Hydrogen absorption and diffusion behaviors in cube-shaped palladium nanoparticles revealed by ambient-pressure X-ray photoelectron spectroscopy

Tang, J.*; Seo, O.*; Rivera Rocabado, D. S.*; Koitaya, Takanori*; Yamamoto, Susumu*; Namba, Yusuke*; Song, C.*; Kim, J.*; Yoshigoe, Akitaka; Koyama, Michihisa*; et al.

Applied Surface Science, 587, p.152797_1 - 152797_8, 2022/06

https://doi.org/10.1016/j.apsusc.2022.152797

The hydrogen absorption and diffusion mechanisms on cube-shaped Pd nanoparticles (NPs) which are important hydrogen-storage materials were studied using X-ray photoelectron spectroscopy and DFT calculations. In the surface region, hydrogen absorption showed almost similar behavior regardless of the NPs size. It was found that the octahedral sites are more favorable than the tetrahedral sites for hydrogen occupation. We also clarified that the hydrogen atoms absorbing on the smaller-sized Pd NPs diffuse to the subsurface more actively because of the weakened Pd-H bond by the surface disordering, which plays an important role in hydrogen adsorption at a low H pressure.

Atomic arrangements of quasicrystal bilayer graphene; Interlayer distance expansion

Fukaya, Yuki; Zhao, Y.*; Kim, H.-W.*; Ahn, J.-R.*; Fukidome, Hirokazu*; Matsuda, Iwao*

Physical Review B, 104(18), p.L180202_1 - L180202_5, 2021/11

https://doi.org/10.1103/PhysRevB.104.L180202

no abstracts in English

Mass transport in the PdCu phase structures during hydrogen adsorption and absorption studied by XPS under hydrogen atmosphere

Tang, J.*; Yamamoto, Susumu*; Koitaya, Takanori*; Yoshigoe, Akitaka; Tokunaga, Takuma*; Mukai, Kozo*; Matsuda, Iwao*; Yoshinobu, Jun*

Applied Surface Science, 480, p.419 - 426, 2019/06

https://doi.org/10.1016/j.apsusc.2019.02.180

Mass transports during hydrogen adsorption and absorption processes of PdCu alloys that has advantages of higher hydrogen diffusivity and economically lower-cost than the other Pd-alloys were studied. The research was made with a comparison of the well-known ordered phase of the bcc structure (the B2 phase) and a mixed phase of the fcc and B2 structures. ultrahigh vacuum X-ray photoelectron spectroscopy and ambient pressure X-ray photoelectron spectroscopy using synchrotron radiation were carried out to trace the chemical states of the Pd and Cu atoms as a function of temperatures. It is elucidated that the initial adsorption and absorption processes were similar in the two phases, but a hydrogen diffusion rate to the bulk was higher in the ordered phase than in the mixed one. We found the dynamics of the Pd and Cu atoms during the hydrogen adsorption/absorption processes largely depend on temperature. In the hydrogen atmosphere, the Pd atoms segregate at the surface below 373 K and Cu atoms segregate at the surface above 373 K. The present results agree well with the previous theoretical calculations and, thus, provide appropriate inputs toward developments of the hydrogen permeation materials.

Asymmetric structure of germanene on an Al(111) surface studied by total-reflection high-energy positron diffraction

Fukaya, Yuki; Matsuda, Iwao*; Feng, B.*; Mochizuki, Izumi*; Hyodo, Toshio*; Shamoto, Shinichi

2D Materials (Internet), 3(3), p.035019_1 - 035019_7, 2016/09

https://doi.org/10.1088/2053-1583/3/3/035019

no abstracts in English

Construction of a car-borne survey system for measurement of dose rates in air; KURAMA-II, and its application

Tsuda, Shuichi; Yoshida, Tadayoshi; Nakahara, Yukio; Sato, Tetsuro; Seki, Akiyuki; Matsuda, Norihiro; Ando, Masaki; Takemiya, Hiroshi; Tanigaki, Minoru*; Takamiya, Koichi*; et al.

JAEA-Technology 2013-037, 54 Pages, 2013/10

JAEA-Technology-2013-037.pdf:4.94MB

JAEA has been performing dose rate mapping in air using a car-borne survey system KURAMA-II. The KURAMA system is a GPS-aided mobile radiation monitoring system that has been newly developed by Kyoto University Research Reactor Institute in response to the nuclear disaster. The KURAMA system is composed of an energy-compensated scintillation survey meter for measuring dose rate, electric device for controlling both the dose rates and the position data from a GPS module, a computer server for processing and analyzing data from KURAMA, and client PCs for providing for end users. The KURAMA-II has been improved in small-packaging, durability, and automated data transmission. In consequence, dose rate mapping in wide area has become possible in shorter period of time. This report describes the construction of KURAMA-II, its application and a suggestion of how to manage a large number of KURAMA-II.

Atomic and electronic structures of Si(111)- superstructure

Fukaya, Yuki; Kubo, Keisuke*; Hirahara, Toru*; Yamazaki, Shiro*; Choi, W. H.*; Yeom, H. W.*; Kawasuso, Atsuo; Hasegawa, Shuji*; Matsuda, Iwao*

e-Journal of Surface Science and Nanotechnology (Internet), 10, p.310 - 314, 2012/07

https://doi.org/10.1380/ejssnt.2012.310

no abstracts in English

Atomic structure of two-dimensional binary surface alloys; Si(111)- superstructure

Fukaya, Yuki; Matsuda, Iwao*; Hashimoto, Mie*; Kubo, Keisuke*; Hirahara, Toru*; Yamazaki, Shiro*; Choi, W. H.*; Yeom, H. W.*; Hasegawa, Shuji*; Kawasuso, Atsuo; et al.

Surface Science, 606(11-12), p.919 - 923, 2012/06

https://doi.org/10.1016/j.susc.2012.02.006

no abstracts in English

Electron compound nature in a surface atomic layer of a two-dimensional hexagonal lattice

Matsuda, Iwao*; Nakamura, Fumitaka*; Kubo, Keisuke*; Hirahara, Toru*; Yamazaki, Shiro*; Choi, W. H.*; Yeom, H. W.*; Narita, Hisashi*; Fukaya, Yuki; Hashimoto, Mie*; et al.

Physical Review B, 82(16), p.165330_1 - 165330_6, 2010/10

https://doi.org/10.1103/PhysRevB.82.165330

no abstracts in English

Atomic scale study of surface structures and phase transitions with reflection high-energy positron diffraction

Kawasuso, Atsuo; Fukaya, Yuki; Hashimoto, Mie; Ichimiya, Ayahiko; Narita, Hisashi*; Matsuda, Iwao*

Materials Science Forum, 607, p.94 - 98, 2008/11

Currently, we are performing the surface study with reflection high-energy positron diffraction (RHEPD). The advantage of this method is the appearance of total reflection of positrons at the first surface layer. In this talk, we will present the recent progress of our research on some unknown surface structures and phase transition mechanisms.

Structure determination of silicene on a Ag(111) surface using total-reflection high-energy positron diffraction

Fukaya, Yuki; Mochizuki, Izumi*; Maekawa, Masaki; Wada, Ken*; Hyodo, Toshio*; Matsuda, Iwao*; Kawasuso, Atsuo

no journal, , 

no abstracts in English