Faculty Profiles - SAITO, Nagahiro

Papers - SAITO, Nagahiro

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Effect on percolation threshold of catalytic layer: Pt/N-Doped graphene shell onto SWCNT for ORR electrode Reviewed

Dechojarassri D., Wang X., Chae S., Sawada Y., Hashimoto T., Saito N.

Fuel Cells Vol. 23 ( 1 ) page： 4 - 14 2023.2

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Fuel Cells

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

Low-potential and high-capacity lithium battery anode based on hierarchical assemblies of Na<inf>2</inf>TiSiO<inf>5</inf> nanotubes Reviewed International coauthorship

Zhang Y., Huang J., Saito N., Zhang Z., Yang L., Hirano S.i.

Applied Surface Science Vol. 604 2022.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Surface Science

Titanium-based materials such as TiO2 and Li4Ti5O12 are promising candidates for next-generation lithium-ion batteries (LIBs), but the high operating potential and unsatisfactory specific capacity severely restrict the potential application prospects. Li2TiSiO5 as a novel anode has attracted great attention due to its low-potential and high-capacity properties, but the conversion transition of Li2TiSiO5 to Li4SiO4 and TiO during Li+ intercalation and de-intercalation unfavorably affects the structural stability and hinders Li+ transport. Herein, novel cocoon-like microspheres assembled by Na2TiSiO5 nanotubes (NTSO-T), as the substitute of Li2TiSiO5, are facilely synthesized through a hydrothermal reaction. The hierarchical structure could effectively facilitate the Li+ diffusion, reduces internal strain, and enhances structural stability without greatly reducing the tap density. With a low but safe operating potential of 0.75 V, NTSO-T anode exhibits a high reversible capacity of 400 mAh g−1 which exceeds most reported Ti-based anodes, and durable long-cycling performance (capacity retention after 3000 cycles reaches 77%). Most importantly, the rate capability of NTSO-T is significantly enhanced. Kinetic reaction analysis has demonstrated the pseudocapacitive contribution in NTSO-T anode dominates the lithium storage kinetics. In addition, ex situ XRD and Raman analysis reveal a partially reversible conversion mechanism occurring in the framework. The excellent electrochemical performance of NTSO-T provides a promising anode candidate for next-generation LIBs.

DOI： 10.1016/j.apsusc.2022.154409

Multi-strategy synergistic in-situ constructed gel electrolyte-binder system for high-performance lithium-ion batteries with Si-based anode Reviewed International coauthorship

Zhao E., Luo S., Zhang Z., Saito N., Yang L., Hirano S.i.

Electrochimica Acta Vol. 434 2022.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Electrochimica Acta

Silicon-based material have been considered as the most competitive candidate for next-generation anode in lithium-ion batteries (LIBs) due to its high specific energy density, natural abundance and attractive operating voltage. However, silicon-based anodes generally undergo significant volume changes and structural collapse during cycling, resulting in limited battery lifespan. Herein, a multi-strategy optimized in-situ gel electrolyte-binder system (GEBS) is rationally constructed, and electrochemical performances of the LIBs with Silicon-Graphite (Si-Gr) anodes are systematically evaluated by half-cell and full-cells. The in-situ generated polymer skeleton and improved interfacial compatibility of the GEBS effectively preserve the electrode structural integrity. Compared with the commercial liquid electrolyte, the volume change of the anode cycled with GEBS is suppressed from 208 % to 126 %. Benefiting from these merits, the full-cell with LiFePO4 cathode displays stable cycling stability with the capacity retention of 96.8 % after 260 cycles. Besides, the reversible capacity of the LiNi0.6Co0.2Mn0.2O2║Si-Gr full-cell is as high as 121.7 mAh g−1 after 200 cycles (capacity retention of 85.1 %), and the GEBS also exhibits obvious dominance at 55°C. This contribution effectively integrates multiple optimization strategies for Si-based anode and provides a feasible solution to address the challenge of its practical application in LIBs.

DOI： 10.1016/j.electacta.2022.141299

Remediation of water contaminated with polycyclic aromatic hydrocarbons using liquid phase plasma: Influence of electrical discharge condition

Kim U.J., Saito N., Lee S.H.

Frontiers in Marine Science Vol. 9 2022.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Frontiers in Marine Science

Although the number of vessels with exhaust gas cleaning systems (EGCSs or scrubbers) has sharply increased to comply with strengthened regulations for marine environment, secondary pollutions are caused by discharged polycyclic aromatic hydrocarbons (PAHs) from scrubber effluent. Here, liquid-phase plasma (LPP) is employed to remediate water contaminated with PAHs. The increased frequency and pulse width enhanced the degradation efficiency, and 93.3, 90.7, 86.0, and 85.4% for naphthalene (Nap), acenaphthene (Ace), fluorene (Flu), and phenanthrene (Phe), respectively, are degraded at a frequency of 30 kHz and pulse width of 3 μs in 10 min. Considering physical condition of the plasma, long pulse width accelerated electrons, leading to increased generation of active species from intensified collision between electrons and surrounding molecules. Conversely, high frequency decelerated electrons due to the excessive changes in the polarity. However, the increased number of plasma discharges results in the generation of numerous active species. Generations of •OH and O radicals are confirmed by optical emission spectrometry and electron paramagnetic resonance. In addition, changes in functional groups which are corresponding to hydroxyl and oxygen groups are identified by Fourier transform infrared spectroscopy. Total PAHs in real scrubber are reduced from 1.1 to 0.4 μgL-1 with degradation efficiency of 63.6% after 10 min of LPP treatment. This study suggests LPP can be a promising method to protect diverse aqueous environments and provides optimal electrical discharge condition for degradation of organic pollutants.

DOI： 10.3389/fmars.2022.1033962

Hierarchical Porous Carbon Fibers Synthesized by Solution-Plasma-Generated Soot Deposition and Their CO<inf>2</inf> Adsorption Capacity

Romero Valenzuela A.E., Chokradjaroen C., Thiangtham S., Saito N.

Coatings Vol. 12 ( 11 ) 2022.11

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

Global warming caused by CO2 emissions is a major environmental problem. Thus, the development of materials with innovative architectures that approach the CO2 problem is a necessity. In this study, hierarchical porous carbon fibers (HCFs) were synthesized by a chemical deposition process that operates at 400 °C and uses solution-plasma-generated soot (PGS) as a carbon precursor. Subsequently, the CO2 adsorption capacity of the synthesized material was evaluated. The HCFs showed enhanced surface areas and networks of micropores and mesopores. Moreover, the HCFs were post treated by metal etching and KOH activation. The post treated HCFs achieved a CO2 uptake of 0.8 mmol g−1 at 273 K, which was superior to the simultaneously produced solution plasma carbon (SPC), which has a CO2 uptake of 0.2 mmol g−1.

DOI： 10.3390/coatings12111620

Plasma–Solution Junction for the Formation of Carbon Material

Niu J., Chokradjaroen C., Sawada Y., Wang X., Saito N.

Coatings Vol. 12 ( 11 ) 2022.11

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

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

Layered Perovskite Lithium Yttrium Titanate as a Low-Potential and Ultrahigh-Rate Anode for Lithium-Ion Batteries

Zhang Y., Huang J., Saito N., Yang X., Zhang Z., Yang L., Hirano S.i.

Advanced Energy Materials Vol. 12 ( 31 ) 2022.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Advanced Energy Materials

Graphite, as the dominant anode for commercial lithium-ion batteries, features sluggish electrochemical kinetics and low potential close to lithium deposition, leading to poor rate capability and safety issues. Although titanium-based oxides have received considerable attention, each alternative demonstrates unsatisfactory trade-offs between capacity, operating potential, rate capability, and lifespan. Here, submicrometer-sized lithium yttrium titanate (LYTO) is synthesized through facile sol–gel and ion-exchange reactions. With an average operating potential of 0.3 V versus Li+/Li, the LYTO anode demonstrates a high specific capacity of 236 mAh g–1 and durable cycling performance of 98% capacity retention after 3000 cycles. Impressively, without additional modification, a high-rate capability is achieved under a current density range from 0.5 C to 100 C (1 C = 200 mA g–1), e.g., delivering 112 and 87 mAh g–1 at 60 C and 100 C, respectively. Comprehensive characterizations and computational simulations reveal reversible solid-solution reactions occurring in the LYTO framework with little lattice change and fast 2D Li+ mobility achieved due to a low diffusion energy barrier. After incorporation with a LiFePO4 cathode, the energy density of the as-fabricated full cell reaches 2.4 times that of Li4Ti5O12/LiFePO4 full cell. The double characteristics of LYTO provide a fresh identification for high-performance anodes.

DOI： 10.1002/aenm.202200922

A non-flammable, flexible and UV-cured gel polymer electrolyte with crosslinked polymer network for dendrite-suppressing lithium metal batteries

Gu Y., Yang L., Luo S., Zhao E., Saito N.

Ionics Vol. 28 ( 8 ) page： 3743 - 3759 2022.8

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

A flexible, non-flammable gel polymer electrolyte (GPE) was synthesized by combining UV-cured polymerization of ethoxylated trimethylolpropane triacrylate (ETPTA) within the framework of glass fiber (GF) membrane. Non-flammable hydrofluoroether (1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, FEPE) and high flash point solvent (fluoroethylene carbonate, FEC) were employed as plasticizers for GPE-FEC/FEPE (60:40) to promote the safety of electrolyte and improve the compatibility with lithium metal anode. Non-flammable GPE-FEC/FEPE (60:40) possessed high safety level, high ionic conductivity (1.57 mS cm−1 at 30 °C), excellent oxidation stability (4.6 V vs. Li/Li+), high lithium-ion transference number (0.71) and good thermal stability (120 °C). After 1000 h test, Li/GPE-FEC/FEPE (60:40)/Li displayed better compatibility with lithium metal electrode compared with commercial liquid electrolyte. The test of Li/LFP cells showed that the safe GPE-FEC/FEPE (60:40) had excellent cycling performance at room temperature and elevated temperature. After 1000 cycles at 2 C and room temperature, the capacity retention was as high as 88.4%. XPS spectra proved that GPE-FEC/FEPE (60:40) was beneficial to promote the formation of LiF-rich SEI film on the surface of lithium metal anode, which could effectively inhibit the growth of lithium dendrites.

DOI： 10.1007/s11581-022-04621-4

Nitrogen-doped 3D porous graphene coupled with densely distributed CoO<inf>x</inf> nanoparticles for efficient multifunctional electrocatalysis and Zn-Air battery

Zhao Y., Wang X., Guo X., Shi N., Cheng D., Zhou H., Saito N., Fan T.

Electrochimica Acta Vol. 420 2022.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Electrochimica Acta

Highly efficient and low-cost multifunctional electrocatalysts play a crucial role in energy storage and conversion systems. Herein, a new strategy is developed based on a structured precursor to design and fabricate a hierarchical porous nitrogen doped graphene coupled with densely distributed CoO/Co3O4 heterostructure that exhibits outstanding multifunctional activities. With rational hybridization of graphene and bimetallic nanoparticles, the as-obtained NGPC@CoOx integrated densely distributed CoO/Co3O4 active nanoparticles to 3D interconnected hierarchical N-doped graphene mesh, which gives rise to a multifaceted capability for electron/ion transfer and redox catalyzing. The NGPC@CoOx possesses excellent durability with a superior E1/2 of 0.86 V for oxygen reduction reaction (ORR), and a relatively low potential for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) of 1.61 V, and -0.162 V at 10 mA cm−2, respectively. Additionally, the superior cycling durability and high power density of NGPC@CoOx-based zinc-air batteries (184.4 mW cm−2) further confirm the potential application of prototype devices. This work introduces a new perspective on developing efficient multifunctional electrocatalysts with a well-designed 3D structure anchored with densely distributed nanoparticles towards energy storage and conversion technologies.

DOI： 10.1016/j.electacta.2022.140432

Fundamentals of solution plasma for advanced materials synthesis Reviewed International coauthorship

Chokradjaroen C., Wang X., Niu J., Fan T., Saito N.

Materials Today Advances Vol. 14 2022.6

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Materials Today Advances

Solution plasma is an atmospheric nonequilibrium plasma generated by electrical discharge in liquid phase at room temperature. The plasma configurations, solutions, electrode materials, as well as the characteristics of the power supply can be easily tuned. Due to these features of the solution plasma, various sizes, shapes, compositions of products can be controlled, leading to the effective utilization in several applications, such as a novel catalyst for energy conversion. To accomplish the use of solution plasma as a promising tool for the synthesis and modification of advanced materials, fundamentals and applied knowledge related to the solution plasma should be reviewed and discussed. Therefore, in this review, fundamentals of plasma in liquid are explained relating to the solution plasma, and detailed advanced applications of solution plasma are organized. It is expected to give powerful knowledge to guide the researchers in designing plasma conditions and synthesizing catalysts for different applications in the future.

DOI： 10.1016/j.mtadv.2022.100244

Design of three-dimensional isotropic negative-refractive-index metamaterials with wideband response based on an effective-medium approach

Chang Q., Liu X., Wang Z., Saito N., Fan T.

Applied Physics A: Materials Science and Processing Vol. 128 ( 5 ) 2022.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Physics A: Materials Science and Processing

Negative-refractive-index metamaterials (NRIMs) can provide opportunities for many new applications, but they are difficult to manufacture, especially when forced to work at high frequencies and required to be three-dimensionally isotropic. By integrating an effective-medium approach into all-dielectric left-handed materials (LHMs) and utilizing self-assembly, we developed a method to design three-dimensional NRIMs that can work in high frequencies and are suitable for mass production. The NRIMs are composed of arrays of spheres that are made from artificial media, which are devised under the effective-medium method in advance. Two cases with different close-packed structures were studied for verification purposes. Finite element analysis showed that both cases can achieve negative refraction within 14.5–15.2 GHz (Ku band), which qualifies as wideband. Negative refraction was further confirmed by investigating the resonance mode of units in each model. Dispersion analysis demonstrated isotropism and consistent behaviors in all cases, indicating the robustness of these properties over disorder accompanied by self-assembly. The proposed NRIM model is intrinsically isotropic, three-dimensional, passive, mass-producible, machinable and thus readily applicable.

DOI： 10.1007/s00339-022-05573-2

Flexible, solid-state, fiber-network-reinforced composite solid electrolyte for long lifespan solid lithium-sulfurized polyacrylonitrile battery

Luo S., Zhao E., Gu Y., Saito N., Zhang Z., Yang L., Hirano S.i.

Nano Research Vol. 15 ( 4 ) page： 3290 - 3298 2022.4

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

Solid lithium-sulfur batteries (SLSBs) show potential for practical application due to their possibility for high energy density. However, SLSBs still face tough challenges such as the large interface impedance and lithium dendrite formation. Herein, a high-performance SLSB is demonstrated by using a fiber network reinforced Li6.75La3Zr1.75Ta0.25O12 (LLZTO) based composite solid electrolyte (CSE) in combination with sulfurized polyacrylonitrile (SPAN) cathode. The CSE consisting of an electrospun polyimide (PI) film, LLZTO ionically conducting filler and polyacrylonitrile (PAN) matrix, which is named as PI-PAN/LLZTO CSE, possesses high room-temperature ionic conductivity (2.75 × 10−4 S/cm), high Li+ migration number (tLi+) of 0.67 and good interfacial wettability. SPAN is utilized due to its unique electrochemical properties: reasonable electronic conductivity and no polysulfides shuttle effect. The CSE enables a highly stable Li plating/stripping cycle for over 600 h and good rate performance. Moreover, the assembled SLSB exhibits good cycle performance of accomplishing 120 cycles at 0.2 C with the capacity retention of 474 mAh/g, good rate properties and excellent long-term cycling stability with a high capacity retention of 86.49% from 15th to 1,000th cycles at 1.0 C. This work rationalizes our design concept and may guide the future development of SLSBs. [Figure not available: see fulltext.]

DOI： 10.1007/s12274-021-3981-z

Solution plasma process for synthesizing polydiacetylene materials: Toward industrial utilization of colorimetric sensors

Saymung R., Watthanaphanit A., Saito N., Traiphol N., Traiphol R.

Journal of Industrial and Engineering Chemistry Vol. 106 page： 243 - 252 2022.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Industrial and Engineering Chemistry

A new route for synthesizing polydiacetylene (PDA) is introduced. Plasma is generated in a liquid matrix through a pair of electrodes, producing the excited atomic or molecular species, radicals, and UV radiation. The products of solution plasma process (SPP) act as initiators to induce polymerization of diacetylene monomers. Our results demonstrate that irreversible thermochromic PDA and reversible thermochromic PDA/Zn2+/ZnO nanocomposite can be effectively synthesized. The addition of ethanol significantly increases the polymerization rate. These PDA materials can be fabricated into paper-based colorimetric sensors for detecting volatile organic solvents, acids, bases, and surfactants. This synthetic pathway could be applied for industrial-scale applications.

DOI： 10.1016/j.jiec.2021.10.035

Morphology control of ZnO nanostructures using Zn and W electrodes in solution plasma process

Kim K., Chae S., Masuda Y., Saito N.

Materials Letters Vol. 309 2022.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Materials Letters

The morphology of ZnO nanostructures was controlled by the type of electrodes used, without chemical additives in the solution plasma process. Nanorod and nanosheet-type ZnO were synthesized using Zn and W electrodes, respectively. In the solution plasma process, the ZnO nanostructure can be fabricated because of the unique reaction between ions and radicals at the plasma/liquid interface. During this reaction, ions generated from the metal electrode influence the morphology of ZnO by adsorption on the (0 0 1) facet. Zn(OH)42− ions promoted crystal growth in the [0 0 1] direction, resulting in a rod structure. In contrast, the sheet structure was formed owing to the inhibition of growth in the [0 0 1] direction by WO42− ions.

DOI： 10.1016/j.matlet.2021.131349

Synthesis of nitrogen-doped carbons from single-source precursors by solution plasma

Gasidit Panomsuwan, Chayanapat Chokradjaroen, Nagahiro Saito

Nanomaterials via Single-Source Precursors: Synthesis, Processing and Applications page： 475 - 505 2022.1

Language：English Publishing type：Part of collection (book)

Solution plasma processing is a bottom-up synthetic approach that can be employed for directly preparing nitrogen-doped carbons from single-source precursors with in situ nitrogen doping. Research efforts and interest in this topic have gained at a significant pace over the past years. This chapter provides an overview of solution plasma processing and recent progress on the synthesis of nitrogen-doped carbons from single-source precursors using this approach. The chapter starts by introducing the basic fundamentals of solution plasma and how to apply it in the synthesis of nitrogen-doped carbons. The effects of a solution plasma conditions and the type of precursors on the overall properties of nitrogen-doped carbons are summarized based on the important findings reported in the literature. A potential application of nitrogen-doped carbons as metal-free electrocatalysts for oxygen reduction reaction is explained and discussed in brief. At the end of the chapter, the remaining challenges and future prospects are highlighted for use in further studies. This chapter is intended to be generally informative and a useful guide for researchers who are new to this field.

DOI： 10.1016/B978-0-12-820340-8.00019-8

Asymmetric Porous and Highly Hydrophilic Sulfonated Cellulose/Biomembrane Functioning as a Separator in a Lithium-Ion Battery

Thiangtham S., Saito N., Manuspiya H.

ACS Applied Energy Materials 2022

Language：English Publishing type：Research paper (scientific journal) Publisher：ACS Applied Energy Materials

Biomembranes based on sulfonated cellulose (SC) blended with PLA/PBS composites were fabricated with different SC contents into polymer matrices. The obtained membranes were applied as separators in lithium-ion batteries (LIBs). The porosities of SC/biomembranes with 0.5, 1, and 2 wt % SC contents were estimated to be 66.6, 73.4, and 87.7%, respectively, which are significantly greater than that of the Celgard 2400 membrane, a commercial monolayer polypropylene (PP) separator membrane (42.1%). Due to its high porosity, hydrophilicity, and good interfacial compatibility with electrodes, the SC/biomembranes offer high electrolyte uptake and low interfacial resistance, leading to enhanced ionic conductivity. The cell with the 2 wt % SC/biomembrane also exhibited stable cycle performance and improved rate capacity, especially when discharged at the 0.2C rate. A 106 mAh/g capacity retention rate was achieved for a battery with the 2 wt % SC/biomembrane after 100 cycles at the 1C rate; meanwhile, the Celgard 2400 membrane exhibited a capacity of 81 mAh/g. These results show that SC has great innovative potential for use as a biofiller in biomembranes, which is suitable for LIB applications.

DOI： 10.1021/acsaem.2c00602

Au nanoparticle-decorated TiO<inf>2</inf>hollow fibers with enhanced visible-light photocatalytic activity toward dye degradation

Panomsuwan G., Wongcharoen S., Chokradcharoen C., Tipplook M., Jongprateep O., Saito N.

RSC Advances Vol. 12 ( 1 ) page： 193 - 200 2021.12

Language：English Publishing type：Research paper (scientific journal) Publisher：RSC Advances

TiO2 hollow fibers (THF) were prepared by a template method using kapok as a biotemplate and subsequently decorated by plasmonic Au nanoparticles using a solution plasma process. The THF exhibited an anatase phase and a hollow structure with a mesoporous wall. Au nanoparticles with a diameter of about 5-10 nm were uniformly distributed on the THF surface. Au nanoparticles-decorated TiO2 hollow fibers (Au/THF) have enhanced photocatalytic activity toward methylene blue degradation under visible light-emitting diode (Vis-LED) as compared to pristine THF and P25. This could be attributed to combined effects including effective light-harvesting by a hollow structure, large surface area due to a mesoporous wall of THF, and visible-light absorption and efficient charge separation induced by Au nanoparticles. The Au/THF also showed good recyclability and separation ability.

DOI： 10.1039/d1ra07323k

Synergetic design of dopant-free defect-enriched 3D interconnected hierarchical porous graphene mesh for boosting oxygen reduction reaction

Zhao Y., Wang X., Guo X., Cheng D., Zhou H., Saito N., Fan T.

Carbon Vol. 184 page： 609 - 617 2021.10

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

To resolve Pt-dependency problems in energy convention systems, we provide an idea for construct a highly active 3D interconnected hierarchical porous graphene mesh (3D-PGM) with effective exposure active sites. By a facile controllable process through self-assembly and chemical etching of reduced-graphene oxide, synergetic enhancement of oxygen reduction reaction (ORR) performance from intrinsic activity to apparent activity was realized. The as-obtained materials exhibit 3D interconnected hierarchical porosity for efficient mass transport, a high surface defect content with increased numbers of active sites and a robust conductive network, leading to a comprehensive multiscale electron transfer capability that ultimately enhances the ORR catalytic activity. Incredibly, the alkaline ORR performance of as-obtained catalyst exhibits a 4-electron pathway reaction with an onset potential (Eonset) of 0.89 V, half-wave potential (E1/2) of 0.84 V, and a lower Tafel slope of 58 mV dec−1, showing activity comparable to that of Pt/C catalysts. Moreover, the as assembled primary Zn–air batteries (ZABs) demonstrate a higher power density (182.6 mW cm−2) and a higher specific capacity (809.1 mA h g−1) than the Pt/C-based counterpart. The outstanding electrochemical performance and facile fabrication techniques make this material a promising alternative to commercial Pt/C for renewable energy devices.

DOI： 10.1016/j.carbon.2021.08.066

Structure and properties of nanocarbons-encapsulated WC synthesized by solution plasma process in palm oils

Islam, MZ; Watthanaphanit, A; Chae, S; Niitsu, K; Saito, N

MATERIALS EXPRESS Vol. 11 ( 9 ) page： 1602 - 1607 2021.9

High electrical conductivity and oxidation reduction reaction activity of tungsten carbide/carbon nanocomposite synthesized from palm oil by solution plasma process

Islam, MZ; Watthanaphanit, A; Chae, S; Niitsu, K; Saito, N

MATERIALS EXPRESS Vol. 11 ( 9 ) page： 1587 - 1593 2021.9

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