School Of Basic And Applied Sciences

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Author: search.filters.author.Mondal, KrishnakantaSubject: search.filters.subject.Hydrogen

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    Unraveling the Role of Orbital Interaction in the Electrochemical HER of the Trimetallic AgAuCu Nanobowl Catalyst
    (American Chemical Society, 2023-03-24T00:00:00) Biswas, Rathindranath; Dastider, Saptarshi Ghosh; Ahmed, Imtiaz; Barua, Sourabh; Mondal, Krishnakanta; Haldar, Krishna Kanta
    Unraveling the origins of the electrocatalytic activity of composite nanomaterials is crucial but inherently challenging. Here, we present a comprehensive investigation of the influence of different orbitals� interaction in the AuAgCu nanobowl model electrocatalyst during the hydrogen evolution reaction (HER). According to our theoretical study, AgAuCu exhibits a lower energy barrier than AgAu and AgCu bimetallic systems for the HER, suggesting that the trimetallic AgAuCu system interacts optimally with H*, resulting in the most efficient HER catalyst. As we delve deeper into the HER activity of AgAuCu, it was observed that the presence of Cu allows Au to adsorb the H* intermediate through the hybridization of s orbitals of hydrogen and s, dx2-y2, and dz2 orbitals of Au. Such orbital interaction was not present in the cases of AgAu and AgCu bimetallic systems, and as a result, these bimetallic systems exhibit lower HER activities. � 2023 American Chemical Society.
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    Ab Initio Modeling of the ZnO-Cu(111) Interface
    (American Chemical Society, 2021-12-31T00:00:00) Mondal, Krishnakanta; Megha; Banerjee, Arup; Fortunelli, Alessandro; Walter, Michael; Moseler, Michael
    The morphology at the catalytically active interfacial site of ZnO/Cu in the commercial ZnO/Cu/Al2O3 catalyst for CO2 hydrogenation to methanol is still an open question. In the present study, we employ ab initio density functional theory based methods to gain insight into the structure of the ZnO-Cu interface by investigating the morphology of supported ZnO nano-ribbons at the interface with the Cu(111) surface in the presence of hydrogen and water molecules. We find that the stabilities of free-standing ZnO nano-ribbons get enhanced when they are supported on the Cu(111) surface. These supported nano-ribbons are further stabilized by the adsorption of hydrogen atoms on the top of O atoms of the nano-ribbons. Interestingly, the hydrogenated nano-ribbons are found to be equally stable and they appear to be an array of independent chains of ZnOH motifs, suggesting that the hydrogenated nano-ribbons are structurally fluxional. The edge of these fluxional nano-ribbons is stabilized via a triangular reconstruction with a basic composition of Zn6O7H7 in the presence of water molecules. Such a triangular structure gets further stabilized when it is attached to a bulk-like part of the ZnO/Cu(111) system. Furthermore, we find that the triangular reconstruction is energetically favorable even at the methanol synthesis conditions. Therefore, we propose that, under methanol synthesis conditions, the motif Zn6O7H7 represents a stable form at the interface between the bulk-like part of ZnO and the Cu(111) surface in the ZnO/Cu/Al2O3 based commercial catalyst. � 2021 American Chemical Society
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    Bio-assisted Synthesis of Au/Rh Nanostructure Electrocatalysts for Hydrogen Evolution and Methanol Oxidation Reactions: Composition Matters!
    (American Chemical Society, 2023-08-11T00:00:00) Biswas, Rathindranath; Dastider, Saptarshi Ghosh; Ahmed, Imtiaz; Biswas, Sayani; Mondal, Krishnakanta; Haldar, Krishna Kanta
    In the field of catalysis, bimetallic nanostructures have attracted much interest. Here, we discuss the effect of Au/Rh bimetallic composition-tuned nanostructure and electrocatalytic activity. A simple bio-assisted technique was used to fabricate multiple Au:Rh nanoplate ratios (25:75, 50:50, and 75:25). XRD and XPS studies show that both Au and Rh phases coexist in a bimetallic nanostructure, and electron microscopy confirms the formation of a triangle-shaped nanoplate. Au0.25Rh0.75 exhibited the maximum catalytic activity and good stability for hydrogen evolution reaction (HER) with an overpotential of 105 mV at a current density of 10 mA/cm2. On the other hand, Au0.50Rh0.50 exhibits a higher activity for methanol oxidation reaction (MOR) compared to the other compositions. Theoretical studies indicate that the electrocatalytic enhancement obtained for both HER and MOR relies on electronic modification effects of the surface, with the overall reaction energy profile being optimized due to Au/Rh d-band mixing. � 2023 American Chemical Society.
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    Dithiophosphonate Anchored Heterometallic (Ag(I)/Fe(II)) Molecular Catalysts for Electrochemical Hydrogen Evolution Reaction
    (American Chemical Society, 2022-08-12T00:00:00) Jangid, Dilip Kumar; Dastider, Saptarshi G.; Biswas, Rathindranath; Khirid, Samreet; Meena, Sangeeta; Kumar, Pankaj; Sahoo, Subash C.; Verma, Ved Prakash; Makde, Ravindra D.; Kumar, Ashwani; Jangir, Ravindra; Mondal, Krishnakanta; Haldar, Krishna Kanta; Dhayal, Rajendra S.
    The dichalcogenide ligated molecules in catalysis to produce molecular hydrogen through electroreduction of water are rarely explored. Here, a series of heterometallic [Ag4(S2PFc(OR)4] [where Fc = Fe(?5-C5H4)(?5-C5H5), R = Me, 1; Et, 2; nPr, 3; isoAmyl, 4] clusters were synthesized and characterized by IR, absorption spectroscopy, NMR (1H, 31P), and electrospray ionization mass spectrometry. The molecular structures of 1, 2, and 3 clusters were established by single-crystal X-ray crystallographic analysis. The structural elucidation shows that each triangular face of a tetrahedral silver(I) core is capped by a ferrocenyl dithiophosphonate ligand in a trimetallic triconnective (?3 ?2, ?1) pattern. A comparative electrocatalytic hydrogen evolution reaction of 1-5 (R = iPr, 5) was studied in order to demonstrate the potential of these clusters in water splitting activity. The experimental results reveal that catalytic performance decreases with increases in the length of the carbon chain and branching within the alkoxy (-OR) group of these clusters. Catalytic durability was found effective even after 8 h of a chronoamperometric stability test along with 1500 cycles of linear sweep voltammetry performance, and only 15 mV overpotential was increased at 5 mA/cm2 current density for cluster 1. A catalytic mechanism was proposed by applying density functional theory (DFT) on clusters 1 and 2 as a representative. Here, a ?1 coordinated S-site between Ag4 core and ligand was found a reaction center. The experimental results are also in good accordance with the DFT analysis. � 2022 American Chemical Society.