One-step facile hydrothermal synthesis of Fe₂O₃@LiCoO₂ composite as excellent supercapacitor electrode materials

Gopi, Chandu V.V. Muralee,Somasekha, A.,Reddy, Araveeti Eswar,Kim, Soo-Kyoung,Kim, Hee-Je Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.435 No.-

<P><B>Abstract</B></P> <P>Herein, for the first time, we demonstrate the fabrication of Fe<SUB>2</SUB>O<SUB>3</SUB>@LiCoO<SUB>2</SUB> hybrid nanostructures on Ni foam substrate by facile one-step hydrothermal technique. Morphological studies reveal that aggregated Fe<SUB>2</SUB>O<SUB>3</SUB> nanoflakes anchored on the surface of sphere-like LiCoO<SUB>2</SUB> nanoflakes. Electrochemical studies are used to examine the performance of the supercapacitor electrodes. The composite Fe<SUB>2</SUB>O<SUB>3</SUB>@LiCoO<SUB>2</SUB> electrode exhibited excellent electrochemical performance than Fe<SUB>2</SUB>O<SUB>3</SUB> and LiCoO<SUB>2</SUB> electrodes, such as a low charge transfer resistance, a high specific capacitance of 489 F g<SUP>−1</SUP> at 5 mA cm<SUP>−2</SUP> and an enhanced capacity retention of 108% over 3000 cycles at 15 mA cm<SUP>−2</SUP>. The composite Fe<SUB>2</SUB>O<SUB>3</SUB>@LiCoO<SUB>2</SUB> holds great promise for electrochemical applications due to well-defined hierarchical morphology, synergetic effect of Fe<SUB>2</SUB>O<SUB>3</SUB> and LiCoO<SUB>2</SUB>, enhanced electrical conductivity, efficient electrolyte penetration and fast electron transfer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fe<SUB>2</SUB>O<SUB>3</SUB>@LiCoO<SUB>2</SUB> composites successfully fabricated by facile hydrothermal route. </LI> <LI> Fe<SUB>2</SUB>O<SUB>3</SUB>@LiCoO<SUB>2</SUB> shows unique surface morphology with large surface area and superior conductivity. </LI> <LI> Fe<SUB>2</SUB>O<SUB>3</SUB>@LiCoO<SUB>2</SUB> electrode exhibit excellent supercapacitor performances. </LI> <LI> Fe<SUB>2</SUB>O<SUB>3</SUB>@LiCoO<SUB>2</SUB> electrode shows superior cycling stability with retention of 108%. </LI> </UL> </P>

One-pot hydrothermal synthesis of tungsten diselenide/reduced graphene oxide composite as advanced electrode materials for supercapacitors

Gopi, Chandu V.V. Muralee,Reddy, Araveeti Eswar,Bak, Jin-Soo,Cho, In-Ho,Kim, Hee-Je Elsevier 2018 Materials letters Vol.223 No.-

<P><B>Abstract</B></P> <P>Nanosheet-like tungsten diselenide (WSe<SUB>2</SUB>)/reduced graphene oxide (rGO) hybrid has been developed for the first time by facile one-step hydrothermal route for supercapacitor applications. Electrochemical measurements show that the WSe<SUB>2</SUB>/rGO-based supercapacitor electrode exhibits a maximum specific capacitance of 389 F g<SUP>−1</SUP> at 1 A g<SUP>−1</SUP> with capacitance retention of 98.7% after 3000 charge/discharge cycles at a high current density of 7 A g<SUP>−1</SUP>, and delivered a energy density of 34.5 W h kg<SUP>−1</SUP> at 400 W kg<SUP>−1</SUP> and 22.4 W h kg<SUP>−1</SUP> at a high power density of 4000 W kg<SUP>−1</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Novel WSe<SUB>2</SUB>/rGO firstly synthesized for energy storage applications. </LI> <LI> WSe<SUB>2</SUB>/rGO shows large surface area and superior conductivity. </LI> <LI> WSe<SUB>2</SUB>/rGO composite exhibits high specific capacitance and outstanding cycling stability. </LI> </UL> </P>

Wearable superhigh energy density supercapacitors using a hierarchical ternary metal selenide composite of CoNiSe₂ microspheres decorated with CoFe₂Se₄ nanorods

Muralee Gopi, Chandu V. V.,Reddy, Araveeti Eswar,Kim, Hee-Je The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.17

<P>A rational and multicomponent design of hierarchical CoFe2Se4 (CFS) nanorods adhered to CoNiSe2 (CNS) microsphere composites is prepared for the first time <I>via</I> facile and eco-friendly synthesis methods. The hierarchical CFS-CNS robust architectures enhance the specific surface area and porosity and also increase the availability of electrochemically active sites, which provides ideal pathways for electrolyte diffusion and facilitates electron transportation. As a result, the as-prepared fabric-based CFS-CNS electrode delivers a maximum specific capacity of 183.4 mA h g<SUP>−1</SUP> at a current density of 1 A g<SUP>−1</SUP>, with an excellent rate capability of 172.4 mA h g<SUP>−1</SUP> at 8 A g<SUP>−1</SUP> and outstanding cycling stability with 99.2% retention over 3000 cycles in aqueous 3 M KOH electrolyte solution. Moreover, the assembled fabric-based CFS-CNS//CFS-CNS symmetric SC achieves a high energy density of 80.2 W h kg<SUP>−1</SUP> at 1000 W kg<SUP>−1</SUP> and delivers an exceptional cycling stability with 97.02% retention over 3000 cycles as well as exhibiting excellent flexibility to sustain various deformations including bending and twisting. Utilizing the outstanding energy storage performance, the symmetric SC can light up a light-emitting diode for real-time applications.</P>

CNT@rGO@MoCuSe Composite as an Efficient Counter Electrode for Quantum Dot-Sensitized Solar Cells

Gopi, Chandu V. V. Muralee,Singh, Saurabh,Eswar Reddy, Araveeti,Kim, Hee-Je American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.12

<P>This paper reports an efficient and simple strategy for the synthesis of molybdenum copper selenide (MoCuSe) nanoparticles decorated with a combination of a carbon nanotube (CNT) network and reduced graphene oxide (rGO) nanosheets to form an integrated hybrid architecture (CNT@rGO@MoCuSe) using a two-step hydrothermal approach. The synthesized hybrid CNT@rGO@MoCuSe material onto the Ni foam substrate is applied successfully as an effective counter electrode (CE) in quantum dot-sensitized solar cells (QDSSCs). A highly conductive CNT@rGO network grown on electrochemically active MoCuSe particles provides a large surface area and exhibits a rapid electron transport rate at the interface of CE/electrolyte. As a result, the QDSSC with the designed CNT@rGO@MoCuSe CE shows a higher power conversion efficiency of 8.28% under 1 sun (100 mW cm<SUP>-2</SUP>) irradiation, which is almost double the efficiency of 4.04% for the QDSSC with the MoCuSe CE. Furthermore, the QDSSC based on the CNT@rGO@MoCuSe CE delivers superior stability at a working state for over 100 h. Therefore, CNT@rGO@MoCuSe is very promising as a stable and efficient CE for QDSSCs and offers new opportunities for the development of hybrid, effective, and robust materials for energy-related fields.</P> [FIG OMISSION]</BR>

Facile synthesis of a NiO/NiS hybrid and its use as an efficient electrode material for supercapacitor applications

Kim, Sang-Yong,Gopi, Chandu V. V. Muralee,Reddy, Araveeti Eswar,Kim, Hee-Je The Royal Society of Chemistry 2018 NEW JOURNAL OF CHEMISTRY Vol.42 No.7

<P>In the current work, cost-effective NiO nanosheets decorated with NiS nanoparticles were successfully fabricated on Ni foam by following a facile two-step hydrothermal route, and investigated as an efficient electrode material for supercapacitor applications for the first time. The obtained NiO/NiS hybrid electrode was found to deliver rapid diffusion of ions and fast electron transport, due to the high electrical conductivity, large surface area, and unique surface morphology of the NiO/NiS. As a result, this electrode exhibited a high specific capacitance of 386.7 F g<SUP>−1</SUP> at 1 A g<SUP>−1</SUP> and good cycling stability, specifically retaining 97.6% of the initial capacitance after 3000 charge-discharge cycles at 5 A g<SUP>−1</SUP>. These results indicated NiO/NiS to be a promising electrode material for supercapacitor applications.</P>

Hydrothermal synthesis of MoS₂ and WS₂ nanoparticles for high-performance supercapacitor applications

Nagaraju, Chandu,V. V. Muralee Gopi, Chandu,Ahn, Jin-Woo,Kim, Hee-Je The Royal Society of Chemistry 2018 NEW JOURNAL OF CHEMISTRY Vol.42 No.15

<P>Nanoparticle-featured MoS2 and WS2 have been synthesized using a facile one-step hydrothermal approach and their application as electroactive materials for high-performance supercapacitors has been investigated. The electrochemical results of the MoS2 electrode exhibit a higher specific capacitance (<I>C</I>s) of 1531.2 F g<SUP>−1</SUP> at 5 mA cm<SUP>−2</SUP> with good cycling stability (up to 81.6% retention over 3000 cycles). The WS2 electrode delivers a high <I>C</I>s of 1439.5 F g<SUP>−1</SUP> at 5 mA cm<SUP>−2</SUP> and excellent cycling stability with 77.4% retention after 3000 cycles. The outstanding performance of the MoS2 and WS2 electrodes indicates their potential in next-generation high-performance supercapacitor applications.</P>

Layer by layer approach to enhance capacitance using metal sulfides for supercapacitor applications

Subramanian, Archana,Punnoose, Dinah,Raman, Vivekanandan,Gopi, Chandu V.V. Muralee,Rao, Sunkara Srinivasa,Khan, Muhammad Adil,Kim, Hee-Je Elsevier 2018 Materials letters Vol.231 No.-

<P><B>Abstract</B></P> <P>Layer-by-layer approach for NiS, CoS and PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) is being fabricated. Metal sulfides have always been chosen for their remarkable electrochemical characteristics and wide beneficial domains, such as electrochemical energy conversion and storage. This work presents the preparation of cost-effective metal sulfides (NiS, NiS/CoS, NiS/CoS/PEDOT:PSS) developed on nickel foam sheets for supercapacitor (SC) applications. The assembled NiS/CoS/PEDOT:PSS array SC device exhibits an utmost energy density of 30.3 W h kg<SUP>−1</SUP> and specific capacitance of 353 F g<SUP>−1</SUP>. All wet processing methods of fabrication accompanied with superior performance characteristics make these SCs very attractive for the next generation flexible energy storage systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> NiS/CoS/PEDOT:PSS on nickel foam is coated by Chemical Bath Deposition method. </LI> <LI> Metal sulfides extend active area due to low electronegativity of sulfur over oxygen. </LI> <LI> PEDOT:PSS on NiS/CoS is coated to increase surface area and conductivity. </LI> <LI> NiS/CoS/PEDOT:PSS showed maximal specific capacitance of 353 F g<SUP>−1</SUP> at 15 mA cm<SUP>−2</SUP>. </LI> </UL> </P>

Facile preparation of nanoflake MnNi₂O₄-PbS nanoparticle composites on Ni foam as advanced electrode materials for supercapacitors

Park, Tae-Yong,V. V. Muralee Gopi, Chandu,Ahn, Jin-Woo,Kim, Hee-Je The Royal Society of Chemistry 2018 NEW JOURNAL OF CHEMISTRY Vol.42 No.17

<P>MnNi2O4-PbS composites have been successfully deposited on a nickel (Ni) foam substrate using a simple and cost-effective two-step hydrothermal route for application as supercapacitor electrode materials in energy storage devices. The morphological, structural and physical behaviors of the as-prepared composite were evaluated, and the results indicate that the PbS nanoparticles were successfully anchored onto the surface of MnNi2O4 nanoflakes. The electrochemical studies reveal that the MnNi2O4-PbS composite exhibits a higher supercapacitor performance with a high specific capacitance of 1176.76 F g<SUP>−1</SUP> at 1 A g<SUP>−1</SUP> and improved cycling stability with 98.86% retention after 4000 cycles, which are much higher than that of the MnNi2O4 electrode. The improved electrochemical performance of the composite electrode is mainly due to its unique hierarchical structure, which provides a better contact of the electrolyte and electrode surface, and a large number of active sites. These results suggest that the unique MnNi2O4-PbS electrode would be a promising electrode for high-performance supercapacitor applications.</P>

Facile synthesis of hierarchical ZnMn₂O₄@ZnFe₂O₄ microspheres on nickel foam for high-performance supercapacitor applications

Reddy, Araveeti Eswar,Anitha, Tarugu,Muralee Gopi, Chandu V. V.,Durga, Ikkurthi Kanaka,Kim, Hee-Je The Royal Society of Chemistry 2018 NEW JOURNAL OF CHEMISTRY Vol.42 No.4

<P>Unique ZnMn2O4@ZnFe2O4 microspheres were fabricated on Ni foam using a facile and cost-effective hydrothermal method for high-performance supercapacitor applications. The resulting ZnMn2O4@ZnFe2O4 electrode was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electrochemical techniques. The ZnMn2O4@ZnFe2O4 electrode exhibited a microsphere-like morphology with a mean size of ∼50-115 nm. The electrochemical performance of the ZnMn2O4@ZnFe2O4 electrode was investigated and the results showed that the ZnMn2O4@ZnFe2O4 electrode exhibits a high specific capacitance of 1024.66 F g<SUP>−1</SUP> at 10 mA cm<SUP>−2</SUP>, low internal resistance, and remarkable cycling stability with 95.8% capacitance retention after 3000 charge-discharge cycles, which was superior to those of the ZnMn2O4 and ZnFe2O4 electrodes. Such enhanced electrochemical performance and the facile synthetic method of ZnMn2O4@ZnFe2O4 electrode materials offer great promise in next generation supercapacitor applications.</P>

NiMoO₄@NiWO₄ honeycombs as a high performance electrode material for supercapacitor applications

Reddy, Araveeti Eswar,Anitha, Tarugu,Muralee Gopi, Chandu V. V.,Srinivasa Rao, S.,Kim, Hee-Je The Royal Society of Chemistry 2018 Dalton Transactions Vol.47 No.27

<P>In this study, we report a facile two-step fabrication of honeycomb-like NiMoO4@NiWO4 nanocomposites on Ni foam as the electrode for high-performance supercapacitor applications. Structural characterization and compositional analysis of the as-prepared NiMoO4@NiWO4 nanocomposites was performed using scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, cyclic voltammetry, galvanostatic charge-discharge cycling, and electrochemical impedance spectroscopy. The electrochemical properties of the as-synthesized NiMoO4@NiWO4 nanocomposites were studied in a 3 M KOH electrolyte solution for application as electrode material of supercapacitors. A maximum specific capacitance of 1290 F g<SUP>−1</SUP> was achieved for NiMoO4@NiWO4 at a current density of 2 A g<SUP>−1</SUP>. This electrode exhibits excellent long cycle-life stability with 93.1% specific capacitance retention after 3000 cycles at a current density of 6 A g<SUP>−1</SUP>. Our studies indicate that the as-synthesized NiMoO4@NiWO4 nanocomposites could be a promising candidate as the electrode material in high-performance electrochemical energy storage applications.</P>