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602 results on '"Nishihara, Hirotomo"'

28. Probing Basal and Prismatic Planes of Graphitic Materials for Metal Single Atom and Subnanometer Cluster Stabilization.

Author

Vidal, Mathieu, Pandey, Jyoti, Navarro‐Ruiz, Javier, Langlois, Joris, Tison, Yann, Yoshii, Takeharu, Wakabayashi, Keigo, Nishihara, Hirotomo, Frenkel, Anatoly I., Stavitski, Eli, Urrutigoïty, Martine, Campos, Cristian H., Godard, Cyril, Placke, Tobias, del Rosal, Iker, Gerber, Iann C., Petkov, Valeri, and Serp, Philippe

Subjects
CARBON-based materials, HETEROGENEOUS catalysis, HOMOGENEOUS catalysis, ATOMIC clusters, CATALYTIC hydrogenation, METAL clusters, RHODIUM catalysts
Abstract

Supported metal single atom catalysis is a dynamic research area in catalysis science combining the advantages of homogeneous and heterogeneous catalysis. Understanding the interactions between metal single atoms and the support constitutes a challenge facing the development of such catalysts, since these interactions are essential in optimizing the catalytic performance. For conventional carbon supports, two types of surfaces can contribute to single atom stabilization: the basal planes and the prismatic surface; both of which can be decorated by defects and surface oxygen groups. To date, most studies on carbon‐supported single atom catalysts focused on nitrogen‐doped carbons, which, unlike classic carbon materials, have a fairly well‐defined chemical environment. Herein we report the synthesis, characterization and modeling of rhodium single atom catalysts supported on carbon materials presenting distinct concentrations of surface oxygen groups and basal/prismatic surface area. The influence of these parameters on the speciation of the Rh species, their coordination and ultimately on their catalytic performance in hydrogenation and hydroformylation reactions is analyzed. The results obtained show that catalysis itself is an interesting tool for the fine characterization of these materials, for which the detection of small quantities of metal clusters remains a challenge, even when combining several cutting‐edge analytical methods. [ABSTRACT FROM AUTHOR]

Published
2024
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29. Carbon-coated anodic aluminum oxide: Synthesis, characterization, and applications.

Author

Liu, Hongyu, Pan, Zheng-Ze, Itoh, Tetsuji, Kyotani, Takashi, and Nishihara, Hirotomo

Subjects
CARBON-based materials, POROUS materials, ALUMINUM oxide, POROSITY, ENERGY storage
Abstract

Ordered porous carbon materials with regularly arranged pores and adjustable pore sizes have attracted significant attention due to their versatile applications across various fields. In this context, uniform carbon coating of anodic aluminum oxide (AAO) membranes is an effective approach to fabricating an ordered array of cylindrical carbonaceous nanopores with adjustable pore diameter and length. The resulting carbon-coated AAO (C/AAO) composite exhibits a meticulously ordered array of meso/macropores, devoid of inter-particle pores and resistance, setting it apart from conventional ordered porous carbons with powder forms. The pore dimensions of C/AAO can be precisely controlled over a wide range, and the carbon chemistry can be customized through heteroatom doping and chemical modifications, all without altering the pore structure. These inherent advantages position C/AAO as a highly promising material with broad application prospects. This review article provides a comprehensive overview of the synthesis and characterization of C/AAO and related materials, along with their diverse utilization in the fields of optics, field emission, gas sensing, energy storage, electrocatalyst support, and bionics. Furthermore, an outlook on the C/AAO materials is given at the end, highlighting their potential and associated challenges. [ABSTRACT FROM AUTHOR]

Published
2024
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30. Rational bottom-up synthesis of sulphur-rich porous carbons for single-atomic platinum catalyst supports.

Author

Chida, Koki, Yoshii, Takeharu, Kawaguchi, Ryo, Inoue, Masataka, Tani, Fumito, Sobue, Tatsuki, Ohtani, Shunsuke, Kato, Kenichi, Ogoshi, Tomoki, Nakahata, Shoko, Kamiya, Kazuhide, and Nishihara, Hirotomo

Subjects
PROTON exchange membrane fuel cells, SUSTAINABLE chemistry, PLATINUM catalysts, CARBON-based materials, CATALYST supports, PLATINUM nanoparticles, PLATINUM
Abstract

Single-atomic metal catalysts are attractive for green chemistry in terms of their outstanding catalytic performance and savings in precious metal usage owing to maximized metal utilization, including anode catalysts in polymer electrolyte fuel cells (PEFCs). Heteroatom-doped porous carbons are extensively used as supports, where the heteroatoms contribute to the immobilization of single-atomic metals. However, high-content doping of heteroatoms, especially sulphur (S), into carbon supports is still challenging because S species can be readily desorbed during heat treatment. Herein, we present a bottom-up fabrication approach for S-rich porous carbons from molecular precursors via a thermal polymerization process. A simple carbonization of molecules with thermally stable S-containing building blocks and polymerizable ethynyl moieties at 900 °C yields microporous carbon materials with record-high S content (over 15 wt%). The abundant S species function as an effective anchoring site for single-atomic platinum (Pt) species. Toward anode catalysts in PEFCs, the prepared single-atomic Pt catalysts efficiently promote the electrochemical hydrogen oxidation reaction, whose activity is comparable to that of commercial Pt/C, despite the significantly low Pt loading amount. [ABSTRACT FROM AUTHOR]

Published
2024
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33. Prominent structural dependence of quantum capacitance unraveled by nitrogen-doped graphene mesosponge

Author

Tang, Rui, Aziz, Alex, Yu, Wei, Pan, Zheng-Ze, Nishikawa, Ginga, Yoshii, Takeharu, Nomura, Keita, Taylor, Erin E, Stadie, Nicholas P, Inoue, Kazutoshi, Kotani, Motoko, Kyotani, Takashi, Nishihara, Hirotomo, Tang, Rui, Aziz, Alex, Yu, Wei, Pan, Zheng-Ze, Nishikawa, Ginga, Yoshii, Takeharu, Nomura, Keita, Taylor, Erin E, Stadie, Nicholas P, Inoue, Kazutoshi, Kotani, Motoko, Kyotani, Takashi, and Nishihara, Hirotomo

Abstract

Porous carbons are important electrode materials for supercapacitors. One of the challenges associated with supercapacitors is improving their energy density without relying on pseudocapacitance, which is based on fast redox reactions that often shorten device lifetimes. A possible solution involves achieving high total capacitance (Ctot), which comprises Helmholtz capacitance (CH) and possibly quantum capacitance (CQ), in high-surface carbon materials comprising minimally stacked graphene walls. In this work, a templating method is used to synthesize 3D mesoporous graphenes with largely identical pore structures (≈2100 m2 g−1 with an average pore size of ≈7 nm) but different concentrations of oxygen-containing functional groups (0.3–6.7 wt.%) and nitrogen dopants (0.1–4.5 wt.%). Thus, the impact of the heteroatom functionalities on Ctot is systematically investigated in an organic electrolyte excluding the effect of pore structures. It is found that heteroatom functionalities determine Ctot, resulting in the cyclic voltammetry curves being rectangular or butterfly-shaped. The nitrogen functionalities are found to significantly enhance Ctot owing to increased CQ.

Published
2024

35. Fluorinated Amide-Based Electrolytes Induce a Sustained Low-Charging Voltage Plateau under Conditions Verifying the Feasibility of Achieving 500 Wh kg–1Class Li–O2Batteries

Author

Nishioka, Kiho, Tanaka, Mizuki, Goto, Terumi, Haas, Ronja, Henss, Anja, Azuma, Shota, Saito, Morihiro, Matsuda, Shoichi, Yu, Wei, Nishihara, Hirotomo, Fujimoto, Hayato, Tobisu, Mamoru, Mukouyama, Yoshiharu, and Nakanishi, Shuji

Abstract

Although lithium–oxygen batteries (LOBs) hold the promise of high gravimetric energy density, this potential is hindered by high charging voltages. To ensure that the charging voltage remains low, it is crucial to generate discharge products that can be easily decomposed during the successive charging process. In this study, we discovered that the use of amide-based electrolyte solvents containing a fluorinated moiety can notably establish a sustained voltage plateau at low-charging voltages at around 3.5 V. This occurs under conditions that can verify the feasibility of achieving a benchmark energy density value of 500 Wh kg–1. Notably, the achievement of the low-voltage plateau was accomplished solely by relying on the intrinsic properties of the electrolyte solvent. Indeed, synchrotron X-ray diffraction measurements have shown that the use of fluorine-containing amide-based electrolyte solvents results in the formation of highly decomposable discharge products, such as amorphous and Li-deficient lithium peroxides.

Published
2024
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36. Ordered Carbonaceous Framework Synthesized from Hexaazatrinaphthylene with Enediyne Groups via Solid-State Bergman Cyclization Reaction

Author

Sano, Yuki, Toyoda, Ryojun, Chida, Koki, Yoshii, Takeharu, Nishihara, Hirotomo, Nishina, Yuta, Asanoma, Daisuke, Takaishi, Shinya, Sugimoto, Kunihisa, and Sakamoto, Ryota

Abstract

Porous materials synthesized through bottom-up approaches, such as metal–organic frameworks and covalent organic frameworks, have attracted attention owing to their design flexibility for functional materials. However, achieving the chemical and thermal stability of these materials for various applications is challenging considering the reversible coordination bonds and irreversible covalent bonds in their frameworks. Thus, ordered carbonaceous frameworks (OCFs) emerge as a promising class of bottom–up materials with good periodicity, thermal and chemical stability, and electrical conductivity. However, a few OCFs have been reported owing to the limited range of precursor molecules. Herein, we designed a hexaazatrinaphthylene-based molecule with enediyne groups as a precursor molecule for synthesizing an OCF. The solid-state Bergman cyclization of enediyne groups at a low temperature formed a microporous polymer and an OCF, exhibiting redox activity and demonstrating their potential for electrochemical applications. The microporous polymer was used as an active material in sodium-ion batteries, while the OCF was used as an electrochemical capacitor. These findings illustrate the utility of the Bergman cyclization reaction for synthesizing microporous polymers and OCFs with a customizable functionality for broad applications.

Published
2024
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38. Thermodynamically Favorable Route to the Synthesis of Nanoporous Graphene Templated on CaO via Chemical Vapor Deposition

Author

Pirabul, Kritin, primary, Zhao, Qi, additional, Sunahiro, Shogo, additional, Pan, Zheng-Ze, additional, Yoshii, Takeharu, additional, Hayasaka, Yuichiro, additional, Hoi-Sing Pang, Eddie, additional, Crespo-Otero, Rachel, additional, Di Tommaso, Devis, additional, Kyotani, Takashi, additional, and Nishihara, Hirotomo, additional

Published
2024
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41. A thermodynamically favorable route to the synthesis of nanoporous graphene templated on CaO via chemical vapor deposition.

Author

Pirabul, Kritin, Zhao, Qi, Sunahiro, Shogo, Pan, Zheng-Ze, Yoshii, Takeharu, Hayasaka, Yuichiro, Hoi-Sing Pang, Eddie, Crespo-Otero, Rachel, Di Tommaso, Devis, Kyotani, Takashi, and Nishihara, Hirotomo

Subjects
CHEMICAL vapor deposition, GRAPHENE synthesis, NANOPOROUS materials, ELECTRIC capacity, SUSTAINABILITY, SUBSTRATES (Materials science)
Abstract

Template-assisted chemical vapor deposition (CVD) is a promising approach for fabricating nanoporous materials based on graphene walls. Among conventional metal oxide templates, CaO, produced through the thermal decomposition of CaCO3, offers improved environmental sustainability and lower production costs, thereby potentially making it a viable candidate for green template materials. Nevertheless, the underlying reaction mechanisms of the interaction on the CaO surface during the CVD process remain indeterminate, giving rise to challenges in regulating graphene formation and obtaining high-quality materials. In this work, a comprehensive experimental–theoretical investigation has unveiled the CVD mechanism on CaO. CaO exhibits efficient catalytic activity in the dissociation of CH4, thereby facilitating a thermodynamically favorable conversion of CH4 to graphene. These findings highlight the potential of using CaO as a substrate for graphene growth, combining both sustainability and cost-effectiveness. When the shell-like graphene layer deposited on CaO particles is released through the dissolution of CaO with HCl, the resulting nanoporous graphene-based materials can be readily compacted by the capillary force of the liquid upon drying. The folded surfaces, however, can become available for electric double-layer capacitance via electrochemical exfoliation under a low applied potential (<1.2 V vs. Ag/AgClO4). [ABSTRACT FROM AUTHOR]

Published
2024
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42. Prominent Structural Dependence of Quantum Capacitance Unraveled by Nitrogen‐Doped Graphene Mesosponge

Author

Tang, Rui, primary, Aziz, Alex, additional, Yu, Wei, additional, Pan, Zheng‐Ze, additional, Nishikawa, Ginga, additional, Yoshii, Takeharu, additional, Nomura, Keita, additional, Taylor, Erin E., additional, Stadie, Nicholas P., additional, Inoue, Kazutoshi, additional, Kotani, Motoko, additional, Kyotani, Takashi, additional, and Nishihara, Hirotomo, additional

Published
2023
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49. Water‐Dispersible Carbon Nano‐Test Tubes as a Container for Concentrated DNA Molecules

Author

Hoshikawa, Yasuto, primary, Kanno, Yasuyuki, additional, Tawata, Hanako, additional, Sagae, Takuya, additional, Ishii, Takafumi, additional, Imoto, Shuhei, additional, Hagihara, Shinya, additional, Wada, Takehiko, additional, Nagatsugi, Fumi, additional, Aziz, Alex, additional, Nishihara, Hirotomo, additional, Kyotani, Takashi, additional, and Itoh, Tetsuji, additional

Published
2023
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