Faculty Publications
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Item 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. © 2019 Elsevier Ltd. All rights reserved.Item 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.Item 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.