Cerium oxide mixed LaMnO₃ nanoparticles as the negative electrode for aqueous asymmetric supercapacitor devices

Nagamuthu, Sadayappan,Vijayakumar, Subbukalai,Ryu, Kwang-Sun Elsevier Sequoia S.A 2017 Materials chemistry and physics Vol.199 No.-

<P><B>Abstract</B></P> <P>CeO<SUB>2</SUB> mixed LaMnO<SUB>3</SUB> nanocomposites were synthesized using a hydrothermal route. Sodium dodecyl sulfate was used as the surfactant. Cerium oxide was mixed in the LaMnO<SUB>3</SUB> perovskite nanoparticles and the crystal structure was confirmed by X-ray diffraction and X-ray photoelectron spectroscopy. Field emission scanning electron microscopy and high-resolution transmission electron were used to identify the morphology of the prepared nanoparticles. The CeO<SUB>2</SUB> mixedLaMnO<SUB>3</SUB> nanocomposites exhibited a mesopore size and high surface area in the N<SUB>2</SUB> adsorption/desorption measurements. Three electrode measurements indicate the CeO<SUB>2</SUB> mixed LaMnO<SUB>3</SUB> nanocomposites to be a suitable negative electrode material for supercapacitor device fabrication and exhibited a high specific capacitance of 262 F g<SUP>−1</SUP> at a specific current of 1 A g<SUP>−1</SUP>. The asymmetric supercapacitor device showed a maximum energy density of 17.2 W h kg<SUP>−1</SUP> at a power density of 1015 w kg<SUP>−1</SUP>. These electrochemical studies show that CeO<SUB>2</SUB> mixed LaMnO<SUB>3</SUB> nanocomposites are an appropriate negative electrode material for supercapacitor device fabrication.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CeO<SUB>2</SUB> mixed LaMnO<SUB>3</SUB> perovskite was used as the negative electrode for supercapacitor. </LI> <LI> XRD and XPS measurements confirm the CeO<SUB>2</SUB> mixed in the LaMnO<SUB>3</SUB> perovskites. </LI> <LI> CeO<SUB>2</SUB> mixed LaMnO<SUB>3</SUB> nanocomposites exhibit a specific capacitance of 262 F g<SUP>−1</SUP>. </LI> <LI> The asymmetric supercapacitor device yields the energy density of 17.2 W h kg<SUP>−1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Hybrid supercapacitor devices based on MnCo₂O₄ as the positive electrode and FeMn₂O₄ as the negative electrode

Nagamuthu, S.,Vijayakumar, S.,Lee, S.H.,Ryu, K.S. New York] ; North-Holland 2016 APPLIED SURFACE SCIENCE - Vol.390 No.-

MnCo<SUB>2</SUB>O<SUB>4</SUB> nanosheets and FeMn<SUB>2</SUB>O<SUB>4</SUB> nanospheres were synthesized using a hydrothermal method. Choline chloride was used as the capping agent during the preparation of the nanoparticles. XRD patterns confirmed the spinel structure of MnCo<SUB>2</SUB>O<SUB>4</SUB> and FeMn<SUB>2</SUB>O<SUB>4</SUB>. XPS measurements were used to determine the oxidation state of the prepared spinel metal oxides. HRTEM images revealed the formation of hexagonal nanosheets of MnCo<SUB>2</SUB>O<SUB>4</SUB> and nanospheres of FeMn<SUB>2</SUB>O<SUB>4</SUB>. Electrochemical measurements were made for both positive and negative electrodes using three electrode systems. MnCo<SUB>2</SUB>O<SUB>4</SUB> Exhibits 282Cg<SUP>-1</SUP> and FeMn<SUB>2</SUB>O<SUB>4</SUB> yields 110Cg<SUP>-1</SUP> at a specific current of 1Ag<SUP>-1</SUP>. Hybrid supercapacitor device was fabricated using MnCo<SUB>2</SUB>O<SUB>4</SUB> as the positive and FeMn<SUB>2</SUB>O<SUB>4</SUB> as the negative electrode material. The hybrid supercapacitor device was delivered a maximum power of 37.57kWkg<SUP>-1</SUP>.

Porous thin layered nanosheets assembled ZnCo₂O₄ grown on Ni-foam as an efficient electrode material for hybrid supercapacitor applications

Vijayakumar, Subbukalai,Nagamuthu, Sadayappan,Lee, Seong-Hun,Ryu, Kwang-Sun Pergamon Press 2017 International journal of hydrogen energy Vol.42 No.5

<P><B>Abstract</B></P> <P>Thin layered nanosheets of ZnCo<SUB>2</SUB>O<SUB>4</SUB> with desirable porous nanoarchitecture grown on Ni-foam were prepared using a simple surfactant free hydrothermal method. The Ni-foam supported ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanostructure was characterized using X-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). FESEM clearly revealed thin nanosheets which were randomly connected together to form a porous structure. The binder-free Ni-foam supported ZnCo<SUB>2</SUB>O<SUB>4</SUB> electrode was applied directly to hybrid supercapacitor analysis. In three electrode measurement, thin layered nanosheets of ZnCo<SUB>2</SUB>O<SUB>4</SUB> exhibited a maximum specific capacity of 886 C g<SUP>−1</SUP> at a current density of 2 mA cm<SUP>−2</SUP>. When the current density was increased from 2 to 50 mA cm<SUP>−2</SUP>, the specific capacity value was 362.5 C g<SUP>−1</SUP>. After 2000 continuous charge–discharge cycles, about 94% of the maximum specific capacity was retained. This high specific capacity, better rate capacity, and excellent cyclic stability of thin layered nanosheets of ZnCo<SUB>2</SUB>O<SUB>4</SUB> suggest that the prepared electrode is a promising candidate for hybrid supercapacitor applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This paper reports the hydrothermal preparation of ZnCo<SUB>2</SUB>O<SUB>4</SUB> on Ni-foam. </LI> <LI> The ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanosheet exhibits maximum specific capacity of 886 C g<SUP>−1</SUP>. </LI> <LI> After 2000 cycles, 103% of the initial specific capacity was retained. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Binder-free, Ni-foam supported thin layered nanosheets of ZnCo<SUB>2</SUB>O<SUB>4</SUB> were successfully fabricated via a surfactant-free hydrothermal method. This desirable thin layered nanosheets of ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoarchitecture grown on Ni-foam exhibited the high specific capacity of 886 C g<SUP>−1</SUP> at 2 mA cm<SUP>−2</SUP> with excellent cyclic stability (103%) for 2000 charge–discharge cycles.</P> <P>[DISPLAY OMISSION]</P>

<i>In situ</i> preparation of MgCo₂O₄ nanosheets on Ni-foam as a binder-free electrode for high performance hybrid supercapacitors

Vijayakumar, Subbukalai,Nagamuthu, Sadayappan,Ryu, Kwang-Sun Royal Society of Chemistry 2018 Dalton Transactions Vol. No.

<P>A binder-free, MgCo2O4 nanosheet-like architecture was prepared on Ni-foam using a hydrothermal method. MgCo2O4/Ni-foam was characterized by X-ray diffraction, field emission scanning electron microscopy (FESEM), and transmission electron microscopy techniques. The FESEM image revealed a nanosheet array-like architecture. The MgCo2O4 nanosheets grown on Ni-foam exhibited the maximum specific capacity of 947 C g<SUP>−1</SUP> at a specific current of 2 A g<SUP>−1</SUP>. Approximately 96% of the specific capacity was retained from the maximum specific capacity after 5000 continuous charge-discharge cycles. This hybrid device exhibited a maximum specific capacity of 52 C g<SUP>−1</SUP> at a specific current of 0.5 A g<SUP>−1</SUP>, and also exhibited a maximum specific energy of 12.99 W h kg<SUP>−1</SUP> at a specific power of 448.7 W kg<SUP>−1</SUP>. These results confirmed that the binder-free MgCo2O4 nanosheets grown on Ni-foam are a suitable positive electrode material for hybrid supercapacitors.</P>

CuCo₂O₄ flowers/Ni-foam architecture as a battery type positive electrode for high performance hybrid supercapacitor applications

Vijayakumar, Subbukalai,Nagamuthu, Sadayappan,Ryu, Kwang-Sun Elsevier 2017 ELECTROCHIMICA ACTA Vol.238 No.-

<P><B>Abstract</B></P> <P>The battery type CuCo<SUB>2</SUB>O<SUB>4</SUB> electrode was evaluated as a positive electrode material for its hybrid supercapacitor applications. CuCo<SUB>2</SUB>O<SUB>4</SUB> flowers were prepared on Ni-foam through a simple hydrothermal process and post calcination treatment. The structure and morphology of the CuCo<SUB>2</SUB>O<SUB>4</SUB> flowers/Ni-foam was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy. FESEM clearly revealed the flower-like morphology, which was composed of large number of petals. The length and width of the petals ranged from approximately 5–8μm and approximately 50–150nm, respectively. The CuCo<SUB>2</SUB>O<SUB>4</SUB> flowers/Ni-foam electrode was employed for electrochemical characterization for hybrid supercapacitor applications. The specific capacity of the CuCo<SUB>2</SUB>O<SUB>4</SUB> flower-like electrode was 692.4Cg<SUP>−1</SUP> (192.3mAhg<SUP>−1</SUP>) at a scan rate of 5mVs<SUP>−1</SUP>. The flower-like CuCo<SUB>2</SUB>O<SUB>4</SUB> electrode exhibited a maximum specific capacity of 645.1Cg<SUP>−1</SUP> (179.2mAhg<SUP>−1</SUP>) at a specific current of 1Ag<SUP>−1</SUP> and good long term cyclic stability. The high specific capacity, good cyclic stability, and low internal and charge transfer resistance of the CuCo<SUB>2</SUB>O<SUB>4</SUB> flowers/Ni-foam electrode confirmed the suitability of the prepared material as a positive electrode for hybrid supercapacitor applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This paper reports the hydrothermal preparation of CuCo<SUB>2</SUB>O<SUB>4</SUB> flowers on Ni-foam. </LI> <LI> The CuCo<SUB>2</SUB>O<SUB>4</SUB> flowers exhibits maximum specific capacity of 645.1Cg<SUP>−1</SUP>. </LI> <LI> After 2000 cycles, 109% of the initial specific capacity was retained. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The Ni- foam supported CuCo<SUB>2</SUB>O<SUB>4</SUB> flowers exhibits a high specific capacity with superior long term cyclic stability.</P> <P>[DISPLAY OMISSION]</P>

Cu-Zn-Co oxide nanoflakes on Ni-foam as a binder free electrode for energy storage applications

Vijayakumar, Subbukalai,Lee, Seong-Hun,Nagamuthu, Sadayappan,Ryu, Kwang-Sun Elsevier 2018 Materials letters Vol.219 No.-

<P><B>Abstract</B></P> <P>Cu-Zn-Co oxide nanoflakes were grown on Ni-foam using a hydrothermal method. FESEM revealed a thin nanoflake-like morphology. The Cu-Zn-Co oxide nanoflakes exhibited a maximum specific capacity of 215 C g<SUP>−1</SUP> at a scan rate of 5 mV s<SUP>−1</SUP> and 178 C g<SUP>−1</SUP> at a specific current of 1 A g<SUP>−1</SUP>. When used as a Li-ion battery electrode, the Cu-Zn-Co oxide nanoflakes exhibited a specific discharge capacity of 1117 mA h g<SUP>−1</SUP> in the second cycle with excellent cycling stability. This superior cycling stability of the Cu-Zn-Co oxide nanoflakes was attributed to the direct attachment of Cu-Zn-Co oxide nanoflakes on Ni-foam.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The Cu-Zn-Co oxide grown on Ni-foam shows thin nanoflake like morphology. </LI> <LI> Cu-Zn-Co oxide nanoflakes exhibits a maximum specific capacity of 215 C g<SUP>−1</SUP>. </LI> <LI> Cu-Zn-Co oxide nanoflakes exhibits a specific discharge capacity of 1603 mA h g<SUP>−1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>