Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Advance online publication
Showing 1-19 articles out of 19 articles from Advance online publication
  • Daisuke IGARASHI, Kei KUBOTA, Tomooki HOSAKA, Ryoichi TATARA, Tsuyoshi ...
    Article ID: 21-00062
    Published: 2021
    [Advance publication] Released: June 24, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material
    Download PDF (1983K)
  • Shingo IDE, Ken WATANABE, Koichi SUEMATSU, Yasuhiro SETO, Isamu YASHIM ...
    Article ID: 21-00057
    Published: 2021
    [Advance publication] Released: June 09, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    An oxide-ion-conductor-based oxygen pumping system can serve as an on-site oxygen separation system. Herein, we present the oxygen permeation capability of a Pt electrode/La-Sm-doped CeO2 (L-SDC) intermediate layer/c-axis-oriented La9.66Si5.3B0.7O26.14 (c-LSBO) solid electrolyte cell. A significant increase in the oxygen permeation flux is observed on applying a DC voltage of ≥4 V at temperatures <600 °C. A remarkably high flux of 5.2 mL cm−2 min−1 is obtained even at 500 °C. Furthermore, in situ X-ray diffraction studies under applied voltages reveal an increase in the lattice constant of L-SDC, accompanied by a drastic increase in the oxygen permeation flux, indicating the reduction of Ce4+ and formation of oxygen vacancies. These results suggest that the observed change in L-SDC under the applied voltage results in the in situ formation of a mixed electron- and oxide-ion-conducting L-SDC electrode, indicating that the oxygen reduction reaction and incorporation is significantly enhanced.

    Download PDF (4425K)
  • Takumi KUSANO, Keita FUNAYAMA, Yukihiro TADOKORO, Hiroya TANAKA
    Article ID: 21-00059
    Published: 2021
    [Advance publication] Released: June 05, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    Potential barrier plays a key role in ionic transport through nanoporous membranes. We numerically study the contribution of the potential barrier to the ionic current through a cylindrical Si3N4 nanopore using molecular dynamics simulations. We extract the height of the potential barrier from the best fit using a simple polynomial model of the ionic current. We reveal that the surface atoms make a contribution to the potential barrier. This study provides the height of the potential barrier so that it is valuable information about the underlying mechanism of ionic transport through nanopores.

    Download PDF (1928K)
  • Seiju MATSUDA, Shogo SUZUKI, Kai YABUMOTO, Hideaki OKADA, Yuki MIMA, N ...
    Article ID: 21-00007
    Published: 2021
    [Advance publication] Released: June 04, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    The aim of this study is to observe the spatial inhomogeneity of a rechargeable battery’s electric conductivity distribution. Therefore, we have developed a system that uses the measurement results of a minute magnetic field that leaks from the cell to visualize, in real time, the cell’s electric conductivity distribution. This system has a magnetic detection capability of 30 pT/Hz0.5 (at 1 Hz); it measures the magnetic field distribution in the 240 × 240-mm range. This system has the ability to detect the 500-µA electric current that flows in a rechargeable battery 5 mm away from the sensor module. Because the magnetic signals are detected at the frequency synchronized with the alternating current flowing in the cell, this system is not affected by environmental magnetic field noise. Using this system, we have successfully visualized the short-circuit spot in a cell with significant self-discharge. Furthermore, we observe that the magnetic field distribution changes continually when the short circuit is being generated. The coordinate where the magnetic field distribution changed and the coordinate where metal precipitates were confirmed significant agreement.

    Download PDF (4220K)
  • Kentaro ITO, Kumi Y. INOUE, Tsubasa MIURA, Tomokazu MATSUE, Hitoshi SH ...
    Article ID: 21-00058
    Published: 2021
    [Advance publication] Released: May 26, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    In this work, we report a simple electrochemical sensor that detects proteinuria upon immersion into a sample. We immobilized peptidases in conjunction with glutamate oxidase (GluOx) on a Prussian blue-modified glassy carbon (PB-GC) electrode. In the sensor, albumin, which is a major protein in urine, was degraded by peptidases to produce glutamate that was detected by GluOx on PB-GC. Initially, we validated the strategy for the detection of proteinuria using glutamate sensing. We quantified the amount of glutamate produced by degrading human serum albumin with HCl and carboxypeptidase A (CPA). The results indicated that an increase in the enzyme degradation rate was necessary for daily proteinuria sensing that needs to be completed within 1 h. Therefore, we investigated the use of endopeptidase in conjunction with CPA. The combination of proteinase K and CPA liberated glutamate from albumin at 17.5 times higher comparing to solely CPA. The subsequent glutamate assay using peptidase-modified GluOx-PB-GC electrode did not exhibit changes in the electrochemical signal with increases in the glutamate concentration, because peptidase degraded the GluOx on the modified electrode. To prevent this, GluOx was encapsulated in ZIF-8. Glutamate was successfully detected using peptidase and GluOx encapsulated in the ZIF-8-modified PB-GC (peptidase-ZIF-8/GluOx-PB-GC) electrode. Finally, an albumin assay was performed using the peptidase-ZIF-8/GluOx-PB-GC electrode, wherein albumin was detected with a sensitivity of 0.1 mg/mL within 30 min. Our simple and easy-to-use method for albumin detection provides a viable sensor for daily urinalysis.

    Download PDF (2224K)
  • Athchaya SUWANSOONTORN, Katsuhiro YAMAMOTO, Shusaku NAGANO, Jun MATSUI ...
    Article ID: 21-00042
    Published: 2021
    [Advance publication] Released: May 21, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    Investigation of interfacial proton transport is necessary to elucidate biological systems. As commonly found in biomaterials, the carboxylic acid group was proven to act as a proton-conducting group. This study investigated the influence of carboxylic acid concentration on both interfacial and internal proton transport. Several styrene-based polymers containing the carboxylic acid group were synthesized. The amount of carboxylic acid group in the polymer chain was varied to explore the effects of weak acid concentration on polymer thin films’ electrical properties. The IR p-polarized multiple-angle incidence resolution spectrometry (pMAIR) spectra show the higher ratio of the free carboxylic acid groups rather than cyclic dimers in polymers with a higher concentration of carboxylic acid group, facilitating the more hydrogen bonding networks in films. The water uptake results reveal the similar number of adsorbed water molecules per carboxylic acid group in all thin films. Remarkably, polymer thin films with high carboxylic acid concentration provide internal proton conduction because of the relative increase in the amount of the free carboxylic acid group. In contrast, interfacial proton conduction was found in low carboxylic acid concentration polymers because of the relatively large amount of cyclic dimer carboxylic acid group and poor amount of free carboxylic acid group. This study provides insight into interfacial proton transport behavior according to the weak acid concentration, which might explain proton transport in biological systems.

    Download PDF (3342K)
  • Kosuke NAKAMOTO, Ryo SAKAMOTO, Yuki NISHIMURA, Jingyu XIA, Masato ITO, ...
    Article ID: 21-00056
    Published: 2021
    [Advance publication] Released: June 02, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    A safe and low-cost aqueous electrolyte, in which maximum amount of sodium trifluoroacetate (NaTFA) is dissolved (26 mol kg−1), showed high ionic conductivity of 23 mS cm−1 and provided wide electrochemical stability window of 3.1 V. These attractive features may originate from so-called “water-in-salt” effect of the highly concentrated electrolyte in addition to a robust fluoride layer formed on anode thereof. This novel electrolyte enabled reversible operation of NASICON-type Na2VTi(PO4)3 as symmetrical operation based on V3+/4+ at cathode and Ti3+/4+ and V2+/3+ at anode, respectively.

    Download PDF (3607K)
  • Xuehu ZHANG, Jian ZHANG, Beibei HAN, Kun WANG, Guiying XU, Yingxin WAN ...
    Article ID: 21-00039
    Published: 2021
    [Advance publication] Released: May 12, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    The biomass-derived carbon materials were successfully fabricated by precursor mixtures of eggplants, urea and CaCl2. It is promisingly observed that controlling the mixing ratios of eggplants, urea and CaCl2 can regulate the structures of fabricated carbon materials. On the basis of investigations about correlations between structures and Na+ storage capacity, it is verified that weight ratio of eggplants : urea : CaCl2 = 1 : 2 : 2 is optimal to fabricate the carbon materials, which have the suitable porous structures and specific surface area to store Na+. For instance, the fabricated carbon materials show the Na+ storage capacity is 200.8 mAh/g at 0.1 A/g, after being carried out the charge-discharge 500 times. Meanwhile, the same materials also display the impressive long cycling performance. When cycling the charge-discharge 1000 times at 2.0 A/g, the fabricated carbon materials still manifest the Na+ storage capacity at 137.8 mAh/g.

    Download PDF (5786K)
  • Yohei SUZUKI, Keisei SOWA, Yuki KITAZUMI, Osamu SHIRAI
    Article ID: 21-00044
    Published: 2021
    [Advance publication] Released: May 12, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    The effect of mutation on the redox potentials (E°′) of the heme moieties in the variants of d-fructose dehydrogenase (FDH) was investigated by mediated spectroelectrochemical titrations. The replacement of the axial ligand of heme from methionine to glutamine changes the E°′ value more negatively than that of the corresponding heme moiety in the recombinant (native) FDH (rFDH). The determined E°′ values of non-targeted heme moieties in the variants were also shifted in a negative direction from that in rFDH. Thus, enzyme modification changes E°′ of the heme moieties in unmodified protein regions.

    Download PDF (1290K)
  • Yushi FUJITA, Yusuke KAWASAKI, Takeaki INAOKA, Takuya KIMURA, Atsushi ...
    Article ID: 21-00049
    Published: 2021
    [Advance publication] Released: April 29, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Development of oxide solid electrolytes for all-solid-state batteries is attracting increasing attention. In this study, amorphous Li2O–LiI materials are prepared via a mechanochemical process to achieve high lithium ionic conductivity and good compatibility to lithium metal. Amorphous 66.7Li2O·33.3LiI (mol%) electrolyte shows a high ionic conductivity of 3.1 × 10−5 S cm−1 at 25 °C with a relative density of 96 %. An all-solid-state Li symmetric cell (Li/66.7Li2O·33.3LiI/Li) operates without an increase in overvoltage. A simple combination of lithium oxide and lithium iodide exhibits high ionic conductivity, ductility, and stability to lithium metal.

    Download PDF (1388K)
  • Shinji KONDOU, Kaoru DOKKO, Masayoshi WATANABE, Kazuhide UENO
    Article ID: 21-00052
    Published: 2021
    [Advance publication] Released: May 12, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    For the rapid charge-discharge performance of Li-ion batteries (LIBs), ionic conductivity (σ) and Li ion transference number (t+) are important parameters of electrolytes. Electrolytes with high t+ alleviate the concentration polarization upon fast charge-discharge, and prevent the diffusion-limited mass transfer of Li+ ions. Recent studies have suggested that certain highly concentrated electrolytes exhibit better rate performances than conventional organic electrolytes despite their lower σ. However, the relationship between the transport properties (t+ and σ) of highly concentrated electrolytes and the enhanced rate performance of LIBs is yet to be elucidated. To evaluate the rate performance of LIBs with highly concentrated electrolytes in terms of transport properties, we investigated the discharge rate capability of LiCoO2 (LCO) half-cells using highly concentrated lithium bis(fluorosulfonyl)amide (Li[FSA]) electrolyte in γ-butyrolactone (GBL), acetonitrile (AN), dimethyl carbonate (DMC), and 1,2-dimethoxyethane (DME) solvents. There was a remarkable solvent dependence of t+, and the highest tLi+current of 0.67 was observed for GBL-based electrolyte measured using the very-low-frequency impedance spectroscopy (VLF–IS) method. The LCO half-cell with GBL-based electrolyte delivered higher discharge capacities than the cells with DMC- and DME-based electrolytes at high current densities. The improved rate performance in GBL-based electrolytes was attributable to enhanced Li+ ion mass transfer derived from the high tLi+current. We demonstrated the importance of tLi+current on the rate capability of LCO half-cells with highly concentrated electrolytes for high-rate battery performance.

    Download PDF (2149K)
  • Yuto NAKAMURA, Yasushi SATO, Naoki SHIDA, Mahito ATOBE
    Article ID: 21-00053
    Published: 2021
    [Advance publication] Released: May 12, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    In this study, we report one step electrochemical trimerization of catechol to 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) for the first time. Electrochemical trimerization was demonstrated in a flow microreactor, which offers advantages for reaction screening owing to short reaction time and small reaction scale, as well as avoiding the further oxidation of HHTP. The use of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as a solvent was essential for the efficient production of HHTP. Computational simulation, pKa calculation, and electrochemical measurements gave some important insights into the mechanism of the electrochemical oxidation of catechol in HFIP.

    Download PDF (2155K)
  • Minato EGASHIRA, Kouki MATSUBARA
    Article ID: 21-00041
    Published: 2021
    [Advance publication] Released: April 28, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Non-aqueous electrolytes containing magnesium chloride complex in which magnesium is coordinated by synthesized phenoxyimine ligand have unique properties for magnesium deposition and dissolution. Those properties have been compared using ligands with different terminal groups. For electrochemical and Raman spectroscopic studies, mixed electrolytes were prepared by dissolving a phenoxyimine–magnesium-chloride complex and magnesium [bis(trifluoromethane sulfonyl)imide] in triglyme solvent. An electrolyte containing phenoxyimine with an n-butyl terminal group shows higher Coulombic efficiency of magnesium deposition than the electrolyte prepared with dimethylamine-terminated phenoxyimine, probably because of preferred formation of active triglyme–magnesium-chloride coordinated cations. By contrast, adding aluminum chloride to the electrolyte with n-butyl-terminated phenoxyimine adversely affected reversible magnesium deposition, probably because trapping of chloride occurred preferentially.

    Download PDF (1909K)
  • Tetsuo NAGAMI, Toyokazu NOMOTO, Harue SUGIYAMA, Shoji TACHIKI, Ren SAK ...
    Article ID: 21-00031
    Published: 2021
    [Advance publication] Released: April 03, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    We report detailed studies of capacity deterioration mechanism of Li[Ni1/3Co1/3Mn1/3]O2 (NCM) cathode after several numbers of cycling with the voltage range of 3.0–4.1 V/cell at 85 °C and after storage at charged states (3.7, 4.0 and 4.1 V/cell) at 70 °C for 150 days by soft X-ray absorption spectroscopy (XAS) and X-ray powder diffraction (XRD). Morphological changes were also observed by scanning electron microscopy (SEM).

    Ni, Co, and Mn L-edge XAS analysis revealed that Ni, a part of Co and no Mn were active for charge/discharge in the above-described voltage range. Only Ni L-edge XAS exhibited significant spectral changes by capacity deterioration. Ni mean valence at discharged state increased with the capacity deterioration rate of each sample either after storage test or after cycling test, which corresponds to the increase of the lattice constant ratio c/a, obtained by the XRD analysis. Chemically decomposed species on the NCM particle surfaces increased with capacity deterioration. Many cracks were observed in the SEM image of the sample after extended cycling. Crack generation, formation of the cubic spinel phase on the surface and deposition of decomposed species on the particles hamper the Li ion insertion to the cathode material at discharge, which is responsible for capacity deterioration. The crack generation is enhanced in case of the cycling test, while the deposition of decomposed species and the formation of the cubic spinel phase on the surface are more enhanced in case of the storage test.

    Download PDF (2220K)
  • Ryoji MARUBAYASHI, Yoshitsugu YAMAMOTO, Mitsuhiro HIROTA
    Article ID: 21-00035
    Published: 2021
    [Advance publication] Released: April 09, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    Five types of micrometer-sized Sn and acetylene black (AB) composite powders were prepared by mechanical milling for 1, 3, 6, 12, and 24 h. The Sn/AB powders obtained, in addition to Sn-only powders were added to a binder and conductive material, and then dried under vacuum to prepare negative electrodes (anodes) for sodium-ion batteries (SIBs). SIBs were fabricated with the anodes in the form of 2032-type coin cells, and were evaluated using charge-discharge tests up to 50 cycles within the cutoff voltage range of 0.005–0.65 V at a constant current of 50 mA g−1 at 25 °C. Maximum discharge capacities of 614 to 651 mAh g−1 were obtained with all the anodes prepared with both the Sn-only and the Sn/AB composites. However, the discharge capacities of the Sn-only and Sn/AB composites milled for 1 and 3 h were significantly decreased as the charge-discharge cycle increased. In contrast, the Sn/AB composites milled for 6 h or more exhibited improved cycle characteristics; capacities of 635, 619, and 584 mAh g−1 were maintained during 50 cycles of testing with the Sn/AB_6h, Sn/AB_12h, and Sn/AB_24h samples, respectively, which were significantly higher than the anode prepared with the Sn-only powder (135 mAh g−1).

    Download PDF (2845K)
  • Wei HUANG, Fengping LIU, Yingying HUANG, Wei YANG, Huifang ZHONG, Jiny ...
    Article ID: 21-00027
    Published: 2021
    [Advance publication] Released: March 16, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    A novel non-enzymatic glucose sensor based on hollow-structured copper sulfide/cuprous sulfide (CuS/Cu2S) hybrid was developed by using a facile and one-pot solvothermal method. The crystal structure, morphology and surface property of the prepared CuS/Cu2S hybrid were characterized by X-ray diffraction spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The electrochemical performances of this hybrid modified glassy carbon electrode for glucose oxidation were monitored by cyclic voltammograms and amperometric technology. Results showed that the novel integrated electrode exhibited excellent electrocatalytic performances to the oxidation of glucose with a wide line range of 3.0–1100.0 µM, high sensitivity of 321.3 µA mM−1 cm−2, low detection limit of 1.1 µM (3δ/S), fast response, good anti-interference ability and excellent stability. The proposed sensor was successfully applied for the determination of glucose in human blood serum sample with satisfactory recoveries.

    Download PDF (4936K)
  • Kouhei HATTORI, Hekiru KURAKAKE, Junko IMAI, Takuya HASHIMOTO, Mihoko ...
    Article ID: 21-00032
    Published: 2021
    [Advance publication] Released: March 16, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Supplementary material

    Neurostimulation is an essential technique to trigger and modulate the spatiotemporal activity of local neuronal circuits. Current stimulation methods have a trade-off relationship among aiming precision, temporal resolution, and noninvasiveness, making it difficult to stimulate and monitor a single target neuron for a long term. Here, we show that a method using two needle electrodes in combination of micropatterning techniques provides new possibilities for targeting and stimulating a single neuron selectively. Results of physiological experiments as well as analog circuit simulation reveal that two needle electrodes can stimulate a target neuron selectively by placing the two needle electrodes in proximity to and to straddle the target neuron, and that the steepness of voltage applied to two needle electrodes is important for the target neuron to fire at a low voltage. The proposed method enables a noninvasive stimulation suitable for measuring long-term activity of local neuronal circuits.

    Download PDF (2319K)
  • Yuta KIMURA, Keita FUNAYAMA, Mahunnop FAKKAO, Takashi NAKAMURA, Naoaki ...
    Article ID: 21-00033
    Published: 2021
    [Advance publication] Released: March 16, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    We experimentally evaluated the influence of stress on the Li chemical potential (μLi) and phase equilibrium in the two-phase battery electrode materials through the emf measurements while applying a mechanical load. In our measurements, we prepared an electrochemical cell by depositing a thin film of a two-phase electrode material (LiFePO4 or LiCoO2 in the two-phase region) on each of the solid electrolyte surfaces. Then we applied a mechanical load to the electrochemical cell through four-point bending, and the resulting μLi variation in the electrode material was measured as the emf between the two thin films. Our results indicated that μLi in the two-phase electrode materials immediately changed just after loading and then gradually changed while maintaining a constant mechanical load. Besides, the loading and unloading led to the μLi variation in the opposite direction. Such characteristic μLi variations could be explained by considering the change in the phase equilibrium between the two phases, which led to the Li content variation in the two phases and the stress relaxation due to the volume fraction variation of the two phases. Our results can provide valuable insights regarding the influence of stress on the performances of energy storage devices with two-phase electrode materials.

    Download PDF (4584K)
  • Naoya ISHIDA, Ryuta NISHIGAMI, Masaki MATSUI, Toshihiko MANDAI, Kiyosh ...
    Article ID: 21-00038
    Published: 2021
    [Advance publication] Released: April 08, 2021
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION

    Chemically-delithiated Li1.2Mn0.54Ni0.13Co0.13O2 is regarded as a potential candidate of cathode active materials for magnesium rechargeable batteries owing to its large deliverable capacity and high operation voltage compared to conventional layered transition metal oxides. Our previous study suggested its chemical composition as Li0.13Mn0.54Ni0.13Co0.13O2−δ by X-ray diffraction combined with XAFS analysis. We herein re-analyzed the substantial composition and crystal structure by employing titration technique and combination of neutron and synchrotron X-ray diffractions. Two topotactic phases both belonging to the space group of R3m were strongly suggested by Rietveld analysis, and the chemical formula was subsequently re-defined as Li0.17Mn0.72Ni0.18Co0.18O2 where oxygen defects were filled by a rearrangement from C2/m structure. Although the battery performance of that active material was poor in the previous study, the discharge capacity greater than 400 mAh g−1, ca. 95 % of the theoretical capacity, was achieved by using certain anodically stable electrolytes and specific cell configuration. This result strongly implies that the R3m structure is particularly suitable as a host material for Mg2+ intercalation.

    Download PDF (3027K)
feedback
Top