研究者詳細 - 春山　哲也

論文 - 春山　哲也

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Elucidation of the behavior of oxygen remaining in water molecules after hydrogen atom abstraction in the plasma/liquid (P/L) interfacial reaction: improvement in the selectivity of ammonia synthesis and parallel production of hydrogen gas 査読有り

Yoshida S., Murakami N., Takatsuji Y., Haruyama T.

Green Chemistry 25 ( 2 ) 579 - 588 2023年02月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

The plasma/liquid interfacial (P/L) reaction is a non-catalytic reaction conducted at an ambient temperature and pressure. The reaction employs activated (dissociated or excited) nitrogen and abstracted hydrogen from water molecules to form ammonia. Herein we demonstrated that dissociated nitrogen (atomic nitrogen; Natom) promoted ammonia selectivity more efficiently than excited nitrogen molecules in P/L reactions. We investigated the behavior of water-derived oxygen after abstracting a hydrogen atom from a water molecule. We constructed a connecting reactor that directly connects the P/L reaction locus with a titania bead-filled packed-bed dielectric barrier discharge (PbDBD) device that exhibits high Natom generation efficiency. In this reactor, the P/L reaction produced aqueous ammonia with high selectivity and minimal aqueous nitrate ions, which are the typical by-products of the reaction. We also observed that oxygen and hydrogen atoms from water were released into the gas phase to form NO and hydrogen gases. The removal of oxygen as NO gas from the P/L reaction locus significantly improved the ammonia synthesis selectivity of the P/L reaction. Additionally, the ability to generate hydrogen gas during ammonia synthesis in the P/L reaction enables the simultaneous production of ammonia and hydrogen gas.
* Journal published Feb 2023
* WEB (just accepted) published 14 Dec 2022

DOI： 10.1039/d2gc03491c

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Drastically Increase in Atomic Nitrogen Production Depending on the Dielectric Constant of Beads Filled in the Discharge Space. 査読有り国際誌

Yuto Tsuchida, Naoya Murakami, Tatsuya Sakakura, Yoshiyuki Takatsuji, Tetsuya Haruyama

ACS Omega ( American Chemical Society ) 6 29759 - 29764 2021年10月

Excitation of H2O at the plasma/water interface by UV irradiation for the elevation of ammonia production 査読有り

Sakakura T., Uemura S., Hino M., Kiyomatsu S., Takatsuji Y., Yamasaki R., Morimoto M., Haruyama T.

Green Chemistry ( Royal Society of Chemistry ) 20 ( 3 ) 627 - 633 2018年01月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2018 The Royal Society of Chemistry. Ammonia is well known to be a very important chemical substance for human life. Simultaneously, the conventional ammonia production process needs pure nitrogen and pure hydrogen. Hydrogen has been produced from either liquid natural gas (LNG) or coal. In this study, water is used as a direct hydrogen source for ammonia production, thereby obviating the need for catalysts or water electrolysis. We have studied and developed a plasma/liquid interfacial reaction (P/L reaction) that can be used to produce ammonia from air (nitrogen) and water at ambient temperature and pressure, without any catalysts. In this study, the P/L reaction entails enhanced ultraviolet (UV) irradiation of the surface of the water phase. The nitrogen plasma/water interface reaction locus can produce ammon ia. In contrast, the vacuum ultraviolet (VUV) irradiated interface reaction locus produces increased amounts of ammonia. In a spin trap electron spin resonance (st-ESR) experiment, large amounts of atomic H (H) were produced by UV irradiation, especially by VUV irradiation. The derived H effectively enhanced the P/L reaction rate.

DOI： 10.1039/c7gc03007j

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Electrodeposited Cu-Sn Alloy for Electrochemical CO2 Reduction to CO/HCOO− 査読有り国際誌

Masayuki Morimoto, Yoshiyuki Takatsuji, Ryota Yamasaki, Hikaru Hashimoto, Ikumi Nakata, Tatsuya Sakakura, Tetsuya Haruyama

Electrocatalysis ( Springer-Nature ) 9 323 - 332 2017年11月

Non-catalyzed One-step Synthesis of Ammonia from Atmospheric Air and Water 査読有り国際誌

Tetsuya Haruyama, Takamitsu Namise, Naoya Shimoshimizu, Shintaro Uemura, Yoshiyuki Takatsuji, Mutsuki Hino, Ryota Yamasaki, Toshiaki Kamachi, Masahiro Kohno

Green Chemistry ( Royal Society of Chemistry ) 18 4536 - 4541 2016年07月

Promoting Degradation of Polyamide-Microplastic Fibers Using Hydroxy Radical Generated by Electrochemical Advanced Oxidation Processes 査読有り

Meboso T., Takatsuji Y., Takamura E., Haruyama T., Sakamoto H.

Journal of the Electrochemical Society 170 ( 12 ) 2023年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

Microplastic fibers (MPFs) generated by washing textile products made of synthetic fibers cannot be removed at sewage treatment plants and are released into rivers and oceans. In this study, we proposed using hydroxy radical (•OH) to degrade MPF. •OH exhibits strong oxidizing ability, allowing MPFs to be degraded. Herein, electrochemical advanced oxidation processes, which combines electrochemical oxygen reduction in water and UV irradiation, was used to generate •OH. In this paper, we investigated the degradation of polyamide 6/6 (PA6/6), as a common MPF. After 120 h degradation process, the sample thickness and fiber diameter decreased 32.0% and 13.7% respectively. After only 12 h, the sample toughness decreased 78.9%. Infrared spectroscopy confirmed that the signal of amide bonds (-CONH-) were reduced and new signal of carboxyl groups (-COOH) were formed in the sample after degradation. Gas chromatography confirmed that several short-chain amide compounds were released into the degraded solution. These results suggest that the amide bonds in the PA6/6 molecular structure are cleaved by the •OH, thereby accelerating the degradation of PA6/6. The proposed degradation method achieved a much faster degradation rate than other methods using microorganisms, and is expected to be a novel MPF degradation method.

DOI： 10.1149/1945-7111/ad0d1b

Kyutacar

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Photoelectrochemical C-H activation of methane to methyl radical at room temperature 査読有り国際誌

Amano F., Shintani A., Sakakura T., Takatsuji Y., Haruyama T.

Catalysis Science and Technology 2023年01月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

Herein, we report a continuous gas-fed photoelectrochemical (PEC) system with a proton exchange membrane for CH4 activation at ambient temperature and pressure. We found that both water splitting and steam reforming of CH4 were induced over oxide photoanodes. When the CH4 concentration was low, O2 and CO2 were formed on titanium oxide (TiO2) and tungsten trioxide (WO3) photoanodes under ultraviolet light irradiation. We also found that visible light enhanced CH4 activation and ethane (C2H6) formation over the WO3 photoanode. When the CH4 concentration increased, O2 formation was suppressed, with increasing production rates of CO2, C2H6, and CO. Under optimised conditions, the selectivity of C2H6 reached 57% on a carbon basis over the WO3 photoanode under visible-light irradiation. The production of C2H6 implies the formation of methyl radicals during the CH4 gas-fed PEC process. We also demonstrated the PEC coupling of ethane to n-butane and the visible-light-induced oxidation of CH4 without external bias.

DOI： 10.1039/d3cy00632h

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触媒電極の開発と二酸化炭素資源化への展望招待有り査読有り

高辻義行、春山哲也

材料の科学と工学 ( 日本材料科学会 ) 59 ( 3 ) 86 - 89 2022年06月

Anodized Zn electrode for formate selectivity during the electrochemical reduction of CO<inf>2</inf> at low applied potential 査読有り国際誌

Takatsuji Y., Morimoto M., Nakatsuru Y., Haruyama T.

Electrochemistry Communications 138 2022年05月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

It is well known that the main product of the CO2 electrochemical reduction on zinc electrodes is CO. In this study, it was observed that an anodized Zn electrode can produce formate with high selectivity during the electrochemical reduction of CO2 at low applied potentials. The Zn electrode obtained using a simple anodization method produced formate with a Faradaic efficiency of more than 60% via reduction of CO2 at a low potential of −1.19 V vs. the reversible hydrogen electrode (RHE). According to several previous studies, selectivity toward formate production requires a large potential of approximately −2.0 V vs. RHE. X-ray diffraction analysis of this electrode suggests that the surface of this electrode is dominated by the Zn (1 0 1) plane and that Zn (1 0 1) is highly active in formate formation. This study confirms that an anodized Zn (1 0 1) facet can generate formate during CO2 electrochemical reduction at a low applied potential.

DOI： 10.1016/j.elecom.2022.107281

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Anodized Zn electrode for formate selectivity during the electrochemical reduction of CO2 at low applied potential. 査読有り国際誌

Yoshiyuki Takatsuji, Masayuki Morimoto, Yukimasa Nakatsuru, and Tetsuya Haruyama

Electrochemistry Communications 138 107281 - 107286 2022年04月

Quick and environmentally friendly sterilization process of dental instruments by radical vapor reactor. 査読有り国際誌

Kaede Okita, Ryota Yamasaki, Yohei Nakamura, Tatsuya Sakakura, Aki Kawano, Yoshiyuki Takatsuji, Tetsuya Haruyama, Yoshie Yoshioka, Wataru Ariyoshi

Process Biochemistry 113 22 - 26 2022年02月

Decreasing the Overpotential for Formate Production in Electrochemical CO2 Reduction Achieved by Anodized Sn Electrode. 査読有り国際誌

Masayuki Morimoto, Namiki Fujita, Yoshiyuki Takatsuji, Tetsuya Haruyama

Electrocatalysis 13 72 - 80 2022年01月

Decreasing the Overpotential for Formate Production in Electrochemical CO<inf>2</inf> Reduction Achieved by Anodized Sn Electrode 査読有り国際誌

Morimoto M., Fujita N., Takatsuji Y., Haruyama T.

Electrocatalysis 13 ( 1 ) 72 - 80 2022年01月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Abstract: The Sn electrode possesses a high selectivity for formate production in electrochemical CO2 reduction. Understanding the relationship between the selectivity of formate and surface characteristics such as structure and chemical state is important for obtaining high activity. In this study, we fabricated a porous Sn electrode using a simple method of anodization in lactic acid. The anodized electrode had numerous 1-μm pores and its surface chemical state had a relatively high ratio of Sn0 compared with that of a bare Sn electrode. In the CO2 reduction reaction, the anodized Sn electrode showed a Faradaic efficiency (FE) of 35% for formate production at a low applied potential of −0.6 V vs. a reversible hydrogen electrode (RHE), with suppressed H2 generation. A Tafel analysis revealed that the slope of the anodized Sn electrode was 70 mV/decade, suggesting an increase in the stability of the CO2 radical anion. These results indicated that a coordinative unsaturation site such as the edge site formed by anodization contributes to a decrease in the overpotential and an increase in the reactive sites for formate production. Moreover, the surface structure appeared to be a significant factor in the production of formate at a very low applied potential relative to the surface oxidation state. Textual abstract: The porous Sn electrode was prepared by anodization in lactic acid to increase the selectivity for formate at a low applied potential. Prepared porous Sn electrode enhances formate production from the CO2RR at a low applied potential due to the stabilization of the CO2 or its reaction intermediates. Graphical Abstract: [Figure not available: see fulltext.].

DOI： 10.1007/s12678-021-00695-2

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Reactive Oxygen Species Penetrate Persister Cell Membranes of Escherichia coli for Effective Cell Killing 査読有り

Kawano A., Yamasaki R., Sakakura T., Takatsuji Y., Haruyama T., Yoshioka Y., Ariyoshi W.

Frontiers in Cellular and Infection Microbiology 10 2020年09月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Persister cells are difficult to eliminate because they are tolerant to antibiotic stress. In the present study, using artificially induced Escherichia coli persister cells, we found that reactive oxygen species (ROS) have greater effects on persister cells than on exponential cells. Thus, we examined which types of ROS could effectively eliminate persister cells and determined the mechanisms underlying the effects of these ROS. Ultraviolet (UV) light irradiation can kill persister cells, and bacterial viability is markedly increased under UV shielding. UV induces the production of ROS, which kill bacteria by moving toward the shielded area. Electron spin resonance-based analysis confirmed that hydroxyl radicals are produced by UV irradiation, although singlet oxygen is not produced. These results clearly revealed that ROS sterilizes persister cells more effectively compared to the sterilization of exponential cells (**p < 0.01). These ROS do not injure the bacterial cell wall but rather invade the cell, followed by cell killing. Additionally, the sterilization effect on persister cells was increased by exposure to oxygen plasma during UV irradiation. However, vapor conditions decreased persister cell sterilization by reducing the levels of hydroxyl radicals. We also verified the effect of ROS against bacteria in biofilms that are more resistant than planktonic cells. Although UV alone could not completely sterilize the biofilm bacteria, UV with ROS achieved complete sterilization. Our results demonstrate that persister cells strongly resist the effects of antibiotics and starvation stress but are less able to withstand exposure to ROS. It was shown that ROS does not affect the cell membrane but penetrates it and acts internally to kill persister cells. In particular, it was clarified that the hydroxy radical is an effective sterilizer to kill persister cells.

DOI： 10.3389/fcimb.2020.00496

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Nitrogen Fixation in a Plasma/Liquid Interfacial Reaction and Its Switching between Reduction and Oxidation 査読有り

Sakakura T., Murakami N., Takatsuji Y., Haruyama T.

Journal of Physical Chemistry C 124 ( 17 ) 9401 - 9408 2020年04月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

There are multiple active species at the interface between the discharged gas phase and the water phase. Activated nitrogen species are generated in the nitrogen plasma gas by dielectric barrier discharge (DBD). The reaction at the interface between the gas phase containing the activated nitrogen species and water phase (P/L reaction) can produce nitrogen-derived compounds (N-compounds) in water. We have already clarified the mechanism of the P/L reaction focusing on highly active atomic nitrogen in a previous study. In this study, we report the mechanism of the P/L reaction by excited but metastable nitrogen molecules. Involving excited nitrogen molecules [N2(A3ςu+)] with a long lifetime, the reaction selectivity of N-compounds was clarified by quantitative analysis. Moreover, the active species in the water phase (H·, HO·, H2O2) of the P/L reaction were measured, and the involvement of the reaction in the generation of N-compounds was confirmed. The findings clarify that each activated nitrogen species reacts differently with H2O. These results suggest that the occurrence of either an oxidation reaction or a reduction reaction can be regulated by controlling the activated nitrogen species.

DOI： 10.1021/acs.jpcc.0c02392

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Photoelectrochemical reduction of CO<inf>2</inf> using a TiO<inf>2</inf> photoanode and a gas diffusion electrode modified with a metal phthalocyanine catalyst 査読有り

Kobayashi K., Lou S.N., Takatsuji Y., Haruyama T., Shimizu Y., Ohno T.

Electrochimica Acta 338 2020年04月

記述言語：英語掲載種別：研究論文（学術雑誌）

The mass transport limitations encountered in classical H-cells for electrochemical CO2 reduction reaction (CO2RR) have spurred research in gas diffusion electrode (GDE) systems. However, current reports on CO2RR required large biases (anode potential vs. cathode potential > -2.0 V) for high current efficiencies. In this work, we combined a TiO2 photoanode and a GDE modified with a Co, Ni or Sn metal phthalocyanine (MPc) catalyst to reduce the external bias requirement for CO2RR. We found the Faradaic efficiencies and the selectivity of the photoelectrolysis products were influenced by (i) the metal cation (Ni, Co or Sn) coordinated to the phthalocyanine, (ii) the electrolyte temperature and concentration and (iii) the magnitude of the applied bias. In addition, analyzes of the voltage distributions between the TiO2 photoanode and the MPc-GDE revealed the current efficiency of the TiO2/MPc-GDE cell was limited predominantly by a high ohmic polarization loss at the TiO2 photoanode due to an excessive thickness of the TiO2 layer. The cathodic process at the MPc-GDE was governed by the activation energy of the electrode. The thickness of the TiO2 photoanode was subsequently optimized for higher current efficiency. The highest Faradaic efficiency for PEC CO2RR was obtained when a NiPc catalyst was utilized as the CO2RR catalyst and the optimum cell conditions were as follows: (i) a GDE electrolyte temperature of <11 °C, (ii) a GDE electrolyte concentration of >1 M aq. Na2SO4 electrolyte solution and (iii) a TiO2 oxidation time of 3 h. Using these optimized cell conditions and under UV illumination, the as-prepared TiO2/NiPc-GDE cell shows a notably high CO2RR Faradaic efficiency and selectivity for CO (at 98%) and at a lowest reported cell bias of 0.8 V (anode potential vs cathode potential). This work provides an improved understanding of the cell designs of a vapor-fed CO2RR reactor based on a TiO2/MPc-GDE photoelectrochemical system.

DOI： 10.1016/j.electacta.2020.135805

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Nitrogen fixation through the plasma/liquid interfacial reaction with controlled conditions of each phase as the reaction locus 査読有り

Sakakura T., Takatsuji Y., Morimoto M., Haruyama T.

Electrochemistry ( 公益社団法人電気化学会 ) 88 ( 3 ) 190 - 194 2020年01月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

In the plasma/liquid (P/L) interfacial reaction, nitrogen fixation is performed on a water phase surface. In the P/L reaction, discharged nitrogen gas reacts with water molecules at the interface between the plasma gas phase and the water phase, followed by either a reduction reaction, ammonia production or oxidation reaction, nitric acid production. The production of nitric acid in the P/L reaction is influenced by the concentration of oxygen present in each gas phase and water phase, and the atomic nitrogen contained in the nitrogen plasma. For the reduction reaction at the P/L reaction locus, the water phase was modulated in order to make ammonia production dominant in nitrogen fixation. Ammonia is released into the gas phase under conditions of high water temperature and high pH. To obtain only ammonia using this reaction, it is necessary to incorporate a process for raising the temperature of the water. In the P/L reaction, only the ammonia gas can be obtained in one-step by using the rise in water temperature due to the discharged heat plasma gas. A reaction system was developed to control the water and the gas phase to enable high purity ammonia trapping as released by the gas phase.

DOI： 10.5796/electrochemistry.19-00080

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CiNii Article

CiNii Research

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水を直接の水素源として窒素還元を行う「相界面反応」によるアンモニア合成招待有り

酒倉辰弥、高辻義行、春山哲也

化学工業 70 ( 11 ) 805 - 809 2019年11月

Contribution of discharge excited atomic N, N2*, and N2+ to a plasma/liquid interfacial reaction as suggested by quantitative analysis. 査読有り

Tatsuya Sakakura, Naoya Murakami, Yoshiyuki Takatsuji, Masayuki Morimoto, Tetsuya Haruyama

ChemPhysChem 20 ( 11 ) 1467 - 1474 2019年09月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Electric-discharge nitrogen comprises three main types of excited nitrogen species-atomic nitrogen (Natom), excited nitrogen molecules (N2*), and nitrogen ions (N2+) – which have different lifetimes and reactivities. In particular, the interfacial reaction locus between the discharged nitrogen and the water phase produces nitrogen compounds such as ammonia and nitrate ions (denoted as N-compounds generically); this is referred to as the plasma/liquid interfacial (P/L) reaction. The Natom amount was analyzed quantitatively to clarify the contribution of Natom to the P/L reaction. We focused on the quantitative relationship between Natom and the produced N-compounds, and found that both N2* and N2+, which are active species other than Natom, contributed to P/L reaction. The production of N-compounds from N2* and N2+ was enhanced upon UV irradiation of the water phase, but the production of N-compounds from Natom did not increase by UV irradiation. These results revealed that the P/L reactions starting from Natom and those starting from N2* and N2+ follow different mechanisms.

DOI： 10.1002/cphc.201900212

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Highly Selective Methane Production Through Electrochemical CO<inf>2</inf> reduction by Electrolytically Plated Cu-Co Electrode 査読有り

Takatsuji Y., Nakata I., Morimoto M., Sakakura T., Yamasaki R., Haruyama T.

Electrocatalysis 10 ( 1 ) 29 - 34 2019年01月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2018, Springer Science+Business Media, LLC, part of Springer Nature. Among the electrode materials used for electrolytic CO2 reduction, only Cu shows a special function of producing not only carbon monoxide (CO), but also hydrocarbons from CO2. We found that, in electrolytic CO2 reduction using an electrolytically plated Cu-Co electrode, a hydrocarbon product with high faradaic efficiency (FE) could be obtained with low-FE CO. The plated electrodes have a Co solid solution on the Cu surface. The non-localized Co changes the adsorption energy of the reaction intermediate in CO2 reduction. Consequently, by increasing the Co content in Cu, HCOOH can be selectively produced. Further, in electrolytic CO2 reduction with an applied potential of − 1.19 V vs. reversible hydrogen electrode (RHE), the selectivity of methane (CH4) production improved, while the selectivity of ethylene (C2H4) formation lowered. In the reduction using the plated electrode containing 14% Co, the FE of CH4 production reached the highest at 47.7%. These results suggested that mixing Co in Cu promotes the hydrogenation of CH2* to CH3* and inhibits the dimerization of CH2* species. Furthermore, this research on plated electrodes is useful for the development of catalytic electrodes for electrolytic CO2 reduction. [Figure not available: see fulltext.]

DOI： 10.1007/s12678-018-0492-0

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