School Of Basic And Applied Sciences

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Author: search.filters.author.Dastider, Saptarshi GhoshSubject: search.filters.subject.Density functional theory

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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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    Does Water Play a Crucial Role in the Growth of ZnO Nanoclusters in ZnO/Cu Catalyst?
    (American Chemical Society, 2023-05-04T00:00:00) Dastider, Saptarshi Ghosh; Panigrahi, Abhishek Ramachandra; Banerjee, Arup; Haldar, Krishna Kanta; Fortunelli, Alessandro; Mondal, Krishnakanta
    The catalytically active configuration of ZnO/Cu in the commercial ZnO/Cu/Al2O3 catalyst for methanol synthesis from CO2 is still not clear. In this study, we employ density functional theory based methods to shed light on the structure and stoichiometry of ZnO clusters both free in the gas phase and also deposited on the Cu(111) surface under methanol synthesis conditions. Specifically, we investigate the structural evolution of ZnO clusters in the presence of hydrogen and water. We find that the stability of ZnO clusters increases with the concentration of water until the ratio of Zn and OH in the clusters reaches 1:2, with a morphological transition from planar to 3D configurations for clusters containing more than 4 Zn atoms. These clusters exhibit weak interaction with CO2, and water is predicted to block the active center. The Cu(111) surface plays an important role in enhancing the adsorption of CO2 on the ZnO/Cu(111) systems. We infer that ZnO nanostructures covered with OH species may be the morphology of the ZnO during the methanol synthesis from the hydrogenation of CO2 on the industrial catalyst. � 2023 American Chemical Society.
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    Mechanism of Iron Integration into LiMn1.5Ni0.5O4for the Electrocatalytic Oxygen Evolution Reaction
    (American Chemical Society, 2022-09-14T00:00:00) Ahmed, Imtiaz; Biswas, Rathindranath; Dastider, Saptarshi Ghosh; Singh, Harjinder; Mete, Shouvik; Patil, Ranjit A.; Saha, Monochura; Yadav, Ashok Kumar; Jha, Sambhu Nath; Mondal, Krishnakanta; Singh, Harishchandra; Ma, Yuan-Ron; Haldar, Krishna Kanta
    Spinel-type LiMn1.5Ni0.5O4 has been paid temendrous consideration as an electrode material because of its low cost, high voltage, and stabilized electrochemical performance. Here, we demonstrate the mechanism of iron (Fe) integration into LiMn1.5Ni0.5O4 via solution methods followed by calcination at a high temparature, as an efficient electrocatalyst for water splitting. Various microscopic and structural characterizations of the crystal structure affirmed the integration of Fe into the LiMn1.5Ni0.5O4 lattice and the constitution of the cubic LiMn1.38Fe0.12Ni0.5O4 crystal. Local structure analysis around Fe by extended X-ray absorption fine structure (EXAFS) showed Fe3+ ions in a six-coordinated octahedral environment, demonstrating incorporation of Fe as a substitute at the Mn site in the LiMn1.5Ni0.5O4 host. EXAFS also confirmed that the perfectly ordered LiMn1.5Ni0.5O4 spinel structure becomes disturbed by the fractional cationic substitution and also stabilizes the LiMn1.5Ni0.5O4 structure with structural disorder of the Ni2+ and Mn4+ ions in the 16d octahedral sites by Fe2+ and Fe3+ ions. However, we have found that Mn3+ ion production from the redox reaction between Mn4+ and Fe2+ influences the electronic conductivity significantly, resulting in improved electrochemical oxygen evolution reaction (OER) activity for the LiMn1.38Fe0.12Ni0.5O4 structure. Surface-enhanced Fe in LiMn1.38Fe0.12Ni0.5O4 serves as the electrocatalytic active site for OER, which was verified by the density functional theory study. � 2022 American Chemical Society.