Language：Japanese   Publisher：The Japan Photovoltaic Society  

DOI： 10.57295/jpvsproc.1.0_119

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：American Scientific Publishers  

In this study, the enhancement of electrical conductivity and Oxidation Reduction Reaction (ORR) activity of tungsten carbide/carbon (WC/C) nanocomposite was successfully synthesized from palm oil by solution plasma process (SPP). For the synthesis, plasma fields with different frequency
were applied the bipolar pulsed power supply connected with two tungsten electrodes. The properties of the synthesized WC/C nanocomposite were varied by using a different frequency. The electrical conductivity increased with the frequencies. The highest electrical conductivity was 4.27×10⁻²
S cm⁻¹, which is higher than that of Ketjen Black (7.37 × 10⁻³ S cm⁻¹). The WC/C nanocomposites were observed the surface area 160 m² g⁻¹, pore volume 0.53 cm³ g⁻¹, average pore
diameter 16.29 nm, basal plane crystallite size 18.0 nm, and the average compound granule diameter less than 100 nm. The cyclic voltammetry measurement was showed that the ORR activity of WC/C nanocomposites were obtained the good performance in alkaline solution for fuel cell application.

DOI： 10.1166/mex.2021.2035

Web of Science

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：American Scientific Publishers  

Palm oil is produced in the ASEAN region. The overhang of stocks, propellant fouling in the production process and used oils existed there. It is a crucial issue to make efficient use of such palm oils. Solution plasma process (SPP) is one step non-thermal plasma in the liquid phase.
Our laboratory has already synthesized the nanocarbons materials, graphene, hetero-graphene from organic molecules by SP. Organic ones engineer these material sources. When the functionalized nanocarbon can be synthesized from natural products and their dust, the functionalized carbon materials
are supplied by the green process and low price. We had already synthesized nanocarbons by SP from the palm oils. The nanocarbons were covered enhanced electrical conductivity of nanocarbons, which is referred to the nanocarbons-encapsulated WC (tungsten carbides). In this study, we aimed
to evaluate the structure and the properties of nanocarbons-encapsulated WC to provide the nanocarbons-encapsulated. The solution plasma was generated by the bipolar pulsed power supply through two tungsten electrodes using 2 <italic>μ</italic>s pulse widths and frequencies (100, 150, and 180 kHz)
for 30 min. We found that the observed plasma types depended on the discharge conditions. Conversion percentage of the oil to WC-encapsulated nanocarbon (% yield) was increased with frequency. The obtained X-ray diffraction patterns are showed the crystalline structure. The morphology of nanocarbon
capsules WC are spherical shapes and less than 10 nm size. The electrochemical properties indicate that the ORR activity in an acidic medium under saturated O₂ significantly disappears in the case of the nanocarbon-encapsulated WC synthesised in the high frequency (180 kHz). The
synthesized nanocarbons-encapsulated WC might be applied in data storage and energy applications.

DOI： 10.1166/mex.2021.2034

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>ZnO nano-bullets were synthesized using only Zn electrode and water by solution plasma and new electrode geometry improved discharge time up to 1 h.</p>

DOI： 10.1039/d1ra05008g

Web of Science

Scopus

PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：{IOP} Publishing  

This research paper reports the enhanced hole-transporting ability of widely utilized poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) achieved by applying cationic nitrogen-doped graphene (CNG) as a p-type modifier for efficient organic solar cells (OSCs). The power conversion efficiency (PCE) of the CNG-coated PEDOT:PSS-applied OSC reaches 2.76%, which is an increase of 40% compared to that of the pristine PEDOT:PSS-applied OSC (1.96%). The significantly enhanced performance is contributed by the increased hole-transporting ability, and the improved interfacial morphology of PEDOT:PSS, which affords high-quality active layers. (c) 2020 The Japan Society of Applied Physics.

DOI： 10.35848/1347-4065/ac00fc

Web of Science

Scopus

Publishing type：Research paper (scientific journal)  

Nanocarbons were successfully synthesized from benzene (BZ), nitro-benzene (BZ-NO2) and aniline (BZ-NH2) by solution plasma process (SPP). The SPP was generated by a bipolar pulsed power supply between two tungsten electrodes at room temperature. The synthesized nanocarbons were investigated. The highest synthesis rate, 40 mg min-1, was for the BZ nanocarbon. The transmission electron microscopy (TEM) morphology showed that the nanocarbon sizes were 15-25 nm. The Brunauer-Emmett-Teller (BET) analysis shows a highest surface area of 220 m2 g-1, pore size of 0.45 cm3 g-1, and average pore diameter of 20.0 nm for the BZ nanocarbon. Cyclic voltammetry (CV) in an acidic medium exhibited the oxygen reduction reaction (ORR) of the nanocarbons. The nanocarbon from BZ-NH2 obtained a high special capacity of 15 500 mA h per g of carbon at the discharge rate of 0.1 mA cm-2 with 1.0 mg carbon loading for the lithium (Li)-air battery. The ORR is an important reaction in Li-air batteries and fuel cells for the application of next-generation batteries and energy conversion devices.

DOI： 10.1039/d0ma00926a

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Scopus

Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society  

At present, human beings are facing two major problems: energy crisis and environmental pollution. Massive anthropogenic emissions of carbon dioxide (CO₂) associated with increased consumption of fossil fuels have contributed to global warming and the energy crisis. The photocatalytic CO₂ reduction (PCCR) to solar fuels such as methane, methanol and carbon monoxide is considered to be one of the best solutions to solve these problems. In recent years, with the invention of graphene and its derivatives, heterographene photocatalytic materials have become the focus of attention, especially for the development of photocatalysts and the application of photocatalysis. Heterographene and its derivatives can overcome the limitations of traditional photocatalysts, due to their excellent physicochemical and electrical properties like high specific surface area, stability, corrosion resistance, photosensitivity, and electrical conductivity. Therefore, heterographene-based photocatalysts could be a viable strategy to break new grounds in the area of PCCR to useful chemicals/fuels, i.e. converting sunlight to fuels. The current methods for the synthesis of heterographene are complex or harsh conditions, so it is urgent to develop new methods for the synthesis of doped graphene. In this study, the B-doped graphene derivatives were synthesized for PCCR by solution plasma (SP), which can provide us a rapid synthesis at room temperature and atmospheric pressure.

Acknowledgements

This work was financially supported by JST-OPERA (JPMJOP1843), JST-SICORP (JPMJSC18H1) and JSPS-KAKENHI (JP18K18998).

DOI： 10.1149/ma2020-0271140mtgabs

Other Link： https://iopscience.iop.org/article/10.1149/MA2020-0271140mtgabs/pdf

Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society  

Cationic N-doped graphene (CNG) was synthesized through a new method called Solution Plasma (SP) in a mixture of ionic liquid and organic solution, at ambient temperature and atmospheric pressure. The originality of the research consists in two things. First, the process allows one-step, rapid, substrate-free synthesis and simultaneously doping of CNG. X-ray diffraction, transmission electron microscopy, X-ray photoelectron and Raman spectroscopy confirmed that the graphene synthesis had proceeded, the material contains a high-level of nitrogen (13.4 at%) with the presence of cationic nitrogen, and has a few-layer structure (about 3-layer). Second, CNG behave like p-type semiconductor with a high sheet resistance of 16 Ω sq⁻¹ and a high carrier concentration of 10¹⁹ cm⁻³; indicating that process can significantly control the electrical properties of graphene. The combination of SP and ILs shows a promising strategy for the design and synthesis of NG using cationic N-doping, which cannot be achieved with other methods.

Acknowledgements

This work was financially supported by JST-OPERA (JPMJOP1843), JST-SICORP (JPMJSC18H1) and JSPS-KAKENHI (JP18K18998).



Figure 1

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DOI： 10.1149/ma2020-0271139mtgabs

Other Link： https://iopscience.iop.org/article/10.1149/MA2020-0271139mtgabs/pdf

Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society  

Carbon materials are widely used as anode on Li-ion battery (LIB). In particular, the effect of electrical conductivity (EC) on the anode is related to capacity and retention, which are important factors for LIB performance. However, the relationship between carbon properties and battery performance is still unclear. This uncertainty is due to the sp3 and sp2 bond states, the diversity of carbon like amorphous structures, and impurities.

In this study, we investigate the structure-EC relationship from over 50 carbon samples. The carbon used was graphite, carbon nanotube (CNT), carbon black (CB), hetero atom doped carbon, and the ones synthesized by solution plasma. The carbon materials are evaluated by X-ray diffraction (XRD), Raman spectroscopy, Thermogravimetric analysis (TGA), Energy-dispersive X-ray spectroscopy (EDX), and four-point probe (FPP) measurement. The characterized values were extracted from the results and analyzed by Cluster analysis (CA) with JMP software. CA was used to classify how carbons are related to each other.

The clusters were divided into 3 big groups according to the presence of 002 peak and the degree of defects. Some clusters have been shown high conductivity when they have high crystallinity. It was also found that the heteroatomic effect was higher than the crystallinity in the part showing low EC range. However overall correlation with EC is still unclear. This is because XRD and Raman can only provide information of symmetric or periodic structures rather than the effect of disorder or amorphous parts, sizes and shapes are not considered. Thus, analysis of shapes and sizes such as SEM and BET, and additional measurements related to amorphous structures may be helpful to clarifying the correlation.



Figure 1

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DOI： 10.1149/ma2020-0271138mtgabs

Other Link： https://iopscience.iop.org/article/10.1149/MA2020-0271138mtgabs/pdf

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

The exploration of novel carbon material systems has emerged as a promising strategy for yielding unique and unconventional functional properties. In this study, a cationic nitrogen-doped carbonwrapped single-walled carbon nanotube (CN-C@SWCNT) was synthesized for the first time via solution plasma (SP) by using an aniline aqueous solution with the SWCNT dispersion under ambient conditions. The reactive species produced from SP led to the formation of cationic nitrogendoped carbon (CN-C) completely wrapped around SWCNT. Raman spectroscopy, electron diffraction, and X-ray photoelectron spectroscopy confirmed the presence of cationic nitrogen. CN-C@SWCNT exhibited an excellent electrical conductivity of 120.30 S cm-1. Room-temperature halleffect measurements revealed p-type semiconducting behavior for CN-C@ SWCNT, with a carrier concentration of 4.6 × 1020 cm-3. The electrical conductivity and carrier concentration of p-type CN-C@SWCNT were greater than those reported previously for carbon-based materials. The high electrical properties of CN-C@SWCNT were synergistically related to a conducting bridge between CN-C and SWCNT conducting domains and the presence of doped cationic nitrogen. The SP-synthesized CN-C@SWCNT demonstrates immense potential as an emerging class of p-type carbon materials in advanced electrocatalytic applications.

DOI： 10.1021/acsanm.0c02164

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Scopus

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

Metal-carbon core-shell nanostructures have gained research interest due to their better performances in not only stability but also other properties, such as catalytic, optical, and electrical properties. However, they are limited by complicated synthesis approaches. Therefore, the development of a simple method for the synthesis of metal-carbon core-shell nanostructures is of great significance. In this work, a novel Cu-core encapsulated by a N-doped few-layer graphene shell was successfully synthesized in a one-pot in-liquid plasma discharge, so-called solution plasma (SP), to our knowledge for the first time. The synthesis was conducted at room temperature and atmospheric pressure by using a pair of copper electrodes submerged in a DMF solution as the precursor. The core-shell structure of the obtained products was confirmed by HR-TEM, while further insight information was explained from the results of XRD, Raman, and XPS measurements. The obtained Cu-core encapsulated by the N-doped few-layer graphene shell demonstrated relatively high stability in acid media, compared to the commercial bare Cu particles. Moreover, the stability was found to depend on the thickness of the N-doped few-layer graphene shell which can be tuned by adjusting the SP operating conditions. This journal is

DOI： 10.1039/d0ra07162e

Web of Science

Scopus

PubMed

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

The synthesis of carbon nanoparticles (Cn) and oxygen-doped nanocarbon (OCn) was successfully done through a one-step synthesis by the solution plasma process (SPP). The Cn and OCn were nitrogen-doped by nitridation under an ammonia atmosphere at 800 C for 2 h to yield NCn and NOCn, respectively, for carbon dioxide (CO ) adsorption. The NOCn exhibited the highest specific surface area (~570 m g ) and highest CO adsorption capacity (1.63 mmol g at 25 C) among the synthesized samples. The primary nitrogen species on the surface of NOCn were pyridinic-N and pyrrolic-N. The synergistic effect of microporosity and nitrogen functionality on the NOCn surface played an essential role in CO adsorption enhancement. From the thermodynamic viewpoint, the CO adsorption on NOCn was physisorption, exothermic, and spontaneous. The NOCn showed a more negative enthalpy of adsorption, indicating its stronger interaction for CO on the surface, and hence, the higher adsorption capacity. The CO adsorption on NOCn over the whole pressure range at 25–55 C best fitted the Toth model, suggesting monolayer adsorption on the heterogeneous surface. In addition, NOCn expressed a higher selective CO adsorption than Cn and so was a good candidate for multicycle adsorption. ◦ 2 −1 −1 ◦ ◦ 2 2 2 2 2 2 2

DOI： 10.3390/nano9121776

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Scopus

PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

Tailoring electrical properties of graphene by nitrogen doping is currently of great significance in a broad area of advanced applications. Bonding configuration of nitrogen atoms in graphene plays a vital role in controlling its electrical, chemical, and optical properties. Here, we report for the first time a simple bottom-up synthesis of a novel cationic nitrogen-doped graphene (CNG) by a solution plasma (SP). A mixture of ionic liquid and organic solvent was used as starting precursor. CNG exhibited an orthorhombic structure possibly due to the presence cationic nitrogen in hexagonal graphene lattice. Nitrogen doping content was found to be as high as 13.4 atom %. Electrical characterization demonstrated that the CNG exhibited a p-type semiconducting behavior with superior electrical conductivity and carrier concentration. Such unique electrical characteristics of CNG are mainly attributed to the presence of cationic nitrogen with preserved planar structure.

DOI： 10.1021/acsanm.8b02237

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Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Scientific Publishers  

DOI： 10.1166/nnl.2018.2716

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

Compared with conventional graphene, few-layer graphene is an easy-to-use material because of its interesting mechanical and chemical properties. Meanwhile, solution plasma (SP) represents a nonequilibrium discharge, which induces electron exchange similar to a catalyst. Thus, SP serves as an electron donor and acceptor between organic molecules and graphite flakes in a solution. Finally, electron exchange leads to the formation of few-layer graphene by peeling graphite flakes. Furthermore, CN-functionalized few-layer graphene (f-FLG) exhibits excellent stability and dispersibility because of the balance of attractive and repulsive forces, i.e., the van der Waals force between the planes and the electrostatic force of the nitrile functional groups on the edges. In this study, f-FLG was successfully synthesized by peeling graphite flakes via electron exchange induced by SP in an aqueous solution containing an ionic liquid (IL) (1-ethyl-3-methylimidazolium dicyanamide (EMIM-DCA)). X-ray diffraction measurements revealed that the intensity of the 002 diffraction of graphite and the crystallite size along the [001] direction decreased to about 5 nm after SP treatment, indicating the progress of graphite flake peeling. Furthermore, the purified product comprised three layers with a crystallite size along the basal plane of about 80 nm evaluated by the deconvolution of the Raman 2D band. X-ray photoelectron spectroscopy confirmed that the synthesized f-FLG contains 7.7 atom % nitrogen, and the IR spectrum revealed the presence of the CN functional group. To understand the peeling mechanism, the ionization potential (I ) and electron affinity (E ) of the IL in water, and the averaged electron excitation temperature (T ) in plasma were estimated by ab initio molecular orbital calculations, cyclic voltammetry, and optical emission spectroscopy. An energy diagram of I , E , and T shows that SP served to pump electrons for their circulation via EMIM-DCA and to remove electrons from graphite flakes and inject into f-FLG. P A e P A e

DOI： 10.1021/acs.jpcc.7b08516

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