Browsing by Author "Singh, Abhay Narayan"

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    Effect of strontium doping on the electrochemical pseudocapacitance of Y1?xSrxMnO3?? perovskites
    (Royal Society of Chemistry, 2022) Singh, Abhay Narayan; Nigam, Krishna Gopal; Mondal, Rakesh; Kushwaha, Vishal; Gupta, Asha; Rath, Chandana; Singh, Preetam
    Grid-scale bulk energy storage solutions are needed to utilize the full potential of renewable energy technologies. Pseudocapacitive electrochemical energy storage can play a vital role in developing efficient energy storage solutions. The use of perovskites as anion intercalation-type pseudocapacitor electrodes has received significant attention in recent years. In this study, Sr-doped YMnO3i.e. Y1?xSrxMnO3?? perovskite was prepared by the solid-state ceramic route and studied for electrochemical pseudocapacitance in aqueous KOH electrolyte. Microstructures, morphologies, and electrochemical properties of these materials were investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance method. The formation of the mostly cubic phase, with 50% strontium doped YMnO3 (YSMO-50) provides an equivalent three-dimensional network and superior conductivity due to Mn3+-O2?-Mn4+ hopping conduction. YSMO-50 exhibited low intrinsic resistance, 1.45 ? cm?2, and the highest specific capacity, 259.83 F g?1 at a current density of 1 A g?1 in 2 M KOH aqueous electrolyte. Redox-mediated interconversion of oxide to hydroxide (M2+O2? + H2O + e? ? M+OH? + OH?) in aqueous media is shown to be the reason behind the high capacitance of YSMO-50. The excellent electrochemical performance of YSMOs was attributed to the reversible interconversion of oxide-ion into hydroxide ion coupled with surface redox reaction of Mn2+/Mn3+ and Mn3+/Mn4+ occurring during the charge-discharge process. The maximum energy density of 65.13 W h kg?1 was achieved at a power density of 0.45 kW kg?1 for an asymmetric mode, in which YSMO serves as a negative electrode and Activated carbon (AC) as a positive electrode in the PVA-KOH gel electrolyte. Our study reveals that the doping of low valence atom (Sr) at the A-site in perovskite manganites (YMnO3) may be an effective tool to enhance the pseudocapacitive performance of perovskite-based electrodes. � 2023 The Royal Society of Chemistry.
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    Electrochemical Performance of Delafossite, AgFeO2: A Pseudo-Capacitive Electrode in Neutral Aqueous Na2SO4Electrolyte
    (IOP Publishing Ltd, 2021) Singh, Abhay Narayan; Mondal, Rakesh; Rath, Chandana; Singh, Preetam
    Layered delafossite AgFeO2 with open channel structure is envisaged as a pseudo capacitor electrode using Fe2+/Fe3+ redox couple. A simple co-precipitation method was employed for the phase formation of delafossite AgFeO2 resulting in a mixture of 2H and 3R-phase. Phase tuning of 2H phase was done by controlling the calcination conditions and characterizing by powder XRD, FT-IR, and Raman methods. 2H AgFeO2 was used to synthesize as a majority phase because it have the larger inter layer spacing than 3R phase shown. HRTEM study confirms the formation 2H phase in majority. All of the synthesized samples exhibit predominantly faradic battery-type redox behavior along with surface charge storage. Flower like microarchitectures of AgFeO2 show outstanding electrochemical performance with high specific capacity of 110.4 F g-1 at 1 A g-1 current density, that retained up to 89% after 2000th times charge/discharge in 1 M Na2SO4 electrolyte. In an asymmetric device mode, AFO-400//AC full cell exhibits superior electrochemical performance by delivering high energy density (33.5 Wh kg-1) and high power density (454.3 W kg-1) with excellent cycling stability (86% retention after 2000th cycles). The results clearly demonstrate that the synthesized delafossite AgFeO2 containing mixture of 2H and 3R-phases have remarkable potential to be used as a negative electrode material for supercapacitor and other energy storage technologies. � 2021 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.
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    Fabrication and electrochemical performance of pseudocapacitive ABO2-type AgFeO2@C
    (Elsevier Ltd, 2023) Singh, Abhay Narayan; Yadav, Akhilesh Kumar; Gupta, Asha; Rath, Chandana; Singh, Preetam
    To make effective utilization of renewable energy sources, a highly efficient large-scale energy storage solution is needed that can fill the gap between the batteries (high energy density) and the capacitors (high power density). Supercapacitors are being a bridge between batteries and capacitors, suffer from low energy density, and need to be further upgradation for utilization as a grid-level energy storage solution. A higher energy density can be achieved by constructing an asymmetric cell (ASC) in which both, the electrodes (positive and negative) are worked in a separate potential window. Pseudocapacitive ABO2-type electrode in the form of an asymmetric cell (ASC), AgFeO2@C//K0.4MnO2. xH2O is envisaged here as high high-performing battery-type supercapacitor cell to develop large-scale energy storage solutions. Herein, crystallites of K0.4MnO2. xH2O were successfully grown via a facile chemical flux method that gives a birnessite-type layered structure having a lateral dimension in the range of 2�5 ?m. Thus, the incorporation of birnessite- K0.4MnO2. xH2O as a positive electrode (cathode), and the thin carbon layer coated AgFeO2 as a negative electrode (anode) in aqueous 1 M Na2SO4 electrolyte in the form of ASC exhibited high energy density as well as power density with excellent cycle life up to cell voltages close to 1.8 V. The presented battery-type supercapacitor cell can deliver a maximum energy density equivalent to 61.51 Wh kg?1 and a power density of 450 W kg?1 at a current density of 0.5 A g?1, which is substantially larger than the previously reported aqueous electrolyte-based asymmetric supercapacitor devices. The newly developed high-voltage aqueous asymmetric battery-type supercapacitors device has a low-cost and enviro-friendly, that can replace currently market-available hazardous lead-acid batteries for fast energy storage applications. � 2023