Browsing by Author "Halder, Krishna Kamal"

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    Dumbbell-Shaped Ternary Transition-Metal (Cu, Ni, Co) Phosphate Bundles: A Promising Catalyst for the Oxygen Evolution Reaction
    (American Chemical Society, 2022-01-27T00:00:00) Singh, Harjinder; Biswas, Rathindranath; Ahmed, Imtiaz; Thakur, Pooja; Kundu, Avinava; Panigrahi, Abhishek Ramachandra; Banerjee, Biplab; Halder, Krishna Kamal; Lahtinen, Jouko; Mondal, Krishnakanta; Haldar, Krishna Kanta
    Development of economical and high-performance electrocatalysts for the oxygen evolution reaction (OER) is of tremendous interest for future applications as sustainable energy materials. Here, a unique member of efficient OER electrocatalysts has been developed based upon structurally versatile dumbbell-shaped ternary transition-metal (Cu, Ni, Co) phosphates with a three-dimensional (3D) (Cu2(OH)(PO4)/Ni3(PO4)2�8H2O/Co3(PO4)2�8H2O) (CNCP) structure. This structure is prepared using a simple aqueous stepwise addition of metal ion source approach. Various structural investigations demonstrate highly crystalline nature of the composite structure. Apart from the unique structural aspect, it is important that the CNCP composite structure has proved to be an excellent electrocatalyst for OER performance in comparison with its binary or constituent phosphate under alkaline and neutral conditions. Notably, the CNCP electrocatalyst displays a much lower overpotential of 224 mV at a current density of 10 mA cm-2 and a lower Tafel slope of 53 mV dec-1 with high stability in alkaline medium. In addition, X-ray photoelectron spectroscopy analysis suggested that the activity and long-term durability for the OER of the ternary 3D metal phosphate are due to the presence of electrochemically dynamic constituents such as Ni and Co and their resulting synergistic effects, which was further supported by theoretical studies. Theoretical calculations also reveal that the incredible OER execution was ascribed to the electron redistribution set off in the presence of Ni and Cu and the most favorable interaction between the *OOH intermediate and the active sites of CNCP. This work may attract the attention of researchers to construct efficient 3D ternary metal phosphate catalysts for various applications in the field of electrochemistry. � 2022 American Chemical Society.
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    Genomic DNA-mediated formation of a porous Cu2(OH)PO4/Co3(PO4)2�8H2O rolling pin shape bifunctional electrocatalyst for water splitting reactions
    (Royal Society of Chemistry, 2022-01-28T00:00:00) Singh, Harjinder; Ahmed, Imtiaz; Biswas, Rathindranath; Mete, Shouvik; Halder, Krishna Kamal; Banerjee, Biplab; Haldar, Krishna Kanta
    Among the accessible techniques, the production of hydrogen by electrocatalytic water oxidation is the most established process, which comprises oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Here, we synthesized a genomic DNA-guided porous Cu2(OH)PO4/Co3(PO4)2�8H2O rolling pin shape composite structure in one pot. The nucleation and development of the porous rolling pin shape Cu2(OH)PO4/Co3(PO4)2�8H2O composite was controlled and stabilized by the DNA biomolecules. This porous rolling pin shape composite was explored towards electrocatalytic water oxidation for both OER and HER as a bi-functional catalyst. The as-prepared catalyst exhibited a very high OER and HER activity compared to its various counterparts in the absence of an external binder (such as Nafion). The synergistic effects between Cu and Co metals together with the porous structure of the composite greatly helped in enhancing the catalytic activity. These outcomes undoubtedly demonstrated the beneficial utilization of the genomic DNA-stabilised porous electrocatalyst for OER and HER, which has never been observed. This journal is � The Royal Society of Chemistry.
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    Graphitic Carbon Nitride Composites with MoO3-Decorated Co3O4Nanorods as Catalysts for Oxygen and Hydrogen Evolution
    (American Chemical Society, 2021-10-22T00:00:00) Ahmed, Imtiaz; Biswas, Rathindranath; Patil, Ranjit A.; Halder, Krishna Kamal; Singh, Harjinder; Banerjee, Biplab; Kumar, Bhupender; Ma, Yuan-Ron; Haldar, Krishna Kanta
    We have prepared a graphitic carbon nitride (g-C3N4) composite with MoO3-decorated Co3O4 nanorods (Co3O4/MoO3/g-C3N4) via the hydrothermal approach, and this hybrid material acts as a highly active and durable electrocatalyst for water splitting reactions. This material could fundamentally influence the catalytic processes and performance of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The OER and HER activities of Co3O4-/MoO3-based nanorods are enhanced by blending with conducting support, for example, graphitic carbon nitrides (g-C3N4). The X-ray diffraction pattern and the attenuated total reflectance-Fourier transform infrared data revealed that the as-synthesized nanorods are highly crystalline in nature and are attached to the g-C3N4 support. Transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy studies also affirm the successful heterointerface formation between Co3O4/MoO3 nanorods and g-C3N4. This Co3O4/MoO3/g-C3N4 rod-shaped catalyst is highly stable in comparison to its individual constituent and generates a current density of 10 mA cm-2 at a low overpotential of 206 mV for OER and 125 mV for HER in alkaline and acidic media, respectively. This work could pave the way for developing Co3O4/MoO3/g-C3N4 composite materials as electrocatalysts for overall water splitting reactions. � 2021 American Chemical Society. All rights reserved.
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    Green Synthesis of Bimetallic Au/Ag Nanostructures Using Aqueous Extract of Eichhornia crassipes for Antibacterial Activity
    (Springer, 2022-02-12T00:00:00) Halder, Arindom; Biswas, Rathindranath; Kushwaha, Prem Prakash; Halder, Krishna Kamal; Ahmed, Imtiaz; Singh, Harjinder; Kumar, Shashank; Haldar, Krishna Kanta
    Biosynthesis of nanostructured materials is an arising feature of the interdisciplinary relationship between nanotechnology and biotechnology and acquiring consideration because of developing interest to foster ecologically favorable innovations in material preparation. In the present study, we synthesized an environmentally friendly and green method for the synthesis of gold/silver bimetallic nanostructure using Eichhornia crassipes leaf extract as reducing and capping agent. Au/Ag nanostructures were characterized by UV�Visible spectroscopy, X-ray photoelectron spectroscopy, and power X-ray diffraction. Transmission electron microscopy images also confirmed the formation of Au/Ag nanostructures. Antibacterial activity of Au/Ag nanostructures was studied and it has been found that Ag/Au nanostructure at 100��M concentration significantly inhibited the bacterial growth of Escherichia coli bacteria. Moreover, the Hoechst 33342 staining method was used to study the effect of Ag/Au nanostructure particles on the morphological changes in breast cancer cell (MDA-MB-231) nucleus. Staining of the Ag/Au nanostructure particle�treated MDA-MB-231 cells (4�h treatments) showed the appearance of emblematic features of apoptosis such as cell membrane blabbing and shrinkage. Graphical Abstract: [Figure not available: see fulltext.]. � 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.