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Author: search.filters.author.Dulyaseree, PaweenaSubject: search.filters.subject.Supercapacitor

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    Nitrogen-doped graphene nanosheet-double-walled carbon nanotube hybrid nanostructures for high-performance supercapacitors
    (2021-09-01)
    Muangrat, Worawut
    ;
    Obata, Michiko
    ;
    Htay, Myo Than
    ;
    Fujishige, Masatsugu
    ;
    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<sup>−1</sup> 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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    Facile synthesis of hybrid manganese oxide and multiwalled carbon nanotube by two-step electrodeposition for supercapacitor electrode
    (2017-01-01)
    Wanchaem, Thanthamrong
    ;
    Rattanamai, Songsak
    ;
    Dulyaseree, Paweena
    ;
    Khanchaitit, Paisan
    ;
    Wongwiriyapan, Winadda
    This work presents a facile synthesis of hybrid manganese oxide and multiwalled carbon nanotube (MnO<inf>x</inf>/MWCNT) by two-step electrodeposition technique for supercapacitor electrode application. Firstly, MWCNT was deposited onto SS304 substrate by electrophoretic deposition at a constant voltage of 7 V for 5 min. MWCNT solution was prepared using sodium dodecylbenzenesulfonate (SBDS) as a surfactant. Next, MnO<inf>x</inf> was deposited onto the pre-deposited MWCNT/SS304 substrate by galvanostatic electrodeposition using 0.1 M manganese sulfate (MnSO<inf>4</inf>) solution as a precursor. The electrodeposition condition was set at a constant current of 1 mA/cm<sup>2</sup> for 5-15 min. Nanosheet array of MnO<inf>x</inf> was formed uniformly on MWCNT. At the deposition time of 10 min, the thickness of MnO<inf>x</inf> nanosheet was approximately 40 nm. Hybrid MnO<inf>x</inf>/MWCNT was characterized its electrochemical properties by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical Impedance spectroscopy. Hybrid MnO<inf>x</inf>/MWCNT shows an improved specific capacitance of 267.03 F·g<sup>-1</sup> with a series resistance of 5.17 Ω, surpassing electrode material with only MnO<inf>x</inf> or MWCNT. The high specific capacitance would be ascribed to the integration of MWCNT and MnO<inf>x</inf> functions. MWCNT may act as a platform for MnO<inf>x</inf> deposition, resulting in an increase in electrochemically active surface area of MnO<inf>x</inf>. The obtained results indicate that this two-step electrodeposition method allows tailor-made hybrid materials with nanoscale control without using harsh and toxic chemicals or high synthesis temperature.
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    Optimized manganese oxide nanosheet/manganese oxide thin film/ multiwalled carbon nanotubes as hybrid electrode materials for supercapacitors
    (2017-01-01)
    Rattanamai, Songsak
    ;
    Dulyaseree, Paweena
    ;
    Wanchaem, Thanthumrong
    ;
    Wongwiriyapan, Winadda
    Manganese oxide nanosheet/manganese oxide thin film/multiwalled carbon nanotubes(s-MnO<inf>x</inf>/f-MnO<inf>x</inf>/MWNTs) were used as hybrid electrode materials for supercapacitor application. Supercapacitor performance based on these hybrid materials was optimized by varying morphologies of s-MnO<inf>x</inf>. Firstly, a MWNT paste was coated onto nickel (Ni) foam and subsequently f-MnO<inf>x</inf> was deposited onto the pre-coated MWNTs/Ni foam by galvanostatic (GS) mode of electrodeposition technique at a constant current of 1 mA/cm<sup>2</sup> using 0.1 M KMnO<inf>4</inf> as a precursor with a fix deposited time of 5 min. Finally, s-MnO<inf>x</inf> was deposited onto the prepared f-MnO<inf>x</inf>/MWNTs/Ni foam by GS mode of electrodeposition technique at a constant current of 1 mA/cm<sup>2</sup> using 0.1 M KMnO<inf>4</inf> as precursor with different deposited times of 10, 15 and 20 min. Each hybrid s-MnO<inf>x</inf>/f-MnO<inf>x</inf>/MWNTs electrode was characterized by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The s-MnO<inf>x</inf>/f-MnO<inf>x</inf>/MWNTs electrode prepared by 15-min-deposited s-MnO<inf>x</inf> shows the highest specific capacitance. The capacitance improvement is attributed to the increase of electrode surface area.