School Of Basic And Applied Sciences

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Author: search.filters.author.Kour, SimranSubject: search.filters.subject.Supercapacitor

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    Theoretical investigation of quantum capacitance of Co-doped ?-MnO2 for supercapacitor applications using density functional theory
    (Royal Society of Chemistry, 2023-09-07T00:00:00) Vijayan, Ariya K.; Sreehari, M.S.; Kour, Simran; Dastider, Saptarshi Ghosh; Mondal, Krishnakanta; Sharma, A.L.
    The rapid depletion of fossil fuels and ever-growing energy demand have led to a search for renewable clean energy sources. The storage of renewable energy calls for immediate attention to the fabrication of efficient energy storage devices like supercapacitors (SCs). As an electrode material for SCs, MnO2 has gained wide research interest because of its high theoretical capacitance, variable oxidation state, vast abundance, and low cost. However, the low electric conductivity of MnO2 limits its practical application. The conductivity of MnO2 can be enhanced by tuning the electronic states through substitution doping with cobalt. In the present work, first principles analysis based on density functional theory (DFT) has been used to examine the quantum capacitance (CQC) and surface charge (Q) of Co-doped MnO2. Doping enhanced the structural stability, electrical conductivity, potential window, and quantum capacitance of ?-MnO2. The shortened band gap and localized states near the Fermi level improve the CQC of ?-MnO2. For the narrow potential range (?0.4 to 0.4 V), the CQC is observed to increase with doping concentration. The highest CQC value at +0.4 V is observed to be 2412.59 ?F cm?2 for Mn6Co2O16 (25% doping), five times higher than that of pristine MnO2 (471.18 ?F cm?2). Mn6Co2O16 also exhibits better CQC and �Q� at higher positive bias. Hence, it can be used as an anode material for asymmetric supercapacitors. All these results suggest better capacitive performance of Co-doped ?-MnO2 for aqueous SCs and as an anode material for asymmetric supercapacitors. � 2023 The Royal Society of Chemistry.
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    All-redox hybrid supercapacitors based on carbon modified stacked zinc cobaltite nanosheets
    (Royal Society of Chemistry, 2023-09-12T00:00:00) Kour, Simran; Kour, Pawanpreet; Sharma, A.L.
    The role of energy in the present century has increased with the fast advancement of the global economy. In this regard, hybrid supercapacitors (HSCs) as energy storage systems have become an extensive research focus worldwide. This study reports the synthesis of carbon-loaded ZnCo2O4 stacked nanosheets via an in situ hydrothermal process followed by annealing. The electrochemical response was tested in a 2-electrode system. The optimized composite exhibited a capacitance of ?527.6 F g?1 at 5 mV s?1. The symmetric SC (SSC) possessed an energy density (Ed) of ?17.3 W h kg?1 corresponding to a power density (Pd) of 2.25 kW kg?1. Two asymmetric all-redox HSCs have also been fabricated using an optimized composite material as the positive electrode. The previously synthesized MnCo2O4/AC (HSC1) and MnO2/AC (HSC2) were taken as negative electrodes. HSC1 exhibited an Ed of ?24.4 W h kg?1 corresponding to a Pd of ?0.8 kW kg?1. On the other hand, HSC2 exhibited the highest Ed of ?30.8 W h kg?1 at 2.4 kW kg?1. The real-time application of the composite is tested with the fabricated HSCs. HSC1 exhibited a capacitive retention of ?72.2% after 10 000 cycles. On the other hand, HSC2 exhibited a capacitive retention of ?73.4% after 10 000 cycles. The SSC, HSC1, and HSC2 illuminated a 39 red LED panel for ?3 min, 7 min, and 13 min, respectively. The results suggested the promising performance of all-redox HSCs. The overall results present a sustainable approach for creating hierarchical energy materials for the construction of future energy-storage systems. � 2023 The Royal Society of Chemistry.
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    MnO2 nanorod loaded activated carbon for high-performance supercapacitors
    (Elsevier Ltd, 2022-03-31T00:00:00) Kour, Simran; Tanwar, Shweta; Sharma, A.L.
    Nowadays, transition metal oxides (TMOs) have gained much attention as potential candidates for supercapacitors owing to their remarkable properties for instance vast abundance, a high value of theoretical capacitance, easy accessibility, and eco-friendly nature. But low electric conductivity of TMOs restrains them from reaching their theoretically predicted value for capacitance. Activated carbon with enormous surface area and excellent conductivity has been chosen to augment the conductivity of TMO-based electrodes. Here in this paper, we have synthesized MnO2 nanorods via a facile hydrothermal process. These nanorods have been loaded onto activated carbon via a straight-forward sol-gel approach at room temperature. The obtained nano-composite exhibited superior capacitance of 398.5 F g?1 at 1 A g?1 than MnO2 (161.8 F g?1). The composite attained excellent energy of 105.2 Wh kg?1 (at 2 kW kg?1). Further, the composite was tested for device application. Three symmetric supercapacitor cells joined in series were proficient to glow a blue LED for about one minute while the red LED was illuminated for about 12 min. This suggested that the composite material has broad potential applicability as supercapacitor electrode material. � 2022 Elsevier B.V.