-B microcrystal and also provided detailed chemical state evaluation of Cr<inf>2</inf>B<inf>3</inf> phase. Our integration of these techniques enabled to distinguish and evaluate micro-scale phases within complex materials, identifying different phases or unexpected secondary products of microcrystal.

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Courses Taught 【 Display / hide 】

Courses Taught 【 Display / hide 】

• LABORATORIES IN CHEMISTRY 1

  2026

• LABORATORY IN SCIENCE

  2026

• LABORATORY IN SCIENCE

  2025

• LABORATORIES IN CHEMISTRY 1

  2025