Department Of Physics
Permanent URI for this communityhttps://kr.cup.edu.in/handle/32116/57
Browse
5 results
Search Results
Item Hydrogen-impurity-induced unconventional magnetism in semiconducting molybdenum ditelluride(American Physical Society, 2023-04-28T00:00:00) Krieger, Jonas A.; Tay, Daniel; Rusinov, Igor P.; Barua, Sourabh; Biswas, Pabitra K.; Korosec, Lukas; Prokscha, Thomas; Schmitt, Thorsten; Schr�ter, Niels B. M.; Shang, Tian; Shiroka, Toni; Suter, Andreas; Balakrishnan, Geetha; Chulkov, Evgueni V.; Strocov, Vladimir N.; Salman, ZaherLayered transition-metal dichalcogenides are proposed as building blocks for van der Waals heterostructures due to their graphenelike two-dimensional structure. For this purpose, a magnetic semiconductor could represent an invaluable component for various spintronics and topotronics devices. Here, we combine different local magnetic probe spectroscopies with angle-resolved photoemission and density-functional theory calculations to show that 2H-MoTe2 is on the verge of becoming magnetic. Our results present clear evidence that the magnetism can be "switched on"by a hydrogenlike impurity. We also show that this magnetic state survives up to the free surface region, demonstrating the material's potential applicability as a magnetic component for thin-film heterostructures. � 2023 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Item 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 KantaUnraveling 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.Item Janus ?-Te2X (X = S, Se) monolayers for efficient excitonic solar cells and photocatalytic water splitting(Royal Society of Chemistry, 2023-01-04T00:00:00) Singh, Jaspreet; Kumar, AshokHighly efficient, environmentally friendly and renewable sources of energy are of great need today to combat increasing energy demands and environmental pollution. In this work, we have investigated the novel 2D allotropes, i.e., ?-Te2X (X = S, Se), using first-principles calculations and study their potential applications in light harvesting devices. Both the monolayers possess high stability and semiconducting nature with an indirect band gap. The high carrier mobilities and excellent optical absorption of these monolayers make them potential candidates for solar conversion applications. We have proposed the type-II heterojunction solar cells and calculated their power conversion efficiencies (PCEs). The small conduction band offset and appropriate band gap of donor material in the case of ?-Te2S(S-Side)/?-Te2S(Te-Side) heterojunction results in a PCE of ?21%. In addition, the band alignments of these monolayers properly engulf the redox potentials of water. The overpotentials required to trigger hydrogen reduction (HER) and water oxidation (OER) half reactions reveal that HER and OER preferred acidic and neutral media, respectively. The calculated solar-to-hydrogen (STH) efficiencies of ?-Te2S (?-Te2Se) monolayers turn out to be ?13% (?12%), respectively, which implies their practical applications in water splitting. Thus, our work provides strong evidence regarding the potential applications of these materials in the field of light harvesting devices. � 2023 The Royal Society of Chemistry.Item Two-dimensional ?-PdX2 (X = S, Te) monolayers for efficient solar energy conversion applications(Royal Society of Chemistry, 2022-02-09T00:00:00) Jakhar, Mukesh; Kumar, AshokThe search for highly effective and environmentally safe photocatalysts for water splitting and photovoltaic solar cells is essential for renewable solar energy conversion and storage. Based on first-principle calculations, we show that novel 2D ?-PdX2 (X = S, Te) monolayer possesses excellent stability and great potential in solar energy conversion applications. Comprehensive studies show that the ?-PdS2 monolayer exhibits semiconductor characteristics with an indirect gap, suitable band alignment, efficient carrier separation, and high solar to hydrogen (STH) efficiency, supporting its good photoelectronic performance. The surface catalytic and adsorption/intercalation energy calculation reveals that the photogenerated electrons have adequate driving forces to render hydrogen reduction half-reactions to proceed spontaneously and the ability to cover and incorporate water molecules on the ?-PdS2 monolayer. Besides, the ?-PdTe2 monolayer is a promising donor material for excitonic solar cells with high photovoltaic performance. More importantly, due to suitable donor band gap and small conduction band offset in the proposed type-II heterostructure, the power conversion efficiencies (PCE) were calculated up to ?23% (?-PdTe2/WTe2), ?21% (?-PdTe2/MoTe2) and ?18% (?-PdTe2/?-PdS2), making it a promising candidate for solar energy conversion applications. � 2022 The Royal Society of ChemistryItem 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, MichaelThe 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