Faculty Publications
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Item Mechanistic insights and DFT analysis of bimetal doped styrofoam-like LaFeO3 perovskites with in-built dual redox couples for enhanced Photo-Fenton degradation of Tetracycline(Elsevier B.V., 2024) James, A.; Naik, S.; Rodney, J.D.; Joshi, S.; Udayakumar, U.; Kim, B.C.; Udayashankar, N.K.The rising number of contaminants released into the environment and the inadequacies of traditional wastewater treatment techniques have led to the demand for enhanced oxidation technologies like photo-Fenton. In this study, bimetal co-doped lanthanum orthoferrite (BixLa1-xCuyFe1-yO3 (x = 0, 0.01, 0.05, 0.1; y = 0, 0.01, 0.05, 0.1, 0.15)) based photo-Fenton catalysts with the in-built redox couples Fe3+/Fe2+, Cu2+/Cu+ and oxygen vacancies have been successfully synthesised via a facile one-pot solution combustion route. Systematic studies show that the Bi0.05La0.95Cu0.1Fe0.9O3 (LFOBC) exhibits an optimal photo-Fenton degradation rate of 0.0497/min for Tetracycline (TC) removal, being ∼ 1.8 and ∼ 6.2 times greater than Bi0.05La0.95FeO3 (LFOB) and pristine LaFeO3 (LFO) respectively. DFT analysis confirmed the better adsorption and dissociation of H2O2 on a bimetal co-doped catalyst and identified the electron density difference in LFOBC, which can induce the H2O2 dissociation. A detailed investigation of various influencing reaction parameters is explored. The degradation pathway for the LFOBC catalyst with the toxicological characteristics of each intermediate is analysed. This study presents the Bi0.05La0.95Cu0.1Fe0.9O3 as a potential photocatalyst for enhanced photo-Fenton degradation with excellent efficiency observed for the degradation of various harmful pollutants for environmental remediation. © 2024 Elsevier B.V.Item Peculiarities of Electrical Switching and Phase Transition Dynamics in Bismuth-Infused Se-Te Chalcogenide Glasses: From Bulk to Thin Film Devices(American Chemical Society, 2024) Joshi, S.; Rodney, J.D.; Udayashankar, N.K.Herein, the electrical switching behavior of both bulk and thin film forms of Se86-xTe14Bix (0 ≤ x ≤ 4) chalcogenide glasses was investigated. The melt-quench-derived glasses were found to be amorphous, and the switching behavior exhibited a threshold-type response below a certain current limit (Ith) for bismuth (Bi)-doped bulk samples. Interestingly, as current levels surpassed this threshold, a noteworthy change occurred in the switching behavior, converting it into a memory-type response. The threshold voltage (Vth) exhibited a decreasing trend from ∼228 V to ∼36 V with an increasing Bi content, and differential scanning calorimetry (DSC) was utilized to study the phase transition phenomena and thermal stability of the amorphous glasses. These DSC results unequivocally confirmed that the transition from amorphous to crystalline phase occurred readily and at lower temperatures in the Se82Te14Bi4 composition. Furthermore, annealing studies were carried out to gain insight into the phase transformations that occur when the material makes the transition from an amorphous to a crystalline state. Subsequently, the same melt-quench-derived glasses were deposited as a thin film using physical vapor deposition (PVD) into a three-layered Al/Se-Te-Bi/Al device, and the memory switching voltage experienced a remarkable drop to 2.88 V compared to the bulk material. This exploration sheds light on the captivating electrical switching behavior of Se86-xTe14Bix chalcogenide glasses and holds promise for potential applications spanning the realm of emerging electronics and phase change material (PCM) devices. © 2024 American Chemical Society.Item Growth of octahedral structured AgBiS2 single crystals and its insights on the high performance electrocatalytic hydrogen generation(Elsevier Ltd, 2024) Jauhar, R.O.M.; Ramachandran, K.; Deepapriya, S.; Joshi, S.; Ghfar, A.A.; Rao, L.; Badekai Ramachandra, B.R.; Udayashankar, N.K.; Vadivel, V.; Raji, R.; Kim, B.C.; Rodney, J.D.Given the enormous depletion of fossil fuels and growing environmental concerns, there is an immediate need to develop alternative and clean energy sources. Hydrogen (H2), recognized for its cleanliness and renewability, is poised to meet future energy requirements. Consequently, ongoing research is focused on the development of electro-active, durable, and cost-effective catalysts to replace expensive noble metal-based electrocatalysts. In this study, microscale AgBiS2 chalcogenide derived from a single crystal is reported as promising electrocatalysts for the Hydrogen Evolution Reaction (HER) with a remarkably low overpotential. The physico-chemical characterization of the AgBiS2 catalyst has been investigated using various analytical techniques. The synthesized AgBiS2 catalyst exhibits excellent HER activity, manifesting a low overpotential of 86 mV at a current density of 10 mA cm−2 and a Tafel slope of 44 mV dec−1, along with superior stability even after 24 h in HER at a very high current density. The developed AgBiS2 also showcased stable production when subjected to a two-electrode system. The enhanced alkaline HER activity of AgBiS2 can be attributed to its phase purity, high crystallinity, and the presence of high active sites. The observed high electrochemical performance and stability position AgBiS2 as a potential electrocatalyst for the hydrogen evolution reaction. This finding holds significant promise in the quest for efficient, durable, and economically viable catalysts to drive the shift towards clean and renewable energy sources. © 2024 Hydrogen Energy Publications LLCItem Defect-engineered single crystal Bi2Te3 via Sb and Se doping for enhanced thermoelectric performance(Springer, 2025) Puthran, S.; Hegde, G.S.; Prabhu, A.N.; Wang, Y.-L.; Kuo, Y.K.; Joshi, S.; Udayashankar, N.K.; Nayak, R.The limitation of the single crystal melt growth method to tune the microstructure of the materials in a controlled way and the need for enhancing the thermoelectric properties of single crystal grown Bismuth telluride (Bi2Te3), through defect and microstructural engineering, has motivated this work. In this work, we address this limitation through a controlled doping strategy using antimony (Sb) and selenium (Se) to introduce targeted defects and microstructural modifications within single-crystalline Bi2Te3. Sb and Se substitutions create atomic scale strain, point defects, and micro-grain structures, enhancing phonon scattering without significantly disrupting the crystalline order. The resulting defect-engineered single crystals exhibit improved thermoelectric performance, with a notable reduction in lattice thermal conductivity and retention of excellent electrical properties. The co-doped compositions, Bi2Te2.7Se0.3 and (Bi0.98Sb0.02)2Te2.7Se0.3, exhibited significantly enhanced thermoelectric performance, with Seebeck coefficients reaching ~ 253 ?V/K and ? 211 ?V/K, respectively, over the 10–400 K range. The power factor improved remarkably, showing a ~ 30-fold increase for Bi2Te2.7Se0.3 and ~ 20-fold for the Sb-doped variant, while the figure of merit (ZT) improved by ~ 28.5 and ~ 14 times, respectively. Further, a flexible thermoelectric device fabricated from these optimized materials generated output power of 2.7 nW and 3.35 nW at ambient temperature. The non-monotonic variation of the Seebeck coefficient with Sb content, showing an optimal enhancement at x = 0.04, highlights the delicate balance between carrier concentration and band structure modification, emphasizing moderate Sb substitution achieves the most favorable conditions for thermoelectric performance. Our results present a scalable strategy for bridging the performance gap between pristine single crystals and heavily nanostructured thermoelectrics, opening new avenues for high-efficiency energy harvesting devices. © The Author(s) 2025.Item Optimizing thermoelectric properties of Bi2Te3 via Sb and Se Co-doping: experimental insights and finite elemental simulations using COMSOL(Springer, 2025) Puthran, S.; Prabhu, A.N.; Kamble, M.; Babu, P.D.; Joshi, S.; Udayashankar, N.K.In this study, we investigated the impact of antimony (Sb) and selenium (Se) co-dopants on the thermoelectric properties of bismuth telluride (Bi2Te3). Our findings reveal that Sb doping significantly enhances the electrical conductivity of the material, increasing it by a factor of 2.83 for (Bi0.98Sb0.02)2Te2.7Se0.3, primarily due to an increase in carrier concentration. The electrical resistivity of pristine Bi2Te3 at 300 K is 2.79 × 10?4 ?·m, which decreases substantially to 0.006 × 10?4 ?·m at 303 K with Sb doping at x = 0.02. Additionally, (Bi0.96Sb0.04)2Te2.7Se0.3 composition achieves the highest power factor of 9.744 × 10?5 W/m·K2 at 300 K, a 3-times improvement over the pristine Bi2Te3 (3.143 × 10?5 W/m·K2). The ZT value of Bi2Te2.7Se0.3 is 3.5 times higher than that of the pristine material at 350 K. COMSOL simulations support the experimental findings, revealing a maximum temperature gradient of 35 °C (hot end: 20 °C, cold end: ? 15 °C) for the (Bi0.98Sb0.02)2Te2.7Se0.3 module with comparable p-type and n-type parameters. The increased temperature gradient in the COMSOL simulation correlates with the improved thermoelectric performance observed experimentally, indicating that co-doping Bi2Te3 with Sb and Se effectively enhances its thermoelectric properties. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.