Mesoporous polypyrrole-Ag nanocomposites for supercapacitors

Singu, Bal Sydulu,Yoon, Kuk Ro Elsevier 2018 Journal of alloys and compounds Vol.742 No.-

<P><B>Abstract</B></P> <P>We demonstrate a simple novel approach for the preparation of polypyrrole-Ag nanocomposites via oxidative aqueous polymerization (PPy-Ag-Aq) and interfacial polymerization (PPy-Ag-IF) methods. The prepared PPy-Ag-Aq and PPy-Ag-IF nanocomposites systematically analyzed by FT-IR, TGA, XRD, FE-SEM, TEM and XPS, confirming the formation of PPy-Ag nanocomposites. From the FE-SEM analysis, PPy-Ag-Aq nanocomposite was present in the highly porous form and TEM analysis shows the PPy-Ag-Aq nanocomposite was present in the form of nanospindles (∼30 nm) and nanospheres (∼5 nm) and PPy-Ag-IF nanocomposite present in the nanospheres form (∼2–10 nm). The PPy-Ag-Aq and PPy-Ag-IF nanocomposites used to study the applicability of the electrode material for supercapacitor by cyclic voltammetry and galvanostatic charge-discharge analysis. Mesoporous PPy-Ag-Aq nanocomposite was showing more capacitive response than PPy-Ag-IF nanocomposite.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Synthesis of porous polypyrrole-Ag nanocomposite. </LI> <LI> The polypyrrole-Ag nanocomposite showing the maximum capacitance of 266.7 F g<SUP>−1</SUP>. </LI> <LI> Excellent capacity retention after completion of 5000 charge-discharge cycles. </LI> </UL> </P>

Porous 3D-β-nickel hydroxide microflowers for electrochemical supercapacitors

Singu, B.S.,Yoon, K.R. Korean Society of Industrial and Engineering Chemi 2016 Journal of industrial and engineering chemistry Vol.33 No.-

<P>In this work we have carried out synthesis of porous three dimensional nickel hydroxide (3D-beta-Ni(OH)(2)) microflowers by chemical bath deposition. The structure of the porous 3D-beta-Ni(OH)(2) microflowers characterized by using FT-IR, TGA, XRD, FE-SEM, TEM and XPS. The specific capacitance of the porous 3D-beta-Ni(OH)(2) microflowers were showing around 249 F/g from cyclic voltammetry. The discharge specific capacitance of the porous 3D-beta-Ni(OH)(2) microflowers were found to be 170 and 245 F/g for the 1st and 8000th cycles, respectively. The energy and power density of the porous 3D-beta-Ni(OH)(2) microflowers found to be 8.5W h/kg and 2497.9 W/kg, respectively at the discharge current density of 0.05 A/g. (C) 2015 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.</P>

Exfoliated graphene-manganese oxide nanocomposite electrode materials for supercapacitor

Singu, Bal Sydulu,Yoon, Kuk Ro Elsevier 2019 Journal of alloys and compounds Vol.770 No.-

<P><B>Abstract</B></P> <P>In this paper, one-pot approach was used to produce the highly exfoliated reduced graphene oxide-manganese oxide nanocomposites (rGO-MnO<SUB>x</SUB> and rGO-Mn<SUB>3</SUB>O<SUB>4</SUB>) and systematically analyzed by spectral, thermal, elemental and electron microscope. From the FE-SEM analysis confirms the exfoliated reduced graphene oxide-manganese oxide nanocomposites formation. In the nanocomposites, manganese oxide nanoparticles present in the spherical (rGO-Mn<SUB>3</SUB>O<SUB>4</SUB>), spherical and cube shape (rGO-MnO<SUB>x</SUB>). The electrochemical properties of the rGO-MnO<SUB>x</SUB> and rGO-Mn<SUB>3</SUB>O<SUB>4</SUB> nanocomposites were analyzed by cyclic voltammetry and charge-discharge study. The highly exfoliated rGO-MnO<SUB>x</SUB> nanocomposite show the higher electrochemical capacitive responsive than rGO-Mn<SUB>3</SUB>O<SUB>4</SUB> nanocomposite. The rGO-MnO<SUB>x</SUB> nanocomposite exhibiting the utmost capacitance of 398.8 F g<SUP>−1</SUP> at a sweep rate of 5 mV s<SUP>−1</SUP>, the energy density of 23.3 Wh kg<SUP>−1</SUP> and power density of 2001 W kg<SUP>−1</SUP>, owing to the synergistic effect of reduced graphene oxide and spherical and cubical shape of manganese oxide nanoparticles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Exfoliated reduced graphene oxide-manganese oxide nanocomposites are prepared. </LI> <LI> The rGO-MnO<SUB>x</SUB> nanocomposite exhibiting the utmost capacitance of 398.8 F g<SUP>−1</SUP>. </LI> <LI> The rGO-MnO<SUB>x</SUB> has showing the capacitance retention of 80% over 5000 cycles. </LI> </UL> </P>

Polyaniline–nickel oxide nanocomposites for supercapacitor

Singu, B. S.,Palaniappan, S.,Yoon, K. R. Springer Science + Business Media 2016 Journal of applied electrochemistry Vol.46 No.10

<P>Polyaniline-nickel oxide (PANI-NiO) nanocomposites were synthesized by in situ aqueous oxidative polymerization and were used for supercapacitor applications. The NiO nanosheets were prepared using sodium dodecyl sulfate as the anionic surfactant. The morphology and microstructure of the samples were examined by X-ray diffraction, scanning electron microscope, and thermogravimetric analysis. The obtained results indicated that the NiO nanosheets were uniformly distributed in the polyaniline (PANI) nanofibrous matrix. The electrochemical properties of the PANI-NiO nanocomposites were studied using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. Notably, such nanocomposites showed high specific capacitances up to 514 F g(-1) at a scan rate of 1 mV s(-1). [GRAPHICS]</P>

Synthesis and characterization of MnO₂-decorated graphene for supercapacitors

Singu, Bal Sydulu,Yoon, Kuk Ro Pergamon Press 2017 Electrochimica Acta Vol. No.

<P><B>Abstract</B></P> <P>We report the simple one-step synthesis of a reduced graphene oxide–manganese oxide (rGO-MnO<SUB>2</SUB>) nanocomposite using graphene oxide (GO) and KMnO<SUB>4</SUB> in the presence of sulfuric acid. The crystal structure, morphology, thermal, pore size, and other physical properties of the rGO-MnO<SUB>2</SUB> nanocomposite were systematically analyzed by X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller analysis. XPS analysis confirmed the synthesis of exfoliated GO and rGO-MnO<SUB>2</SUB> nanocomposite. The rGO-MnO<SUB>2</SUB> nanocomposite exhibited a maximum specific capacitance, energy, and power density of 290Fg<SUP>−1</SUP>, 25.7Whkg<SUP>−1</SUP>, and 8008.7Wkg<SUP>−1</SUP>, respectively, in a 1M Na<SUB>2</SUB>SO<SUB>4</SUB> electrolyte, and a high retention (87.5%) of capacitance after 5000 cycles. The enhanced electrochemical properties are caused by good contact between MnO<SUB>2</SUB> nanorods and graphene nanosheets, and the higher conductive and capacitive behavior of graphene.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Chemical Synthesis of Sea-Urchin Shaped 3D-MnO₂ Nano Structures and Their Application in Supercapacitors

Singu, Bal Sydulu,Hong, Sang Eun,Yoon, Kuk Ro American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.6

<P>Sea-urchin shaped alpha-MnO2 hierarchical nano structures have been synthesized by facile thermal method without using any hard or soft template under the mild conditions. The structural and morphology of the 3D-MnO2 was characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). From the XRD analysis indicates that MnO2 present in the alpha form. Morphology analysis shows that alpha-MnO2 sea-urchins are made by stacked nanorods, the diameter and length of the stacked nanorods present in the range of 50-120 nm and 200-400 nm respectively. The electrochemical behaviour of alpha-MnO2 has been investigated by cyclic voltammetry (CV) and charge-discharge (CD). The specific capacitance, energy density and power density are 212.0 F g(-1), 21.2 Wh kg(-1) and 1200 W kg(-1) respectively at the current density of 2 A g(-1). The retention of the specific capacitance after completion of 1000 charge-discharge cycles is around 97%. The results reveal that the prepared Sea-urchin shaped alpha-MnO2 has high specific capacitance and exhibit excellent cycle life.</P>

Honeycomb-like manganese oxide nanospheres for redox supercapacitors

Singu, Bal Sydulu,Hong, Sang Eun,Yoon, Kuk Ro INSTITUTE FOR IONICS 2018 IONICS -KIEL- Vol.24 No.2

<P>Honeycomb-like MnO2 nanospheres were synthesized using stainless steel substrates by a facile chemical bath deposition method. The obtained nanospheres were about 200-400 nm in diameter and consisted of porous ultrathin nanosheets. Honeycomb-like MnO2 nanospheres exhibited a high specific capacitance of 240 F g(-1) and 87.1% capacitance retention after 1000 cycles at a current density of 0.5 A g(-1). These remarkable electrochemical results imply great potential for applications of the honeycomb-like MnO2 nanospheres in supercapacitors.</P>

Optimization of Pen Printing Technique for Scale Down of Printed Organic Electronics

Singu Han,Hwasung Lee 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Porous manganese oxide nanospheres for pseudocapacitor applications

Singu, B.S.,Yoon, K.R. Elsevier 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.695 No.-

<P><B>Abstract</B></P> <P>Mesoporous, uniform manganese oxide nanosphere thin films were grown on a stainless-steel substrate using the successive ionic layer adsorption and reaction (SILAR) method. The amorphous manganese oxide nanosphere thin films (AMONTFs) were characterized by grazing incidence X-ray diffraction (GI-XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The GI-XRD analysis reveals that the manganese oxide nanosphere thin films were present in the forms of α-MnO<SUB>2</SUB> and γ-MnO<SUB>2</SUB>. XPS demonstrates that the thin films contain a mixture of manganese oxides: MnO<SUB>2</SUB> (Mn<SUP>4+</SUP>) and MnOOH (Mn<SUP>3+</SUP>). The effect of the number of SILAR cycles on the morphology was observed systemically by FE-SEM and greatly influences the size of these unique nanospheres. The electrochemical properties of the AMONTF electrodes were analyzed by cyclic voltammetry (CV) and the galvanostatic charge-discharge (CD) method. The outcomes of the FE-SEM and electrochemical measurements reveal that the thin film obtained after 60 SILAR cycles has a uniform nanosphere size distribution and large specific capacitance. The manganese oxide thin films exhibit a maximum specific capacitance, energy, and power density of 262.0 F g<SUP>−1</SUP>, 18.3 Wh kg<SUP>−1</SUP>, and 7999.4 W kg<SUP>−1</SUP>, respectively, in an aqueous 1 M Na<SUB>2</SUB>SO<SUB>4</SUB> electrolyte solution.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Synthesis of porous manganese oxide nanosphere thin films. </LI> <LI> The size of the nanospheres well depended on the number of SILAR cycles. </LI> <LI> Maximum specific capacitance of manganese oxide nanosphere thin films showing around 262.0 F g<SUP>−1</SUP>. </LI> </UL> </P>

Sulfur-doped nickel oxide spherical nanosheets for redox supercapacitors

Singu, Bal Sydulu,Hong, Sang Eun,Yoon, Kuk Ro THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2018 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.62 No.-

<P><B>Abstract</B></P> <P>We have synthesized sulfur-doped nickel oxide (S-NiO) spherical nanosheets by emulsion method. The structure of the S-NiO nanosheets is characterized by using TGA, XRD, XPS, BET, FE-SEM and FE-TEM. From the TGA, XPS and EDAX results conclude the nickel oxide is doped with sulfur. The specific capacitance of the S-NiO nanosheets was showing 313Fg<SUP>−1</SUP> at the sweep rate of 5mVs<SUP>−1</SUP> by cyclic voltammetry. The S-NiO nanosheets showing the high rate performance of 80% at the current density ranging from 1 to 8Ag<SUP>−1</SUP> and high retention of the capacitance 99% after completion of 1000 charge–discharge cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Synthesis of sulfur-doped nickel oxide spherical nanosheets with the thickness of <10nm. </LI> <LI> As prepared nickel hydroxide present in the form of nanodiscs. </LI> <LI> S-NiO exhibiting high capacitance of 313Fg<SUP>−1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>