The electrode materials which show high stability and energy density are essential to design efficient and stable energy storage devices. Herein, we use a novel and binder free method to synthesize ...NiCo2S4@NiCo2O4 core@shell nanoneedle like structures over the graphene sheet (rG/NCS/NCO). The core@shell nanostructured arrays provide high active surface area, which facilitates to electrolyte diffusion and provides enough space for sulfur integration during charge-discharge reaction. As a result, the rG/NCS/NCO electrode shows specific capacitance (SC) of 1590 F/g at a current density of 5 A/g and high stability (2000 charge-discharge cycle) with impressive rate capability. Further, an asymmetric supercapacitor (ASC) device is fabricated with rG/NCS/NCO as a positive electrode and reduced graphene oxide (rGO) synthesized using lemon juice as a negative electrode. The as-fabricated rG/NCS/NCO//rGO ASC device delivers SC of 104 F/g at current density 3 A/g with energy density 32 Wh/kg and power density 375 W/kg with long durability for 1000 charge-discharge cycles. This study signifies a giant step towards the fabrication of high-performance commercial supercapacitors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Asymmetric supercapacitor (ASC) device is fabricated using NiCo2O4@MnMoO4 core@shell nanoarrays. The fabricated device demonstrated a SC of 294 F/g at a current density of 4 A/g, with energy density ...of 91.87 Wh/kg at power density of 374.15 W/kg. Using the fabricated ASC device, nine green color LEDs were glow for 35 mins.
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NiCo2O4@MnMoO4 core@shell nanostructures are synthesized as electrode material using hydrothermal method for the fabrication of asymmetric supercapacitor (ASC) device. The NiCo2O4@MnMoO4 electrode shows better electrochemical performance with specific capacitance (SC) of 1821 F/g at current density of 5 A/g and cycling stability of 94%. The NiCo2O4@MnMoO4 core@shell electrode shows better SC compared to pure NiCo2O4 and MnMoO4 electrodes. An ASC device is fabricated using NiCo2O4@MnMoO4 as a positive and rGO/Fe2O3 as negative electrode materials. Remarkably, the fabricated device shows a SC of 294 F/g at current density 4 A/g, with an energy density of 91.87 Wh/kg at a power density of 374.15 W/kg. The device shows good reversibility with cycling stability of 68% after 2,000 cycles. The ASC device is used to illuminate nine green color LEDs for 35 min. Therefore, the present report provides a simple method to fabricate efficient and stable energy storage devices for industrial applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Porous NiCo2O4 NWs and NFs type structures are grown over the rGO sheets using hydrothermal method.•The rGO sheets are mainly responsible for the growth of NiCo2O4 NWs and NFs.•rGO@NiCo2O4 NFs based ...electrode show improved supercapacitor performance.•rGO@NiCo2O4 NFs based electrode also show improved cycling stability.•rGO@NiCo2O4 NFs may be used as supercapacitor electrode material for device fabrication.
Porous nanowires (NWs) and nanoflowers (NFs) type structures of nickel cobaltite (NiCo2O4) were synthesized on rGO sheet (rGO@NiCo2O4) as supercapacitor electrode material. The synthesized materials are characterized using different experimental techniques. The growth of NiCo2O4 over rGO sheet is confirmed by the appearance of D and G bands in the Raman spectrum. The rGO@NiCo2O4 NFs electrode revealed relatively high value of specific capacity (436 C/g at current density of 1 A/g) with good capacity retention compared to other electrodes. The improved electrochemical activity of the rGO@NiCo2O4 NFs electrode may be due to the porous nanostructure of NiCo2O4 on rGO sheet. The rGO sheets provide easy access to ions, large surface area and large active sites with stable structural integrity. The Nyquist plot of the rGO@NiCo2O4 NFs electrode shows relatively low values of Rs and Rct compared to other electrodes, which essentially refer to its improved electrical conductivity. Thus, the rGO@NiCo2O4 NFs may be used as a supercapacitor electrode material for device fabrication.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this article, charcoal is used as a new raw material for the synthesis of high yield graphene quantum dots (GQDs). The synthesized GQDs were characterized using various characterization ...techniques. The supercapacitive properties of the GQDs were investigated using electrochemical measurements. The electrode made using GQDs shows a specific capacitance (SC) of 257 F g
−1
at a current density of 3 A g
−1
with a better cyclic stability and a capacitance retention of 96% after 3000 cycles. A flexible symmetric supercapacitor (SSC) device, using GQDs as the active material, was built using a simple fabrication method. The fabricated device delivers an energy density of 17.36 W h kg
−1
and a power density of 191.7 W kg
−1
with excellent durability and 91% capacitance retention after 1000 cycles. This study does not only explain the experimental observations but also provides insightful direction to develop a method for the synthesis and engineering of GQDs, which could be useful for making flexible energy-oriented devices.
In this article, charcoal is used as a new raw material for the synthesis of high yield graphene quantum dots (GQDs) for supercapacitor application.
We have developed rGO-WO3 composite which can be used to remove both types of pollutants (organic and bacterial) present in water.
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•Well control 2D rectangular sheet of WO3 was grown ...over the rGO sheet using hydrothermal method.•2D sheet of WO3 and rGO-WO3 composite are utilized for the photocatalytic degradation of MB and RhB dyes under sunlight.•The rGO-WO3 shows excellent photocatalytic degradation (85%) of RhB dye under sunlight.•The greater degradation of RhB dye was explained in terms of MESP calculated using DFT calculations.•The 2D sheet of WO3 and rGO-WO3 composite show better antibacterial activity for gram positive microbes.
Finding the materials, which help to control the water pollution caused by organic and bacterial pollutants is one of the challenging tasks for the scientific community. 2D sheets of WO3 and composite of WO3 and reduced graphene oxide (rGO) have been synthesized in a well-controlled way using a hydrothermal method. The as synthesized 2D sheet of WO3 and rGO-WO3 composite were characterized by various techniques. The 2D sheets of WO3 and rGO-WO3 composite are efficiently utilized for the photocatalytic degradation of methylene blue (MB) and Rhodamine B (RhB) dyes under sunlight. The rGO-WO3 composite reveals excellent photocatalytic degradation of RhB dye by degrading it upto 85% under sunlight. However, the MB dye was degraded by 32%. The greater degradation of RhB dye was explained in terms of the molecular electrostatic potential. We found that RhB has a more positive potential compared to MB dye where O2− and OH̊ radicals interact more strongly, resulting in a greater degradation of the RhB dye. The antibacterial activity of the 2D sheets of WO3 and rGO-WO3composite was also investigated on gram positive (B. subtilis) and gram negative (P. aeroginosa) microbes for the first time.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Micro-sized graphene sheets are synthesized using coal as a starting material. A maximum value of specific capacitance of 277 F/g at scan rate of 5 mV/s is found in 1M Na2SO4. It shows long cycle ...stability and the low value of RCT indicates fast ion/electron transport and rapid adsorption-desorption rates of ions in the electrode.
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•Micro-sized graphene sheets were synthesized using coal as a starting material.•It shows excitation independent photoluminescence emission.•A maximum value of specific capacitance of 277 F/g at scan rate of 5 mV/s was found in 1 M Na2SO4.•It shows long cycle stability.•The low value of RCT indicates fast ion/electron transport and rapid adsorption-desorption rates of ions in the electrode.
We report simple and cost effective production of water soluble graphene sheets using coal. The synthesized coal derived graphene (CDG) sheets were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), Raman, Fourier transform infrared (FTIR), ultra-violet visible (UV–vis) spectroscopy, and photoluminescence (PL) measurements. The presence of edge oxygen functionalities in CDG sheets causes to induce fluorescent properties. The nature emission peak does not change with varying the excitation wavelength. To determine its energy storage properties, cyclic voltammetry (CV), charge-discharge and electrochemical impedance spectroscopy (EIS) measurements were done in different electrolytes. The value of specific capacitance (SC) of CDG in 1 M Na2SO4 electrolyte turns out to be 277 F/g at scan rate of 5 mV/s. CDG show long cycle stability i.e., the value of SC remains at ~91% after 2000 cycles at the current density of 10 mA/g.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The optical and electronic properties of semiconducting materials are modified by the doping of suitable elements. Pure and Zn doped (1%, 3%, 5% and 7%) CdS nanostructures are synthesized by facile, ...one-pot solvothermal method. The synthesized materials are characterized using different characterization techniques. The XRD results revealed that the synthesized nanostructures have both, cubic and hexagonal crystalline phases. The optical band gap is increased with the increase of Zn content in the CdS matrix. The change in absorption and emission features with doping has made the doped materials suitable for photocatalytic applications under sun light and ultra-violet (UV) irradiation. The pure and Zn doped CdS nanostructures are used for photodegradation of rhodamine B (RhB) dye under UV and sun light irradiation. The Zn (3%) doped CdS nanostructures show better photocatalytic degradation (93%) of RhB under sun light irradiation. It could be due to the combined effects of the shifting in energy levels and change in shape and size of the nanostructures with doping.
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•Pure and Zn doped (1%, 3%, 5% and 7%) CdS nanostructures are synthesized by solvothermal method.•Zn2+ doing enhance the structural, optical and photocatalytic performance CdS nanostructures.•Synthesized nanostructures are used to degrade RhB dye under the sun and UV–vis light.•Zn 3% doped nanostructures show better photocatalytic degradation (93%) of RhB dye.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Rod shaped structures of molybdenum trioxide (MoO3) were synthesized at low temperature using simple and low cost method. The synthesized materials were characterized by different characterization ...techniques. The effect of annealing temperature on crystal structure and optical properties of MoO3 was investigated. The hexagonal phase (h-MoO3) was observed up to 300 °C and beyond this temperature, the phase of the MoO3 is changed to orthorhombic (α-MoO3). The transition of crystal phase (h-MoO3 to α-MoO3) was investigated by analyzing the X-ray diffraction (XRD), Raman and DSC measurements. The shift in the wavenumber position of 971 cm−1 (Mo–O stretching) peak with temperature also substantiates the phase transition in MoO3 structure. The shape of nanostructured MoO3 was modified with annealing temperature. The change in crystal phases and shapes with temperature may result defects in the structure, which essentially modify the structural and optical properties of the material. The photocatalytic properties of the synthesized materials were studied on methylene blue (MB) dye under UV-irradiation. The sample annealed at 400 °C (M4) show excellent photodegradation compared to other samples. It could be due to the combined effects of shape (helical) and defects (oxygen vacancies) present in M4, as supported by the electron paramagnetic resonance (EPR) measurements. Among the various radicals, OH plays an important role in photodegardation of the MB dye.
•Hexagonal and orthorhombic crystal phases of MoO3 were synthesized.•Raman peak at ∼971 cm−1 is designated as a signature peak to characterize temperature induced phase transition in MoO3.•The α-MoO3 shows excellent photocatalytic activity compared to h-MoO3.•The .•OH is the main reactive species involved in the photodegradation of MB dye.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZRSKP
The study of processing biomass waste into porous carbon materials as active electrode materials for energy storage applications has been the subject of immense research interest due to its low cost, ...abundance of raw materials and environmental friendliness. In this work, orange peel-derived porous carbon material has been produced via carbonization followed by chemical activation with KOH (KOPC). The synthesized materials were characterized using different characterization techniques. Microstructural features confirm that the porous structure has pores in the KOPC material. The Fourier transform infrared and Raman analysis revealed that various functional groups, defects and pores exist in the KOPC sample, which could minimize the diffusion length and facilitate the ion diffusion path for improved electrochemical performances. The electrochemical measurements of KOPC were performed as electrode material with an extended and optimized potential window of 0.0 to −1.2 V. The KOPC-based electrode shows a specific capacitance of 267 F/g at 3 A/g with excellent coulombic efficiency and good cycling stability over 5000 charge–discharge cycles at 50 A/g. Thus, this study will utilize biomass wastes to make efficient energy storage devices.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A suitable substitution of the organic cation in hybrid organic–inorganic perovskite is an effective approach to tune carrier concentration, electronic structure, band gap, and optical absorption. ...Immense research efforts have been made to find perovskite with enhanced stability, red shift with high absorption yield, and better charge-transport properties. Presently, a new perovskite CH3NH2FPbI3 has shown relatively improved properties in terms of structural stability, band gap, red-shifted absorption with high yield, and optical properties compared to CH3NH3PbI3 (MAPbI3). It infers that the CH3NH2FPbI3 may be a better option for perovskite solor cell. The reaction enthalpy of CH3NH2FPbI3 turns out to be −1.6 eV. It indicates that the designed perovskite is more stable compared to MAPbI3. The calculated partial density of states and electron localization functions revealed electronic coupling between organic and inorganic networks of CH3NH2FPbI3. The enhanced hydrogen-bond interaction between the cation and inorganic network modifies the covalent/ionic character of Pb–I bonds. The increased octahedral tilting in CH3NH2FPbI3 compared to MAPbI3 improves its optical properties significantly. The calculated results demonstrate that the strength of the hydrogen bond can be used as an additional control parameter to optimize the photovoltaic properties and structural stability of perovskites.
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IJS, KILJ, NUK, PNG, UL, UM
