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4. Distinct variation of electronic states due to annealing in La$_{1.8}$Eu$_{0.2}$CuO$_4$ and Nd$_{2}$CuO$_4$

Author

Asano, Shun, Ishii, Kenji, Matsumura, Daiju, Tsuji, Takuya, Kudo, Kota, Taniguchi, Takanori, Saito, Shin, Sunohara, Toshiki, Kawamata, Takayuki, Koike, Yoji, and Fujita, Masaki

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Strongly Correlated Electrons
Abstract

We performed Cu {\it K}-edge X-ray absorption fine structure measurements on T'-type La$_{1.8}$Eu$_{0.2}$CuO$_4$ (LECO) and Nd$_2$CuO$_4$ (NCO) to investigate the variation in the electronic state associated with the emergence of superconductivity due to annealing. The X-ray absorption near-edge structure spectra of as-sintered (AS) LECO are quite similar to those of AS NCO, indicating that the ground state of AS T'-type LECO is a Mott insulator. We found a significant variation of the electronic state at the Cu sites in LECO due to annealing. The electron density after annealing ($n_{\rm AN}$) was evaluated for both superconducting LECO and non-superconducting NCO and found to be 0.40 and 0.05 electrons per Cu, respectively. In LECO but not in NCO, extended X-ray absorption fine structure analysis revealed a softening in the strength of the Cu-O bond in the CuO$_2$ plane due to annealing, which is consistent with the screening effect on phonons in the metallic state. Since the amounts of oxygen loss due to annealing ($\delta$) for LECO and NCO are comparable with each other, these results suggest distinct electron-doping processes in the two compounds. That electron-doping in NCO approximately follows the relation $n_{\rm AN}=2\delta$ can be understood if electrons are doped through oxygen deficiency, but the anneal-induced metallic nature and large $n_{\rm AN}$ of LECO suggest a variation of the electronic band structure causes self-doping of carriers. The origin of the difference in doping processes due to annealing is discussed in connection with the size of the charge transfer gap., Comment: 6 pages, 4 figures, 1 table

Published
2020
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7. Computational Discovery of Optimal Dopants for Nickel Iron Oxyhydroxide to Enhance OER Activity and Saline Water Compatibility

Author

Jung, Hyeonjung, primary, Song, Jihyeon, additional, Lee, Yechan, additional, Jung, Han Sol, additional, Noh, Kyung-Jong, additional, Im, Hyeonae, additional, Lee, Yoojin, additional, Kim, Tae Yong, additional, Seo, Okkyun, additional, Watanabe, Takeshi, additional, Rosantha Kumara, Loku Singgappulige, additional, Matsumura, Daiju, additional, Park, Sangmin, additional, and Han, Jeong Woo, additional

Published
2024
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8. Ce-doping and reduction annealing effects on electronic states in Pr$_{2-x}$Ce$_{x}$CuO$_4$ studied by Cu ${K}$-edge X-ray absorption spectroscopy

Author

Asano, Shun, Ishii, Kenji, Matsumura, Daiju, Tsuji, Takuya, Ina, Toshiaki, Suzuki, Kensuke M., and Fujita, Masaki

Subjects
Condensed Matter - Superconductivity
Abstract

We investigated Ce-substitution and reduction annealing effects on the electronic states at copper sites by Cu ${K}$-edge x-ray absorption near-edge structure measurements in Pr$_{2-x}$Ce$_x$CuO$_{4+\alpha-\delta}$ (PCCO) with varying $x$ and $\delta$ (the amount of oxygen loss during annealing) values. Absorption near-edge spectra were modified by Ce-substitution and reduction annealing in a similar manner with increasing $x$ and $\delta$. Considering electron doping by Ce-substitution, this similarity indicates an increase of electron number at the copper sites due to annealing $n_{\rm AN}$. Thus, the total number of electrons is determined by the amount of Ce and oxygen ions. Furthermore, quantitative analyses of the spectra clarified that the number of Cu$^+$ sites, corresponding to the induced electron number by Ce-substitution $n_{\rm Ce}$ increases linearly with $x$ in the as-sintered PCCO ($\delta=0$), whereas $n_{\rm AN}$ is not exactly equal to twice of $\delta$, which is expected from charge neutrality. For each $x$-fixed sample, $n_{\rm AN}$ tends to exceed 2$\delta$ with increasing $\delta$, suggesting the emergence of two types of carrier due to annealing.

Published
2018
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10. Structure of Active Sites of Fe-N-C Nano-Catalysts for Alkaline Exchange Membrane Fuel Cells.

Author

Kishi, Hirofumi, Sakamoto, Tomokazu, Asazawa, Koichiro, Yamaguchi, Susumu, Kato, Takeshi, Zulevi, Barr, Serov, Alexey, Artyushkova, Kateryna, Atanassov, Plamen, Matsumura, Daiju, Tamura, Kazuhisa, Nishihata, Yasuo, and Tanaka, Hirohisa

Subjects
HO2− generation, anion exchange membrane fuel cells (AEMFCs), iron-nitrogen-carbon electrocatalysts (Fe-N-C), oxygen reduction reaction
Abstract

Platinum group metal-free (PGM-free) catalysts based on transition metal-nitrogen-carbon nanomaterials have been studied by a combination of ex situ and in situ synchrotron X-ray spectroscopy techniques; high-resolution Transmission Electron Microscope (TEM); Mößbauer spectroscopy combined with electrochemical methods and Density Functional Theory (DFT) modeling/theoretical approaches. The main objective of this study was to correlate the HO₂- generation with the chemical nature and surface availability of active sites in iron-nitrogen-carbon (Fe-N-C) catalysts derived by sacrificial support method (SSM). These nanomaterials present a carbonaceous matrix with nitrogen-doped sites and atomically dispersed and; in some cases; iron and nanoparticles embedded in the carbonaceous matrix. Fe-N-C oxygen reduction reaction electrocatalysts were synthesized by varying several synthetic parameters to obtain nanomaterials with different composition and morphology. Combining spectroscopy, microscopy and electrochemical reactivity allowed the building of structure-to-properties correlations which demonstrate the contributions of these moieties to the catalyst activity, and mechanistically assign the active sites to individual reaction steps. Associated with Fe-Nx motive and the presence of Fe metallic particles in the electrocatalysts showed the clear differences in the variation of composition; processing and treatment conditions of SSM. From the results of material characterization; catalytic activity and theoretical studies; Fe metallic particles (coated with carbon) are main contributors into the HO₂- generation.

Published
2018

33. A Semantic and Pragmatic Analysis of Adversative Usage of English Preposition on

Author

Matsumura, Daiju

Abstract

本稿では，多義語である英語前置詞on の意味ネットワークにおいて「迷惑」の意味が1つの固着した意味をなしているかどうかを判断すべく，Tyler and Evans（2003）に基づき，on が持つ迷惑の意味・用法を分析した。まず迷惑の意味に関しては，その意味的動機付けと成立年代に着目し，共時的にon の多義的構造を分析した先行研究の議論と通時的にon の意味を捉えたOED の記述を分析した。これを踏まえ，本稿は，迷惑の意味が「影響」の意味から成立したこと，ゆえに迷惑の意味は他のon の意味から区別されることを主張する。他方の用法に関しては，母語話者に対するアンケート調査の結果に基づき，迷惑の意味が文脈に応じて現れたり消えたりするのかどうかを検討した。そして，Mary ate ice cream on me. のような表現の容認度が迷惑を意味する文脈において著しく増加したり，My father has died on me. のような典型的な迷惑表現における迷惑性が矛盾する文脈において取り消されたりすることが確認された。この点でon の迷惑の意味は文脈依存性が高いのではないかと考えられる。従って，on の迷惑の意味は，他の意味と区別される一方で文脈依存性が高く慣習化の度合いが低いと見られることから，on の意味ネットワークにおいて完全に固着しているとは言えないものの現時点で固着化の途上にあると言える。

Published
2022

37. Synergistic Hybrid Electrocatalysts of Platinum Alloy and Single-Atom Platinum for an Efficient and Durable Oxygen Reduction Reaction

Author

Liu, Bowen, primary, Feng, Ruohan, additional, Busch, Michael, additional, Wang, Sihong, additional, Wu, Haofei, additional, Liu, Pan, additional, Gu, Jiajun, additional, Bahadoran, Ashkan, additional, Matsumura, Daiju, additional, Tsuji, Takuya, additional, Zhang, Di, additional, Song, Fang, additional, and Liu, Qinglei, additional

Published
2022
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38. Changes in electronic structure of carbon supports for Pt catalysts induced by vacancy formation due to Ar+ irradiation.

Author

Okazaki, Hiroyuki, Kakitani, Kenta, Kimata, Tetsuya, Idesaki, Akira, Koshikawa, Hiroshi, Matsumura, Daiju, Yamamoto, Shunya, and Yamaki, Tetsuya

Subjects
CATALYST supports, X-ray absorption, INTERFACE structures, OXYGEN reduction, CARBON, PLATINUM nanoparticles, ELECTRONIC structure, STEAM reforming
Abstract

X-ray absorption spectroscopy measurements were performed for the C K-edge of Pt nanoparticles on Ar+-irradiated carbon supports in order to elucidate the origin of improved catalyst performance after the introduction of vacancies into the carbon support. We observed a change in the electronic structure at the interface between the Pt nanoparticles and the carbon support after vacancy introduction, which is in good agreement with theoretical results. The results indicated that vacancy introduction resulted in a drastic change in the Pt–C interactions, which likely affected the d-band center of the Pt nanoparticles and led to the enhancement of the oxygen reduction reaction in catalysts. [ABSTRACT FROM AUTHOR]

Published
2020
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42. Repeatable Photoinduced Insulator-to-Metal Transition in Yttrium Oxyhydride Epitaxial Thin Films

Author

Komatsu, Yuya, primary, Shimizu, Ryota, additional, Sato, Ryuhei, additional, Wilde, Markus, additional, Nishio, Kazunori, additional, Katase, Takayoshi, additional, Matsumura, Daiju, additional, Saitoh, Hiroyuki, additional, Miyauchi, Masahiro, additional, Adelman, Jonah R., additional, McFadden, Ryan M. L., additional, Fujimoto, Derek, additional, Ticknor, John O., additional, Stachura, Monika, additional, McKenzie, Iain, additional, Morris, Gerald D., additional, MacFarlane, W. Andrew, additional, Sugiyama, Jun, additional, Fukutani, Katsuyuki, additional, Tsuneyuki, Shinji, additional, and Hitosugi, Taro, additional

Published
2022
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44. Application of augmentation method to MCR-ALS analysis for XAFS and Raman data matrices in structural change of isopolymolybdates

Author

Saeki, Morihisa, Yomogida, Takumi, Matsumura, Daiju, Saito, Takumi, Nakanishi, Ryuzo, Tsuji, Takuya, Ohba, Hironori, Morihisa, Saeki, Ryuzo, Nakanishi, and Hironori, Oba

Abstract

We measured X-ray absorption fine structure (XAFS) and Raman spectra of isopolymolybdates(VI) in highly concentrated HNO3 solution (0.15–4.0 M), which change their geometries depending on acid concentration, and performed simultaneous resolution of the XAFS and Raman data using a multivariate curve resolution by alternating least-squares (MCR-ALS) analysis. In iterative ALS optimization, initial data matrices were prepared by two different methods. For low sensitivity of the XAFS spectra to geometrical change of the isopolymolybdates, the MCR-ALS result of single XAFS data matrix shows large dependence on the preparation method of the initial data matrices. This problem is improved by the simultaneous resolution of the XAFS and Raman data: the MCR-ALS result of an augmented matrix of these data has little dependence on the initial data matrices. It indicates that the augmentation method effectively improves the rotation ambiguities in the MCR-ALS analysis of the XAFS data.

Published
2020

45. Electron Storage Performance of Hybrid Materials Comprising Polyoxometalates and Carbon Nanohorns as Cathode‐Active Materials.

Author

Wakamatsu, Katsuhiro, Sekihara, Akinori, Yamaguchi, Yoshihiko, Matsushima, Ryo, Matsumura, Daiju, Kuila, Tapas, and Yoshikawa, Hirofumi

Subjects
HYBRID materials, CARBON nanohorns, POLYOXOMETALATES, X-ray absorption, LITHIUM-ion batteries
Abstract

Nanohybrid materials comprising polyoxometalates (POMs) and nanocarbons have attracted considerable attention as electrode‐active materials for rechargeable lithium‐ion batteries (LIBs). These materials exhibit multi‐electron redox reactions, resulting in an improved battery capacity. This study focuses on carbon nanohorns (CNHs) as a nanocarbon material and evaluates the battery performance using POM/CNH hybrids as cathode‐active materials. X‐ray absorption fine structural analysis was performed to investigate the reaction mechanism of these hybrids. POM/oxidized CNH (CNHox) hybrid materials maintain high capacities at high current densities as the high surface area availability of CNHox leads to high electrical double‐layer capacitances. These findings show an improved performance of the as‐developed material when compared with those reported in previous papers and can contribute toward an improved design of cathode‐active materials for high‐performance supercapacitors. [ABSTRACT FROM AUTHOR]

Published
2023
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48. An Automotive Intelligent Catalyst that Contributes to Hydrogen Safety for the Decommissioning of Fukushima Daiichi Nuclear Power Station (1FD)

Author

Tanaka, Hirohisa, primary, Masaki, Sayaka, additional, Aotani, Takuro, additional, Inagawa, Kohei, additional, Iwata, Sogo, additional, Aida, Tatsuya, additional, Yamamoto, Tadasuke, additional, Kita, Tomoaki, additional, Ono, Hitomi, additional, Takenaka, Keisuke, additional, Taniguchi, Masashi, additional, Matsumura, Daiju, additional, and Reinecke, Ernst-Arndt, additional

Published
2022
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