研究者詳細 - 清水　陽一

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Effects of Microwave-Assisted Reflux in Wet-Chemical Synthesis of High Sodium-Ion Conductive Na5DySi4O12 査読有り国際誌

Satoko Takase, Kazuaki Nakashima, Masato Arima, Kouki Terada, Youichi Shimizu

Solid State Ionics ( Elsevier B.V. ) 364 115607 Article number 115607 2021年06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）

Sodium rare-earth silicate with Na5DySi4O12 components is known as a highly conductive and stable sodium ion solid electrolyte though are difficulties in obtaining a single-phase, highly conductive Na5DySi4O12 pellet because it has low conductivity impurity phases. In this study, microwave heating for aqueous solution of starting materials was performed for the formation of homogeneous precursor of Na5DySi4O12. A single-phase Na5DySi4O12 was successfully obtained from the aqueous solution heated with 2.45GHz microwave at 80 °C after calcination at 700 °C and sintering at 1050 °C. The Na5DySi4O12 showed high conductivity of 2.9 × 10−4 at 30 °C and an activation energy of 0.25 eV. The precursor particles with microwave heating were fine particles with a narrower particle size distribution than those without microwaving. The results of thermal analysis showed different thermal behaviors with and without microwaves. The crystalline phase after calcination at 700 °C was different with and without microwave. After sintering at 1050 °C with microwaves was a single-phase Na5DySi4O12, but the pellets without the microwaves heating process did not have a crystalline phase of Na5DySi4O12. These results demonstrated that microwave heating of aqueous solution affects the formation of single-phase Na5DySi4O12.

DOI： 10.1016/j.ssi.2021.115607

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A Cobalt-Nickel Metal-Alloy Thin-Film Sensor for Hydrogen-Phosphate Ion 査読有り国際誌

Hideyasu Nakamura, Satoko Takase, Youichi Shimizu

Analytical Science ( 日本分析化学会 ) 37 ( 2 ) 337 - 340 accepted 2020.9.7, Published on-line 2020.9.11 2021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）

Cobalt-nickel alloy thin-films were prepared by electrodepositing on Au-coated Al2O3substrate from aqueous solutions of metal-salts, and applied as a potentiometric hydrogen-phosphate ion sensor. A doping of 20 mol% nickel in cobalt contributed to enhancing hydrogen-phosphate ion sensing performances, i.e., the sensing range and response time were drastically improved. The Co80Ni20inf>thin-film electrode showed good potentiometric response to hydrogen-phosphate ion between 1.0 × 10–5and 1.0 × 10–3M with a slope of –59 mV/decade and high anion selectivity. The 90% response time to 1 mM H2PO4–was as short as 15 s at pH 5.0, 30°C. A mixed potential sensing mechanism could be proposed on the basis of the results.

DOI： 10.2116/analsci.20P290

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Impedancemetric Sensor Using Eu2CuO4 Thick-film for Detection of CO 査読有り国際誌

Yoshihiko Tanioka, Satoko Takase, Youichi Shimizu

IEEJ Transactions on Sensors and Micromachines ( 電気学会 ) 141 ( 1 ) 37 - 38 accepted 2020.7.8 2021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）

An impedancemetric thick-film CO sensor using RE2CuO4 (RE = La, Sm, Eu, Gd) oxides was examined for monitoring carbon monoxide. The thick-film sensor using Eu2CuO4 showed a high response to CO. The response was almost linear to CO concentration between 50 and 600 ppm, and the 90% response time to 300-ppm CO was approximately 90 s, although the CO response of the sensor was affected by NO and NO2 at low concentration.

DOI： 10.1541/ieejsmas.141.37

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Solid-State HCl Gas Sensor Using Na5DySi4O12 and RuO2 Electrode 査読有り国際誌

Yoshiyuki Hashimoto, Masaho Kanou, Satoko Takase, Youichi Shimizu

IEEJ Transactions on Sensors and Micromachines ( 電気学会 ) 141 ( 11 ) 386 - 387 2021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）

A potentiometric solid-state sensor using a Na5DySi4O12 solid-electrolyte and oxide electrodes was tried to examine for monitoring HCl gas. Among the oxides tested, the sensor using RuO2 electrode showed relatively good HCl response at 400°C. The electromotive force was almost linear to the logarithm of HCl concentration between 100 and 1000 ppm. This HCl sensor showed also good selectivity to CO2, NO, and NO2, and few effect of oxygen. A mixed potential sensing mechanism is tentatively proposed.

DOI： 10.1541/ieejsmas.141.386

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ガスセンサの呼気検出によるヘルスケア分野への応用招待有り

清水陽一

ぶんせき ( 日本分析化学会 ) 551 ( 11 ) 467 - 468 2020年11月

Journal of the Ceramic Society of Japan the 58<sup>th</sup> Symposium on Basic Science of Ceramics

Nakajima A., Kakihana M., Shimizu Y., Saito H., Inumaru K., Kirihara S., Fuji M.

Journal of the Ceramic Society of Japan 128 ( 11 ) 2020年11月

Photoelectrochemical Reduction of CO2 using a TiO2 Photoanode and a Gas Diffusion Electrode Modified with a Metal Phthalocyanine Catalyst 査読有り国際誌

Katsuichiro Kobayashi, Shi Nee Lou, Yoshiyuki Takatsuji, Tetsuya Haruyama, Youichi Shimizu, Teruhisa Ohno

Electrochimica Acta 338 Article number 135805 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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ペロブスカイト型酸化物担持電極の亜硝酸イオン応答特性

森山実加子、高瀬聡子、清水陽一

Chemical Sensors 36 ( Sup. A ) 52 - 54 2020年03月

A Lithium-Ion Conductive Li1.5Al0.25Ga0.25Ti1.5(PO4)3 Solid Electrolyte for Electrochemical Device 査読有り国際誌

Kengo Oda, Hiroaki Saitoh, Yuto Hoaki, Hayato Shimoda, Toyoki Hirao, Wataru Ichiyoshi, Satoko Takase, and Youichi Shimizu

Solid State Ionics 346 Article number 115212 2020年03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）

Lithium-ion solid electrolyte disc with high conductivity even at low temperature for electrochemical devices were designed using Li1+x+yAlxGayTi2-x-y(PO4)3 (x + y = 0–0.5) with NASICON-type structure. The solid-electrolyte discs were synthesized by a solution method at 900–1000 °C. Effects of Al and/or Ga dopants and crystal structures on ionic conductivity of the solid electrolytes were investigated. Almost single phase of Li1+x+yAlxGayTi2-x-y(PO4)3 (x + y = 0–0.5) systems could be synthesized at sintering temperatures above 900 °C up to x = 0.5, y = 0.25. An ionic conductivity as high as 9.3 × 10−4 S/cm at 30 °C and activation energy of 0.29 eV were obtained with the trivalent-cation double-doped Li1.5Al0.25Ga0.25Ti1.5(PO4)3 disc sintered at 900 °C.

DOI： 10.1016/j.ssi.2019.115212

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Preparation of layered perovskite-type cuprate thick-film electrode by electrophoretic deposited method and its nitrite-ion sensing properties 査読有り国際誌

Mikako Moriyama, Haruna Shimoji, Yasunari Shinoda, Satoko Takase, Norahim Ibrahim, Youichi Shimizu

Journal of the Ceramic Society of Japan ( 公益社団法人日本セラミックス協会 ) 127 ( 10 ) 703 - 707 2019年10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）

Detection of nitrite-ion has become very important for various industrial fields due to its wide application range such as food additives and a rust preventive agent for steels. In this study, we attempted at developing an advanced method to produce layered perovskite-type cuprates based thick-film device for highly sensitive electrochemical sensor for nitrite-ion with a capacity of wide concentration range. Here, layered perovskite-type oxide powders could be synthesized by a polymer precursor method which was deposited on alumina supports with gold electrode by an electrophoretic deposition method. The sensor performance was measured by an amperometric method for nitrite-ion detection. It was found that the Gd2CuO4-based electrode showed fast and good linear responses to nitrite-ion for a wide range of concentration.

DOI： 10.2109/jcersj2. 19078

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Effects of Crystallographic Structures of Metal-Phthalocyanine on Electrocatalytic Properties of Oxygen Reduction in Acidic Condition 査読有り国際誌

Satoko Takase, Yuki Aoto, Daiki Ikeda, Hideaki Wakita and Youichi Shimizu

Electrocatalysis 10 ( 6 ) 653 - 662 2019年10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）

Effects of the crystallographic structures of metal-phthalocyanines (metal: Co, Ni, Cu, Zn) between α and β phases on electrochemical oxygen reduction catalytic activities were investigated in acidic condition. As the distances of centered-metal in the structures of α and β phases are 3.8 Å and 4.8 Å, respectively, they were closed to the size of an oxygen molecule (3.6 Å). The phases of metal-phthalocyanines were conducted by an interface deposition method. The obtained catalyst powders were characterized by means of X-ray diffraction and X-ray photoelectron spectra analyses. Electrochemical oxygen reduction performances were mainly measured by using a gas diffusion type carbon electrode loaded with a metal-phthalocyanine. It was confirmed that the catalytic activities of cobalt- and copper-centered phthalocyanines were enhanced by the conversion from β to α phases. The effects of the distance between the metals in the crystallographic structures of metal-phthalocyanines should be explained by the adsorbed oxygen states that depend on the distance between the metals. The α phase has the distance which allows to form the bridge configuration of oxygen molecule which requires two adsorption sites and that eventually produces H2O by the direct 4-electron pathway. Analysis with the rotating disk electrode system showed that the α-phased metal-phthalocyanines enhance the 4-electron reduction pathway. [Figure not available: see fulltext.].

DOI： 10.1007/s12678-019-00553-2

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電気泳動法によるペロブスカイト系酸化物厚膜電極の作製とアニオンセンサの応用

森山実加子、篠田泰成、下地春菜、高瀬聡子、清水陽一

Chem. Sensors 35 ( Sup. A ) 67 - 69 2019年03月

Improvement of Sensing Performance of Imedancemetric C2H2 Sensor Using SmFeO3 Thin-Film Prepared by a Polymer Precursor Method 査読有り

Tomohisa Tasaki, Satoko Takase, Youichi Shimizu

Sensors 19 ( 4 ) 773(1/11) - （11/11） 2019年02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）

A sensitive an impedancemetric acetylene (C 2 H 2 ) gas sensor device could be fabricated by using perovskite-type SmFeO 3 thin-film as a sensor material. The uniform SmFeO 3 thin-films were prepared by spin-coating and focusing on the effects of polymer precursor solutions. The prepared precursors and thin-films were characterized by means of thermal analysis, Fourier-transform infrared spectroscopy, ultraviolet–visible spectroscopy, X-ray diffraction analysis, scanning electron microscopy and X-ray photoelectron spectroscopy . It was found that particle growth and increase in homogeneity of the prepared thin-film could be accelerated by the addition of acetyl acetone (AcAc) as a coordination agent in the polymer precursor solution. Moreover, the highly crystallized thin-film-based sensor showed good response properties and stabilities to a low C 2 H 2 concentration between 0.5 and 2.0 ppm.

DOI： 10.3390/s19040773

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表面機能材料の研究動向と将来展望－化学センサの研究動向－招待有り

清水陽一

セラミックス ( 日本セラミックス協会 ) 54 ( 1 ) 48 - 51 2019年01月

Pyrochlore-type Bi2Sn2O7 oxide as an electrocatalyst for carbon dioxide reduction 査読有り国際誌

Mori A., Kawamura M., Takase S., Shimizu Y.

Journal of the Ceramic Society of Japan ( 公益社団法人日本セラミックス協会 ) 126 ( 10 ) 843 - 846 2018年10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）

Pyrochlore-type A2B2O71z (A = Pb, Bi; B = Nb, Ru, Sn, Ir) oxide fine powders were synthesized by a wet-chemical method. The electrochemical reduction properties of carbon dioxide were investigated with carbon-based gas-diffusion-type electrodes loaded with various pyrochlore-type oxide catalysts. The currentvoltage curves under pure CO2 gas flow showed that the Sn-based pyrochlore-type oxides gave high electrocatalytic activities for the electrochemical CO2 reduction. Among the pyrochlore-type oxides tested, Bi2Sn2O7 showed the highest CO2 reduction reaction which gave CO as a main product at very high concentration. XPS analyses showed that the high performance for the electrochemical CO2 reduction of Bi2Sn2O7 was come from the valence state of Sn and/or oxygen adsorptiondesorption properties of the pyrochlore-type oxide.

DOI： 10.2109/jcersj2.18079

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金属フタロシアニン系薄膜電極のH2O2応答特性

髙瀨聡子, 森山実加子, 清水陽一

Chem. Sensors 34 ( Sup. A ) 67 - 69 2018年03月

ゼオライト系レセプタを用いた固体電解質インピーダンス型NOxセンサの応答特性

福島悠太, 髙瀨聡子, 清水陽一

Chem. Sensors 34 ( Sup. A ) 112 - 114 2018年03月

Solid Electrolyte Impedancemetric NOx Sensor Attached with Zeolite Receptor 査読有り

Youichi Shimizua, Hikaru Nakanoa, Satoko Takasea, and Jeong-Hwan Song

Sensors & Actuators B 264 177 - 183 2018年02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）

A new type solid-electrolyte impedancemetric sensor using a zeolite as a receptor and a Li1.5Al0.5Ti1.5(PO4)3 (LATP) disc as a transducer, respectively, was designed and its sensing properties were investigated for detection of NO and NO2 in the range of 100–500 ppm at 300–500 °C. It was revealed that the impedance responses of the sensor device attached with a zeolite receptor changed with depending on NOx concentration. Cation-exchange in zeolites gave good improvement of the sensor responses. Among the ion-exchanged zeolites, K+-doped Y-type zeolite-based sensor showed the highest sensitivity and selectivity to NO2.

DOI： 10.1016/j.snb.2018.02.146