Browsing by Author "Patil, Ranjit A."

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    Coupling Nonstoichiometric Zn0.76Co0.24S with NiCo2S4Composite Nanoflowers for Efficient Synergistic Electrocatalytic Oxygen and Hydrogen Evolution Reactions
    (American Chemical Society, 2022-12-15T00:00:00) Biswas, Rathindranath; Thakur, Pooja; Ahmed, Imtiaz; Rom, Tanmay; Ali, Mir Sahidul; Patil, Ranjit A.; Kumar, Bhupender; Som, Shubham; Chopra, Deepak; Paul, Avijit Kumar; Ma, Yuan-Ron; Haldar, Krishna Kanta
    Transition-metal sulfide-based composite nanomaterials have garnered extensive interest not only for their unique morphological architectures but also for exploring as a noble-metal-free cost-effective, durable, and highly stable catalyst for electrochemical water splitting. In this work, we synthesized in situ nonstoichiometric Zn0.76Co0.24S with NiCo2S4binary composite flowers (Zn0.76Co0.24S/NiCo2S4) in one step by thermal decomposition of Zn2[PDTC]4and Ni[PDTC]2complexes by a solvothermal process in a nonaqueous medium from their molecular precursor, and their potential application in electrochemical oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) was investigated. Field-emission scanning electron microscopy and transmission electron microscopy analyses revealed the flower-shaped morphology of as-synthesized Zn0.76Co0.24S/NiCo2S4. Again, the structural and chemical compositions were confirmed through powder X-ray diffraction and X-ray photoelectron spectroscopy studies, respectively. The as-obtained 3D flower-type Zn0.76Co0.24S/NiCo2S4nanostructure was further subject to electrochemical OER and HER in alkaline and acidic media, respectively. Zn0.76Co0.24S/NiCo2S4showed low overpotential values of 248 mV (Tafel slope, 85 mV dec-1) and 141 mV (Tafel slope, 79 mV dec-1) for OER and HER activities, respectively, due to the synergistic effects of Zn0.76Co0.24S and NiCo2S4. Several long-term stability tests also affirmed that the Zn0.76Co0.24S/NiCo2S4composite nanostructure is a highly stable and efficient electrocatalyst toward OER and HER activities as compared to the recently reported superior bifunctional electrocatalysts as well as state-of-the-art materials. � 2023 American Chemical Society. All rights reserved.
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    Efficient MoS2/V2O5 Electrocatalyst for Enhanced Oxygen and Hydrogen Evolution Reactions
    (Springer, 2023-04-29T00:00:00) Haldar, Krishna Kanta; Ahmed, Imtiaz; Biswas, Rathindranath; Mete, Shouvik; Patil, Ranjit A.; Ma, Yuan-Ron
    Electrochemical (EC) water splitting is a promising approach for the generation of renewable hydrogen (H2) fuels and oxygen (O2) evolution. Composite structured molybdenum disulphide (MoS2)/vanadium pentoxide (V2O5) with low overpotential is a promising electrocatalyst for anodic and cathodic material for an alternative energy source. We fabricated a flower shape MoS2/V2O5 composite via a hydrothermal approach where V2O5grew on the surface of the MoS2 petals. The unique flower-type composite structure alleviates the surface expansion of electrode material. The electrochemical studies show that the composite possesses good stability with low overpotential and smaller Tafel slope compared to its constituents. It has been found that the MoS2/V2O5 composite exhibits a stable rate performance under the current density of 10�mA�cm?2 which indicates that the MoS2/V2O5 composite might be a good candidate for both oxygen and hydrogen evolution reactions.; Graphical Abstract: [Figure not available: see fulltext.] � 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
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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 Approach for the Fabrication of Au/ZnO Nanoflowers: A Catalytic Aspect
    (American Chemical Society, 2021-03-19T00:00:00) Biswas, Rathindranath; Banerjee, Biplab; Saha, Monochura; Ahmed, Imtiaz; Mete, Shouvik; Patil, Ranjit A.; Ma, Yuan-Ron; Haldar, Krishna Kanta
    An easy, environmentally benign, and biomimetic approach employing Azadirachta indica (neem) leaf extract as a reducing as well as capping agent was used for the fabrication of gold (Au)/zinc oxide (ZnO) hybrid nanoflowers in one pot without utilizing any hazardous chemicals. The different phytoconstituents, for example, nimbolide, azadirachtin, ascorbate, etc., present in A. indica (neem) leaf extract synergistically reduce gold(III) ions to gold(0), which later on acts as an active surface for the growth of zinc oxide (ZnO) via thermal decomposition of sodium zincate [Na2Zn(OH)4]. The development of Au/ZnO hybrid nanoflowers was observed by estimating the absorption maxima at various time intervals in the wake of adding a Au precursor to the aqueous extract. X-ray diffraction (XRD) studies and X-ray photoelectron spectroscopy (XPS) investigation unambiguously confirm the formation of highly crystalline Au/ZnO composed of Au(0) and ZnO. The as-synthesized Au/ZnO hybrid nanoflowers were analyzed utilizing different spectroscopic and microscopic techniques. The transmission electron microscopy (TEM) images clearly show that the synthesized hybrid Au/ZnO nanoflowers are monodisperse and uniform. The fabricated Au/ZnO nanoflowers were used as a catalyst for the efficient reduction of various aromatic nitro compounds to corresponding amino compounds with excellent yield (76-94%) in the presence of reducing agent sodium borohydride. The superior catalytic properties were credited to the extraordinary nanoflower morphology and the synergistic impact of the typified Au nanoparticles. � 2021 American Chemical Society.
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    Green synthesis of hybrid papain/Ni3(PO4)2 rods electrocatalyst for enhanced oxygen evolution reaction
    (Royal Society of Chemistry, 2022-10-21T00:00:00) Ahmed, Imtiaz; Biswas, Rathindranath; Singh, Harjinder; Patil, Ranjit A.; Varshney, Rohit; Patra, Debabrata; Ma, Yuan-Ron; Haldar, Krishna Kanta
    Hydrogen production using electrocatalytic water splitting provides encouraging innovations for enduring and clean energy generation as an option in contrast to traditional energy sources. Improvement in exceptionally dynamic electrocatalysts is of tremendous interest for work on the proficiency of gas generation, which has been emphatically blocked because of the sluggish kinetics of the oxygen evolution reaction (OER). We have synthesized a noble rod-shaped papain/Ni3(PO4)2 catalyst, which was further explored for electrocatalytic OER activity. An environmentally benign approach was applied to prepare binary papain/Ni3(PO4)2 in the presence of papain obtained from green papaya fruit. The yield of Ni3(PO4)2 rod structures could be controlled by varying the amount of papain extract during reaction conditions. The morphology and structural properties of the biogenic papain/Ni3(PO4)2 electrocatalyst were investigated with various microscopic and spectroscopic techniques, for example, FE-SEM, XRD, XPS, and FTIR. To show how such a papain/Ni3(PO4)2 hybrid structure could deliver more remarkable electrocatalytic OER activity, we inspected the correlation between catalytic demonstrations of the papain/Ni3(PO4)2 catalyst and its constituents, and the role of papain on its own was studied during the OER process. A biosynthesised papain/Ni3(PO4)2 catalyst exhibits excellent electrochemical OER performance with the smallest overpotentials of 217 mV, 319 mV and 431 mV in alkaline, neutral and acidic conditions, respectively, at 10 mA cm?2 current density. Transport of ions and electrons is also assisted by the long peptide backbone present in papain, which plays an important role in boosting OER activity. Our results reveal that papain/Ni3(PO4)2 shows better electrocatalytic OER execution along with cyclic stability compared to its different counterparts, owing to synergism-assisted enhancement by several amino acids from papain with metal ions in Ni3(PO4)2 � 2022 The Royal Society of Chemistry.
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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.
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    Rational Design of Bimetallic Au/Cu Nanostructure: An Efficient Catalyst for Methanol Oxidation
    (Wiley-VCH Verlag, 2020-12-04T00:00:00) Biswas, Rathindranath; Singh, Simranjeet; Ahmed, Imtiaz; Patil, Ranjit A.; Ma, Yuan-Ron; Haldar, Krishna Kanta
    We show the design of noble Au/Cu bimetallic nanostructures by a gentle solution process. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis confirm the presence of both Au and Cu in the Au/Cu bimetallic nanostructures. The Au/Cu catalyst was explored as an efficient electrocatalyst for methanol oxidation with a current density of 5.71 mA/cm2 at 0.46 V. � 2020 Wiley-VCH GmbH