研究者詳細 - 小川　智史

論文 - 小川　智史

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Synthesis of Ag nanoparticles prepared by a solution plasma method and application as a cocatalyst for photocatalytic reduction of carbon dioxide with water

Yoshida T., Yamamoto N., Mizutani T., Yamamoto M., Ogawa S., Yagi S., Nameki H., Yoshida H.

Catalysis Today 303 巻頁： 320 - 326 2018年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Catalysis Today

Silver nanoparticles (Ag NPs) were synthesized by a solution plasma method (SPM) in an aqueous solution of ammonia. Optical emission spectra of the plasma revealed that Ag NPs are fabricated with the sputtering of Ag rods as electrode by the produced energetic plasma particles such as H, OH and O radicals. In-situ optical absorption measurements of the solution during the discharge directly presented the concerted formation and aggregation processes of the Ag NPs, which controlled the size of Ag NPs. The synthesized Ag NPs were loaded on gallium oxide (Ga2O3) photocatalyst, and the photocatalytic activities of the obtained Ag loaded Ga2O3 (Ag/Ga2O3) samples were evaluated. Although the photocatalytic reaction proceeded over all the samples to produce CO, the CO production rates decreased with the reaction time. Measurements of DR UV–vis spectra and TEM images revealed that a part of the Ag NPs migrated and aggregated on the photocatalyst surface to become larger particles during the photocatalytic reaction, which would be related to the decrease of the photocatalytic activity. It was also found that the photoirradiation treatment on the prepared Ag/Ga2O3 sample before the use for the photocatalytic reaction improves the photocatalytic performance.

DOI： 10.1016/j.cattod.2017.08.047

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Characterization by synchrotron-radiation X-ray photoelectron spectroscopy of NO adsorption on Rh

Koda Y., Sumida H., Ogawa S., Tsukada C., Namatame H.

e-Journal of Surface Science and Nanotechnology 16 巻頁： 36 - 40 2018年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：e-Journal of Surface Science and Nanotechnology

Rhodium nanoparticles were deposited by the evaporation method on a silicon wafer. The process used He gas in a Rh evaporation chamber that was connected to the load-lock chamber of BL6N1 at Aichi Synchrotron Radiation Center (Aichi SR). NO gas was introduced into the evaporation chamber, and the deposited Rh nanoparticles were exposed to NO with and without an ambient atmosphere to study the effect of O2 on the electronic properties of the Rh nanoparticles and the behavior of NO molecules using synchrotron-radiation X-ray photoelectron spectroscopy (SR-XPS). The diameter of the Rh nanoparticles was estimated by transmission electron microscopy to be 2.7±0.6 nm. The XPS analysis indicates that the deposited Rh nanoparticles before NO exposure were in the metallic state. After exposure to NO, a part of the outermost surface of the Rh nanoparticles changed into Rh oxide, and NO molecules, atomic N and O species, and NO2 were detected. On the other hand, after exposure to NO in ambient air, the surface of the Rh nanoparticles was preferentially oxidized. In addition, a few NO molecules were adsorbed on the surface of Rh, and a small amount of the adsorbed NO that reacted with the surface oxygen turned into NO2.

DOI： 10.1380/ejssnt.2018.36

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Fabrication and in/ex situ XPS characterization of Rh nanoparticles

Koda Y., Sumida H., Ogawa S., Tsukada C., Namatame H.

e-Journal of Surface Science and Nanotechnology 15 巻頁： 50 - 54 2017年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：e-Journal of Surface Science and Nanotechnology

Rh nanoparticles have been fabricated by the evaporation method using the He gas in the Rh evaporation chamber, connected with the pre-evacuation chamber of BL6N1 at Aichi Synchrotron Radiation Center (Aichi SR). The electronic and geometric properties of the Rh nanoparticles have been verified without atmosphere exposure (in situ XPS) and after atmosphere exposure (ex situ XPS) using SR-XPS and TEM. The size of Rh nanoparticles is estimated 1.8±0.5 nm in diameter and deposited on a substrate. Judging from the result of the in situ XPS analysis with photon energy of 2.0 keV and 3.5 keV, the surface of the deposited Rh nanoparticles without atmosphere exposure is the metallic state. On the other side, the outermost surface changes into Rh oxide after atmosphere exposure even in a short time. For a long time atmosphere exposure moreover, the Rh oxide increases in the depth direction, and the deep area is in the higher oxidation state.

DOI： 10.1380/ejssnt.2017.50

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Hydrogen storage of binary nanoparticles composed of Mg and Pd 査読有り

Satoshi Ogawa, Taishi Fujimoto, Tsuyoshi Mizutani, Masahiro Ogawa, Naoki Uchiyama, Kazuo Kato, Toshiaki Ohta, Tomoko Yoshida, Shinya Yagi

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 40 巻 ( 35 ) 頁： 11895 - 11901 2015年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

The hydrogen storage property of the binary nanoparticles composed of Mg and Pd has been investigated by the QCM technique without the exposure to the air. The two types of nanopardcles have been fabricated by the gas evaporation method with the He gas. The one is the nanoparticles composed of the both Mg and Pd atoms (Mg-Pd NPs) and the other one is the composite of the Mg and Pd nanoparticles (Mg NPs-Pd NPs). Both the Mg-Pd NPs and the Mg NPs-Pd NPs can absorb the hydrogen under the room temperature and 1 atm of H-2 gas. However, the desorptions of the hydrogen have not been observed about the both samples. We have also studied the chemical state of the NPs by XPS and XAFS. The XAFS analyses have revealed that the MgH2 in the NPs can not be dehydrogenated at the room temperature even if the catalytic effect of the Pd. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijhydene.2015.04.087

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金属ナノ粒子を用いた水素吸蔵材料の分光学的手法による化学状態分析査読有り

小川智史, 内山直樹, 藤本大志, 金井友美, 八木伸也

日本金属学会誌 79 巻 ( 3 ) 頁： 118-123 2015年

XAFS and XPS study of hydro-/dehydrogenation reaction of Mg-Pd nanoparticles 査読有り

Ogawa, S; Fujimoto, T; Mizutani, T; Ogawa, M; Yogi, C; Kato, K; Ohta, T; Yoshida, T; Yagi, S

SURFACE AND INTERFACE ANALYSIS 46 巻 ( 12-13 ) 頁： 1143 - 1146 2014年12月

Influence of CO 2 and H 2 O on Air Oxidation of Mg Nanoparticles Studied by NEXAFS 査読有り

Journal of Surface Analysis 17 巻 ( 3 ) 頁： 319 - 323 2011年1月

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