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Plasma-electric field controlled growth of oriented graphene for energy storage applications
Ghosh, Subrata,Polaki, S R,Kamruddin, M,Jeong, Sang Mun,Ostrikov, Kostya (Ken) IOP 2018 Journal of Physics. D, Applied Physics Vol.51 No.14
<P>It is well known that graphene grows as flat sheets aligned with the growth substrate. Oriented graphene structures typically normal to the substrate have recently attracted major attention. Most often, the normal orientation is achieved in a plasma-assisted growth and is believed to be due to the plasma-induced <I>in-built</I> electric field, which is usually oriented normal to the substrate. This work focuses on the effect of an <I>in-built</I> electric field on the growth direction, morphology, interconnectedness, structural properties and also the supercapacitor performance of various configurations of graphene structures and reveals the unique dependence of these features on the electric field orientation. It is shown that tilting of growth substrates from parallel to the normal direction with respect to the direction of <I>in-built</I> plasma electric field leads to the morphological transitions from horizontal graphene layers, to oriented individual graphene sheets and then interconnected 3D networks of oriented graphene sheets. The revealed transition of the growth orientation leads to a change in structural properties, wetting nature, types of defect in graphitic structures and also affects their charge storage capacity when used as supercapacitor electrodes. This simple and versatile approach opens new opportunities for the production of potentially large batches of differently oriented and structured graphene sheets in one production run.</P>
Ghosh, Subrata,Polaki, S.R.,Sahoo, Gopinath,Jin, En-Mei,Kamruddin, M.,Cho, Jung Sang,Jeong, Sang Mun Elsevier 2019 Journal of industrial and engineering chemistry Vol.72 No.-
<P><B>Abstract</B></P> <P>The asymmetric electrochemical capacitor was realized by MnO<SUB>2</SUB>/Vertical graphene nanosheets (VGN) and Fe<SUB>2</SUB>O<SUB>3</SUB>/VGN as positive and negative electrodes, respectively. The surface of VGN skeleton is independently decorated with MnO<SUB>2</SUB> having sponge gourd-like morphology and Fe<SUB>2</SUB>O<SUB>3</SUB> having nanorice like morphology. Both the electrodes have shown around 250 times higher charge-storage capacity than the bare VGN (0.47mF/cm<SUP>2</SUP>) with the specific capacitance of 118 (MnO<SUB>2</SUB>/VGN) and 151mF/cm<SUP>2</SUP> (Fe<SUB>2</SUB>O<SUB>3</SUB>/VGN). The fabricated asymmetric device exhibited a specific capacitance of 76mF/cm<SUP>2</SUP> and energy density of 71μWh/cm<SUP>2</SUP> with an excellent electrochemical stability up to 12,000 cycles, over a potential window of 2.6V.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Metal oxide-vertical graphene electrodes were prepared. </LI> <LI> Metal oxide-vertical graphene nanoshees structure was found to be super-hydrophilic. </LI> <LI> A plausible formation mechanism of metal oxides on the surface of vertical graphene is propsed. </LI> <LI> As fabricated asymmetric supercapacitor device was operated in an extended window of 2.6V. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Subrata Ghosh,S.R. Polaki,Gopinath Sahoo,En Mei Jin,M. Kamruddin,조정상,정상문 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.72 No.-
The asymmetric electrochemical capacitor was realized by MnO2/Vertical graphene nanosheets (VGN)and Fe2O3/VGN as positive and negative electrodes, respectively. The surface of VGN skeleton isindependently decorated with MnO2 having sponge gourd-like morphology and Fe2O3 having nanoricelike morphology. Both the electrodes have shown around 250 times higher charge-storage capacity thanthe bare VGN (0.47 mF/cm2) with the specific capacitance of 118 (MnO2/VGN) and 151 mF/cm2 (Fe2O3/VGN). The fabricated asymmetric device exhibited a specific capacitance of 76 mF/cm2 and energydensity of 71 mWh/cm2 with an excellent electrochemical stability up to 12,000 cycles, over a potentialwindow of 2.6 V.
A review on metal nitrides/oxynitrides as an emerging supercapacitor electrode beyond oxide
Subrata Ghosh,정상문,Shyamal Rao Polaki 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.7
Electrode materials design is the most significant aspect in constructing a supercapacitor device. The evolution of metal nitrides/oxynitrides as supercapacitor electrode is strikingly noticeable today besides prevailing carbon or 2D materials, metal oxides/hydroxides and conducting polymers electrode materials. The theoretically estimated specific capacitance of a nitride-based supercapacitor is 1,560 F g1. These nanostructures exhibit an excellent capacitive behavior with a specific capacitance of 15-951.3mF cm2 or 82-990 F g1, high energy density (16.5-162Wh Kg1) and power density (7.3-54,000W Kg1). On this account, supercapacitor performance of metal nitrides/oxynitrides is reviewed exclusively. The major focus of the present review is directed towards state-of-art progress in supercapacitor performance of nitrides/oxynitrides, underlying charge-storage mechanism, important outcomes and their limitations. Finally, we conclude with challenges and prospects of metal nitrides/oxynitrides for supercapacitor electrodes.