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Nitrogen-doped graphene nanosheet-double-walled carbon nanotube hybrid nanostructures for high-performance supercapacitors
(2021-09-01)
Muangrat, Worawut
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Obata, Michiko
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Htay, Myo Than
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Fujishige, Masatsugu
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Dulyaseree, Paweena
A hybrid nitrogen-doped graphene nanosheet-grafted double-walled carbon nanotube (NG-DWCNT) was synthesized by chemical vapor deposition (CVD). Double-walled carbon nanotube (DWCNT) was synthesized by floating catalytic CVD using ferrocene and thiophene dissolved in ethanol. NG was directly grafted onto the DWCNT bundles by thermal CVD using mixed ethanol-urea solution. The NG possess sharp-edged petal-like structure on one-dimensional DWCNT bundle. The NG-DWCNT showed the nitrogen content of approximately 1.93 at%. The NG-DWCNT hybrid nanostructures exhibited a higher specific capacitance of 563 F g−1 than that of the DWCNT and un-doped G-DWCNT. The improvement of capacitance value is attributed to the synergic effect of the nitrogen doping together with the sharp-edged petal-like structure of the NG. The facile technique by CVD method provides a promising approach for simple and low-cost technique to synthesize the NG-DWCNT hybrid nanostructures. A hybrid carbon nanostructure of NG-DWCNT has a potential application in electrochemical conversion and energy storage devices.
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Na–Ge glass anode network mixed with bismuth oxide nanocrystallites: A high capacity anode material for use in advanced sodium-ion battery design
(2020-02-15)
Gandi, Suman
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Mekprasart, Wanichaya
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Pecharapa, Wisanu
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Dutta, Dimple P.
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Jayasankar, C. K.
Exploring the growing phenomenon of amorphous intermediate domains at nanoscale and its application as flexible active centres in a glass anode network is decisively significant to enhance sodium-ion battery performance. The outstanding stability of nanosized h-Na<inf>3</inf>Bi and NaGe domains in the glass anode network makes it more electrochemically efficient and increases its ionic conductivity. Subsequently, improved cycle stability and rate capability of glass anode half-cell have been achieved due to optimum void space between domains and open glass network. It also exhibits enhanced ability to withstand extensive volume variations during the repetitive sodiation/de-sodiation process. The size of the amorphous intermediate domains, structure, and lattice planes separation has been estimated based on the HRTEM and SAED images. The advantages gained by the growth of amorphous domains in the sodium-germanate glass network highlights its potential application as high-performance anode components for the advancement of Na-ion battery (NIB) efficiency.
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Horse manure derived nitrogen-doped porous carbon via hydrothermal carbonization for promising applications
(2020-01-01)
Liamprawat, Tanatorn
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Verasarut, Panupong
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Kaewtrakulchai, Napat
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Panomsuwan, Gasidit
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Fuji, Masayoshi
Horse manure, organic waste from livestock, has been used for the production of nitrogen-doped porous carbons (NPC) which could be applied as functional material. The variety of different NH4OH solution concentrations (0.5, 1, 1.5, 2 M) were introduced in hydrothermal treatment as activating agent. Also, the nitrogen precursor was served. Horse manure derived NPC were characterized through varied physicochemical properties including NPC yields, FTIR, SEM, XPS and N2 sorption analyzer to characterize specific properties such as elemental composition on surface, surface functional bonding, physical morphology, and porosity of NPC. In addition, the incorporation of nitrogen dopant into the carbon was intended to further enhance the electrochemical performance.
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Structural and electrochemical studies of undoped and In3+-doped co-binary Cu2-xTe and Bi2Te3 thin films for aqueous Na–S batteries
(2019-10-01)
Sreerung, Rawita
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Raknual, Duanghatai
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Vailikhit, Veeramol
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Teesetsopon, Pichanan
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Kitisripanya, Nareerat
WO<inf>3</inf> electrodes coated with co-binary Cu<inf>2-x</inf>Te and Bi<inf>2</inf>Te<inf>3</inf> thin films were fabricated for sodium-sulfur (Na–S) batteries. Film fabrication was controlled by adjusting the pH of the solution and the indium doping concentration. The phases of orthorhombic CuTe and hexagonal Cu<inf>2</inf>Te with rhombohedral Bi<inf>2</inf>Te<inf>3</inf> were formed on the WO<inf>3</inf> electrode. After In3+ doping, In3+ ions act as Frenkel defects in the Cu<inf>2-x</inf>Te structure. This indicated that In3+ ions are located at interstitial sites in the Cu<inf>2-x</inf>Te structure with higher defect creation energy. Furthermore, more interconnected-like nanoparticles and reduced porosity were observed, thereby indicating that indium segregation with grain boundaries presented and contributed to an enhancement of the surface mobility, nucleation density, and a smoother surface. For electrochemical characteristics, a polysulfide solution was used as a redox electrolyte for ion transport. Optimization of the pH and indium concentration attributed to improve the exchange current density (J<inf>0</inf>) and time responses for the colored and bleached states because of faster movement of Na+ and S2− ions during inter/de-intercalation. Furthermore, optimization of the electrode by adjusting the pH and doping with indium is advantageous for both Na–S and rechargeable batteries because of long life cycle, reasonably high power and energy density of 306 W/kg and 9.35 Wh/kg, respectively. The highest specific capacity (C<inf>s</inf>) values of the charge and discharge cycles for In3+-doped electrodes are ∼ 21 and 19 mAh/g, respectively with the coulombic efficiency approximates 100% (average value of ∼96%). This approach may provide a general path for the fabrication of undoped and In3+-doped co-binary Cu<inf>2-x</inf>Te and Bi<inf>2</inf>Te<inf>3</inf> films on WO<inf>3</inf> electrodes and may increase our knowledge regarding Na–S batteries for further performance improvement.

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