Faculty Publications
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Item Calcium copper titanate a perovskite oxide structure: effect of fabrication techniques and doping on electrical properties—a review(Springer, 2022) Infantiya, S.G.; Aslinjensipriya, A.; Reena, R.S.; Deepapriya, S.; Rodney, J.D.; Jerome das, S.J.; Justin Raj, C.J.The discovery of innovative multifunctional ceramics is an important topic in the recent field of research and development. Perovskite oxide ceramics exhibit a wide range of multifunctional characteristics, such as ferromagnetism, ferro-, piezo-, and pyro-electricity and nonlinear dielectric properties. These characteristics are significant for use in environmental remediation, sensors, filters, energy conversion, and storage, corrosion-resistance coatings, aerospace industries, separators, detectors, antennas, etc. The calcium copper titanate (CCTO) with colossal dielectric constant with low dielectric loss tangent, and its isomorphs have piqued the interest of the development of advanced capacitor materials for electronic industries. CaCu3Ti4O12 (CCTO) exhibits the most extraordinary characteristic, with a dielectric permittivity at 1 kHz of ~ 104 that is essentially constant from ambient temperature to 300 °C. The substitution of metal cations/anions is an effective strategy to enhance the properties of the CCTO ceramics and extend their applications. In this review, we systematically examined the advancements of CCTO ceramics, including their structural morphology, tolerance factor, extrinsic/intrinsic mechanisms, different synthesis techniques, sintering techniques, and the effect of single doping as well as the co-doping mechanism for the enhancement of the dielectric and electrical properties. A series of CCTO-based ceramics have been summarized and explained their mechanisms and electrical properties. We anticipate that our study will help as an overview and motivate other researchers to continue working on the fabrication of CCTO or other electro-ceramics in the upcoming years. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Item Boosting overall electrochemical water splitting via rare earth doped cupric oxide nanoparticles obtained by co-precipitation technique(Elsevier Ltd, 2022) Rodney, J.D.; Deepapriya, S.; Jerome das, S.J.; Robinson, M.C.; Perumal, S.; Sadhana, S.; Periyasamy, P.; Jung, H.; Justin Raj, C.J.The development of electrocatalyst based on nonprecious metals has been a persistent issue as electrochemical water splitting requires electrocatalyst with advanced activity and stability. Further, the electrocatalyst must require low overpotential above the standard potential (>1.23 V) of water splitting to produce hydrogen. This study presents the facile co-precipitation derived rare earth dysprosium (Dy) doped cupric oxide nanoparticles (Cu1−xDyxO) as a non-noble transition metal oxide nanoparticle. The 3 % Dy doped CuO (3 % Dy/CuO) and 1 % Dy doped CuO (1 % Dy/CuO) electrocatalysts showed excellent Oxygen Evolution Reaction (OER) at 1.55 V vs RHE and Hydrogen Evolution Reaction (HER) at − 0.036 V vs RHE in aqueous 1 M KOH aqueous electrolyte to attain the benchmark current density (10 mA cm−2). The stability of the driven electrocatalyst in a bi-functional electrocatalytic setup was monitored for 24 h and was found to be exhibiting a cell voltage of about 2.1 V at 30 mA cm−2 constant current density. Further, the retention capability of the electrode was observed to be 99 % with a very minimal loss. This study hugely suggests the promising consequence of doping rare earth onto a non-precious metal oxide-based electrocatalyst, making it a highly effective bifunctional material for water splitting. © 2022 Elsevier B.V.Item A novel effective immobilization of glucose oxidase on Ni0.25Zn0.25Cu0.25Co0.25La0.06Fe1.94O4 – Chitosan nanocomposite as an enzymatic glucose biosensor(Elsevier B.V., 2023) Deepapriya, S.; Rodney, J.D.; John, J.; Joshi, S.; Udayashankar, N.K.; Lakshmi Devi, S.; Jerome das, S.An effectual enzymatic glucose biosensor has drawn significant attention in the natural world due to its continuous glucose monitoring systems on human beings. A need for accurate and dependable glucose biosensors is needed and has notably augmented the keen interest to synthesize new non-invasive glucose monitoring systems in the recent phase. A novel Ni0.25Zn0.25Cu0.25Co0.25La0.06Fe1.94O4 nanocomposite has been synthesized via the combustion method to develop an appreciable glucose biosensor. The glucose biosensor was fabricated by immobilization of glucose oxidase (GOx) onto chitosan (CH)-Ni0.25Zn0.25Cu0.25Co0.25La0.06Fe1.94O4 heterojunction nanocomposite on FTO glass substrate. The performance of the as-prepared enzymatic glucose biosensor was estimated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical studies revealed an enhanced diffusion of molecules on the electrode surface, superior charge transfer rate, high sensitivity, and fast response time. The Ni0.25Zn0.25Cu0.25Co0.25La0.06Fe1.94O4-CH bi-junction conjoining with GOx exhibits a higher sensitivity of 52.76 µAmM-1cm−2 in a comprehensive undeviating range. The catalytic properties of the electrode in the H2O2 solution were studied using cyclic voltammetry, which showed a good linear response with an increase in scan rate and peak current resulting in enriched electrostatic interaction. In addition, the fabricated biosensor with a low Michaelis-Menten constant contributes a better affinity of the electrode surface towards glucose oxide. © 2023 Elsevier B.V.Item Structural, dielectric and impedance functionalities of La0.01Cu0.99O nanocrystals(Springer, 2023) Deepapriya, S.; Rodney, J.D.; Udayashankar, N.K.The necessity for materials designed with high and low-K dielectric constant having unique thermal stability has been a prime factor for the continuous development of the microelectronics-based industries. To address this issue, pure and 1% lanthanum (La) substituted copper oxide (CuO) nanoparticles were synthesized through an eco-friendly and time effective co-precipitation route for new unanticipated facts. The thermal effisivity of the material was determined by means of photoacoustic spectroscopy (PAS). The dielectric analysis of the monoclinic structured pure and La doped CuO nanoparticles in the frequency range of 1 Hz–1 MHz for various temperatures was noted, Dielectric constant and loss factor had a declining trend with surge in applied frequency and turned out to be independent of frequency at higher frequencies. The AC conductivity observed has confirmed the semi-conducting nature of the nanoparticle and obeyed Jonscher’s universal law. The temperature-dependant electric relaxation process was revealed using complex impedance spectroscopic studies suggesting non-Debye type behaviour of the material. The electrical activity of the nanoparticles is established for the circuit model devised from the calculated relaxation time constant. The impact of the thermal property and the hopping mechanism in the material with indices of interest is confirmed from the electric modulus. The obtained impedance spectra indicate the effect of lanthanum on the grain boundaries and the higher basicity and electropositive nature of lanthanum on the dielectric relaxation process. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.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 Electrocatalytic synergies of melt-quenched Ni-Sn-Se-Te nanoalloy for direct seawater electrolysis(Elsevier B.V., 2024) Rodney, J.D.; Joshi, S.; Ray, S.; Rao, L.; Deepapriya, S.; Carva, K.; Badekai Ramachandra, B.R.; Udayashankar, N.K.; Perumal, S.; Sadhana, S.; Justin Raj, C.J.; Kim, B.C.The study focuses on the development of binary nanoalloys based on metal dichalcogenides (Sn30Se70, Ni30Te70) and quaternary nanoalloy (Ni15Sn15Se35Te35) using the melt quenching technique. The nanoalloys show extensive water splitting in fresh and real seawater. Sn30Se70-coated nickel foam achieved a benchmark current density of 349 mV for the oxygen evolution reaction (OER), while Ni15Sn15Se35Te35-coated nickel foam (NF) required only 185 mV for the hydrogen evolution reaction (HER) in 1 M KOH. The study also shows that a two-electrode system can achieve sustained total water splitting at higher current densities (1 A.cm?2). Modification with a CuSx layer over NF at the OER end facilitated faster kinetics and mitigated chlorine corrosion enabling direct seawater splitting at 1.26 V. Continuous direct splitting of seawater at 100 mA cm?2 for 120 h required only 1.88 V, showing an efficiency of 92.9 % for H2 production in real seawater. © 2024 Elsevier B.V.Item Sustained hydrogen production through alkaline water electrolysis using Bridgman–Stockbarger derived indium-impregnated copper chromium selenospinel(Elsevier Ltd, 2024) Jauhar, R.M.; Raji, R.; Deepapriya, S.; Raja, A.; Rao, L.; Joshi, S.; Era, P.; Badekai Ramachandra, B.R.; Udayashankar, N.K.; Vadivel, V.; Mangalaraja, R.V.; J, J.; Ghfar, A.A.; Senthilpandian, M.; Kim, B.C.; Rodney, J.D.The depletion of conventional fossil fuels necessitates the development of sustainable energy alternatives, with electrochemical water splitting for hydrogen (H2) production being a promising solution. However, large-scale hydrogen generation is hindered by the scarcity of cost-effective electrocatalysts to replace noble metals such as Pt and RuO2 in the Oxygen Evolution Reaction (OER) and Hydrogen Evolution Reaction (HER). In this study, we report the synthesis of CuCr2-xInxSe4 (x = 0, 0.2, 0.4) using a dual approach combining the Bridgman-Stockbarger method and ball milling. Among the synthesized materials, CuCr1.8In0.2Se4 demonstrates outstanding HER activity in 1.0 M KOH, achieving a potential of ?0.16 V vs. RHE at a current density of 10 mA cm?2. Moreover, the material shows remarkable durability during a three-electrode accelerated degradation test in an alkaline medium, maintaining its performance over 24 h at a constant current density of ?200 mA cm?2, with a stable potential of ?0.57 V vs. RHE. Additionally, CuCr1.8In0.2Se4 was tested in a two-electrode configuration alongside CoFe LDH, achieving a benchmark of 1.7 V for overall water splitting. It sustained a current density of 400 mA cm?2 for 24 h in an accelerated degradation test, exhibiting a minimal loss of 0.1 V after the testing period. These results highlight CuCr1.8In0.2Se4 as a promising non-noble metal catalyst for HER, demonstrating its potential to reduce reliance on noble materials for large-scale hydrogen production. © 2024 Hydrogen Energy Publications LLC