Faculty Publications
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Item Waste dry cell derived photo-reduced graphene oxide and polyoxometalate composite for solid-state supercapacitor applications(Royal Society of Chemistry, 2023) Maity, S.; Biradar, B.R.; Srivastava, S.; Chandewar, P.R.; Shee, D.; Das, P.; Mal, S.S.In the modern era, realizing highly efficient supercapacitors (SCs) derived through green routes is paramount to reducing environmental impact. This study demonstrates ways to recycle and reuse used waste dry cell anodes to synthesize nanohybrid electrodes for SCs. Instead of contributing to landfill and the emission of toxic gas to the environment, dry cells are collected and converted into a resource for improved SC cells. The high performance of the electrode was achieved by exploiting battery-type polyoxometalate (POM) clusters infused on a reduced graphene oxide (rGO) surface. Polyoxometalate (K5[α-SiMo2VW9O40]) assisted in the precise bottom-up reduction of graphene oxide (GO) under UV irradiation at room temperature to produce vanadosilicate embedded photo-reduced graphene oxide (prGO-Mo2VW9O40). Additionally, a chemical reduction route for GO (crGO) was trialed to relate to the prGO, followed by the integration of a faradaic monolayer (crGO-Mo2VW9O40). Both composite frameworks exhibit unique hierarchical heterostructures that offer synergic effects between the dual components. As a result, the hybrid material's ion transport kinetics and electrical conductivity enhance the critical electrochemical process at the electrode's interface. The simple co-participation method delivers a remarkable specific capacity (capacitance) of 405 mA h g−1 (1622 F g−1) and 117 mA h g−1 (470 F g−1) for prGO-Mo2VW9O40 and crGO-Mo2VW9O40 nanocomposites alongside high capacitance retentions of 94.5% and 82%, respectively, at a current density of 0.3 A g−1. Furthermore, the asymmetric electrochromic supercapacitor crGO//crGO-Mo2VW9O40 was designed, manifesting a broad operating potential (1.2 V). Finally, the asymmetric electrode material resulted in an enhanced specific capacity, energy, and power of 276.8 C g−1, 46.16 W h kg−1, and 1195 W kg−1, respectively, at a current density of 0.5 A g−1. The electrode materials were tested in the operating of a DC motor. © 2023 The Royal Society of Chemistry.Item High areal capacitance polyoxotungstate-reduced graphene oxide-based supercapacitors(Elsevier B.V., 2023) Biradar, B.R.; Maity, S.; Chandewar, P.R.; Shee, D.; Das, P.P.; Mal, S.S.The modern lifestyle has driven the advent of high-power electronic gadgets to need high-efficiency energy storage devices. Towards that goal, reduced graphene oxide (rGO) mediated polyoxometalates (POMs) based electrode materials are increasingly showing promising performance for building efficient energy storage devices primarily due to their redox properties. In this report, the silicotungstate [K5[SiVW11O40]. nH2O (SiVW11) embedded rGO nanocomposites as electrode materials in supercapacitor applications were synthesized via chemical and hydrothermal methods. The synthesized nanocomposites were characterized by various techniques, such as Fourier-Transform-Infrared (FTIR) Spectroscopy, Powder X-ray Diffraction (XRD) and Energy Dispersive X-ray Spectroscopy (EDS), Thermogravimetric Analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) measurement. The nanocomposite's electrochemical properties were examined by adopting a two-electrode setup with cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) in a 0.5 M H2SO4 electrolyte medium. The hydrothermally reduced graphene oxide (HrGO) nanocomposite exhibited a noticeable surge in areal capacitance of 377.4 mF/cm2 at a current density of 1.5 mA/cm2. The resulting composite had 52.4 µWh/cm2 and 1500 µW/cm2 as energy and power density, respectively at 1.5 mA/cm2 current density. In addition, the capacitance retention is over 81% after 5000 cycles at a current density of 9 mA/cm2. The highest specific power of 5000 µW/cm2 was obtained at 5 mA/cm2 current density. On the other hand, chemically reduced graphene (CrGO) nanocomposite showed an areal capacitance of 277.2 mF/cm2 at the same current density. As a result, the SiVW11 clusters coupled with the rGO increase the areal capacitance of nanocomposites with exceptional electrical and mechanical stability. From an application standpoint, both composites were employed successfully for running a DC motor in a series cell connection. © 2023 Elsevier B.V.Item Pseudocapacitive effects of polyoxometalate implanted on graphene oxide matrix with polypyrrole for symmetric Supercapacitor applications(Elsevier B.V., 2024) Biradar, B.R.; Thathron, N.; Das, P.P.; Mal, S.S.Modern technological requirements emphasize designing and manufacturing electrochemical energy storage devices with high energy and power densities and longer cycle life. Supercapacitors with hybrid electrode materials have gained considerable attention as one of these systems due to their potential usage in futuristic applications such as electric vehicles and smart electric grids, among others. In this work, we synthesize potassium 9-tungsto-2-molybdo-1-vanadosilicate K5[α-SiMo2VW9O40]⋅10H2O and graphene oxide (GO) complex treating the latter as the supporting matrix for the former. We prepare the SiMo2VW9-polypyrrole (PPy) complex and then combine that with the GO matrix. The resulting nanohybrids GO-SiMo2VW9 and GO-PPy/SiMo2VW9 are found to have enhanced electrochemical properties when used in symmetric cells. Combining GO and pseudocapacitive materials can augment SC performance owing to their excellent redox properties. GO-SiMo2VW9 and GO-PPy/SiMo2VW9 showed 55.8 % and 85.5 % capacitive behavior at a scan rate of 10 mV/s, suggesting their use as high-performance pseudocapacitive materials as hybrid electrodes. GO-PPy/SiMo2VW9 electrode material shows a specific capacitance of 351.6 F/g with energy and power densities of 48.83 Wh/kg and 999.93 W/kg, respectively, at 0.5 A/g current density. Both the electrode materials yield capacitance retention of 60 % (GO-SiMo2VW9) and 80 % (GO-PPy/SiMo2VW9) after 5000 cycles at an 8A/g current density with almost 100 % coulombic efficiency, implying the stability of the electrode material. © 2024 Elsevier B.V.Item Multistate nonpolar resistive switching in nickel embedded polyoxovanadate for high density data storage(Elsevier Ltd, 2024) Thathron, N.; Biradar, B.R.; Pandey, S.K.; Mal, S.S.; Das, P.P.The evolution of the electronic industry constantly relies on downscaling of electronic devices and integrating novel materials in active regions to accomplish ever-higher speeds and new features in device structures. Employing materials that display multistate switching for resistive-random-access-memory or simply resistive memory could be a simple and effective way to realize high density data storage. In this context, we report multistate “nonpolar” resistive switching in a nickel embedded polyoxovanadate cluster, (K2H5[NiV14O40]) – a molecule that belongs to the larger polyoxometalate family. We observed unique and distinctive nonpolar resistive switching behaviour for the first time in a multi-redox polyoxometalate cluster. The switching characteristics were repeatable for more than 200 cycles. Our two terminal Al/K2H5[NiV14O40])/ITO memory cells exhibited considerably high resistance window (105) and also long retention time (2000 s). This work holds promise for a novel strategy in order to achieve multilevel storage by exploiting different varieties of polyoxometalate molecules as active switching element that can possibly connect memory with neuromorphic computing. © 2024 Elsevier B.V.Item Development of a cholesterol biosensor and energy storage system based on polypyrrole coated polyoxometalate(Elsevier Ltd, 2025) Biradar, B.R.; Thathron, N.; Hanchate, A.; Das, P.P.; Mal, S.S.Designing sustainable and environmentally acceptable multifunctional electrode materials is vital for various purposes, such as energy storage and healthcare. The redox property of polyoxometalates is attractive for different electrochemistry fields, such as sensors, energy storage, catalysis, etc. In this study, potassium 9-tungsto-2-molybdo-1-vanadosilicate K5[?-SiMo2VW9O40].10H2O (hereafter acronym as SiMo2VW9) embedded on polypyrrole (PPy), which acts as a nanohybrid, was synthesized for supercapacitor and biosensor applications. The electrochemical analysis for both applications was carried out using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The PPy-SiMo2VW9 nanohybrid showed the highest specific capacitance of 174.5 F g?1 with power and energy densities of 799.94 W kg?1 and 15.51 Wh kg?1, respectively, at 0.5 M H2SO4 electrolytic medium. The nanohybrid showed the diffusion-dominant charge storage mechanism with 92.24 % at a 5 mV s?1 scan rate, which refers to the battery-type material. Furthermore, electrochemical sensing for cholesterol was also carried out using the cyclic voltammetry approach in the range of 0.03–0.58 mM cholesterol concentration. The PPy-SiMo2VW9 nanohybrid showed a sensitivity of 7.97 mAm M cm?2 with limit-of-detection (LOD) and limit-of-quantification (LOQ) of 0.06 and 0.2 mM, respectively. The outcomes show that PPy-SiMo2VW9 nanohybrid material is promising in sensing and supercapacitor studies. © 2025 Elsevier B.V.Item Dual oxygen reservoir model for nonpolar resistive switching in nickel tetradecavanadate based molecular switch(Elsevier B.V., 2025) Thathron, N.; Biradar, B.R.; Pandey, S.K.; Mal, S.S.; Das, P.P.The data explosion and computing limitations of traditional computer systems have led researchers to find alternate data storage devices. Resistive random access memory devices have been accepted as a promising candidate to meet the growing demand for multi-bit memory storage and unconventional computing applications. In this report, we provide a comprehensive mechanistic insight into the multistate nonpolar resistive switching in nickel-embedded polyoxovanadate molecules, K2H5[NiV14O40] based memory device having the architecture Al/K2H5[NiV14O40]/ITO. Such molecular cluster belongs to a larger group of polyoxometalate family. The formation and rupture of multiple conductive filaments made up of oxygen vacancies and their lateral widening with different compliance currents allow the device to exhibit multiple resistance states. The resistance states are likely to be modulated by the multiple redox reactions of Ni and V centers of the active switching layer. The coexistence of two unipolar and two bipolar modes of resistive switching suggests that the device can be modeled as having a dual oxygen reservoir structure where both thermochemical and electrochemical mechanisms of filament theory for resistive switching coexist in the same memory cell. The observation of quantized steps in the conductance plot confirms the conductive filament based resistive switching. The enhancement and reduction in conductance with the increase in the number of pulses can mimic the potentiation and depression in biological synapses. This promises that the polyoxometalate based resistive switching devices can connect memory with neuromorphic applications. © 2025 Elsevier B.V.Item Carbon Nanotube-Supported Vanadium Substituted Phospho-Molybdate Nanohybrid for Supercapacitor Applications(John Wiley and Sons Inc, 2025) Biradar, B.R.; Swetha, M.T.; Thathron, N.; Puniyanikkottil, M.A.; Hanchate, A.; Das, P.P.; Mal, S.S.Owing to the depletion of conventional energy sources, our civilization is slowly transitioning to renewables. Therefore, designing effective energy storage systems is one of the most pressing technical demands. The quest for improved energy and power densities in energy storage devices, particularly those with long cycle life, has pushed the investigation of novel materials intended to build effective supercapacitors. In this work, nanohybrid materials are synthesized using a hydrothermal technique by mixing carbon nanotubes and a polyoxometalate cluster, H4[PVMo11O40].xH2O. Henceforth, this complex is acronymed as CNT-PVMo11. Further, electrochemical analysis of CNT-PVMo11 nanohybrid is carried out to examine various characteristics of the supercapacitor cell made with this nanohybrid. The cyclic voltammetry confirms the diffusive-dominant charge-storage process, quantifying a 72.83% diffusion mechanism at a scan rate of 1 mV s?1. The galvanostatic charge–discharge analysis of CNT-PVMo11 nanohybrid material showed a specific capacitance of 229.35 F g?1 with energy and power densities of 31.85 Wh kg?1 and 2000 W kg?1, respectively, at 1 A g?1 current density. The electrode material also shows 90% capacitance retention even after 6000 cycles at 8 A g?1 current density, indicating the material's remarkable stability. The high specific capacitance, excellent energy density, and impressive cycling stability of the hybrid material make it a promising candidate for next-generation supercapacitor electrodes. © 2025 Wiley-VCH GmbH.