Browsing by Author "Sethi, M."

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A porous graphene-NiFe2O4nanocomposite with high electrochemical performance and high cycling stability for energy storage applications
(Royal Society of Chemistry orders@rsc.org, 2020) Sethi, M.; Shenoy, U.S.; Bhat, D.K.
It is well agreed that supercapacitors form an important class of energy storage devices catering to a variety of needs. However, designing the same using eco-friendly and earth abundant materials with high performance is still the dire need of the day. Here, we report a facile solvothermal synthesis of a porous graphene-NiFe2O4 (PGNF) nanocomposite. Thorough elemental, diffraction, microscopic and spectroscopic studies confirmed the formation of the PGNF composite, in which the NF nanoparticles are covered over the PG surface. The obtained 10 PGNF composite showed a surface area of 107 m2 g-1, with large pore volume which is favorable for charge storage properties. When utilizing the material as an electrode for a supercapacitor in a 2 M KOH aqueous electrolyte, the electrode displayed an impressive specific capacitance value of 1465.0 F g-1 at a scan rate of 5 mV s-1 along with a high capacitance retention of 94% after 10?000 discharge cycles. The fabricated symmetrical supercapacitor device exhibited an energy density of 4.0 W h kg-1 and a power density of 3600.0 W kg-1 at a high applied current density of 14 A g-1. The superior electrochemical performance is attributed to the synergetic effect of the composite components which not only provided enough electroactive channels for the smooth passage of electrolyte ions but also maintained the hybrid structure intact in the ongoing electrochemical process. The obtained results underpin the promising utility of this material for future electrochemical energy storage devices. © The Royal Society of Chemistry.
Eco-friendly synthesis of porous graphene and its utilization as high performance supercapacitor electrode material
(Elsevier Ltd, 2019) Sethi, M.; Bantawal, H.; Shenoy, U.S.; Bhat, D.K.
The successful application of porous graphene (PG) is hindered due to the lack of efficient and cost-effective method for its synthesis. Herein, we report a facile and eco-friendly method to produce PG through a low temperature solvothermal method. The structural and morphological characteristics of PG samples were investigated thoroughly. The as synthesized material is found to be a few layers thick (?4–6 layers) with a surface area of 420 m2 g?1 and consisting of hierarchical pores on the surface of the sheets. A high specific capacitance of 666 F g?1 was obtained at a scan rate of 5 mV s?1, apart from longer cyclic stability with 87% retention of initial capacitance value after 10000 cycles for the PG 28 sample. The fabricated supercapacitor displayed an energy density of 26.3 Wh kg?1 and power density of 6120 W kg?1. Density functional theory calculations were also carried out to qualitatively support the enhanced capacitance by providing theoretical insight from electronic structure and density of states of PG. These results open a new avenue for greener synthesis of high-quality PG using environmentally friendly solvents, without the use of toxic chemicals, for excellent supercapacitor performance. © 2019 Elsevier B.V.
Electrochemical study of graphene-NiCo2O4 nanocomposite prepared through solvothermal approach
(2019) Sethi, M.; Krishna, Bhat, D.
A green approach was employed for the synthesis Graphene-NiCo2O4 nanocomposite and its electrochemical property has been studied. The formation of phase and morphology was studied by diffraction and microscopic analysis. The prepared material was studied as an electrode material for supercapacitor application in a 2 M KOH electrolyte. In order to examine the electrochemical behavior of the prepared material cyclic voltammetry (CV), Galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) measurements were carried out in a 3-electrode system. Electrochemical studies revealed a high specific capacitance of 242 F g-1 and 165 F g-1 were obtained at a high scan rate of 10 mV s-1 and at an applied current density of 0.5 A g-1, respectively. A high initial capacitance retention value and coulombic efficiency of about 96% and 98% was retained after a long 1000 discharge cycles. Hence, the prepared material can be a potential candidate for high performance supercapacitor applications. � 2019 American Institute of Physics Inc.. All rights reserved.
Electrochemical study of graphene-NiCo2O4 nanocomposite prepared through solvothermal approach
(American Institute of Physics Inc. subs@aip.org, 2019) Sethi, M.; Krishna Bhat, D.
A green approach was employed for the synthesis Graphene-NiCo2O4 nanocomposite and its electrochemical property has been studied. The formation of phase and morphology was studied by diffraction and microscopic analysis. The prepared material was studied as an electrode material for supercapacitor application in a 2 M KOH electrolyte. In order to examine the electrochemical behavior of the prepared material cyclic voltammetry (CV), Galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) measurements were carried out in a 3-electrode system. Electrochemical studies revealed a high specific capacitance of 242 F g-1 and 165 F g-1 were obtained at a high scan rate of 10 mV s-1 and at an applied current density of 0.5 A g-1, respectively. A high initial capacitance retention value and coulombic efficiency of about 96% and 98% was retained after a long 1000 discharge cycles. Hence, the prepared material can be a potential candidate for high performance supercapacitor applications. Â© 2019 American Institute of Physics Inc.. All rights reserved.
Engineered porous nanopillars of Co3O4: Hydrothermal synthesis and energy storage application
(American Institute of Physics Inc. subs@aip.org, 2020) Sethi, M.; Bhat, D.K.
The ever increasing demand of energy for daily needs is knocking globally and in this scenario the energy storage devices were paid more attention as they store more charge and release it efficiently which can be used in many applications. Nanopillars like porous Co3O4 nanostructures were synthesized by using a facile hydrothermal method which could be a potential candidate for energy storage applications. The as synthesized Co3O4 nanostructures are thoroughly analyzed by diffraction and microscopic tools which corroborated its successful synthesis. The porous Co3O4 nanostructures when utilized as an electrode material for supercapacitor application, a high capacitance value of 495.5 F g-1 is obtained at a scan rate of 5 mV s-1 from cyclic voltammetry (CV) data and 275 F g-1 (110 C g-1) at a current density of 1 A g-1 from charge-discharge (CD) data in 6 M KOH electrolyte. The charge bearing capacity of porous Co3O4 in other electrolytes like 4 M and 2 M KOH electrolyte is also studied and a capacitance value of 361.7 and 349.5 F g-1 is obtained in 4 M, and 2 M KOH electrolyte, respectively at a scan rate of 5 mV s-1. From the experiment it is found that the charge storage capacity is decreasing as the electrolyte concentration decreases and the value is 220 F g-1 (88 C g-1), and 214 F g-1 (86 C g-1) at a current density of 1 A g-1 for 4 M and 2 M KOH, respectively. Similarly the resistance value also decreases as the electrolyte concentration is increasing and vice-versa. The exciting result produced by this novel material suggests its suitable utility for energy storage applications. Â© 2020 Author(s).
Facile solvothermal synthesis and high supercapacitor performance of NiCo2O4 nanorods
(Elsevier Ltd, 2019) Sethi, M.; Bhat, D.K.
NiCo2O4 nanorod arrays were synthesized employing a facile low-temperature solvothermal approach, followed by post-calcination treatment. The structural, morphological and elemental characterizations were done by diffraction, microscopic and spectroscopic techniques. The prepared sample was studied as an active electrode material for supercapacitor application in 2 M KOH aqueous electrolyte. The cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectral (EIS) studies were carried out to know the electrochemical activity of the prepared material. From the CV study, a high capacitance value of 440 F g?1 was obtained at a scan rate of 5 mV s?1 in a 3-electrode method. Apart from high capacitance value, the prepared electrode depicted 94% initial capacitance retention value after 2000 charge-discharge cycles at a current density of 8 A g?1. The fabricated symmetrical supercapacitor depicted a high energy density of 12.6 Wh kg?1 and a high power density of 4003 W kg?1. This was attributed to the better electrical conductivity of NiCo2O4 nanorods. © 2018 Elsevier B.V.
Facile solvothermal synthesis of NiFe2O4 nanoparticles for high-performance supercapacitor applications
(Higher Education Press, 2020) Sethi, M.; Shenoy, U.S.; Muthu, M.; Bhat, D.K.
We report a green and facile approach for the synthesis of NiFe2O4 (NF) nanoparticles with good crystallinity. The prepared materials are studied by various techniques in order to know their phase structure, crystallinity, morphology and elemental state. The BET analysis revealed a high surface area of 80.0 m2·g?1 for NF possessing a high pore volume of 0.54 cm3·g?1, also contributing to the amelioration of the electrochemical performance. The NF sample is studied for its application in supercapacitors in an aqueous 2 mol·L?1 KOH electrolyte. Electrochemical properties are studied both in the three-electrode method and in a symmetrical supercapacitor cell. Results show a high specific capacitance of 478.0 F·g?1 from the CV curve at an applied scan rate of 5 mV·s?1 and 368.0 F·g?1 from the GCD analysis at a current density of 1 A·g?1 for the NF electrode. Further, the material exhibited an 88% retention of its specific capacitance after continuous 10000 cycles at a higher applied current density of 8 A·g?1. These encouraging properties of NF nanoparticles suggest the practical applicability in high-performance supercapacitors. © 2020, Higher Education Press.
Hassle-free solvothermal synthesis of NiO nanoflakes for supercapacitor application
(Elsevier B.V., 2021) Sethi, M.; Shenoy, U.S.; Bhat, D.K.
A mixed solvent solvothermal approach was employed for the synthesis of NiO (NO) nanostructures under a low temperature route. The nanoflakes when studied for its electrochemical performance in a 3-electrode method in aqueous 2 M KOH revealed a high capacitance value of 305.0 F g?1 at a scan rate of 5 mV s?1 apart from good rate capability, cyclic stability and coulombic efficiency. The fabricated symmetrical supercapacitor device also showed good electrochemical performance of pseudocapacitive nature with a high power density of 8000.0 W kg?1. The extent of surface sites taking part in the electrochemical processes reveals the enhanced performance is due to the high surface area of NO with a mesoporous structure. The enhanced conductivity of the nanoflakes also provided an unhindered path way for the ionic transport. The promising results reveal that the synthetic technique employed could be extended to other oxides as well. © 2021 Elsevier B.V.
Molecular surface-dependent light harvesting and photo charge separation in plant-derived carbon quantum dots for visible-light-driven OH radical generation for remediation of aromatic hydrocarbon pollutants and real wastewater
(Academic Press Inc., 2024) Meena, S.; Sethi, M.; Saini, S.; Kumar, K.; Saini, P.; Meena, S.; Kashyap, S.; Yadav, M.; Meena, M.L.; Dandia, A.; Nirmal, N.K.; Parewa, V.
Despite the growing emphasis on eco-friendly nanomaterials as energy harvesters, scientists are actively searching for metal-free photocatalysts to be used in environmental remediation strategies. Developing renewable resource-based carbon quantum dots (CQDs) as the sole photocatalyst to harvest visible light for efficient pollutant degradation is crucial yet challenging, particularly for addressing the escalating issue of water deterioration. Moreover, the photocatalytic decomposition of H2O2 under visible light irradiation remains an arduous task. Based on this, we designed two types of CQDs, C-CQDs (carboxylic-rich) and A-CQDs (amine-rich) with distinct molecular surfaces. Owing to the higher amount of upward band bending induced by amine-rich molecular surface, A-CQDs efficiently harvest the visible light and prevent recombination kinetics resulting in prolonged lifetimes (25 ps), and augmented charge carrier density (35.7 × 1018) of photoexcited charge carriers. A-CQDs enabled rapid visible-light-driven photolysis of H2O2 (k = 0.058 min−1) and produced higher quantity of •OH radicals (0.158 μmol/sec) for the mineralization of petroleum waste, BETX (i.e. Benzene, Ethylbenzene, Toluene and Xylene) (k = 0.017–0.026 min−1) and real textile wastewater (k = 0.026 min−1). To assess comparative toxicities of both remediated and non-remediated real wastewater samples in a time and dose depended manner, Drosophila melanogaster was used as a model organism. The findings unequivocally demonstrate the potential of remediated wastewater for watering urban forestry. © 2024 Elsevier Inc.
NiO nanoplates for energy storage application: Role of electrolyte concentration on the energy storage property
(Elsevier Ltd, 2020) Sethi, M.; Bhat, D.K.
Here in, synthesis of NiO nanoplates by employing a mixed solvent system under solvothermal method followed by calcining the obtained product nickel hydroxide in air is reported. Diffraction, microscopic, and spectroscopic results confirmed the formation of NiO phase. The as synthesized NiO nanoplates are tested as a robust material for energy storage applications. The effect of electrolyte concentration on the capacitive behavior of NiO is studied thoroughly. The outcome from the electrochemical analysis reveals that NiO nanoplates have a high specific capacity value of 108.4 C g-1 (270 F g-1) in 6 M KOH electrolyte and the value decreases to 85.0 C g-1 (212.5 F g-1) and 78.2 C g-1 (195.5 F g-1) for 4 M, and 2 M KOH electrolyte, respectively. The resistance values also decreased with increase in the KOH concentration. The better electrochemical performance depicted by the 6 M KOH electrolyte is mainly ascribed to the availability of plenty of OH- ions in the electrolyte solution, which helped in the proper wettability of the sample so that the OH- ions can participate to higher extent during the electrochemical redox reactions, due to which the observed charge storage capacity is more in higher electrolyte concentration and vice-versa. Thus, the results suggest the usefulness of this material for energy storage applications. Â© 2019 Elsevier Ltd. All rights reserved.
Novel porous graphene synthesized through solvothermal approach as high performance electrode material for supercapacitors
(American Institute of Physics Inc. subs@aip.org, 2020) Sethi, M.; Bhat, D.K.
A facile solvent mediated chemical route is employed for the fruitful synthesis of porous graphene (PG). The formation of PG is thoroughly characterized by microscopic and spectroscopic techniques. Elemental analysis showed the presence of carbon and oxygen only as elements in the PG sample, indicating the purity of the product. The as synthesized sample is utilized as an energetic electrode material for supercapacitor in 2M KOH aqueous electrolyte. The fabricated symmetrical supercapacitor exhibited a capacitance value of 248.0 F g-1 at an applied current density of 1 Ag-1, and 220.0 F g-1 at a scan rate of 5 mV s-1. The supercapacitor provided an energy density value of 7.3 Wh kg-1 while maintaining a power density of 6405.0 W kg-1 at an applied current density of 8 A g-1. Apart from these values, the supercapacitor device can sustain up to 5000 charge-discharge cycles at a higher applied current density of 8 A g-1, with 96% of initial capacitance retention demonstrating the good rate profile. Hence, considering the above facts, it can be suggested that this material can have high practical utility in supercapacitor application. Â© 2020 Author(s).
Porous Graphene Wrapped SrTiO3 Nanocomposite: Sr-C Bond as an Effective Coadjutant for High Performance Photocatalytic Degradation of Methylene Blue
(American Chemical Society service@acs.org, 2019) Bantawal, H.; Sethi, M.; Shenoy, U.S.; Bhat, D.K.
Porous graphene-SrTiO3 (PGST) composite prepared by a facile solvothermal method was tested for its photocatalytic activity in degradation of methylene blue (MB) dye. First-principles density functional theory calculations were also carried out to study the effect of nanocomposite formation on the electronic structure and density of states. The combined experimental and theoretical study gave insights regarding the formation of the Sr-C bond which enhanced the charge transport, effectively separating the charge carriers and reduced their recombination rate. The formation of PGST nanocomposite favorably tuned the electronic structure with decreased band gap due to introduction of the hybridized states extending the absorption to the visible region of electromagnetic spectrum. The microscopy studies revealed loofah like PG wrapped SrTiO3 nano structures with contusions providing high surface area facilitating adsorption of MB dye. Degradation of ?92% was obtained by 7.5 PGST in 120 min with high cyclic stability indicating its suitability as an efficient photocatalyst for the treatment of pollutants. © 2019 American Chemical Society.
Porous graphene-NiCo2O4 nanorod hybrid composite as a high performance supercapacitor electrode material
(Royal Society of Chemistry, 2020) Sethi, M.; Shenoy, U.S.; Bhat, D.K.
The template free low temperature solvothermal synthesis of high capacitive porous graphene-NiCo2O4 nanorod composites has been carried out. Solvothermal synthesis followed by calcination in air led to the development of a highly porous hybrid nanocomposite, which acts as a buffering channel for fast ion diffusion and provides robust mechanical strength. Advantages of using porous graphene to enhance the capacitance of the material were studied theoretically using First principles calculations. High capacitance values of 1533 F g-1 at a scan rate of 5 mV s-1 and 1684 F g-1 at a current density of 1 A g-1 are obtained from cyclic voltammetry data and galvanostatic charge discharge data, respectively. The electrode material possesses good cyclic stability with the retention of 94% of its initial capacitance even after 10000 charge-discharge cycles at a current density of 8 A g-1 in 2 M KOH electrolyte. The fabricated supercapacitor exhibited a high energy density of 45.3 W h kg-1 and a high power density of 17843.5 W kg-1 due to the synergistic effect of the composite components. The enhanced electrochemical function of the composite makes it a potential candidate for supercapacitor application and future studies. This journal is © 2020 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Simple solvothermal synthesis of porous graphene-NiO nanocomposites with high cyclic stability for supercapacitor application
(Elsevier Ltd, 2021) Sethi, M.; Shenoy, U.S.; Bhat, D.K.
Over the years supercapacitors have established themselves as energy storage devices as well as a subject to reckon with. Thus, not surprisingly tremendous effort has been put in the field of supercapacitor research. However, a device with all desirable characteristics has not yet been realized and hence deserves to be paid utmost heed. Herein, we report a facile synthesis of porous graphene-NiO (PGNO) nanocomposites via a unique mixed solvent system through a solvothermal approach. The microscopic characterization of porous graphene (PG) reveals the presence of pores in the graphene sheets, NiO (NO) shows flake like structure and PGNO composite displays the anchoring of NO nanoflakes on the PG sheets. A series of electrode materials were prepared by varying the percentage composition of PG and the materials were named as 5–30 PGNO, respectively. The electrochemical study represented a good capacitance value of 511.0 F g?1 at a scan rate of 5 mV s?1 for the 10 PGNO composite in a 3-electrode method and 80% retention of initial capacitance after 10,000 cycles at a current density of 8 A g?1. The fabricated symmetrical hybrid supercapacitor by using the 10 PGNO electrodes also depicted a good capacitance value of 86.0 F g?1 at a scan rate of 5 mV s?1. The fabricated device retained 84% of initial capacitance at the end of 10,000 cycles at a current density of 8 A g?1, demonstrating the good electrochemical strength and rate capability of the material. The percentage of double layer capacitance and pseudocapacitance contributions to the overall specific capacitance of the PGNO supercapacitor has also been estimated. Overall, the results exhibited by the composite material warrants its beneficial utility in energy storage devices. © 2020 Elsevier B.V.
Visible-light induced effective and sustainable remediation of nitro organics pollutants using Pd-doped ZnO nanocatalyst
(Nature Research, 2024) Vikal, S.; Meena, S.; Gautam, Y.K.; Kumar, A.; Sethi, M.; Meena, S.; Gautam, D.; Singh, B.P.; Agarwal, P.C.; Meena, M.L.; Parewa, V.
Nitroaromatic compounds represent a class of highly toxic pollutants discharged into aquatic environments by various industrial activities, posing significant threats to ecological integrity and human health due to their persistent and hazardous nature. In this study, Pd-doped ZnO nanoparticles were investigated as a potential solution for the degradation of nitro organics, offering heightened photocatalytic efficacy and prolonged stability. The synthesis of Pd-doped ZnO NPs was achieved via the hydrothermal method, with subsequent analysis through XRD spectra and XPS confirming successful Pd doping within the ZnO matrix. Characterization through FESEM and HRTEM unveiled the heterogeneous morphologies of both undoped and Pd-doped ZnO nanoparticles. Additionally, UV–vis and PL spectroscopy provided insights into the optical properties, chemical bonding, and defect structures of the synthesized Pd-doped ZnO NPs. Pd doping induces a redshift in ZnO’s absorption spectra, reducing the bandgap from 3.12 to 2.94 eV as Pd concentration rises from 0 to 0.2 wt.%. The photocatalytic degradation, following pseudo-first-order kinetics, achieved 90% nitrobenzene abatement (200 µg/L, pH 7) under visible light within 320 min with a catalyst loading of 16 µg/mL. The photocatalytic efficacy of 0.08 wt% Pd-doped ZnO (k = 0.058 min?1) exhibited a 25-fold enhancement compared to bare ZnO (k = 3.1 × 10–4 min-1). Subsequent quenching and ESR experiments identified hydroxyl radicals (OH•) as the predominant active species in the degradation mechanism. Mass spectrometry analysis unveiled potential breakdown intermediates, illuminating a plausible degradation pathway. The investigated Pd-doped ZnO nanoparticles demonstrated reusability for up to five successive treatment cycles, offering a sustainable solution to nitro organics contamination challenges. © The Author(s) 2024.