Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
最新号
選択された号の論文の29件中1~29を表示しています
The 64th special issue “Frontiers of Carbon Materials”
Vision
Review
  • Risheng LI, Yukari SATO
    原稿種別: The 64th special issue “Frontiers of Carbon Materials”
    2020 年 88 巻 5 号 p. 344-346
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/07/17
    ジャーナル オープンアクセス

    Redox flow batteries (RFBs) can employ various carbon materials as electrodes. A carbon electrode must meet a number of requirements when RFBs are constructed. This short review focuses on carbon electrodes with desirable electrode materials for RFBs. They have attributes for active species that assist the construction of stable RFBs for long-term use, realize much higher energy densities, employ a wide range of active chemical redox materials, and achieve a total cost reduction for each of the different types and differently modified carbon electrodes. Here, we summarize recent approaches employed in the search for carbon materials and the development of methods for modifying carbon surfaces for RFBs.

Communications
Articles
  • Yuxin WU, Kazuhide KAMIYA, Takuya HASHIMOTO, Rino SUGIMOTO, Takashi HA ...
    原稿種別: The 64th special issue “Frontiers of Carbon Materials”
    2020 年 88 巻 5 号 p. 359-364
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/06/23
    ジャーナル オープンアクセス
    電子付録

    Ni-doped covalent triazine frameworks (Ni-CTF) has been known as an efficient electrocatalysts that achieve conversion of carbon dioxide (CO2) to carbon monoxide (CO) with the faradaic efficiency (FE) exceeding 90% in neutral electrolytes. Here we report that the FE can reach 60% even in acidic electrolytes, where the hydrogen evolution can proceed competitively, by loading Ni-CTF on gas diffusion electrode (GDE). In the presence of Zn(II) ions, zinc hydroxide analogues that can be formed only in alkaline conditions were deposited on the GDE during the CO2 reduction in an electrolyte with a bulk pH of 2. On the other hand, when a normal plate electrode (PE) was used, the FE was only 1.2% in an electrolyte with the same pH, and the zinc hydroxide analogues were not formed. These results indicate that the local pH around GDE increased during the cathodic process, which led to an increasing FE of CO2 reduction even in an acidic electrolyte.

  • Akane INOO, Tomokazu FUKUTSUKA, Yuto MIYAHARA, Yasuyuki KONDO, Yuko YO ...
    原稿種別: The 64th special issue “Frontiers of Carbon Materials”
    2020 年 88 巻 5 号 p. 365-368
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/06/23
    ジャーナル オープンアクセス

    The performance of the graphite anode of lithium-ion batteries is greatly affected by the solid electrolyte interphase (SEI) generated at the first charge. However, there are few studies on the kinetics of the lithium-ion intercalation/de-intercalation reaction in graphite to investigate the effect of SEI. In this study, the correlation between the interfacial lithium-ion transfer resistance (Rct) and the double layer capacitance (Cdl) of graphite composite electrodes coated with various SEIs was investigated. It was found that the value of 1/RctCdl was different for each SEI, that is, the frequency (or rate) of intercalation and de-intercalation of lithium ions into graphite was different for each SEI. The activation energy of Rct was almost the same for all the electrolyte solutions. These results indicate that the pre-exponential factor of the Arrhenius equation governing the rate of interfacial ion transfer in a practical graphite anode is dependent on the nature of SEI.

  • Izuru SHIMABUKURO, Yoshikiyo HATAKEYAMA, Soshi SHIRAISHI
    原稿種別: The 64th special issue “Frontiers of Carbon Materials”
    2020 年 88 巻 5 号 p. 369-373
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/06/23
    ジャーナル オープンアクセス
    電子付録

    Recently, the single-walled carbon nanotube (SWCNT) has been the focus as a durable electrode with a high rate performance for the electric double layer capacitor (EDLC). However, it has not yet been clarified whether these reported outstanding properties are universal for all SWCNTs. The authors compared various self-standing SWCNT membranes (buckypapers) as the EDLC electrode to evaluate their stability to a floating high-voltage charge. Some SWCNTs exhibited an excellent rate performance even after the floating durability test, but other electrodes were degraded and showed a lower capacitance-retention. This variability in the durability for the SWCNTs can be attributed to the presence of residual metal impurities. Thus, it should be noted that the purity is a significant factor when using SWCNTs as the EDLC electrode, in addition to the nano-structure design from the viewpoint of operation stability.

  • Mizue WANIBUCHI, Yui TAKAHASHI, Yuki KITAZUMI, Osamu SHIRAI, Kenji KAN ...
    原稿種別: The 64th special issue “Frontiers of Carbon Materials”
    2020 年 88 巻 5 号 p. 374-379
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/07/03
    ジャーナル オープンアクセス
    電子付録

    Three types of widely used carbon materials were examined as scaffolds for the direct-electron-transfer (DET)-type bioelectrocatalysis of bilirubin oxidase (BOD) as an electrocatalyst for a 4-electron reduction of oxygen (O2). The carbon materials used were: Ketjen Black EC300J (KB) with a primary particle size (ϕp) of ca. 40 nm and a hollow structure, Vulcan XC-72R (Vulcan) with ϕp of 37 nm and a filled structure, and high purity graphite SP series (JSP) with ϕp of 10 µm and well-developed micropore structures. For the three carbon materials, the rotating disk steady-state limiting catalytic current density of the O2-reduction (|jc,lim|) increased with the non-Faradaic current (|jb|) at small |jb| values and was saturated at large |jb| values. The |jc,lim/jb| ratio in low |jb| range was in the following order: JSP ≫ Vulcan > KB. Electrochemical and microscopic data suggested that microporous structures of JSP are highly effective for the DET-type reaction of BOD. Gaps between several primary particles in the KB and Vulcan aggregates play important roles as scaffolds for BOD. The inner surface of partially broken KB particles is electrochemically active to give large |jb| but not effective as BOD scaffolds.

  • Jianke LI, Guiying XU, Kun WANG, Beibei HAN, Lixiang LI, Yingxin WANG, ...
    原稿種別: The 64th special issue “Frontiers of Carbon Materials”
    2020 年 88 巻 5 号 p. 380-386
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/07/31
    ジャーナル オープンアクセス
    電子付録

    Fe7S8@C composite materials are facilely fabricated using the gelatin, FeSO4·7H2O and Na2S·9H2O by one-step method. The obtained Fe7S8@C composite materials show the fabulous rate performances and cycling performances, when controlling the carbon contents in Fe7S8@C composite materials. For instance, the Fe7S8@C-40 shows the cycling performance at 657.3 mAh/g, after carrying out the charge-discharge cycles 400 times. These electrochemical performances lead us to consider our provided preparation method is the effective way to facilitate the application of Fe7S8@C in fabrication of lithium ion batteries (LIBs) as negative electrode materials.

  • Saki OHTA, Shunsuke SHIBA, Tatsuhiko YAJIMA, Osamu NIWA
    原稿種別: The 64th special issue “Frontiers of Carbon Materials”
    2020 年 88 巻 5 号 p. 387-391
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/07/17
    ジャーナル オープンアクセス
    電子付録

    The fouling of electrodes with large molecules and/or electrochemically oxidized biomolecules limits the potential applications of bioelectroanalysis. The present work examined the effects of various plasma treatments when applied to sputtered carbon film electrodes. This was done by assessing the electrode responses to serotonin, a neurotransmitter that can be adsorbed after electrochemical oxidation. Although the oxidation current of serotonin rapidly decreases after five potential cycles with 5-minute intervals at the untreated and H2O plasma-treated carbon films, the magnitudes of the currents were almost unchanged at the films after NH3 and NH3/H2O gas plasma treatments. Cyclic voltammetric measurements of Fe(CN)63−/4− before and after serotonin oxidation revealed that there are no detectable fouling with oxidized serotonin by either the NH3 or NH3/H2O treatment, unlike the case with untreated and H2O plasma-treated carbon film electrodes. Similar to the serotonin response, both 5-hydroxyindoleacetic acid and 5-hydroxytryptophol show improved stable responses after the NH3/H2O plasma treatment. X-ray photoelectron spectroscopy data suggest that the suppression of fouling might be due to the electrostatic repulsion between the amino group of serotonin and surface charges after the NH3 and NH3/H2O treatments, in addition to the effects of hydrophilic surfaces generated by the plasma treatments.

  • Shuhei OGAWA, Masanori HARA, Seiya SUZUKI, Prerna JOSHI, Masamichi YOS ...
    原稿種別: The 64th special issue “Frontiers of Carbon Materials”
    2020 年 88 巻 5 号 p. 392-396
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/07/31
    ジャーナル オープンアクセス
    電子付録

    For hydrogen production by water electrolyzers, iridium dioxide (IrO2) works as a catalyst for oxygen evolution reaction (OER) at an anode. In this report, we aim to study the formation mechanism of IrO2 nanoparticles on graphene by inducing nanoscale defects artificially. The defects on graphene grown on a copper foil by chemical vapor deposition were created by UV-ozone treatment, and IrO2 nanoparticles were deposited by hydrothermal synthesis method. We investigated the amount of defects and oxygen-functional groups on graphene by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The size and distribution of defects and IrO2 nanoparticles on graphene were analyzed by atomic force microscopy (AFM). Raman spectroscopy and XPS measurement showed that defects and oxygen-functional groups increased with the UV-ozone treatment time. The size of IrO2 nanoparticles was reduced to ca. 4.5 nm on defective graphene, whereas the nanoparticles deposited on pristine graphene is ca. 8.8 nm in diameter. It is found that the IrO2 nanoparticles were deposited and anchored on the edge of hole-like defects on graphene. In addition, the size of deposited nanoparticles can be controlled by the extent of modification in graphene.

  • Kensuke HONDA, Ryutaro KOBAYASHI
    原稿種別: The 64th special issue “Frontiers of Carbon Materials”
    2020 年 88 巻 5 号 p. 397-406
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/07/31
    ジャーナル オープンアクセス

    Novel method of fabricating nitrogen-doped carbon-rich amorphous silicon-carbon alloy nanoparticles was successfully established using radio-frequency (r. f.) plasma-enhanced vapor deposition (CVD) system with a porous aluminum plate set between a cathode and an anode. Nanoparticles (Nps) were fabricated in high-density plasma regions generated in pores of the porous aluminum plate. Sizes of Nps were dependent on the transit time required for nuclei to pass through high density plasma regions during CVD synthesis. The average diameter of nitrogen-doped (N-doped) carbon-rich amorphous silicon-carbon alloys (C-rich a-SiC) Nps was successfully controlled within the range from 271.2 to 14.8 nm by changing the conditions of CVD synthesis: transit time, r. f. power, chamber pressure, and plate thickness. The optical gaps of C-rich a-SiC Nps were satisfactorily controlled by changing Si/C ratio at amorphous Si-C network in C-rich a-SiC (changing Si/C ratio of the source material used in CVD synthesis). The optical gaps of C-rich a-SiC Nps were controllable from 2.04 to 1.19 eV. The Nps showed photon-to-current conversion functionality in the photoelectrochemical measurement under 360 nm irradiation. In other words, C-rich a-SiC Nps are applicable to devices using photon-to-electron conversion in nano-meter size.

  • Masanori HARA, Prerna JOSHI, Rajashekar BADAM, Hsin-Hui HUANG, Masamic ...
    原稿種別: The 64th special issue “Frontiers of Carbon Materials”
    2020 年 88 巻 5 号 p. 407-412
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/08/07
    ジャーナル オープンアクセス
    電子付録

    In the present study, we aim to synthesize heteroatom (nitrogen or boron) doped-reduced graphene oxide (N-rGO or B-rGO) as a catalyst for the electro-oxidation of hydroquinones, used as a candidate of fuel (hydrogen carrier molecule) for direct-type fuel cells (DFCs), and evaluate the doping effect on its catalytic activity. N-rGO and B-rGO were prepared from a mixture of graphene oxide (GO) and urea or boron trioxide by pyrolysis method. We characterized the morphology and crystal structure of the prepared materials by transmission electron microscopy, and X-ray diffraction, respectively. Energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy show the loading amount of the heteroatoms, 10.4 wt% N and 2.9 wt% B, as well as their chemical nature. The electrochemical analysis of the prepared materials by rotating disk electrode system reveals high activity of B-rGO, 15 and 85 mV lower overvoltage compared with rGO at the half-wave potential of diffusion-limited current, for the electro-oxidation of hydroquinone and methyl-hydroquinone, respectively, because of its electron-accepting nature. We demonstrate that thus modified carbons exhibit high activity, B-rGO > N-rGO > rGO, for the oxidation of hydroquinone derivatives as non-metallic anodes of DFCs.

  • Masahiro SHINKAWA, Yoshitaka SAITO, Minoru ASHIZAWA, Hidetoshi MATSUMO ...
    原稿種別: The 64th special issue “Frontiers of Carbon Materials”
    2020 年 88 巻 5 号 p. 413-417
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/08/07
    ジャーナル オープンアクセス
    電子付録

    Recent developments of low-power electronic devices have triggered interests towards small-scale energy storage. One promising approach is to fabricate micro-supercapaciors (MSCs). In this work, we demonstrate a facile fabrication of MSCs by laser reduction and patterning of graphene oxide nanoribbon (GONR) thin films coated on poly(ethylene terephthalate) substrate through LightScribe technique. We fabricated the in-plane geometry electrodes consisting of reduced GONRs (i.e., graphene nanoribbons, GNRs) with the lateral spatial resolution of approximately 20 µm in addition to the stacked geometry electrodes for comparison. The fabricated in-plane-GNR electrode device showed superior electrochemical properties compared with the stacked-GNR electrode ones. Our impedance measurements supported that this is due to high lateral ion diffusivity along the basal plane of GNRs. In addition, GNR-based in-plane-electrode device also showed a higher capacitance than the graphene-based one, which is due to the more efficient edge effects of GNRs.

  • Ryuki TSUJI, Dmitry BOGACHUK, Bin LUO, David MARTINEAU, Eiji KOBAYASHI ...
    原稿種別: The 64th special issue “Frontiers of Carbon Materials”
    2020 年 88 巻 5 号 p. 418-422
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/08/12
    ジャーナル オープンアクセス

    Variations in the time courses of the activation of fully-printable carbon-based multi-porous-layered-electrode perovskite solar cells (MPLE-PSCs) can lead to differences between the photocurrent density (Jsc) values obtained from one-sun photocurrent density-voltage (JV) measurements and from incident-photon-to-current efficiency (IPCE) integration when using monochromic light. In the present work, the Jsc calculated from IPCE data was initially equal to half that obtained from one-sun JV measurements. However, equivalent values were obtained when the JV measurements were performed after 10 min of irradiation by a white light LED from the side of the device. This finding will be very important with regard to permitting accurate photovoltaic evaluation of MPLE-PSCs in the future.

Technological Reports
  • Tatsuhiro OKADA, Mutsumasa KYOTANI, Tomoaki YAMAMOTO, Naofumi TERADA, ...
    原稿種別: The 64th special issue “Frontiers of Carbon Materials”
    2020 年 88 巻 5 号 p. 423-428
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/07/03
    ジャーナル オープンアクセス
    電子付録

    New porous carbon materials are proposed in which washi, the Japanese paper as well as cotton and other cellulose materials are carbonized by new method, retaining their original fibrous structures. Porous carbon sheets thus fabricated are used as gas diffusion layer in fuel cells. Fuel cell testing is conducted and the optimum conditions of fabrication are investigated. Low cost and superior characteristics of new carbon structure are demonstrated based on morphological study and fuel cell polarization data.

  • Hiroshi OKANO, Takashi INOUE, Toshihiro HOSOKAWA, Akiyoshi TAKEDA
    原稿種別: The 64th special issue “Frontiers of Carbon Materials”
    2020 年 88 巻 5 号 p. 429-433
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/07/31
    ジャーナル オープンアクセス

    The metal air battery using an expanded natural graphite sheet as the cathode and galvanized plate as the anode was investigated as a power units for emergency. The discharge energy increased to 8 mW/cm3 from 5 mW/cm3 by optimizing the thickness of 0.8 mm and density of 0.5 g/cm3 for the expanded natural graphite sheets. The DC voltage proportionally and theoretically increased by increasing the number of battery cells. The capacity of this battery also increased by increasing the cell size for a case of less than 200 cm2. We hope that this battery can be used in many applications, such as a backup power supply, emergency battery, etc., because a DC 12 V output can be obtained for 15 cells connected in series, and the cathode and anode materials can be stored for a long time in the atmosphere.

Notes
Regular papers
Communication
Articles
  • Wrya O. KARIM, Jamil A. JUMA, Khalid M. OMER, Yousif M. SALIH, Kosar H ...
    2020 年 88 巻 5 号 p. 447-450
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/07/10
    ジャーナル オープンアクセス

    This report presents simple, rapid and an efficient electropolishing of Ti metal in choline chloride-based ionic liquid (so called Ethaline) at 20 °C. This electrolyte is relatively benign and environmentally friendly which is desirable for electropolishing. Potentiostatic method was applied to Ti electropolishing in this electrolyte. Under an electrochemical condition of 6–10 V for 30 min. and at 20 °C, a promising electropolishing process was performed without obvious gas evolution. To characterize the electropolished surface, atomic force microscope (AFM) and scanning electron microscope (SEM) were used. The achieved an apparent mirror-like finished surface with an average surface roughness (Ra) was 5.7 nm which is considerably different from that of unpolished one (Ra = 118.8 nm). The microscopic results showed leveling and brightening of the surface of Ti by carrying out the current procedure. This electrolyte provides sufficient environment to dominate the mass transport mechanism which is responsible for reduction in the surface roughness.

  • Toshi OGUMA, Kazuhisa AZUMI
    2020 年 88 巻 5 号 p. 451-456
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/08/18
    ジャーナル オープンアクセス

    Electrochemical conversion of CO2 gas emitted to the atmosphere to useful chemicals has been expected to suppress the global greenhouse effect and to conserve the natural resources. For the electrochemical reduction of CO2 on an Ag electrode, the effect of the addition of 1-ethyl-3-methylimidazolium ethyl sulfate (EMISE) ionic liquid to the aqueous solution of 0.1 mol dm−3 K2CO3, and the effect of the polarization methods, i.e., the potentiostatic polarization and the potential-pulse polarization, on the reduction efficiency were investigated. From the gas chromatography measurement, CO as the main product of CO2 reduction and H2 as a by-product of water decomposition were obtained. Faraday efficiency of CO formation obtained by the potential-pulse polarization was considerably higher than that obtained by the potentiostatic polarization. The addition of EMISE could add further improvement in the efficiency of CO formation higher than 70%. Such improvement provided by the potential-pulse polarization method and the addition of EMISE was interpreted by the depletion and recovery of the reactants on the electrode in the pulse cycle and promotion of CO2 molecular formation from HCO3 ions in the dense adsorption layer of EMIM cations on the electrode surface.

  • Yuji ISHADO, Atsushi INOISHI, Shigeto OKADA
    2020 年 88 巻 5 号 p. 457-462
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/07/31
    ジャーナル オープンアクセス
    電子付録

    NASICON-type Na3V2(PO4)3 is a promising cathode material for Na-ion batteries. Although it is well known that two Na+ can be extracted from Na3V2(PO4)3 by charging the cathode material, an electrochemical three-Na+ extraction has not been reported yet, to the best of our knowledge. In this work, we studied factors that limit the three-Na+ extraction from Na3V2(PO4)3. In DFT calculations, the voltage of the third-Na+ extraction is predicted to be more than 4.5 V vs. Na+/Na0, which is above the potential windows of the conventional organic electrolytes. Our study of Na3V1.5Al0.5(PO4)3 reveals that such a high voltage is required when Na ions are extracted from Na1 sites in the NASICON structure. From NEB calculations, the activation energy of the Na+ extraction from the Na1 site is predicted to be 753 meV for NaV2(PO4)3. Ab-initio molecular dynamics simulations also suggest that the Na ions which remain in NaV2(PO4)3 are kinetically locked up in Na1 sites. Our results indicate that the three-Na+ extraction is limited due to the high voltage and the large activation energy. We also compare Na3V2(PO4)3 with Li3V2(PO4)3, in which the three-Li+ extraction has been reported.

  • Kazuki YOSHII, Hikari SAKAEBE
    2020 年 88 巻 5 号 p. 463-467
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/08/12
    ジャーナル オープンアクセス
    電子付録

    Metallic lithium is considered to be the ultimate negative electrode for a battery with high energy density due to its high theoretical capacity. In the present study, to construct a battery with high energy density using metallic lithium as a negative electrode, charge/discharge tests were performed using cells composed of LiFePO4 and metallic lithium at various lithium utilization values. A relationship was observed between utilization and cycle performance, and the degradation behavior of metallic lithium was evaluated by cross-sectional FE-SEM observations. We also investigated the effects of additives in the electrolyte and found that FEC and VC effectively improved cycle performance.

  • Takuma NAKAGAWA, Hisayoshi MATSUSHIMA, Mikito UEDA, Hiroshi ITO
    2020 年 88 巻 5 号 p. 468-474
    発行日: 2020/09/05
    公開日: 2020/09/05
    [早期公開] 公開日: 2020/08/07
    ジャーナル オープンアクセス

    In order to investigate the corrosion behavior of SUS 304L steel in alkaline solutions, linear sweep voltammogram measurements were performed in NaOH solutions at pH 12 and 13 at 333 K. Constant potential electrolysis was carried out in an NaOH solution at 333 K at pH 13 from 5 to 20 hours. The surface analysis of the samples before and after the constant potential electrolysis was performed by atomic force microscopy, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The XPS measurements of the samples before the electrolysis showed that Fe and Cr oxide films were formed on the SUS 304L stainless steel surface, and the presence of FeOOH, CrOOH and Ni(OH)2 on the surface was confirmed after the electrolysis. It is suggested that the dissolved metal ions from the SUS 304L surface reacted with OH and formed a precipitated film on the surface in the alkaline environment.

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