Language：English   Publishing type：Research paper (scientific journal)  

An attention to a Li ion battery for electric vehicles has been attracted, but there are two huge problems: a short mileage and slow charging speed. Therefore, it is required to improve the specific capacity and electrical conductivity of the carbon material used for an anode and a conductive agent. To solve these problems, this study organized correlation analysis with descriptor vectors by collecting experimental properties including capacity and conductivity from 21 various types of carbon materials. Focusing on the flux of Li ion, it was found that the capacity was dependent on the intercalation of Li ions, which lead to propose the correlation equation based on the Hill equation. Furthermore, the intercalation occurred at the edge of basal plane lead an increase of the width of the gap between two graphene layers, followed by a diffusion through the basal plane, finally the expanded gap recovered its original width. Also, it was found that the variables which are sensitive to the conductivity are largely dependent on the defects and especially the number of graphene layers around the surface, which proposed a correlation equation that can predict the capacity and conductivity. To validate these functions, we checked the effectiveness of it with both experimental data from 27 previous studies and statistical method. As a result, it was confirmed enough to predict them. Finally, a candidate structure for improving the battery performance was proposed, thus our study aims to guide the exploration of electrode materials for LIBs.

DOI： 10.1016/j.carbon.2023.118479

Open Access

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

Though expensive platinum (Pt) is used as catalyst for oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs), insufficient durability remains as a bottleneck for commercialization of PEFCs. Improving both catalytic performance and durability by graphene encapsulation is an attractive strategy to solve this problem. In this study, graphene-encapsulated PtFe core-shell catalyst is synthesized with dimethyl formamide (DMF) and a pair of Pt and Fe electrodes without using any metal salts by utilizing the solution plasma (SP) process. TEM and EELS results show synthesized PtFe nanoparticles are encapsulated with close to single-layered highly crystallized graphene. Although commercial Pt/C showed significant performance degradation (ECSA −33%, MA −68%) after 50,000 cycles of accelerated durability test (ADT), PtFe core-shell catalyst shows remarkably improved durability (ECSA −13%, MA −19%) while graphene shell clearly remains. The improved durability is more prominent in the single cell test, the decrease in maximum power density after 6000 cycles of ADT was significantly lower as −1.2%, compared to that of Pt/C (−52.1%). This study introduces a novel and attractive catalyst synthesis process by the SP method followed by heat treatments and suggests graphene encapsulation can improve long-term durability of catalyst while maintaining ORR activity.

DOI： 10.1016/j.jpowsour.2023.233419

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Scopus

Language：English   Publishing type：Research paper (scientific journal)  

The ternary Mg–Al–Ti and quaternary Mg–Al–Ti–Cu systems were prepared by mechanical alloying in oxygen-lean atmosphere followed by spark plasma sintering. The ternary Mg–Al–Ti and quaternary Mg–Al–Ti–Cu systems which were sintered at 750 °C after 16 h milling showed the highest hardness of 509 and 947 HV with low densities of 2.9 and 3.9 g/cm3, respectively. The decrease in particle size and uniform dispersion of elements through optimization of the MA process induced the formation of uniform composite microstructure after SPS. Moreover, the addition of the fourth element, Cu, showed a significant impact on the improvement in hardness. This result was explained from the perspective of the microstructure and the electronic nature of elements. Our results provide a facile method for synthesizing oxide/metal composites from elemental powders without a separate oxidation process. Graphical abstract: [Figure not available: see fulltext.]

DOI： 10.1557/s43578-023-01137-z

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

The bacterial mechanosensitive channel of large conductance MscL is activated exclusively by increased tension in the membrane bilayer. Despite many proposed models for MscL opening, its precise mechano-gating mechanism, particularly how the received force at the tension sensor transmits to the gate remains incomplete. Previous studies have shown that along with amphipathic N-terminus located near the cytoplasmic surface of the membrane, Phe78 residue near the outer surface also acts as a “tension sensor,” while Gly22 is a central constituent of the “hydrophobic gate.” Present study focused on elucidating the force transmission mechanism from the sensor Phe78 in the outer transmembrane helix (TM2) to the gate in the inner transmembrane helix (TM1) of MscL by applying the patch clamp and molecular dynamics (MD) simulations to the wild type MscL channel and its single mutants at the sensor (F78N), the gate (G22N) and their combination (G22N/F78N) double mutant. F78N MscL resulted in a severe loss-of-function, while G22N MscL caused a gain-of-function channel exhibiting spontaneous openings at the resting membrane tension. We initially speculated that the spontaneous opening in G22N mutant might occur without tension acting on Phe78 residue. To test this hypothesis, we examined the (G22N/F78N) double mutant, which unexpectedly exhibited neither spontaneous activity nor activity by a relatively high membrane tension. To understand the underlying mechanism, we conducted MD simulations and analyzed the force transduction pathway. Results showed that the mutation at the tension sensor (F78N) in TM2 caused decreased interaction of this residue not only with lipids, but also with a group of amino acids (Ile32-Leu36-Ile40) in the neighboring TM1 helix, which resulted in an inefficient force transmission to the gate-constituting amino acids on TM1. This change also induced a slight tilting of TM1 towards the membrane plane and decreased the size of the channel pore at the gate, which seems to be the major mechanism for the inhibition of spontaneous opening of the double mutant channel. More importantly, the newly identified interaction between the TM2 (Phe78) and adjacent TM1 (Ile32-Leu36-Ile40) helices seems to be an essential force transmitting mechanism for the stretch-dependent activation of MscL given that substitution of any one of these four amino acids with Asn resulted in severe loss-of-function MscL as reported in our previous work.

DOI： 10.3389/fchem.2023.1175443

Open Access

Web of Science

Scopus

PubMed

Language：English  

Publishing type：Research paper (scientific journal)   Publisher：LIDSEN Publishing Inc  

Crystalline lithium fluoride (LiF) has been intensively pursued as potential alternative solid electrolytes (SEs) owing to its excellent chemical and electrochemical oxidation stability, and good deformability. However, due to its low ion conductivity, LiF is still challenging for practical SE applications. Herein, Li-Zr-F composite-based SE by liquid-mediated synthesis is proposed to be studied. methanol (CH<sub>3</sub>OH) was mainly evaluated as a liquid-mediated precursor for synthesizing Li-Zr-F composites under the stoichiometric proportion of LiF and ZrF4 (2:1 and 2:0.8) and a subsequent annealing process at 25°C/150°C, 50°C/150°C, and 70°C/150°C, respectively. X-ray diffraction results revealed that the Li-Zr-F composites could be crystallized in the three main types of phase formations, including Li<sub>2</sub>ZrF<sub>6</sub> ( ), Li<sub>2</sub>ZrF<sub>6</sub> ( ), and Li<sub>4</sub>ZrF<sub>8</sub> ( ) octahedron structures. In addition, the effect of cation stack sublattice synthesized by methanol mediator on the ion conduction of Li-Zr-F composites was investigated by using electrochemical impedance spectroscopy (EIS). Through the Zr<sup>4+</sup>-substitution, Li<sub>2</sub>ZrF<sub>6</sub> ( )-based SE exhibited the highest ion conduction which was increased to 2.40 × 10<sup>-8</sup> S/cm and 3.89 × 10<sup>-8</sup> S/cm under the stoichiometric proportion of LiF and ZrF<sub>4</sub> 2:0.8 at a dried temperature of 50°C/150°C with, respectively. A 0.21 eV activation energy ( ) was achieved for a battery with Li<sub>2</sub>ZrF<sub>6</sub> ( )-based SE. Meanwhile, LiF exhibited up to 0.78 eV leading to a low kinetic rate for ion diffusion. These results implied that Li<sub>2</sub>ZrF<sub>6 </sub>( )-based SE was successfully synthesized under the optimal condition of CH<sub>3</sub>OH-50°C/150°C which could improve the ion-conductivity of LiF.

DOI： 10.21926/jept.2301010

Publishing type：Research paper (scientific journal)  

A high-rate oxygen reduction reaction (ORR) is necessary for polymer electrolyte membrane fuel cells (PEMFC). In this work, by using a solution plasma technique, Pt catalytic particles coated with N-doped graphene (Pt-NG) were effectively produced at 25°C. According to transmission electron microscope images, the average diameter of Pt particles was 4 nm, while the graphene layer thickness was less than 1 nm. A catalytic layer of Pt-NG supported on single-walled carbon nanotubes (Pt-NG/SWCNT) was synthesized. Cyclic voltammetry was used to assess the ORR characteristics of Pt-NG/SWCNT catalytic layers. Only at a density of SWCNT to solvent ratio of 0.75 mg ml−1 were the ORR peaks clearly visible. Because of the high resistivity of SWCNT layers, the ORR peaks in other ranges, 0.4 mg ml−1 to 2.0 mg ml−1, were not clearly observed. The effect of SWCNT concentration on conductivity was proven to follow the basic concept of the percolation threshold.

DOI： 10.1002/fuce.202200020

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Scopus

Publishing type：Research paper (scientific journal)  

The solution plasma process (SPP) can provide a low-temperature reaction field, leading to an effective synthesis of N-doped graphene with a high N content and well-structured planar structure. However, the interactions at the plasma–solution interface have not been well understood; therefore, it needs to be urgently explored to achieve the modulation of the SPP. Here, to address the knowledge gap, we experimentally determined the physical parameters of the spital distribution in the plasma phase, plasma–gas phase, and gas–liquid phase of the SPP by the Langmuir probe system with modification. Based on the assumption that plasma can act similarly to semiconductors with the Fermi level above the vacuum level, an energy band diagram of the plasma–solution junction could be proposed for the first time. It was observed that the Fermi level of the organic molecule could determine the magnitude of electron temperature in plasma, i.e., benzene produced the highest electron temperature, followed by phenol, toluene, and aniline. Finally, we found that the electron temperature at the interface could induce quenching, leading to the formation of multilayer large-size-domain carbon products. It provided significant evidence for achieving nonequilibrium plasma modulation of carbon nanomaterial synthesis.

DOI： 10.3390/coatings12111607

Open Access

Web of Science

Scopus

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：Japanese  

DOI： 10.1016/j.bpj.2017.11.642

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (conference, symposium, etc.)  

DOI： 10.1016/j.bpj.2016.11.2882

Web of Science

Authorship：Lead author   Language：Japanese  

Language：Japanese  

Language：Japanese