2022/05/17 更新

写真a

クニモト マサヒロ
國本 雅宏
所属
理工学術院 先進理工学部
職名
講師(任期付)

学位

  • 早稲田大学   博士(工学)

所属学協会

  •  
     
     

    電気化学会

  •  
     
     

    表面技術協会

 

研究分野

  • 複合材料、界面

論文

  • Direct formation of metal layer on anion exchange membrane using electroless deposition process

    Tatsuki Fujimura, Masahiro Kunimoto, Yasuhiro Fukunaka, Hiroshi Ito, Takayuki Homma

    Electrochemistry   89 ( 2 ) 192 - 196  2021年03月

     概要を見る

    In this work, a novel electroless deposition process on the anion exchange membrane (AEM) is proposed. AEM surface has a positively charged functional group, which in general does not allow the catalyst particle, such as Pd, to be formed on the surface. Hence, a different strategy from the conventional catalyzation process was required. We found that the sensitization process using Sn-containing solution, which is widely applied in the electroless plating on nonconductive substrates, hindered the Pd particle modification, which hence inhibited the following deposition reaction. Our several experiments and density functional theory analyses suggest that for Pd particle modification, anion in the bath turned out to play a key role. In particular, Cl provides the sufficiently strong connection between the precursor Pd and positive functional group of the substrate. This leads to favorable deposition of Pd catalyst particles and metal layer formation on the AEM. Therefore, we conclude that just a single pre-treatment to immerse the AEM films into PdCl /HCl solution is capable to perform electroless plating on it. We applied the novel process to the electrode formation, such as Pt and Ni-P, on the AEM for hydrogen evolution reaction (HER) as a case study. Both Pt and Ni-P was successfully formed on the AEM. The electrochemical measurements show that those electrodes are able to serve as the catalytic electrode for HER. The electroless process proposed here opens possibility of the direct metal fabrication on ion exchange membrane surface. − 2+ 2

    DOI

  • Analysis of the hydrogen evolution reaction at Ni micro-patterned electrodes

    Tatsuki Fujimura, Masahiro Kunimoto, Yasuhiro Fukunaka, Takayuki Homma

    Electrochimica Acta   368  2021年02月

     概要を見る

    The behavior of bubbles generated by the hydrogen evolution reaction (HER) and the effect of these bubbles on HER performance were investigated using Ni micro-patterned electrodes. This study focused on the correlation between bubble behaviors affecting potential increase of HER and the surface microstructures of micro-patterned Ni cathode. Ni microdot array structures with diameters of approximately 5–10 μm, pitch of approximately 5–10 μm, and various dot heights were fabricated for alkaline water electrolysis measurements. The Ni micro-patterned structures controlled the surface wettability of the electrode. The change in the wettability influenced the HER efficiency during galvanostatic electrolysis at –20 mA cm . Moreover, in situ observation of the evolved bubbles on the electrode surface revealed that bubbles with larger diameters evolved on the electrode surface with lower wettability, and bubbles tended to detach from the electrode surface by decreasing the contact area between the bubbles and the electrode. It was also observed that bubbles evolved more easily on the sidewall of Ni microdots and that generated bubbles moved onto the surface of the microdots in high-aspect Ni micro-patterned electrodes, indicating that an increase in the overpotential can be suppressed by different bubble nucleation behaviors. Therefore, the micro-patterned surface texture affected the bubble nucleation and growth behaviors, which would suppress the decrease in HER efficiency. These results can provide insights for fabricating highly efficient surfaces for HER catalytic electrodes. –2

    DOI

  • First-principle study of the oxidation mechanism of formaldehyde and hypophosphite for copper and nickel electroless deposition process

    Y. Onabuta, M. Kunimoto, H. Nakai, T. Homma

    Electrochim. Acta   307   536 - 542  2019年  [査読有り]

  • Effect of Li+ addition on growth behavior of ZnO during anodic dissolution of Zn negative electrode

    T. Otani, T. Yasuda, M. Kunimoto, M. Yanagisawa, Y. Fukunaka, T. Homma

    Electrochim. Acta   305   90 - 100  2019年  [査読有り]

  • In Situ Measurement for Diffusion-Adsorption Process of Cl− and SPS in Through-Silicon Via Using SERS Effect Produced by Cu Nanodot Arrays

    M. Kunimoto, F. Yamaguchi, M. Yanagisawa, T. Homma

    J. Electrochem. Soc.   166 ( 6 ) D212 - D217  2019年  [査読有り]

  • Spectroscopic and Computational Analyses of Liquid–Liquid Interfacial Reaction Mechanism of Boric Acid Esterification with 2,2,4-Trimethyl-1,3-pentanediol in Boron Extraction Processes

    M. Kunimoto, D. Bothe, R. Tamura, T. Oyanagi, Y. Fukunaka, H. Nakai, T. Homma

    J. Phys. Chem. C   122 ( 19 ) 10423 - 10429  2018年05月  [査読有り]

    DOI

  • Surface enhanced Raman spectroscopy measurement of surface pH at the electrode during Ni electrodeposition reaction

    T. Homma, M. Kunimoto, M. Sasaki, T. Hanai, M. Yanagisawa

    J. Appl. Electrochem.   48 ( 6 ) 561 - 567  2018年  [査読有り]

  • Direct observation of the diffusion behavior of an electrodeposition additive in through-silicon via using in situ surface enhanced Raman spectroscopy

    T. Homma, A. Kato, M. Kunimoto, M. Yanagisawa

    Electrochem. Commun.   88   34 - 38  2018年  [査読有り]

  • Depth profiling of APTES self-assembled monolayers using surface-enhanced confocal Raman microspectroscopy

    Yingying Sun, Masahiro Yanagisawa, Masahiro Kunimoto, Masatoshi Nakamura, Takayuki Homma

    SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY   184   1 - 6  2017年09月  [査読有り]

     概要を見る

    The internal structure of self -assembled monolayers (SAMs) such as 3-aminopropyltriethoxysilane (APTES) fabricated on a glass substrate is difficult to characterize and analyze at nanometer level. In this study, we employed surface -enhanced Raman spectroscopy (SERS) to study the internal molecular structure of APTES SAMs. The sample APTES SAMs were deposited with Ag nanoparticles to enhance the Raman signal and to obtain subtler structure information, which were supported by density functional theory calculations. In addition, in order to carry out high -resolution analysis, especially for vertical direction, a fine piezo electric positioner was used to control the depth scanning with a step of 0.1 nm. We measured and distinguished the vertical Raman intensity variations of specific groups in APTES, such as Ag/NH2, CH2, and Si-O, with high resolution. The interfacial bond at the two interfaces of Ag-APTES and APTES-SiO2 was identified. Moreover, APTES molecule orientation was demonstrated to be inhomogeneous from frequency shift. (C) 2017 Elsevier B.V. All rights reserved.

    DOI

  • HAMR EMULATION ON CARBON OVERCOAT AND LUBRICANT FOR NEAR FIELD TRANSDUCER AND MAGNETIC MEDIA USING SURFACE-ENHANCED RAMAN SENSORS

    M. Yanagisawa, M. Kunimoto, T. Homma

    PROCEEDINGS OF THE ASME 26TH ANNUAL CONFERENCE ON INFORMATION STORAGE AND PROCESSING SYSTEMS, 2017    2017年  [査読有り]

     概要を見る

    A plasmonic sensor is used for emulation of near field transducer (NFT). Some overcoat films (thickness of 1nm) were coated on Au nanoparticles (NPs) on a convex quartz glass substrate (plasmonic sensor). Heating behavior of the films was examined by laser heating using novel Raman spectroscopic tools, i.e. surface-enhanced Raman scattering (SERS) with the plasmonic sensor, a continuous laser heating tool, in-situ observation of spectra and temperature with a high speed time resolved measurement. The heating temperature of tetrahedral carbon (ta-C) film in He gas is lower than that in air. This is because the thermal conductivity of He is larger than air. Few spectral change of ta-C film (thickness of 1nm) on Au NP's is observed except initial change in around 100 s at the temperature around 500 degrees C, which corresponds to the temperature of the carbon overcoat (COC) for the media temperature of 327 degrees C (600K, Currie temperature for CoPt alloy). Some carbide films, i.e. SiC, TiC, and WC, showed high heat resistance, that is, few spectral change was observed. It is found that lubricant is evaporated from the COC on magnetic media and transferred to the plasmonic sensor.

  • Fabrication of channel type mixing devices for efficient solvent extraction for high purity silica production

    Yelchur Venkata Akash, Masaki Mimura, Masahiro Kunimoto, Yasuhiro Fukunaka, Takayuki Homma

    ECS Transactions   80 ( 10 ) 1441 - 1446  2017年  [査読有り]

     概要を見る

    As one of the most cost-effective methods to produce solar-grade silicon (SOG-Si), purification of silica solution by extracting its impurities through wet chemical processes has been proposed. This paper reports on the design of channel type reactor for liquid-liquid extraction to purify silica solution, focusing particularly on the extraction of B (boric acid) in aqueous phase with 2,2,4-trimethyl-1,3-pentanediol (TMPD) in organic phase. The reactor fabricated by 3D printing technology was designed to have two characteristic structures: (i) a throat structure that shows gradually diverging part after converging near Y shaped inlets and (ii) obstacles structure on downstream. Two solutions were made to contact with each other by turbulent mixing around the throat structure, causing small droplets formation that was dispersed and retained efficiently even on downstream by obstacles structure. This droplet dispersion shortens diffusion distance of boric acid to meet TMPD at the liquid-liquid interface, providing efficient mass transfer. At higher flow rate i.e., 380 ml/min, the extraction efficiency was 97.43% after the multi stage process. The results suggest that the channel type reactor designed here is profitable for elimination of impurities, such as B or P, in silica solution to produce SOG-Si.

    DOI

  • Analysis of cathodic reaction process of SiCl4 during Si electrodeposition in ionic liquids

    Yasuhiro Tsuyuki, Tatsuki Fujimura, Masahiro Kunimoto, Yasuhiro Fukunaka, Piero Pianetta, Takayuki Homma

    Journal of the Electrochemical Society   164 ( 14 ) D994 - D998  2017年  [査読有り]

     概要を見る

    Elementary steps in the electrochemical reduction process of SiCl4 in trimethyl-n-hexylammonium bis(trifluoromethylsulfonyl) imide (TMHATFSI) was investigated, focusing on molecular level behavior of the reactants at solid-liquid interface. Electrochemical measurements using an electrochemical quartz crystal microbalance (EQCM) identified a reduction peak corresponding to Si electrodeposition and several elementary steps with stable intermediates forming prior to the deposition. For detailed analysis, X-ray reflectivity (XRR) measurements with synchrotron radiation were applied in situ. The change in reflectivity of the electrode surface during the deposition was found to be due to the formation of a polymer-like Si such as Si2Cl6, which is an intermediate layer during the deposition process. These results were theoretically supported by density functional theory (DFT) calculations: after an electron transfers from the electrode, the Si in SiCl4 forms the bond with another SiCl4, rather than the Si of the substrate, resulting in the formation of the intermediate structure. These data suggest an elementary step in the SiCl4 reduction process which can be described as follows
    when SiCl4 is reduced, a polymer-like Si form such as Si2Cl6 is generated. This intermediate species further reacts with other Si reactants after receiving additional electrons, which then finally deposits as Si on the substrate.

    DOI

  • Theoretical Study on the Formation Mechanism of Amino Acid-Cu(II) Complexes on an Enantio-Sensing Device Interface

    Masahiro Kunimoto, Tyusuke Sadaoka, Takuya Nakanishi, Rtetsuya Osaka, Takayuki Homma

    JOURNAL OF PHYSICAL CHEMISTRY C   120 ( 29 ) 15722 - 15728  2016年07月  [査読有り]

     概要を見る

    Theoretical analyses of L-alanine (L-Ala)- and L-homocysteine (L-Hcy)-Cu(II) complexes in basic, neutral, and acidic solutions were carried out using density functional theory to investigate the pH dependence of the formation mechanism of amino acid-Cu(II) complexes. The calculated complex formation energies indicate that the amino acid-Cu(II) complexes were expected to form in basic and neutral solutions but not in acidic solutions. The factors that determine the stability of these complexes are the coordination ability of each amino acid and the significance of intramolecular interactions among ligands within the complexes. As predicted from the molecular structure, in neutral solutions, the coordination ability of amino acid becomes lower than that in basic solutions because of the inert structure of the protonated amino group, -NH3+; however, the coordination ability originating from the -COO- group is estimated to be sufficient for stabilizing the entire complex system. Moreover, two H2O molecules coordinate with the central Cu2+ ion from the equatorial direction and interact with the coordinating amino acids, providing additional stability within the complex. In contrast, in acidic solutions, the complex does not have either sufficient coordination ability of amino acids or effective intramolecular interactions within the complex.

    DOI

  • Estimated phase transition and melting temperature of APTES self-assembled monolayer using surface-enhanced anti-stokes and stokes Raman scattering

    Yingying Sun, Masahiro Yanagisawa, Masahiro Kunimoto, Masatoshi Nakamura, Takayuki Homma

    APPLIED SURFACE SCIENCE   363   572 - 577  2016年02月  [査読有り]

     概要を見る

    A structure's temperature can be determined from the Raman spectrum using the frequency and the ratio of the intensities of the anti-Stokes and Stokes signals (the I-as/I-s ratio). In this study, we apply this approach and an equation relating the temperature, Raman frequency, and I-as/I-s ratio to in-situ estimation of the phase change point of a (3-aminopropyl)triethoxysilane self-assembled monolayer (APTES SAM). Ag nanoparticles were deposited on APTES to enhance the Raman signals. A time-resolved measurement mode was used to monitor the variation in the Raman spectra in situ. Moreover, the structural change in APTES SAM (from ordered to disordered structure) under heating was discussed in detail, and the phase change point (around 118 degrees C) was calculated. (C) 2015 Elsevier B.V. All rights reserved.

    DOI

  • DEPTH PROFILE ANALYSIS OF CHEMICAL STRUCTURES AROUND LUBRICANT/OVERCOAT INTERFACE USING PLASMONIC SENSOR

    M. Yanagisawa, M. Kunimoto, T. Homma

    PROCEEDINGS OF THE ASME CONFERENCE ON INFORMATION STORAGE AND PROCESSING SYSTEMS, 2016    2016年  [査読有り]

     概要を見る

    A chemical depth profile in lubricant films, carbon films, and their interfaces is an informative parameter for hard disk media because molecular features of lubricants bonded to a surface of carbon overcoats (COCs), which usually consist of a nitrogen doped layer, are important to achieve high tribological performance. However, it was difficult to analyze their interfaces with high depth resolution because thickness of lubricant films and COC films are so thin, i.e. 1.5nm and 2nm, respectively. We have developed new method using plasmonic sensors, which has measurement capability for chemical structures with depth resolution of 0.1nm by surface-enhanced Raman spectroscopy (SERS). We examined the lubricant film composed of perfluorinated polyether (PEPE) with phosphazene derivative (A2OH) on a diamond-like carbon (DLC) film. The result shows that the functional group is adsorbed on the DLC surface, where lower shift in the wave number of phenyl group is observed. The depth profile of the intensity ratio of D-peak to G-peak shows the maximum at around the surface of the DLC film. A variety of organic components in the DLC films, fabricated by a chemical vapor deposition (CVD), were observed in it. Besides, the depth profiles shows that organic materials, involving methyl, ethyl, or ethylene groups, Co(OH)x exist in the film

  • LIFE ESTIMATION OF CARBON OVERCOAT ON MAGNETIC MEDIA FOR HEAT-ASSISTED MAGNETIC RECORDING USING NOVEL RAMAN SPECTROSCOPY

    M. Yanagisawa, M. Kunimoto, T. Homma

    PROCEEDINGS OF THE ASME CONFERENCE ON INFORMATION STORAGE AND PROCESSING SYSTEMS, 2016    2016年  [査読有り]

     概要を見る

    A heat-assisted magnetic recording (HAMR) is expected for a future high density recording of a hard disk drive. However, a. carbon overcoat (COC) composed of diamond-like carbon (DLC) or a lubricant film is possibly damaged when a magnetic medium, i.e. CoPt alloy, is heated at around Curie temperature (Tc) of 600K by a near-field HAMR head. We carried out HAMR. simulation experiments by using newly developed Raman spectroscopic systems, composed of plasmonic sensors for surface-enhanced Raman scattering (SERS), a pulsed laser heating, and an in-situ temperature measurement with an intensity ratio of anti-Stokes/Stokes lines. It was found that the heated temperature of the COC is higher than that of the magnetic film, i.e., 580 degrees C and 366 degrees C, respectively. Intensity changes of G-band peak in Raman spectra for DLC films were observed during the pulsed laser heating. The Raman intensity was exponentially decreased by oxidation in air, where time constants were calculated as a parameter of a pulse width. Degradation life of the DLC film can be estimated from a critical pulse width, where the time constant is extrapolated to zero. The estimated pulse width for no degradation was 250 mu s at the heating temperature of 580 degrees C. The result shows no damage can be estimated in DLC films for HAMR. because the effective irradiation time is 5ns and the accumulated irradiation time is 0.5ms in HAMR operations.

  • Transmission-type plasmonic sensors for surface-enhanced Raman spectroscopy

    M. Yanagisawa, M. Saito, M. Kunimoto, T. Homma

    Appl. Phys. Express   9 ( 12 ) 122002  2016年  [査読有り]

  • 無電解めっきプロセスにおける最近の研究動向

    國本雅宏, 本間敬之

    表面技術   66 ( 10 ) 438 - 442  2015年

  • 無電解析出プロセスにおける還元剤BH4-に対するCu及びPd表面の触媒作用機構の理論的解析

    國本雅宏, 中井浩巳, 本間敬之

    表面技術   66 ( 12 ) 666 - 669  2015年  [査読有り]

  • Elimination of boron from soluble silica via solvent extraction with 2,2,4-trimethyl-1,3-pentanediol using a multistage flow-type reactor

    Nobufumi Matsuo, Takafumi Ishihara, Takahiro Oyanagi, Kazuki Nakajima, Masahiro Kunimoto, Yasuhiro Fukunaka, Takayuki Homma

    ECS Transactions   64 ( 45 ) 91 - 97  2015年  [査読有り]

     概要を見る

    Elimination of boron species via solvent extraction with 2,2,4-trimethyl-1,3-pentandiaol was engaged in a flow-type device into which the aqueous solution dissolving diatomaceous earth, a -candidate of the resource for high-purity silicon material. The flow-type device has a 2-stage channel with 1.0 mm width, 0.10 mm depth, and 25 mm length each, and the specific interfacial area is comparable to a typical microchannel device. Residual boron content in the aqueous solution decreased to less than 0.1 ppm after the solvent extraction under the restriction of short contact duration shorter than 100 ms. In addition, the analysis with density functional theory indicated that the number of neighbor carbon on the central carbon is one of the keys for improvement of reactivity of extractant. Hence, it is suggested that the flow-type microchannel device with solvent extraction with alkyldiol extractant can be utilized as an attractive approach toward the production of high-purity silica as a source for solar-grade silicon.

    DOI

  • CHEMICAL ANALYSIS OF ULTRA-THIN DLC FILMS AND LUBRICANT/DLC INTERFACE USING PLASMONIC SENSORS

    M. Yanagisawa, M. Kunimoto, T. Homma

    PROCEEDINGS OF THE ASME CONFERENCE ON INFORMATION STORAGE AND PROCESSING SYSTEMS, 2014    2014年  [査読有り]

     概要を見る

    The technical potential of a new plasmonic sensor, which can acquire surface-enhanced Raman spectra with high sensitivity by controlling surface plasmons is demonstrated for the chemical analysis of diamond-like carbon (DLC) films, lubricant films, and the DLC/lubricant interface on magnetic disks of sub-nanometer scale. The Raman spectra of thin DLC films and lubricated DLC carbon can be acquired with a high S/N ratio. Raman spectra of lubricated DLC carbon can also be acquired with the high S/N ratio. The wavenumber shift and intensity change of the Raman peaks of the phenyl and hydroxyl groups in the mixed lubricants (ADOH and Z-tetraol) show that the chemical interaction with the DLC surfaces of the phenyl group in the lubricant molecule decreases with increasing nitrogen content, whereas that of the hydroxyl group with the nitrogenated carbon increases. Raman spectra of nitrogenated DLC films are also acquired, the peaks show good agreement with density functional theory calculations. The calculated bonding energy indicates that the hydroxyl groups interact with the nitrogenated carbon.

  • DFT Analysis on Cathodic Reaction of Au Thiosulfate Complex at Au(111) Surface – Cathodic Reaction Modeling

    M. Kunimoto, H. Nakai, T. Homma

    ECS Trans.   58 ( 32 ) 73 - 79  2014年  [査読有り]

    DOI

  • Raman and DFT Study of the Reaction of Hydrazine and Hypophosphite on a Cu Surface in the Electroless Deposition Process

    Bin Jiang, Siggi Wodarz, Masahiro Kunimoto, Masahiro Yanagisawa, Takayuki Homma

    ELECTROCHEMISTRY   81 ( 9 ) 674 - 677  2013年09月  [査読有り]

     概要を見る

    Oxidation of the reductants is a dominant factor in the electroless deposition process. In order to obtain fundamental knowledge about the reaction mechanism of reductant oxidation for more precise control of the solid-liquid interface in this process, we have attempted to characterize the behavior of reductants adsorbed on Cu surface by using plasmon antenna enhanced Raman scattering. The concentric-patterned antenna coated with Cu, which consisted of a dimple array with single hole or a single hole with coaxial dimples, was designed by Finite Difference Time Domain (FDTD) calculation to enhance the electric field by focusing surface plasmons. By using this antenna and comparing the spectra to the results of Density Functional Theory (DFT) calculations, Raman peaks of adsorbed reductants on Cu were identified. Furthermore, we examined the conformation of adsorbed reductants by DFT calculation of the adsorption model of reductants on fcc-Cu(111) surface. As a result, the nature of reductant adsorption on Cu surface has been investigated from a computational point of view and an experimental point of view, and such in-situ characterization will be useful for analysis of a variety of systems at solid-liquid interface. (c) The Electrochemical Society of Japan, All rights reserved.

    DOI

  • Analysis of hydrazine on a Cu surface with nanoscale resolution using surface enhanced Raman spectroscopy

    Bin Jiang, Takanari Ouchi, Naofumi Shimano, Akira Otomo, Masahiro Kunimoto, Masahiro Yanagisawa, Takayuki Homma

    ELECTROCHIMICA ACTA   100   317 - 320  2013年06月  [査読有り]

     概要を見る

    This paper described characterization of hydrazine adsorption on Cu surface with high-selectivity of component at right angle down to single molecular level using a plasmonic antenna enhancing Raman scattering. The antenna deposited by Cu with concentric pattern was designed by Finite Difference Time Domain (FDTD) calculation to enhance the electric field by focusing surface plasmon. By using this antenna, Raman peaks of adsorbed hydrazine on Cu was provided at 385 cm(-1). Furthermore, these peaks were only observed at 1-2 nm from the antenna surface which meant that this approach had a potential to define the structure of adsorbed hydrazine just only on the plasmon antenna. The structure of adsorbed hydrazine was gauche-conformation. This data corresponded to the Density Functional Theory (DFT) of adsorption model of hydrazine on fcc-Cu (1 1 1) surface. These results suggest that this method creates a wide range of spin-off effects to the characterization of solid-liquid interface. (c) 2012 Elsevier Ltd. All rights reserved.

    DOI

  • Effect of Thiourea on Oxidation of Hypophosphite Ions on Ni Surface Investigated by Raman Spectroscopy and DFT Calculation

    Bin Jiang, Masahiro Kunimoto, Masahiro Yanagisawa, Takayuki Homma

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY   160 ( 9 ) D366 - D371  2013年  [査読有り]

     概要を見る

    Thiourea is well known and widely used additive for controlling the rate of electroless Ni deposition, and it is known to show complicated behavior in acidic/alkaline electroless deposition baths. To understand this, several experiments and theoretical calculations were performed. In the experiments, the adsorption of thiourea and the reducing agent (i.e., hypophosphite ions) on a Ni surface was characterized with a high-selectivity component at a right angle down to the sub-monolayer level using surface-enhanced Raman spectroscopy. By comparing the results with those obtained from the theoretical calculation, co-adsorption of thiourea and hypophosphite ions on the Ni surface was confirmed. Moreover, the acceleration or suppression effects of thiourea on the oxidation of hypophosphite ions on a Ni surface in acidic/alkaline bath were analyzed from the experimental and computational perspectives. Accordingly, an explanation that unifies both the acceleration and suppression mechanisms of thiourea in terms of its own fundamental characteristics is proposed; this will be one of the most important processes for industrial applications of electroless Ni deposition. (C) 2013 The Electrochemical Society. All rights reserved.

    DOI

  • Acceleration effect of thiourea on the oxidation reaction of hypophosphite ion on Ni surface

    Kunimoto, Masahiro, Endo, Kazuaki, Nakai, Hiromi, Homma, Takayuki

    Electrochimica Acta   100   311 - 316  2013年  [査読有り]

    DOI

  • Theoretical analysis of the influence of surface defects on the reactivity of hypophosphite ions

    Kunimoto, Masahiro, Otomo, Akira, Takahashi, Nana, Nakai, Hiromi, Homma, Takayuki

    Electrochimica Acta   113   785 - 791  2013年  [査読有り]

    DOI

  • Theoretical Analysis of Catalytic Activity of Metal Surfaces on Reaction of Hypophosphite Ion

    Kunimoto, Masahiro, Nakai, Hiromi, Homma, Takayuki

    Electrochemistry   80 ( 3 ) 126 - 131  2012年  [査読有り]

    DOI

  • Theoretical Analysis of Adsorption Structure of Hydrated Hypophosphite Ion on Pd(111) Surface

    M. Kunimoto, K. Seki, H. Nakai, T. Homma

    Electrochemistry   80 ( 4 ) 222 - 225  2012年  [査読有り]

  • Theoretical analysis on catalytic activity of metal surfaces on reaction of hypophosphite ion

    M. Kunimoto, H. Nakai, T. Homma

    J. Electrochem. Soc.   80 ( 3 ) 1 - 6  2011年  [査読有り]

    DOI

  • 量子化学計算手法による無電解析出プロセスの解析

    國本雅宏, 本間敬之

    表面技術   62 ( 12 ) 657 - 662  2011年

  • Density Functional Theory Analysis of Reaction Mechanism of Hypophosphite Ions on Metal Surfaces

    Masahiro Kunimoto, Takuya Shimada, Shuichi Odagiri, Hiromi Nakai, Takayuki Homma

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY   158 ( 9 ) D585 - D589  2011年  [査読有り]

     概要を見る

    The elementary steps of the reactions of hypophosphite ions with Cu, Ni, and Pd were calculated theoretically using Density Functional Theory (DFT) to demonstrate the reaction mechanism and gain insight at the molecular level. The elementary steps of these reactions are adsorption, dehydrogenation, and oxidation (hydroxyl base attack). In the adsorption step, hypophosphite ions adsorb onto each surface spontaneously with stabilities in the order of Ni (111) > Pd (111) > Cu (111). In the dehydrogenation step, hypophosphite ions dehydrogenate on Ni (111) and Pd (111) with small reaction barriers, whereas they react on Cu (111) with a large reaction barrier. The large reaction barrier on Cu (111) is not compensated for by the adsorption energy on the surface. In the oxidation step, dehydrogenated anions on each metal surface react spontaneously with the hydroxyl base. The reaction barriers on each metal surface in this step are not so significant compared to the adsorption energies on each surface, suggesting that a reaction barrier of hypophosphite ion oxidation should exist in the dehydrogenation step and only be observed for Cu (111). This proposition elucidates the experimental catalytic behaviors of metal surfaces in the electroless deposition process using hypophosphite ions. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3609000] All rights reserved.

    DOI

  • Density Functional Theory Analysis for Orbital Interaction between Hypophosphite Ions and Metal Surfaces

    Kunimoto, Masahiro, Nakai, Hiromi, Homma, Takayuki

    Journal of the Electrochemical Society   158 ( 10 ) D626 - D633  2011年  [査読有り]

    DOI

▼全件表示

産業財産権

  • 金属シリコン製造用アーク炉

    本間 敬之, 國本 雅宏, 福中 康博

    特許権

受賞

  • 第2回 日本化学会関東支部大会 学生講演賞

    公益社団法人 日本化学会 関東支部  

    受賞者: 國本雅宏

  • 第14回 表面技術協会講演大会優秀講演賞

    一般社団法人 表面技術協会  

    受賞者: 國本雅宏

  • 平成25年度 電気化学会論文賞

    公益社団法人 電気化学会  

    受賞者: 國本雅宏, 中井浩巳, 本間敬之

  • 平成30年度表面技術協会 進歩賞

    一般社団法人 表面技術協会  

    受賞者: 國本雅宏

共同研究・競争的資金等の研究課題

  • イオン液体からのSi電析における不純物混入機構の分子レベル解析と高純度Si層形成

    研究期間:

    2019年04月
    -
    2021年03月
     

     概要を見る

    太陽光発電デバイス需要拡大に伴い,太陽電池級Siの安定供給プロセスの必要性が高まっている.非水溶媒を用いる電析プロセスはその1つとして有力であるが,形成されるSiの更なる高純度化が課題である.本研究はイオン液体trimethyl-n-hexyl ammonium bis(trifluoromethylsulfonyl)imide(TMHATFSI)を電解液,SiCl4をSi前駆体にそれぞれ用いたSi電析における不純物混入機構を明らかにし,発電デバイス用Si微細構造体を形成することを目的とする.特に解析では,理論計算と独自の表界面分析用ラマン分光測定を用い,理論-実測の両面から検討する.本研究は、電気化学的安定性の高いイオン液体を電解液に用いて、標準電極電位が卑であり通常の水溶液系からでは還元析出困難なSiを太陽光発電デバイス用薄膜として電極基板上に形成する電解析出プロセスを開発する。ここでは理論化学計算の手法や分光計測の手法も援用することによって、Si前駆体の還元反応機構の分子レベルでの解析にも取り組み、その知見に基づく合理的な指針の下プロセス設計を行う。電解液にはtrimethyl-n-hexyl ammonium bis (trifluoromethylsulfonyl)imide(TMHATFSI)を、Si前駆体にはSiCl4をそれぞれ用いる。プロセス設計では、主に電圧印加波形、温度条件、対流条件、を最適化する。今年度の検討では、密度汎関数法(density functional theory,DFT)を用いた理論計算解析とラマン散乱分光測定による、SiCl4前駆体の還元反応機構、及び析出Si膜中への不純物の混入機構の解析に取り組んだ。加えてそれらを基にした電析条件最適化の予備検討まで着手することができた。まずSiCl4は2電子を授受後、近接する別のSiCl4と安定な二量体を形成することが示唆された。この中間体は分光測定でも観測され、知見が理論-実測両面から確かめられた。その後二量体はさらなる電子授受によって多量体化し、徐々に基板に析出するようになるが、計算解析で得られたイオン液体の分子中の各結合エネルギーから判断して、イオン液体分子はこの過程で、分子の状態で不純物として取り込まれると考えられた。このことは、析出のための電圧・電流印加時間の最適化の必要性を示唆している。この知見に基づき、電析条件の中でも電圧印加時間の最適化に着目した電圧パルス波形制御の初期検討に取り組み、数秒単位の比較的長い印加時間で薄膜特性が向上することを確認した。2019年度は、当初の目標を達成し次年度の研究につながる成果を創出することに成功したため、順調な進展と判断した。研究開始当初、2019年度は析出Si薄膜への不純物混入機構を、計算化学的理論解析及び分光計測を通じて理論-実測の両面から分子レベルで解析することを目標としていた。またそれにあたり理論モデルの構築や分光セル開発に取り組むことを計画として挙げていた。理論モデルの検討では、クラスターをベースに構築したSi表面モデルの適用によって、計算コストを抑えつつ必要な計算精度を確保できるようなモデル構築を達成した。分光セル開発では当初予定にはなかった設計も行い、計画当初想定したものよりも測定に適したセルの構築を達成した。当初はAuやAgなどプラズモン活性の高い金属ナノ粒子を蒸着などで表面に修飾した直径2.5 mm程度のマイクロレンズを、ラマンシグナル増強用のセンサとして用い、それを実装した分光セルをSi電析プロセスの解析用に構築、応用する計画としていた。このシステムの大きな利点は、プラズモン活性を示さない電極を含むあらゆる電極に対して前処理なしで表面増強ラマン散乱分光法が行える点である。設計を進めていくと、マイクロレンズをセンサ担体として用いるよりも、ガラス平板を担体として用いた方が精度の高い分光測定を行えることが明らかとなり、その知見を基に設計を改め新規なセルを開発することに成功した。さらにこれらの基礎解析によって、Si前駆体反応機構や不純物混入機構に関する分子レベルの知見を得ることができたため、それらを基に電析プロセスの最適化に着手した。プロセスの条件最適化は当初、2020年度から開始する計画としていたが、モデル構築や計測セル改良、そしてそれらを用いた解析を円滑に行うことができた結果、予備検討ではあるものの2019年度の時点でその検討に着手することができた。今後は当初の計画通り、電析条件の最適化と微細構造Si形成に取り組む。電析条件の最適化では、A. 電流・電圧値及び波形、B. 浴温、C. 対流条件に着目するが、特にA. 電流・電圧値及び波形に関しては、副反応制御の観点から電圧パルス電解に着目しており、したがって電圧値とそのパルス波形を検討する。このパルス電解は、定常的に電圧や電流を印加する通常の電解とは異なり、数十msから数sほどの短期的な電圧・電流印加を周期的にかけていくプロセスであり、そのような短期的印加をかける時間幅、いわゆるon timeと、印加のない時間幅、off timeが交互に訪れる。このon time とoff time の設定を、分子レベルの学術的知見に基づいて検討し、波形を最適化することがこの研究の一つの大きな特色であり2020年度はこの最適化に取り組む計画である。2019年度における予備検討の結果、数秒程度のon time で従来膜の1.5倍のSi純度の膜が得られることが明らかになっているが、膜の平滑性やSi純度のさらなる向上に向けて、on timeとoff timeのバランス、いわゆるデューティー比を一層追い込んで最適化する必要がある。これまでに得られた知見に基づいて検討し、イオン液体分子が膜中に混入しないような off time の工夫を計画している。B. 浴温,C. 対流条件については、電解セルの再構築を通して最適化する。特にC. 対流条件の最適化においては、新規な電解セル設計を通じて強制対流をかけられるセットアップを組むことで、物質移動過程を制御し前述のパルス電析の環境をさらに最適なものに整える。この新規電解セルの設計は、予備検討の一環として既に2019年度に着手しておりセル構築の目途は立っている。そうしたプロセス設計に取り組んだ後、ナノインプリント法などを駆使した微細構造形成に取り組む

  • 大規模エネルギー変換貯蔵デバイスの電気化学プロセシングにおける核発生成長制御

    研究期間:

    2013年04月
    -
    2016年03月
     

     概要を見る

    大規模エネルギー貯蔵デバイス開発には充放電操作に伴う電極表面の微細構造の安定制御が必須課題である。本研究では実験的・理論的アプローチによる精密な解析とモデリング手法の検討から、モデル電析系において単一析出核レベルの極微構造形成プロセスの解析および制御手法を構築すると共に、大規模蓄電池への応用を念頭においたZn電極反応に伴う核発生から樹枝状不規則構造(スポンジ構造)の成長過程に着目した解析を行い、その形成機構を明らかにした

  • プラズモンアンテナ型センサを用いた超高分解能固液界面その場解析手法の確立

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(挑戦的萌芽研究)

    研究期間:

    2011年
    -
    2013年
     

     概要を見る

    Au,Ag,Cuなどの金属からなる同心円溝構造のセンサおよびナノ粒子を光透過基板に形成させたセンサを試作し、表面増強ラマン散乱スペクトルによる固液界面の分子構造を計測可能な系を開発した。実証例としてヒドラジンと次亜リン酸分子の固液界面における吸着挙動を明らかにした。さらにAuめっき添加剤ヤヌスグリーンB(JGB)の吸着状態を解析し、電界印加による分解反応の観察に成功した。またハードディスク表面のサブnm厚のダイヤモンドライクカーボン(DLC)膜と液体潤滑剤の膜厚方向の分子構造変化の測定を行い、窒素添加DLC膜表面近傍の潤滑油分子の界面吸着構造を0.1nmの深さ分解能で測定することに成功した。

講演・口頭発表等

  • Electrochemical Fabrication of Micro/nano Structured Plasmonic Sensors for Surface Enhanced Raman Scattering Analysis

    M. Kunimoto, T. Homma, M. Bertz, M. Saito, M. Yanagisawa  [招待有り]

    69th Annual Meeting of the International Society of Electrochemistry   (Bologna) 

    発表年月: 2018年09月

  • 理論化学計算とマイクロ空間計測による界面反応解析の実例

    國本雅宏  [招待有り]

    電気化学界面シミュレーションコンソーシアム2018年第一回研究会   (東京) 

    発表年月: 2018年05月

  • プラズモンセンサ素子を用いた電極表面反応の解析

    國本雅宏  [招待有り]

    表面技術協会 関東支部 第93回講演会   (長野) 

    発表年月: 2017年12月

  • 無電解めっきプロセスの理論的・実験的解析

    國本雅宏, 本間敬之  [招待有り]

    ナノプレーティング研究会第62回例会   (神奈川) 

    発表年月: 2017年06月

  • 固液界面反応プロセスに対するナノ構造体を用いた実験的・理論的解析

    國本雅宏, 本間敬之  [招待有り]

    日本学術振興会第151委員会 平成27年度 第4回研究会   (東京) 

    発表年月: 2015年12月

  • Quantum Chemical Calculation of Interfaial Reaction in Electrochemical Deposition

    國本雅宏  [招待有り]

    平成27年度第1回CMRI研究会   (宮城) 

    発表年月: 2015年06月

  • 量子化学計算を用いた 界面反応機構の理論的解析

    國本雅宏  [招待有り]

    表面技術協会表協エレクトロニクス部会 電気化学会ナノ・マイクロファブリケーション研究会 合同研究会   (東京) 

    発表年月: 2014年12月

  • 量子化学計算を用いた 固液・液液界面反応解析

    國本雅宏  [招待有り]

    日本鉄鋼協会第168回秋季講演大会   (愛知) 

    発表年月: 2014年09月

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特定課題研究

  • Liイオン二次電池電極におけるSEI形成過程の高精度in-situラマン解析

    2018年  

     概要を見る

     本研究では,Liイオン二次電池の負極表面において形成される電解液分解生成物層,いわゆるSEI層の形成をin situで観察し,その形成過程を明らかにすることを目的とした.観察・解析には,本研究者がこれまでに構築してきた表界面分光分析法としての表面増強ラマン測定(SERS)システムを,さらに発展させたシステムを応用した.電解液にはEC/EMC+1 mol/L LiPF6を,負極にはグラファイト,そして正極にはLiCoO2を,それぞれ適用した.解析の結果,SEI形成は2つの電圧領域で生じることが明らかになった.より正の電圧領域で形成されるSEI層は不安定であり,SEI層形成と成長には主に,2つの中でもより負の電圧領域である第二段階が大きく寄与するものと示唆された.

 

現在担当している科目

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