Sphere-like CoS nanostructures are synthesized in water/ethylene glycol mixed solvents by simple hydrothermal technique using l-cysteine amino acid as a source of sulfur. The results obtained by BET and BJH methods reveal that the CoS has mesoporous bimodal pore distribution in the range of 2-23 nm with a dominant peak around 12.4 nm and a small peak at 2.4 nm. The electrochemical experiments demonstrate that CoS has a high-rate capability for capacitor applications. The reduction of the specific capacitance is very marginal by about 13% of the available capacitance of 363 F g-1 when the scan rate is increased by 10 times. Even at very high frequency of 10 Hz, it retains the specific capacitance value of 150 F g-1, which confirms its higher power capability. Furthermore, during the cycling process, the Coulombic efficiency is better than 90% demonstrating excellent reversibility of CoS electrode. © 2010 Published by Elsevier Ltd on behalf of Professor T. Nejat Veziroglu.

Gangavarapu Ranga Rao

Department Of Chemistry

ELECTROCHEMICAL CAPACITOR

hydrothermal method

L-CYSTEINE

METAL SULFIDE

Amino acids

Capacitance

Capacitors

Electrochemical electrodes

Glycols

Organic acids

Spheres

Sulfur

Transition metal compounds

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

International Journal of Hydrogen Energy

ZnIn2S4 is an important mixed metal sulfide semiconductor with multifunctional properties, endowed upon by its hierarchical structure, large surface area and porosity. In this work, hierarchical ZnIn2S4.1 (ZnInS) microflowers made up of petal like nanostructures are synthesized using a simple and facile hydrothermal method. Nitrogen adsorption-desorption analysis of these microflowers showed porous structures with pores ~3 nm. This material shows a photocurrent density of 3.1 μA cm−2 and activity towards methylene blue (MB) dye degradation under direct sunlight. The sample also shows pseudocapacitive behavior with specific capacitance value of 131 F g−1 at a scan rate of 10 mV s−1. The pseudocapacitive behavior of polycrystalline ZnInS has been explored for the first time to the best of our knowledge. This study demonstrates that the single phase ZnInS is a multifunctional material for photocatalysis and electrochemical charge storage applications. © 2019 International Solar Energy Society

Solar Energy

Multifunctional hierarchical ZnIn2S4±δ microflowers with photocatalytic and pseudocapacitive behavior

Renewable energy sources are cornerstone for a sustainable future. It is however necessary to develop effective energy storage methods to tap the unpredictable energy sources. High surface area materials with a narrow pore size distribution, variable oxidation states and good electronic conductivity are considered to be the best materials for charge storage applications. Transition metal sulfides are currently investigated as electrode materials for energy storage devices. In this work, we have synthesized Cu2MSnS4 (M: Fe, Co, Ni) by one pot solid state sequential crystallization method using thiourea complexes of Cu, Ni, Co and Sn. The final sulfide products are characterized by PXRD, SEM-EDX, Raman, UV–vis–NIR, and HRTEM techniques. The electrochemical charge storage activity of these materials has been investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and impedance spectroscopy (EIS). The quaternary sulfides show promising charge storage behavior. Electrochemical analyses reveal that incorporation of Ni instead of Fe and Co in Cu2MSnS4 lattice can simultaneously improve the charge transfer and ion diffusion, thereby increasing the charge storage performance. Among Cu2FeSnS4, Cu2CoSnS4 and Cu2NiSnS4 samples, Cu2NiSnS4 and Cu2CoSnS4 show specific capacitance value of 1496 and 950 F g−1, respectively at a current density of 1 A g−1, and achieved specific capacities of 161 and 107 mA h g−1, respectively at the same current density. Both Cu2NiSnS4 and Cu2CoSnS4 also exhibit excellent cyclic stability, retaining respectively 77% and 72% capacitance after 4000 cycles. A symmetric supercapacitor based on Cu2NiSnS4 was assembled and it delivered specific capacity of 58.3 mA h g−1 at 1 A g−1 and a high energy density of 7.5 W h kg−1 at power density of 513.6 W kg−1. The redox properties of different metal ions present in the quaternary sulfide nanoparticles are mainly responsible for faradaic charge storage in these quaternary sulfide materials. © 2019 Elsevier Inc.

Journal of Solid State Chemistry

Energy storage study of trimetallic Cu2MSnS4 (M: Fe, Co, Ni) nanomaterials prepared by sequential crystallization method

A facile hydrothermal method has been adopted to synthesize the spherical urchin-like hierarchical CoMn2O4 nanostructures on the nickel foam substrate. The as-synthesized urchins have an average diameter of ∼3–7 μm with numerous self-assembled nanoneedles grown radically in all the directions from its center with a huge void space between them. For comparison, we have also studied the electrochemical as well as other physicochemical properties of parent simple Co3O4 and MnO2 materials, which were also synthesized by a similar hydrothermal method. The results show that CoMn2O4 electrode displayed significantly higher (more than two times) areal and specific capacitances compared to Co3O4 and MnO2 electrodes with excellent capacitance retention and Coulombic efficiency. Moreover, the energy and power densities obtained for CoMn2O4 electrode are also far higher than the parent Co3O4 and MnO2. Long-term cycling tests of CoMn2O4 electrode shows the improved capacitance with high rate capability up to 6000 cycles indicating their potential for high performance supercapacitor applications. The better electrochemical performance of CoMn2O4 electrode can be attributed to the smart urchin-like nanostructures, which has several advantages like, more electroactive sites for faradic reactions emerging from the two metal ions, higher electronic/ionic conductivity and fast electrolyte transportation kinetics promoted by unique morphology. © 2017

Journal of Colloid and Interface Science

Facile hydrothermal synthesis of urchin-like cobalt manganese spinel for high-performance supercapacitor applications

Mixed metal oxides designed by using 3d elements in the Periodic Table are expected to play pivotal role in energy storage. In this work, cetyltrimethyl ammonium bromide (CTAB) assisted hydrothermal homogeneous precipitation method and subsequent calcination are employed to synthesize festuca scoparia-like Ni0.3Co2.7O4 material and compared it with pristine spinel Co3O4 having ultralayered morphology. The specific capacitance (Cs) value for Co3O4 at 1 A g-1 current density is 202 F g-1 which has increased to 396 F g-1 for Ni0.3Co2.7O4 electrode. Further, we have taken two important factors into consideration in fabrication, (i) facile in situ fabrication method, and (ii) desired composition of the active oxide phase on a porous current collector. We have employed same hydrothermal method to grow Ni0.3Co2.7O4 precursor material in situ on Ni foam without using CTAB, and converted it into oxide by heat treatment. The in situ grown Ni0.3Co2.7O4 on Ni foam electrode shows the highest specific capacitance value of 1423 F g-1, which is 3.6 times larger than the value obtained using Ni0.3Co2.7O4 coated on Ni foil at 1 A g-1 current density, and excellent cycling stability up to 4000 cycles. The capacitance loss is only ∼4% at 16 A g-1 and at 32 A g-1. This study confirms the influence of unique features such as current collector, composition, surface area, porosity, and microstructural properties of materials on their electrochemical performance. © 2015 Hydrogen Energy Publications, LLC.

In situ fabrication of porous festuca scoparia-like Ni0.3Co2.7O4 nanostructures on Ni-foam: An efficient electrode material for supercapacitor applications

By taking advantage of the splendid properties of graphene (electrical conductivity) and transition metal oxides (pseudocapacitance nature), we have in situ fabricated novel microstructured globe artichokes of a rGO/Ni0.3Co2.7O4 composite on a nickel foam through a simple surfactant free hydrothermal method followed by calcination process. The globe artichoke flower-like morphology is constructed by hundreds of self-assembled micropetals interconnected with several layers and circles at the base to form microspheres of uniform dimension. The as-obtained morphology of the microstructured globe artichokes enhanced the stability and electrochemical performance of the hybrid electrode due to of its unique structure. Therefore, the synergetic effects and interconnected structure of the thus made binder free rGO/Ni0.3Co2.7O4 hybrid electrode allows better charge transport and exhibits superb specific capacitance and areal capacitance of 1624 F g-1 and 2.37 F cm-2 at a current density of 2 A g-1. Moreover, the specific capacitance increases from 1088 F g-1 to 1728 F g-1 at the end of 7000 cycles, which indicates that the material becomes active with cycling. Furthermore, when the power density increased by 16 times i.e. from 0.5 to 8 kW kg-1 the energy density sinks to 40 from 56.39 W h kg-1 (i.e., 29% reduction only), suggesting a remarkable electrochemical performance for supercapacitor applications. © The Royal Society of Chemistry 2015.

RSC Advances

In situ fabrication of graphene decorated microstructured globe artichokes of partial molar nickel cobaltite anchored on a Ni foam as a high-performance supercapacitor electrode

In this work, NiO powders with a spherical morphology were synthesized by a simple hydrothermal technique using organic surfactants as templates and urea as the hydrolysis controlling agent. The effect of cationic (cetyl trimethyl ammonium bromide), anionic (sodium dodecyl sulfate), and nonionic (Triton X-100) surfactants for tuning the surface area, pore size, pore volume, and electrochemical properties of NiO powders was investigated. The NiO powders were characterized by X-ray diffraction, scanning electron microscopy, the Brunauer-Emmett-Teller method, cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy. We observed that the charge-storage mechanism in our NiO-based electrodes is significantly Faradic in nature rather than capacitive type. The ionic nature of the surfactant used in the preparation of NiO powders shows a considerable effect on their capacitance behavior. The specific capacitance values were found to increase in the order of NiO-T (144 F g-1) NiO-C (239 F g-1) &lt; NiO-S (411 F g-1) at a current density of 200 mA g-1 in 2 M KOH aqueous electrolyte solution. The NiO-S sample exhibits the highest surface redox reactivity and shows the specific capacitance of 235 F g-1 over 100 cycles at a current density of 500 mA g-1 in a life cycle test. © 2010 American Chemical Society.

Journal of Physical Chemistry C

Tuning of capacitance behavior of NiO using anionic, cationic, and nonionic surfactants by hydrothermal synthesis

RuO2/MWNT, TiO2/MWNT, and SnO2/MWNT nanocrystalline composites for supercapacitor electrodes have been synthesized by chemical reduction method using functionalized MWNT and respective salts. MWNT have been synthesized by thermal catalytic chemical vapor deposition (CCVD) over hydrogen decrepitated Mischmetal (Mm)-based AB3 alloy hydride catalysts. Structural and morphological characterizations of metal oxide dispersed MWNT have been carried out using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM and HRTEM), energy dispersive X-ray analysis (EDAX), and Raman spectroscopy. Electrochemical performance of these electrodes has been investigated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. Specific capacitance of RuO2, TiO 2, and SnO2 dispersed MWNT electrodes increases compared to that pure MWNT electrode due to the pseudo capacitance of the nanocrystalline metal oxides dispersed on the functionalized MWNT. The present study shows the potential of cost-effective TiO2/MWNT novel nanocrystalline composite material for electrochemical double layer capacitor. © 2007 American Chemical Society.

Nanocrystalline metal oxides dispersed multiwalled carbon nanotubes as supercapacitor electrodes

The influence of Triton X-100 in enhancing the capacitance of polyaniline-based nickel electrodes is reported. Cyclic voltammetric experiments, galvanostatic charge-discharge studies and impedance analysis were carried out in order to investigate the applicability of the system as an electrochemical supercapacitor. A qualitative interpretation of the enhancement is provided. Fourier transform infrared (FTIR), X-ray diffraction and scanning electron microscopy techniques were employed for characterization of the electrode. © 2005.

Journal	International Journal of Hydrogen Energy
ISSN	03603199
Open Access	No