Faculty Publications
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Item Ultralow Lattice Thermal Conductivity and Enhanced Mechanical Properties of Cu and Sb Co-Doped SnTe Thermoelectric Material with a Complex Microstructure Evolution(American Chemical Society, 2022) Kihoi, S.K.; Shenoy, U.S.; Kahiu, J.N.; Kim, H.; Bhat, D.K.; Lee, H.S.SnTe is an exceptionally promising eco-friendly thermoelectric material that continues to draw immense interest as a source of alternative energy recovered from waste heat energy. Here, we investigate the effect of introducing Cu as a single doping element rather than phase separated in SnTe followed by Sb co-doping to tune the lattice thermal conductivity. A microstructure evolution was observed which influences the thermoelectric performance of these SnTe-based materials. An overall power factor of ∼22 μW/cmK2 and an ultralow lattice thermal conductivity of 0.39 W/mK are reported. A maximum ZT of 0.86 is also reported with an all-time record high hardness value of 165 Hv among SnTe-based thermoelectric materials. Through DFT calculations, we show that Cu opens the band gap of SnTe, whereas Sb in the presence of Cu introduces resonance levels and causes band convergence. This kind of enhanced thermoelectric performance is paramount for the application of SnTe in recovery of heat into useful electrical energy. © 2022 American Chemical SocietyItem Doped BaTiO3 cuboctahedral nanoparticles: Role of copper in photocatalytic degradation of dyes(Elsevier B.V., 2023) Uma, P.I.; Shenoy, U.S.; Bhat, D.K.The discovery of perovskite oxides as photocatalysts has opened unique possibilities for the degradation of pollutants such as dyes. In this work, we carry out both theoretical and experimental study for the design and preparation of copper doped BaTiO3. To begin with, First principles electronic structure calculations revealed the presence of additional levels at the top of the valence band after doping copper, which considerably decreased the band gap making the oxide visible light active. Later, single pot synthesis of copper doped BaTiO3 led to production of a material which was photocatalytically active in degrading both cationic and anionic dyes. From our work, we found that the photocatalyst 0.5 CuBTO decomposed 98.2% of methylene blue dye in 120 min and 99.4% of rose bengal dye within 45 min. Such high efficiency was attributed to the high surface area, appropriate band gap and low recombination rate of the charge carriers. © 2023Item Electronic structure engineering of BaTiO3 cuboctahedrons by doping copper to enhance the photocatalytic activity for environmental remediation(Elsevier Ltd, 2023) Uma, P.I.; Shenoy, U.S.; Bhat, D.K.The advent of perovskites as an efficient photocatalyst has paved the way to newer possibilities in the degradation of contaminants such as dyes and toxic heavy metal ions. The alleged poor photocatalyst BaTiO3 was engineered to perform better by decreasing its bandgap to make it visible light active via doping. The high-risk factor in the reduction of the bandgap is the formation of recombination centers for the charge carriers which decreases the efficiency of the photocatalyst. Herein, we studied the electronic structure tuning of BaTiO3 by doping copper and developed a one pot synthesis method to obtain copper doped BaTiO3 that has a high surface area, lower recombination rate, and higher photocatalytic efficiency towards dye degradation and hexavalent chromium ion reduction. The 0.5 CuBT sample had a photocatalytic efficiency of 99.4 % for methyl violet decomposition within 120 min and 99.8 % for hexavalent chromium ion reduction by fructose in 20 min. © 2023 Elsevier B.V.Item Towards achieving an ideal convergence of light and heavy electron conduction bands in SnTe: Insights into copper doping(Elsevier B.V., 2024) Shenoy, U.S.; Bhat, D.K.In recent years, tin telluride has garnered significant attention in the field of thermoelectrics, offering a promising avenue for sustainable ecofriendly conversion of waste heat into electricity. The unique electronic structure of this material makes it a compelling candidate for exploring innovative strategies to enhance its transport properties by employing substitutional doping. Among myriad elements doped, copper has been considered an intriguing candidate due to its ability to lower the thermal conductivity. However, its impact on the electronic structure has not been thoroughly explored till date. Herein, we investigate a nuanced aspect of copper doping, specifically focusing on its impact on tuning the electronic structure of SnTe. Significantly, our findings reveal a novel dimension to copper doping, showcasing its potential to enhance n-type performance in SnTe through the near-perfect convergence of its conduction bands - a feature not observed when doped in GeTe. We also shed the light on improvement of the p-type performance by means of valence band convergence and increased band gap. Furthermore, we reveal that copper doping allows the contribution of low-lying bands in SnTe to participate in transport, ensuring a higher Seebeck coefficient across the entire temperature range. Overall, this work provides a panoramic view of role of copper in improving the Seebeck co-efficient of SnTe making it a potential lead-free material for several thermoelectric applications. © 2024 Elsevier B.V.Item Exceptional light harvesting in copper doped CaTiO3 nanocuboids with surface nanosteps for the photo remediation of toxic Cr(VI) ions and dyes(Elsevier B.V., 2024) Bhat, D.K.; Uma, P.I.; Shenoy, U.S.Addressing the rising concerns of water pollution caused by harmful inorganic and organic contaminants is very crucial and photocatalysts with exceptional light harvesting capability are a promising way to tackle these issues. This study investigates the transformation of CaTiO3 into a visible light-active photocatalyst via copper doping. Copper-doped CaTiO3 nanocuboids were synthesized via a one-step solvothermal approach, resulting in the formation of distinctive nanostep substructures on the surface. Morphological analysis revealed the successful incorporation of copper ions into the perovskite matrix, as evidenced by the transition from smooth to rough, uneven surface features. X-ray diffraction confirmed the incorporation of Cu2+ ions into the Ti4+ site, while visible range absorption indicated a reduction in the bandgap. Furthermore, doping decreased the rate of charge carrier recombination and increased their average lifetime, prolonging the duration of active species. This modification facilitating efficient absorption of visible light and increase in the charge separation, leads to enhanced photocatalytic activity. The doped catalyst exhibited exceptional performance in the remediation of hexavalent chromium ions (98.5 % Cr6+ ions reduction to Cr3+ ions in 20 min), methylene blue (99.4 % degradation within 120 min), and eosin yellow (99.8 % degradation within 80 min) pollutants. This research underscores the potential of doping as a viable strategy for tailoring photocatalytic properties and addressing water pollution challenges. © 2024 Elsevier B.V.