Browsing by Author "Rodney, J.D."

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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.
Bi-functional LaMxFe1-xO3 (M = Cu, Co, Ni) for photo-fenton degradation of methylene blue and photoelectrochemical water splitting
(Elsevier Ltd, 2023) James, A.; Rodney, J.D.; Rao, L.; Badekai Ramachandra, B.R.; Udayashankar, N.K.
Due to growing concern over environmental remediation and the energy crisis, perovskite nanoparticles have gained wide interest in converting solar energy to sustainable fuel and also in degrading organic effluents. Herein, we report the synthesis and bi-functional activity of one-pot-glycine combustion derived LaMxFe1-xO3 (M = Cu, Co, Ni; x = 0, 0.01) for photo-Fenton degradation of Methylene Blue (MB) and photoelectrochemical water splitting. When used as a photocatalyst, with partial substitution of Cu even at a lower concentration, LaCu0.01Fe0.99O3 has exhibited excellent degradation efficiency of 96.4% in 90 min, which is 2.5 times better than the LaFeO3. On the other hand, Co and Ni modified LaFeO3 photocatalysts have demonstrated prominent activities with degradation efficiency of 93.8% and 74.8% respectively within 180 min of visible light irradiation. The retention and reusability analysis showed that LaCu0.01Fe0.99O3 is stable against photo corrosion and remains unchanged after 5 consecutive cycles of MB dye degradation. In addition, LaCu0.01Fe0.99O3 is complimented as a single catalyst for dual functions such as photocatalysis and electrocatalysis, both of which are assisted by visible light. Under illumination, the overpotential (η) improved from 507.6 mV vs RHE (dark) to 498.1 mV vs RHE (light) for O2 evolution and 220.5 mV vs RHE (dark) to 182.8 mV vs RHE (light) for H2 generation respectively. The light response of the catalyst and improvement in activity is validated by the significant enhancement in current density under exposure at both half cycle of chronoamperometry. © 2023 Hydrogen Energy Publications LLC
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.
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.
Cerium-Modulated Zinc Oxide for enhanced Photoelectrochemical Non-Enzymatic biosensing of Cholesterol: An experimental and First Principle Analysis
(Elsevier B.V., 2024) Rao, L.; Rodney, J.D.; Joy, A.; Shivangi Nileshbhai, C.; James, A.; S, S.; Joyline Mascarenhas, F.; Udayashankar, N.K.; Anjukandi, P.; Chul Kim, B.; Badekai Ramachandra, B.R.
Herein, we synthesized CexZn1-xO (x = 0.00, 0.01, 0.02, and 0.03) using the wet chemical method. The investigation explores photoelectrochemical (PEC) biosensors for enzyme-free detection of cholesterol, employing Ce0.03Zn0.97O (CZO3)/Nickel Foam (NF) as the active material. The investigation revealed notable enhancements in sensitivity for cholesterol detection, with a recorded activity of 2.812 mA.mM?1.cm?2, marking a twofold increase in comparison to dark mode (1.37 mA.mM?1.cm?2). The Limit of Detection (LOD) was determined to be 17 µM (light) and 28 µM (dark), while the Limit of Quantification (LOQ) was measured at 54 µM (light) and 98 µM (dark) in 0.1 M KOH solution. These findings demonstrate a linear detection range spanning from 80 µM to 2 mM. Ab-initio calculations based on Density Functional Theory (DFT) were carried out on 101 surfaces of both pristine ZnO and CZO3 to understand how the doping affected the pristine ZnO band gap. The findings indicate that CZO3 exhibits superior activity compared to pristine ZnO, underscoring its enhanced performance and potential for sensing application. The CZO3/NF photoelectrochemical (PEC) biosensor displayed notable cyclic stability, retaining 97 % of its performance over a 60-day period. This underscores its potential for reliable and enduring operation in biosensing applications. Additionally, CZO3/NF exhibited robust sensing capabilities when utilized with human serum samples, showcasing consistent performance in both dark and illuminated conditions. © 2024 Elsevier B.V.
Cobalt-doped LaFeO3 for photo-Fenton degradation of organic pollutants and visible-light-assisted water splitting
(Springer, 2024) James, A.; Rodney, J.D.; Manojbabu, A.; Joshi, S.; Rao, L.; Badekai Ramachandra, B.R.; Udayashankar, N.K.
The increasing demand for clean energy sources and the growing concerns about environmental pollution have led to a significant interest in developing efficient photocatalytic and photoelectrochemical systems. Here, we report the visible-light-induced photo-Fenton catalytic degradation of Methylene Blue (MB) dye over LaFeO3 and LaCo xFe1−xO3 (x = 0.01, 0.05, 0.1) catalysts synthesized via the facile combustion method. The LaCo0.01Fe0.99O3 has significantly enhanced the photo-Fenton catalytic efficiency of LaFeO3 from 67.75 to 93.85% for MB dye removal after 180 min of light irradiation. The rate constants calculated via the pseudo-first-order kinetics mechanism are found to be 0.00532/min for LaFeO3 and 0.01476/min for LaCo0.01Fe0.99O3, respectively. In addition, the most effective LaCo0.01Fe0.99O3 catalyst has demonstrated remarkable degradation performance towards Tetracycline (TC) and Methyl Orange (MO) dye with an efficacy of 93.81% and 69.67%, respectively, indicating its versatility. Further, the pristine and doped LaFeO3 were structurally optimized using DFT, and the computed band gaps were following the experimental data. Interestingly, the same catalyst can be employed as a light-induced electrocatalyst in addition to water treatment by taking advantage of its dual functionality. The LaCo0.01Fe0.99O3 catalyst achieved a benchmark current density of 10 mA/cm2 for H2 evolution at an overpotential of 297 mV vs. RHE which further improved to 190 mV vs. RHE under illumination. This work provides valuable insights on partial Co incorporation at the B-site of LaFeO3 for the development of visible-light-induced photocatalytic and electrocatalytic systems, which is hoped to contribute to the advancement of sustainable energy production and environmental remediation. © 2024, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Combustion-derived BaNiO3 nanoparticles as a potential bifunctional electrocatalyst for overall water splitting
(Elsevier Ltd, 2023) J, J.; Jayalakshmi, D.; Rodney, J.D.
Electrochemical water electrolyser though an assuring solution for clean hydrogen production, the sluggish kinetics and high cost of existing precious metal electrocatalyst remains a barrier to its effective utilization. Herein, solution combustion route derived perovskite type barium nickelate (BaNiO3) nanoparticles were developed and studied for their bifunctional electrocatalytic properties towards overall water splitting. The unannealed BaNiO3 nanoparticles exhibited the highest OER and HER activity with overpotentials 253 mV and 427 mV respectively to attain 10 mAcm−2 in 1.0 M KOH. Using unannealed BaNiO3 as a bifunctional electrocatalyst in a two-electrode alkaline electrolyser, the cell was able to achieve the benchmark current density at a low cell voltage of 1.82 V. Impressively the setup's electrocatalytic performance improved 4.9% after continuous overall water splitting for 24 h at 30 mAcm−2. Therefore, BaNiO3 nanoparticles can be a low-cost and efficient alternative for noble metal electrocatalysts for clean H2 production. © 2022 Hydrogen Energy Publications LLC
Cu- and Bi-codoped LaFeO3-Decorated MXene Nanosheets for Photo-Fenton Catalysis and Hydrogen Evolution
(American Chemical Society, 2025) James, A.; Ray, S.; Rodney, J.D.; Carva, K.; Udayashankar, N.K.; Kim, B.C.
The increasing release of contaminants into the environment and the demand for sustainable energy solutions have prompted the exploration of advanced oxidation methods such as photo-Fenton and photoelectrochemical water splitting. Herein, hierarchical heterostructures of Cu- and Bi-codoped LaFeO3(Bi0.05La0.95Cu0.1Fe0.9O3) (LFOBC)-decorated Ti3C2(MXene) nanosheets were developed by a low-cost one-pot combustion approach. The optimized LFOBC/Mx-7 (Bi0.05La0.95Cu0.1Fe0.9O3/Ti3C2-7) composite demonstrated superior photo-Fenton degradation of tetracycline (TC), achieving 1.69 times higher efficiency than LFOBC and 10.65 times more efficiency than pristine LaFeO3(LFO). This enhanced performance is attributed to strong interfacial coupling, which suppressed photoexcited carrier recombination, as confirmed by PL, TRPL, EIS, and photocurrent studies. Experimental and theoretical work function analyses revealed band bending and the formation of an Ohmic junction at the interface. Furthermore, a degradation mechanism and a reaction pathway were proposed, and the reduction in toxicity levels was identified. The LFOBC/Mx-7 catalyst also exhibited promising results for H2evolution with an overpotential of 156 mV vs RHE under visible-light illumination, which was 2.37 times less than that of LFOBC. These results, therefore, showcase the LFOBC/Mx composite as a multifunctional photocatalyst for both pollutant degradation and sustainable energy generation. © 2025 American Chemical Society
Defects Enriched p-type Zinc Stannate for Selective Detection of ppb-Level NO2 Gas at Ambient Temperature
(American Chemical Society, 2024) Pawar, N.; Nath, V.G.; Rodney, J.D.; Joshi, S.; Subramanian, A.; Udayashankar, N.K.
In this study, we explore the synthesis and gas-sensing capabilities of zinc stannate (Zn2SnO4) in three morphologies─spherical nanoparticles, urchins, and octahedrons─aiming to investigate the influence of morphology on sensing properties. The fabricated devices exhibit a significant resistance decrease upon exposure to NO2 at room temperature (24 °C), indicating p-type sensing behavior. Among these morphologies, the spherical nanoparticle-based sensor exhibits the highest sensor response of 57% to 6 ppm of NO2, outperforming urchins and octahedrons by approximately 1.2 and 4.1 times, respectively. This superior performance, with response and recovery times of 6.3 s and 224 s, is attributed to enhanced redox reactions from a larger surface area and a higher proportion of oxygen interstitials. The spherical nanoparticle-based sensor also demonstrates exceptional selectivity for NO2 over SO2, CO, NH3, and CH4, with a detection limit of 200 ppb. Furthermore, the sensor exhibits excellent reversibility with only 2% variation across 20 consecutive test cycles and demonstrates remarkable long-term stability, with a performance fluctuation of approximately 2.3% over 63 days without significant degradation. © 2024 American Chemical Society.
Effect of annealing temperature on the bifunctional electrocatalytic properties of strontium nickelate (SrNiO3) nanoparticles for efficient overall water splitting
(Elsevier Ltd, 2022) J, J.; Jayalakshmi, J.; Rodney, J.D.
The global trend in energy demand has paved way for clean hydrogen (H2) energy production at large scale. To address this issue, perovskite (ABX3) nanomaterials are widely researched to replace the noble metal electrocatalysts for electrochemical water splitting. In this work, the effect of annealing temperature on the structural and electrochemical properties of combustion derived strontium nickelate (SrNiO3) nanoparticles are studied. Benefitting from the unique features of perovskites, SrNiO3 nanoparticles displays excellent OER and HER activity in 1.0 M KOH with an overpotential of 259 mV and 451 mV to achieve 10 mAcm−2 respectively. SrNiO3 nanoparticles show superior HER activity when annealed at higher temperature and subtle change in OER activity. The stability of SrNiO3 nanoparticles were noteworthy as it shows no degradation even after 12 h. The overall water splitting of highly active SrNiO3 nanoparticles was carried out in a two-electrode system and the setup posted a cell voltage of 1.88 V at 10 mAcm−2 after continuous water splitting for 24 h. Thus, SrNiO3 nanoparticles may possibly serve as a potential bifunctional electrocatalyst for H2 production. © 2022 Hydrogen Energy Publications LLC
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.
Electrodeposited CoMnS/NiCo2S4 nanocomposite for high performance supercapacitors
(Elsevier Ltd, 2024) Mascarenhas, F.J.; Rodney, J.D.; Rao, L.; Kim, B.C.; Badekai Ramachandra, B.R.
In this work, we report a facile two-step electrodeposition method to fabricate a CoMnS/NiCo2S4/NF (CMS/NCS/NF) composite on nickel foam (NF) for application of supercapacitor electrode. The electrochemical performance of this composite material has been extensively investigated, revealing superior performance compared to individual CMS/NF and NCS/NF materials. The CMS/NCS/NF composite exhibits an exceptionally high specific capacity of 707 C/g at a current density of 1 A/g in a three-electrode system. Remarkably, the material retains 92 % of its specific capacitance after 5000 cycles, indicating excellent cyclic stability and durability. To further explore its practical applications, we constructed a two-electrode symmetric supercapacitor using the CMS/NCS/NF electrode. This symmetric cell demonstrates an outstanding energy density of 97.5 Wh/kg and a peak power density of 12 kW/kg, underscoring its potential for high-performance energy storage applications. These comprehensive studies indicate that the synthesized CMS/NCS/NF is a highly promising candidate for supercapacitor electrodes, offering both high capacity and long-term stability. This work paves the way for the development of efficient and durable energy storage devices. © 2024 Elsevier Ltd
Elucidating mechanisms and DFT analysis of monometallic Vanadium incorporated nanoporous TiO2 as advanced material for enzyme-free electrochemical blood glucose biosensors with exceptional performance tailored for point-of-care applications
(Elsevier Inc., 2024) Rao, L.; Rodney, J.D.; Naik, S.; Udayakumar, U.; Udayashankar, N.K.; Kim, B.C.; Badekai Ramachandra, B.R.
Diabetes is a chronic condition that can last a lifetime and has claimed a great number of lives in recent years. This motivated scientists to design a glucose biosensor to monitor and control blood glucose levels in diabetic patients. Herein, hydrothermal derived Vanadium (V), Nickel (Ni), and Cobalt (Co)-doped TiO2 (MxTi1-xO2 (x = 0.01, 0.02, and 0.03)) was synthesized to achieve the best material to answer the pertaining problem. Of all the materials synthesized, V0.03Ti0.97O2@NF demonstrated the highest level of sensitivity, and selectivity, and has higher electrochemical cycling stability in 0.1 M KOH. It exhibits a very high sensitivity of 1129.31 μAmM-1cm-2 and Limits of Detection (LOD) and Limits of Quantification (LOQ) of 1.8 μM (S/N = 3) and 6.2 μM, respectively, with a broad linear range from 20 μM to 2 mM. The DFT approach was employed computationally to analyze the adsorption of glucose on surfaces of pure TiO2 and TiO2 doped with V, Ni, and Co respectively. The research findings highlight that when it comes to its interaction with glucose, pure TiO2 exhibits significantly less reactivity compared to transition metal-doped TiO2. Experimentally it shows that the V0.03Ti0.97O2@NF surface has the most sensitive glucose detection capability and it also exhibited significant selectivity towards glucose in the presence of additional interference. It demonstrated 100% retention after cycling stability and had a shelf life of ≃30 days. The V0.03Ti0.97O2@NF-based sensor exhibits accurate glucose sensing, even for human serum samples. © 2024 Elsevier B.V.
Engineering of cobalt impregnated sponge like spinel nickel ferrite as an efficient electrocatalyst for sustained overall water splitting
(Elsevier B.V., 2025) Benny, S.; Galeb, W.; Ezhilarasi, S.; Rodney, J.D.; Udayashankar, N.K.; Raja, M.D.; Madhavan, J.; Arulmozhi, S.
The substantial exhaustion of energy resources in the present reality limelight to the exigency for a clean and sustainable energy resource and the key solution for this would be electrocatalytic water splitting to produce clean H2. For achieving this objective amending noble metals with non-noble metals as electrocatalysts which are cost effective and earth abundant would serve as a better option. Herein, combustion derived nickel ferrite (NiFe2O4) and cobalt doped nickel ferrite (NiCoxFe2-xO4) nanoparticles were extensively studied for Oxygen (O2) and Hydrogen (H2) evolution reactions respectively. The NiCo0.01Fe1.99O4 and NiCo0.03Fe1.97O4 Co-doped NiFe2O4 electrocatalyst exhibits excellent Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER) activity in 1.0 M KOH electrolyte requiring a potential of 1.68 V (? = 455 mV) vs RHE for OER and ?0.167 V (? = 167 mV) vs RHE for HER to achieve the benchmark current density of 10 mA cm?2 and ?10 mA cm?2 for OER and HER respectively. The best performing electrodes (NiCo0.03Fe1.97O4
Exploration of electrode-modulated memory and threshold switching behaviour in Se-Te-Sn thin film devices
(Elsevier B.V., 2024) Joshi, S.; Rodney, J.D.; James, A.; Udayashankar, N.K.
Due to their potential use in high-density, three-dimensional stackable cross-point array structures, the electrical switching ability of chalcogenide glasses has captured a lot of attention. Herein, the switching behaviour of unique Se86-xTe14Snx (x = 0, 2, 4, 6) chalcogenide glassy alloys in the form of a thin film were investigated. The electrode modulated dual functionality in switching was achieved by employing Aluminium (Al) and Silver (Ag), as top electrodes. The films with Al/Se86-xTe14Snx/Al interface exhibited memory-type switching due to the phase-changing properties of the material. The threshold voltage (Vth) decreased linearly from 12.75 V to 4.2 V at room temperature as Sn concentration in the glass increased. On the other hand, when the top electrode was replaced with Ag, the Ag/Se86-xTe14Snx/Al interface acted as a programmable metallization cell (PMC) showing threshold-switching properties. Ag/Se82Te14Sn4/Al thin film of thickness 200 nm showed promising results as a material for a unidirectional selector, due to the formation of temporary Ag filament inside chalcogenide material. The composition showed high selectivity (∼104), high endurance (>104 cycles), and low threshold voltage (∼1.6 V). The ability of the composition to exhibit electrode-dependent memory and threshold-switching phenomena makes the material an interesting case. © 2024 Elsevier B.V.
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 LLC
Investigation of Indium doped Se-Te bulk chalcogenide glasses for electrical switching and phase changing applications
(Elsevier Ltd, 2024) Joshi, S.; Rodney, J.D.; James, A.; Behera, P.K.; Udayashankar, N.K.
Recently, Metal-doped Se-Te chalcogenides have gained a lot of interest due to their unique capacity for electrical switching, which makes them desirable for electronic applications. This study examines the electrical switching characteristics of bulk Se86−xTe14Inx (0 ≤ x ≤ 6) amorphous alloys produced by the conventional melt-mix-quench process. The samples with an Indium atomic percentage between 2 to 6 exhibited a remarkable transition from a highly resistive to a low resistive state when subjected to an electric field with a current of 1 mA, displaying quick and reversible switching behaviour. The threshold voltage (Vth) significantly dropped from 410.6 V to 49.2 V with an increase in Indium concentration. Additionally, above the specific current threshold, these bulk glasses demonstrated memory-type switching, demonstrating their potential for data storage applications. To comprehend the trend of glass forming ability, thermal stability range and Hruby's glass stability parameters, with their compositional dependency, Differential Scanning Calorimetry (DSC) was utilized. The sample Se80Te14In6 emerged to be the fastest phase-changing material, with a memory switching current threshold of Ith = 1.3 mA and a threshold voltage value of 49.2 V. To study the formation of crystallites in Se-Te-In alloy, X-ray diffraction patterns of pristine glass and the annealed sample were examined. Furthermore, temperature-dependent conductivity investigations showed a sharp rise in conductivity once the process crystallization begins (Tx), and also the threshold voltage (Vth) of the samples decreased linearly with rising temperature. Overall, this study provides valuable insights into the electrical switching behaviour and thermal properties of Se-Te-In chalcogenide glasses, enhancing their suitability in electronic devices. © 2024 Elsevier B.V.
Kinetic Comparison of Photocatalysis with the Photo-Fenton Process on the Removal of Tetracycline Using Bismuth-Modified Lanthanum Orthoferrite Nanostructures
(American Chemical Society, 2024) James, A.; Rodney, J.D.; Udayashankar, N.K.
In this study, we investigate visible-light-driven photocatalytic and photo-Fenton degradation of tetracycline (TC) using bismuth-impregnated lanthanum orthoferrite (BixLa1-xFeO3 (x = 0, 0.01, 0.05, 0.07)) nanostructures. Bi doping significantly improves the removal of TC, with Bi0.05La0.95FeO3 (LFO-Bi5) exhibiting optimal degradation. In both photocatalysis (PC) and photo-Fenton catalysis (PFC), the reaction follows pseudo-first-order kinetics, with LFO-Bi5 showing rate constants of 0.0065/min for PC and 0.02716/min for PFC, surpassing LaFeO3 by 2.76 and 3.43 times, respectively. The long-term presence of photoexcited carriers in LFO-Bi5 is confirmed through transient PL, TRPL, and EIS studies. The superior degradation capabilities are attributed to radicals in photocatalysis and OH• radicals in photo-Fenton catalysis. The PFC exhibited faster kinetics due to the rapid production of OH• radicals via the Fe-redox cycle and direct dissociation of H2O2 at oxygen vacancies. LFO-Bi5 demonstrates excellent photostability and reusability for up to six consecutive cycles. The degradation pathway and toxicological properties of the intermediates are analyzed, highlighting the potential of LFO-Bi5 catalysts in antibiotic-contaminated water treatment. © 2024 American Chemical Society.
Mechanistic insight and first principle analysis of cation-inverted zinc ferrite nanostructure: A paradigm for ppb-level room temperature NOx sensor
(Elsevier B.V., 2024) Nath, V.G.; Ray, S.; Rodney, J.D.; Prakasha Bharath, S.; Roy, S.; Tarafder, K.; Subramanian, A.; Chul Kim, B.
Herein, we adopted a new paradigm for developing a high-performance gas sensor by leveraging the mixed spinel ZnFe2O4 structure (mZFO) to enhance the adsorption of NOx molecules. Material characterization reveals the formation of the mZFO due to the cation inversion in lattice sites. The estimated value of the inversion degree is observed to shift from 0.78 to 0.39 with an increase in the calcination temperature. The mZFO nanoparticles calcined at 500 °C show exceptional sensing performance due to their suitable grain size (∼2 times Debye length), neck diameter, and surface area. The sensing studies conducted at various NOx concentrations indicate that the sensor can detect ppb level of NOx with a detection limit of about 9 ppb at room temperature. The detailed sensing mechanism is elucidated based on the density functional theory calculations (DFT) and Bader charge analysis. The outstanding sensor performance is attributed to the formation of a mixed spinel structure, wherein the adsorption energy of NOx (∼-0.6 eV) in the presence of surface adsorbed oxygen is higher than that of the normal spinel structure (∼-0.1 eV). Furthermore, the sensor exhibited a fast response and recovery times (7 and 92 s at 800 ppb NO2), excellent stability, and selectivity. The practical suitability of the mZFO sensor was studied by analyzing the vehicle exhaust emissions. We strongly believe this work would pave a novel approach to developing a high-potential gas sensor by modifying the cation distributions in the spinel ferrites. © 2024 Elsevier B.V.
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.