Toyoshima, Ryo

写真a

Affiliation

Faculty of Science and Technology, Department of Chemistry (Yagami)

Position

Research Associate/Assistant Professor/Instructor

 

Papers 【 Display / hide

  • Promotional Effect of Ag on the Catalytic Decomposition of N<inf>2</inf>O in the Presence of O<inf>2</inf> over the Al<inf>2</inf>O<inf>3</inf>-Supported Rh Catalyst

    Jing Y., He C., Zhang N., Murano Y., Toyoshima R., Kondoh H., Kageyama Y., Inomata H., Toyao T., Shimizu K.I.

    ACS Catalysis (ACS Catalysis)  13 ( 19 ) 12983 - 12993 2023.10

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    Catalytic decomposition of N2O into N2 and O2 is one of the most important techniques for removing N2O from the atmosphere to curb global warming. Supported RhOx catalysts are known to show high efficiency for N2O decomposition, even in the presence of O2, compared with other materials, such as supported metal oxides and Fe-based zeolite catalysts. In this study, the addition of Ag was found to enhance the efficiency of an Al2O3-supported RhOx catalyst (RhOx/Al2O3) for N2O decomposition. The promotional effect of Ag was investigated using various operando spectroscopic methods, including X-ray absorption spectroscopy, diffuse reflectance UV-vis spectroscopy (DR UV-vis), ambient-pressure X-ray photoelectron spectroscopy, and kinetic studies. The results demonstrated that the addition of Ag enhanced the catalytic efficiency of the supported RhOx catalysts by enhancing the thermal reduction of Rh oxide, which was identified as the rate-determining step, especially at low temperatures.

  • Operando Spectroscopic Study of Reduction and Oxidation Half-Cycles in NH<inf>3</inf>-SCR over CeO<inf>2</inf>-Supported WO<inf>3</inf>

    Kubota H., Jing Y., Wan L., Tong J., Zhang N., Mine S., Toyao T., Toyoshima R., Kondoh H., Ferri D., Shimizu K.I.

    ACS Catalysis (ACS Catalysis)  13 ( 13 ) 9274 - 9288 2023

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    Operando spectroscopies (in situ Ce and W L3-edge X-ray absorption near-edge structure, ultraviolet-visible (UV-vis), and infrared (IR) spectroscopies, combined with online analysis of gas-phase products) were exploited to elucidate reduction/oxidation half-cycles in the selective catalytic reduction of NO with NH3 (NH3-SCR) over WO3-loaded CeO2. The Ce4+ species was reduced by NO + NH3 to yield N2 and Ce3+ species (reduction half-cycle), which was then reoxidized by O2 (oxidation half-cycle). The oxidation state of the W6+ species remained unchanged under redox conditions. IR and theoretical results indicated that the reduction half-cycle started with the reaction of W6+-OH and adjacent Ce4+-O with NO to afford Ce3+ species and gaseous HONO, which was converted to NO+ species on the catalyst. The NO+ species then reacted with NH3 to generate N2

  • Bifunctionality of Re Supported on TiO<inf>2</inf> in Driving Methanol Formation in Low-Temperature CO<inf>2</inf> Hydrogenation

    Phongprueksathat N., Ting K.W., Mine S., Jing Y., Toyoshima R., Kondoh H., Shimizu K.I., Toyao T., Urakawa A.

    ACS Catalysis (ACS Catalysis)  13 ( 16 ) 10734 - 10750 2023

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    Low temperature and high pressure are thermodynamically more favorable conditions to achieve high conversion and high methanol selectivity in CO2 hydrogenation. However, low-temperature activity is generally very poor due to the sluggish kinetics, and thus, designing highly selective catalysts active below 200 °C is a great challenge in CO2-to-methanol conversion. Recently, Re/TiO2 has been reported as a promising catalyst. We show that Re/TiO2 is indeed more active in continuous and high-pressure (56 and 331 bar) operations at 125-200 °C compared to an industrial Cu/ZnO/Al2O3 catalyst, which suffers from the formation of methyl formate and its decomposition to carbon monoxide. At lower temperatures, precise understanding and control over the active surface intermediates are crucial to boosting conversion kinetics. This work aims at elucidating the nature of active sites and active species by means of in situ/operando X-ray absorption spectroscopy, Raman spectroscopy, ambient-pressure X-ray photoelectron spectroscopy (AP-XPS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Transient operando DRIFTS studies uncover the activation of CO2 to form active formate intermediates leading to methanol formation and also active rhenium carbonyl intermediates leading to methane over cationic Re single atoms characterized by rhenium tricarbonyl complexes. The transient techniques enable us to differentiate the active species from the spectator one on TiO2 support, such as less reactive formate originating from spillover and methoxy from methanol adsorption. The AP-XPS supports the fact that metallic Re species act as H2 activators, leading to H-spillover and importantly to hydrogenation of the active formate intermediate present over cationic Re species. The origin of the unique reactivity of Re/TiO2 was suggested as the coexistence of cationic highly dispersed Re including single atoms, driving the formation of monodentate formate, and metallic Re clusters in the vicinity, activating the hydrogenation of the formate to methanol.

  • Promoting effect of basic metal additives on DeNOx reactions over Pt-based three-way catalysts

    Jing Y., Wang G., Mine S., Kawai J., Toyoshima R., Kondoh H., Zhang X., Nagaoka S., Shimizu K.i., Toyao T.

    Journal of Catalysis (Journal of Catalysis)  416   209 - 221 2022.12

    ISSN  00219517

     View Summary

    Pt has been economically favored over Rh and Pd. However, Pt-based three-way catalysts (TWCs) have been studied less than Pd- and Rh-based TWCs; therefore, their properties have not yet been sufficiently evaluated, especially under conditions relevant to modern three-way catalysis operation, wherein deviations from stoichiometric conditions are often encountered. In this study, we examined the promotional effect of basic metal additives in Pt/M/Al2O3 (M = Ba, La, Sr) on the efficiency of three-way catalytic reactions. The catalytic activities of the Pt/M/Al2O3 catalysts for NO, CO, and total hydrocarbons were superior to those of Pt/Al2O3; moreover, Ba enhanced the catalytic activity of Pt-based catalysts more efficiently than La and Sr. The best-performing catalyst, Pt/Ba/Al2O3, was subjected to kinetic studies and various in situ/operando spectroscopic experiments, namely, X-ray absorption spectroscopy, infrared spectroscopy, and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS), to investigate the role of Ba in the NO reduction reaction. The Pt0 species loaded on Ba/Al2O3 were more electron-rich than those loaded on Al2O3, thereby promoting NO dissociation into N and O atoms, as revealed by the AP-XPS results. Moreover, the efficient formation of intermediate surface NOx species, including nitrites and nitrates, and their reactivities toward reductant gases, such as H2 or CO, were critical for promoting the effect of Ba on the NO reduction reaction.

  • Origin of the High Selectivity of the Pt-Rh Thin-Film H<inf>2</inf>Gas Sensor Studied by Operando Ambient-Pressure X-ray Photoelectron Spectroscopy at Working Conditions

    Toyoshima R., Tanaka T., Kato T., Uchida K., Kondoh H.

    Journal of Physical Chemistry Letters (Journal of Physical Chemistry Letters)  13 ( 36 ) 8546 - 8552 2022.09

     View Summary

    The Pt-Rh thin-film sensors exhibit excellent sensitivity and selectivity for H2 gas detection. Here, we studied the mechanism of highly selective detection of H2 by the Pt-Rh thin-film sensors with ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) measurements at working conditions, which were paralleled with electric resistivity measurements. The elemental composition and chemical state of surface Pt and Rh drastically change depending on the background gas environments, which directly link to the sensor response. It is revealed that surface segregated Pt atoms accelerate dissociative adsorption of H2, resulting in a reduction of the sensor surface and then a decrease of electric resistivity of the film, whereas a thin oxidized Rh layer blocks dissociation of the other reducing agent, that is, NH3. This is supported from the adsorption energetics obtained by the density functional theory (DFT) calculations.

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Papers, etc., Registered in KOARA 【 Display / hide

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Research Projects of Competitive Funds, etc. 【 Display / hide

  • Development and application of operando soft x-ray measurement technique for simultaneous analysis of chemical state and structure

    2023.04
    -
    2026.03

    若手研究, Principal investigator

 

Courses Taught 【 Display / hide

  • LABORATORY IN SCIENCE

    2023

  • LABORATORIES IN CHEMISTRY 1

    2023

  • LABORATORY IN SCIENCE

    2022

  • LABORATORIES IN CHEMISTRY 1

    2022

  • LABORATORY IN SCIENCE

    2021

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