Fast ortho-to-para conversion of molecular hydrogen in chemisorption and matrix-isolation systems

Ueta, Hirokazu; Fukutani, Katsuyuki*; Yamakawa, Koichiro

Frontiers in Chemistry (Internet), 11, p.1258035_1 - 1258035_7, 2023/08

https://doi.org/10.3389/fchem.2023.1258035

Molecular hydrogen has two nuclear-spin modifications called and . Because of the symmetry restriction with respect to permutation of the two protons, the and isomers take only odd and even values of the rotational quantum number, respectively. The -to- conversion is promoted in condensed systems, to which the excess rotational energy and spin angular momentum are transferred. We review recent studies on fast -to- conversion of hydrogen in molecular chemisorption and matrix isolation systems, discussing the conversion mechanism as well as rotational-relaxation pathways.

Long and oriented graphene nanoribbon synthesis from well-ordered 10,10'-dibromo-9,9'-bianthracene monolayer on crystalline Au surfaces

Yano, Masahiro; Yasuda, Satoshi; Fukutani, Katsuyuki; Asaoka, Hidehito

RSC Advances (Internet), 13(21), p.14089 - 14096, 2023/05

https://doi.org/10.1039/D2RA07570A

Bottom-up synthesis on metal surfaces has attracted attention for the fabrication of graphene nanoribbons (GNRs) with atomically-precise chemical structures to realize novel electronic devices. However, control of length and orientation on surfaces during GNR synthesis is difficult, thus, achieving longer and aligned GNR growth is a significant challenge. Herein, we report GNR synthesis from a well-ordered dense monolayer on Au crystalline surfaces for long and oriented GNR growth. Scanning tunneling microscopy showed that 10,10'-dibromo-9,9'-bianthracene (DBBA) precursors deposited on Au(111) at room temperature self-assembled into a well-ordered dense monolayer, and the straight molecular wire structure was formed where Br atoms in each precursor were adjacent along the wire axis. The DBBAs in the monolayer were found to be hardly desorbed from the surface under subsequent heating and efficiently polymerize along with the molecular arrangement, resulting in more long and oriented GNR growth compared to the conventional growth method. The result is attributed to be suppression of random diffusion and desorption of the DBBAs on the Au surface during polymerization due to the densely-packed DBBA structure. Additionally, an investigation of the effect of the Au crystalline plane on the GNR growth revealed further anisotropic GNR growth on Au(100) compared to Au(111) due to the stronger interactions of DBBA with Au(100). These findings provide fundamental knowledge for controlling GNR growth from a well-ordered precursor monolayer to achieve more long and oriented GNRs.

Efficient hydrogen isotope separation by tunneling effect using graphene-based heterogeneous electrocatalysts in electrochemical hydrogen isotope pumping

Yasuda, Satoshi; Matsushima, Hisayoshi*; Harada, Kenji*; Tanii, Risako*; Terasawa, Tomoo; Yano, Masahiro; Asaoka, Hidehito; Gueriba, J. S.*; Dio, W. A.*; Fukutani, Katsuyuki

ACS Nano, 16(9), p.14362 - 14369, 2022/09

https://doi.org/10.1021/acsnano.2c04655

The fabrication of hydrogen isotope enrichment system is essential for the development of industrial, medical, life science, and nuclear fusion fields, therefore alternative enrichment techniques with high separation factor and economic feasibility have been still explored. Herein, we report the fabrication of heterogeneous electrode with layered structures consisting of palladium and graphene layers for polymer electrolyte membrane electrochemical hydrogen pumping for the hydrogen isotope enrichment. We demonstrated significant bias voltage dependence of hydrogen/deuterium (H/D) separation ability and its high H/D at lower bias voltage. Theoretical analysis also demonstrated that the observed high H/D at low bias voltage stems from hydrogen isotopes tunneling through atomically-thick graphene during the electrochemical reaction, and the bias dependent H/D results in a transition from the quantum tunneling regime to classical over- barrier regime for hydrogen isotopes transfer via the graphene. These findings provide new insight for a novel economical methodology of efficient hydrogen isotope enrichment.

Development of ultraslow, monochromatic, and mass-selected ion source toward measurement of hydrogen ion permeability of graphene

Terasawa, Tomoo; Fukutani, Katsuyuki; Yasuda, Satoshi; Asaoka, Hidehito

e-Journal of Surface Science and Nanotechnology (Internet), 20(4), p.196 - 201, 2022/07

https://doi.org/10.1380/ejssnt.2022-032

Graphene is a perfect impermeable membrane for gases but permeable to hydrogen ions. Hydrogen ion permeation shows the isotope effect, i.e., deuteron is slower than proton when permeating graphene. However, the permeation mechanism and the origin of the isotope effect are still unclear. Here, we propose a strategy to discuss the hydrogen ion permeation mechanism of graphene by developing an ion source with ultraslow, monochromatic, and mass-selected hydrogen ion beam. We employed a hemispherical monochromator and a Wien filter for the ion source to achieve the energy and mass resolutions of 0.39 eV and 1 atomic mass unit, respectively. The energetically sharp ion beam is expected to allow us to directly measure the permeability of graphene with high accuracy.

Repeatable photoinduced insulator-to-metal transition in yttrium oxyhydride epitaxial thin films

Komatsu, Yuya*; Shimizu, Ryota*; Sato, Ryuhei*; Wilde, M.*; Nishio, Kazunori*; Katase, Takayoshi*; Matsumura, Daiju; Saito, Hiroyuki*; Miyauchi, Masahiro*; Adelman, J. R.*; et al.

Chemistry of Materials, 34(8), p.3616 - 3623, 2022/04

https://doi.org/10.1021/acs.chemmater.1c03450

Quantitative hydrogen state analysis in the leached layer of soda-lime-silica glass by combination of nuclear reaction analysis and C-X-ray photoelectron spectroscopy

Suehara, Michinori*; Yamamoto, Yuichi*; Ogura, Shohei*; Fukutani, Katsuyuki

Journal of Non-Crystalline Solids, 574, p.121160_1 - 121160_4, 2021/12

https://doi.org/10.1016/j.jnoncrysol.2021.121160

Ortho-para conversion of molecularly chemisorbed H on Pd(210)

Ueta, Hirokazu; Fukutani, Katsuyuki

Vacuum and Surface Science, 64(9), p.430 - 434, 2021/09

https://doi.org/10.1380/vss.64.430

Epitaxial thin film growth of europium dihydride

Komatsu, Yuya*; Shimizu, Ryota*; Wilde, M.*; Kobayashi, Shigeru*; Sasahara, Yuki*; Nishio, Kazunori*; Shigematsu, Kei*; Otomo, Akira*; Fukutani, Katsuyuki; Hitosugi, Taro*

Crystal Growth & Design, 20(9), p.5903 - 5907, 2020/09

https://doi.org/10.1021/acs.cgd.0c00602

Hydrogenation and hydrogen diffusion at the anatase TiO(101) surface

Nagatsuka, Naoki*; Wilde, M.*; Fukutani, Katsuyuki

Journal of Chemical Physics, 152(7), p.074708_1 - 074708_6, 2020/02

https://doi.org/10.1063/1.5142776

Changes of RHEED intensity with hydrogen position on metal surface

Kawamura, Takaaki*; Fukutani, Katsuyuki

Surface Science, 688, p.7 - 13, 2019/10

https://doi.org/10.1016/j.susc.2019.05.005