Department Of Chemistry

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Author: search.filters.author.Ahmed, ImtiazSubject: search.filters.subject.Electrocatalytic

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    Bifunctional electrochemical OER and HER activity of Ta2O5 nanoparticles over Fe2O3 nanoparticles
    (Royal Society of Chemistry, 2023-08-23T00:00:00) Ahmed, Imtiaz; Burman, Vishal; Biswas, Rathindranath; Roy, Ayan; Sharma, Rohit; Haldar, Krishna Kanta
    Hydrogen production via electrocatalytic water splitting offers encouraging innovations for sustainable and clean energy production as an alternative to conventional energy sources. The improvement of extraordinarily dynamic electrocatalysts is of great interest for work on the performance of gas generation, which is firmly blocked due to the sluggish kinetics of the oxygen evolution reaction (OER). The development of highly efficient base metal catalysts for electrochemical hydrogen and oxygen evolution reactions (HER and OER) is a challenging and promising task. In the present work, a particle over particles of Fe2O3 and Ta2O5 was successfully produced by hydrothermal treatment. The prepared composite shows promising catalytic performance when used as an electrochemical catalyst for OER and HER in alkaline and acidic electrolytes with low overpotentials of 231 and 201 mV at 10 mV cm?2, small Tafel slopes of 71 and 135 mV dec?1, respectively, and good stability properties. The calculated electrochemical surface area (ECSA) for composites is five times higher than that of the original oxides. The result of the OER is significantly better than that of commercial IrO2 catalysts and offers a promising direction for the development of water-splitting catalysts. � 2023 The Royal Society of Chemistry.
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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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    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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    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.