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RISS 인기검색어
- 검색키워드
- 저자 : S. Chandra Sekhar (검색결과 42 건)
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Nagaraju, Goli,Cha, Sung Min,Sekhar, S. Chandra,Yu, Jae Su Wiley Blackwell (John Wiley Sons) 2017 Advanced energy materials Vol.7 No.4
<P>Highly flexible and conductive fabric (CF)-supported cauliflower-like nickel selenide nanostructures (Ni3Se2 NSs) are facilely synthesized by a singlestep chronoamperometry voltage-assisted electrochemical deposition (ECD) method and used as a positive electrode in supercapacitors (SCs). The CF substrate composed of multi-layered metallic films on the surface of polyester fibers enables to provide high electrical conductivity as a working electrode in ECD process. Owing to good electrical conductivity, high porosity and intertwined fibrous framework of CF, cauliflower-like Ni3Se2 NSs are densely integrated onto the entire surface of CF (Ni3Se2 NSs@CF) substrate with reliable adhesion by applying a chronoamperometry voltage of -1.0 V for 240 s. The electrochemical performance of the synthesized cauliflower-like Ni3Se2 NSs@CF electrode exhibits a maximum specific capacity (CSC) of 119.6 mA h g(-1) at a discharge current density of 2 A g(-1) in aqueous 1 m KOH electrolyte solution. Remarkably, the specific capacity of the same electrode is greatly enhanced by introducing a small quantity of redox-additive electrolyte into the aqueous KOH solution, indicating the CSC approximate to 251.82 mA h g(-1) at 2 A g(-1) with good capacity retention. Furthermore, the assembled textile-based asymmetric SCs achieve remarkable electrochemical performance such as higher energy and power densities, which are able to light up different colored lightemitting diodes.</P>
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Sekhar, S. Chandra,Nagaraju, Goli,Cha, Sung Min,Yu, Jae Su The Royal Society of Chemistry 2016 Dalton Transactions Vol.45 No.48
<▼1><P>A cost-effective composite electrode featuring MnO2 NSAs@VCFs exhibits good electrochemical performance as an electroactive material for pseudocapacitors.</P></▼1><▼2><P>Manganese dioxide nanosheet arrays with interconnected arrangements are easily synthesized on vapor grown carbon fibers (MnO2 NSAs@VCFs) by a simple wet-chemical method at low temperature. The conductive nature of the VCFs serves as a scaffold and easily reduces potassium permanganate species for the formation of hierarchical MnO2 NSAs@VCFs. When utilized as an electroactive material for pseudocapacitors, the sophisticated configuration of the nanocomposite provides an effective electrochemical activity and an electron pathway for higher electrochemical performance in 1 M Na2SO4 aqueous solution. The hierarchical MnO2 NSAs@VCFs exhibit a maximum specific capacitance of 115.3 F g<SUP>−1</SUP> at a current density of 0.5 A g<SUP>−1</SUP> with an excellent cycling stability of 85.6% after 2000 cycles at a current density of 5 A g<SUP>−1</SUP>. Such facile and cost-effective fabrication of a metal oxide nanocomposite with improved electrochemical performance allows it to be considered as a promising electroactive material for energy storage devices.</P></▼2>
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Sekhar, S. Chandra,Nagaraju, Goli,Ramulu, Bhimanaboina,Yu, Jae Su American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.43
<P>We facilely prepared silver nanoparticle-decorated Ce<SUB>6</SUB>Mo<SUB>10</SUB>O<SUB>39</SUB> marigold flower-like structures (Ag NPs@CM MFs) for use as an effective positive material in hybrid supercapacitors (HSCs). With the aid of ethylenediaminetetraacetic acid (EDTA) as a chelating agent, self-assembled CM MFs were synthesized by a single-step hydrothermal method. When the electrochemical properties were tested in an aqueous alkaline electrolyte, the synthesized CM MFs with 0.15 g of EDTA exhibited a relatively high charge storage property (55.3 μA h/cm<SUP>2</SUP> at 2 mA/cm<SUP>2</SUP>) with a battery-type redox behavior. The high capacity performance is mainly because of the large surface area of the CM MFs, and the hierarchically connected nanoflakes provide wide open wells for rapid accessibility of electrolyte ions and enable fast transportation of electrons. A further improvement in electrochemical performance was achieved (62 μA h/cm<SUP>2</SUP> at 2 mA/cm<SUP>2</SUP>) by decorating Ag NPs on the surface of the CM MFs (i.e., Ag NPs@CM MFs), which is attributed to the increased electric conductivity. Considering the synergistic effect and the high electrochemical activity, Ag NPs@CM MFs were further employed as an effective positive electrode for the fabrication of pouch-type HSC with porous carbon (negative electrode) in an alkaline electrolyte. The HSC exhibited a high cell potential (1.5 V) with maximum energy and power densities of 0.0183 mW h/cm<SUP>2</SUP> and 10.237 mW/cm<SUP>2</SUP>, respectively. The potency of HSC in practical applications was also demonstrated by energizing red and yellow light-emitting diodes as well as a three-point pattern torch light.</P> [FIG OMISSION]</BR>
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Chandra Sekhar, S.,Nagaraju, Goli,Yu, Jae Su Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.435 No.-
<P><B>Abstract</B></P> <P>Porous and ant-cave structured MnCO<SUB>3</SUB>/Mn<SUB>3</SUB>O<SUB>4</SUB> microcubes (MCs) were facilely synthesized via a biopolymer-assisted hydrothermal approach. Herein, chitosan was used as a natural biopolymer, which greatly controls the surface morphology and size of the prepared composite. The amino and hydroxyl group-functionalized chitosan engraves the outer surface of MCs during the hydrothermal process, which designs the interesting morphology of nanopath ways on the surface of MCs. When used as an electrode material for pseudocapacitors, the ant-cave structured MnCO<SUB>3</SUB>/Mn<SUB>3</SUB>O<SUB>4</SUB> MCs showed superior energy storage values compared to the material prepared without chitosan in aqueous electrolyte solution. Precisely, the prepared ant-cave structured MnCO<SUB>3</SUB>/Mn<SUB>3</SUB>O<SUB>4</SUB> MCs exhibited a maximum specific capacitance of 116.2F/g at a current density of 0.7A/g with an excellent cycling stability of 73.86% after 2000 cycles. Such facile and low-cost synthesis of pseudocapacitive materials with porous nanopaths is favorable for the fabrication of high-performance energy storage devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Porous MnCO<SUB>3</SUB>/Mn<SUB>3</SUB>O<SUB>4</SUB> microcubes are prepared using one-step hydrothermal method. </LI> <LI> As a naturally derived biopolymer, chitosan plays an important role in the formation of ant-cave structures. </LI> <LI> The pseudocapacitive material prepared with chitosan delivers higher electrochemical properties. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Chandra Sekhar, S.,Nagaraju, Goli,Yu, Jae Su Elsevier 2018 Nano energy Vol.48 No.-
<P><B>Abstract</B></P> <P>The core-shell-like architectures consisting of NiO nanosheet arrays grafted Co<SUB>3</SUB>O<SUB>4</SUB>-NiO fish thorns-like nanostructures (NiO NSAs@Co<SUB>3</SUB>O<SUB>4</SUB>-NiO FTNs) were successfully prepared by a simple solution-based method. With an aid of ammonium fluoride (NH<SUB>4</SUB>F), the morphological evolution of Co<SUB>3</SUB>O<SUB>4</SUB>-NiO FTNs was elaborated effectively. Subsequently, the NiO NSAs were uniformly decorated on the Co<SUB>3</SUB>O<SUB>4</SUB>-NiO FTNs to form a core-shell-like composite material for positive electrode in hybrid supercapacitors (HSCs). The core-shell-like composite exhibited a large surface area with high open porous channels, which intends to deliver high areal capacity of 313.9 μA h/cm<SUP>2</SUP> (at 4 mA/cm<SUP>2</SUP>) in 1 M KOH, and it is 1.84 and 3.9 times higher than the Co<SUB>3</SUB>O<SUB>4</SUB>-NiO FTNs and solitary NiO NSAs electrodes. Furthermore, we fabricated a pouch-type HSC with core-shell-like NiO NSAs@Co<SUB>3</SUB>O<SUB>4</SUB>-NiO FTNs as a positive electrode and activated carbon as a negative electrode in aqueous alkaline electrolyte. At a current density of 2 mA/cm<SUP>2</SUP>, the fabricated HSC provides high areal capacitance of 623.5 mF/cm<SUP>2</SUP> with a maximum energy density of 216.1 μW h/cm<SUP>2</SUP> and power density of 27.7 mW/cm<SUP>2</SUP>. In addition, the HSC showed superior cycling stability with a capacity retention of 126% after 5000 cycles, indicating the great promise of practical applications. Thanks to the comprehensive electrochemical performance, the pouch-type HSCs effectively operated a toy motor fan and light-emitting diode bulb for real-life applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Co<SUB>3</SUB>O<SUB>4</SUB>-NiO fish thorns-like nanostructures (Co<SUB>3</SUB>O<SUB>4</SUB>-NiO FTNs) are synthesized by a hydrothermal method. </LI> <LI> NH<SUB>4</SUB>F plays a significant role in tuning the surface morphology of Co<SUB>3</SUB>O<SUB>4</SUB>-NiO FTNs. </LI> <LI> Core-shell-like NiO nanosheet arrays are grown on Co<SUB>3</SUB>O<SUB>4</SUB>-NiO FTNs (NiO NSAs@Co<SUB>3</SUB>O<SUB>4</SUB>-NiO FTNs). </LI> <LI> The areal capacity of the core-shell-like electrode is improved compared to the solitary NiO NSAs and Co<SUB>3</SUB>O<SUB>4</SUB>-NiO FTNs electrodes. </LI> <LI> Pouch-type hybrid supercapacitor exhibits high electrochemical performance with excellent cycling stability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Sekhar, S. Chandra,Nagaraju, Goli,Yu, Jae Su Elsevier 2017 Nano energy Vol.36 No.-
<P><B>Abstract</B></P> <P>Silver nanowires (Ag NWs) have attracted particular interest in the development of various electronic and energy storage devices due to their one-dimensional structure, good conductivity, fast charge transportation and direct contact to the current collector. Herein, we have successfully deposited the binder-free nickel-cobalt layered double hydroxide nanosheets on Ag NWs-fenced carbon cloth (NC LDH NSs@Ag@CC) by a facile electrochemical deposition method with a chronoamperometry voltage of −1.0V for 120s. The electrically conductive and superhydrophilic nature of the hybrid nanocomposite electrode led to relatively high areal capacitance (1133.3 mF cm<SUP>−2</SUP> at 1mAcm<SUP>−2</SUP>) and good cycling stability (80.47% after 2000 cycles) compared to the electrode prepared without Ag NWs. Using such hierarchical NC LDH NSs@Ag@CC as a positive electrode, we further fabricated a flexible asymmetric supercapacitor (ASC) with activated carbon coated CC as a negative electrode. The as-assembled ASC exhibited maximum operational potential window of 1.6V, high areal capacitance of 230.2 mF cm<SUP>−2</SUP> and excellent cycling stability of 88.1% with remarkable energy densities at all the charge-discharge conditions (78.8 μWh cm<SUP>−2</SUP> at the power density of 785 μW cm<SUP>−2</SUP> and 40 μWh cm<SUP>−2</SUP> at the high power density of 12.1mWcm<SUP>−2</SUP>, respectively)</P> <P><B>Highlights</B></P> <P> <UL> <LI> Conductive Ag NWs are uniformly decorated on carbon cloth fibers (Ag@CC). </LI> <LI> The highly conductive features and hydrophilicity of Ag@CC induce the dense growth of NC LDH NSs. </LI> <LI> Ag NWs provide the effective pathways for electron transportation during the redox process of NC LDH NSs. </LI> <LI> The areal capacitance of the electrode with Ag NWs is 2.3 times higher than the electrode without Ag NWs. </LI> <LI> The assembled asymmetric supercapacitor delivers high energy and power densities. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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