Browsing by Author "Mal, S."

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Asymmetric polyoxometalate-polypyrrole composite electrode material for electrochemical energy storage supercapacitors
(Elsevier B.V., 2022) Anandan Vannathan, A.; Chandewar, P.R.; Shee, D.; Mal, S.
Nowadays, metal-oxides impregnated conducting polymers as electrode materials are attracted much attention due to their higher stability. Here, the metal-oxide cluster, polyoxometalate (K5H2[PV4W8O40]·11H2O, PV4W8), was introduced into the polypyrrole (PPy) matrix to overcome the polymers stability issues, and thus, the resulting novel PV4W8/PPy (symmetric) composite electrode has been reported. XPS confirmed the presence of all atoms on the polymer backbone with respective oxidation states. Nevertheless, doping of PV4W8 on the conductive PPy matrix's surface can affectively improve the ion's transfer. Finally, the asymmetric PV4W8-PPy/PPy composite exhibits a prodigious specific capacitance of 291 F g−1, larger than the PPy (90.01 F g−1) and PV4W8 (39.03 F g−1) at 0.4 A g−1 current density. The PV4W8-PPy/PPy (asymmetric) electrode showed excellent cycle stability. However, a symmetric supercapacitor device based on PV4W8/PPy composite possesses a specific capacitance of 195.27 F g−1 and an energy density of 8.94 Wh kg−1 at the same current density as PV4W8-PPy/PPy (asymmetric) electrode with remarkable cycle stability. © 2021 Elsevier B.V.
Decavanadate-graphene oxide nanocomposite as an electrode material for electrochemical capacitor
(Taylor and Francis Ltd., 2022) Maity, S.; Das, P.P.; Mal, S.
We have synthesized new electrode material for the supercapacitor application. Polyoxovanadates (POVs) have been used for energy storage electrode materials due to their fast multi-electron redox properties. The formation of SDV/GO composites was confirmed using various analytical methods, e.g., Fourier transforms infrared spectroscopy (FTIR) and powder X-ray diffraction (XRD), followed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The composite electrode’s electrochemical behavior was studied using a neutral 1 M sodium sulphate (Na2SO4) solution in three-electrode cyclic voltammetry (CV) system. The SDV/GO composite electrode showed a specific capacitance of 306 F/g for a scan rate of 5 mV/s and a corresponding energy density of 42.4 Wh/Kg. Galvanostatic charge/discharge exhibits a specific capacitance of 310 F/g with energy densities of 43.08 Wh/kg. Electrochemical impedance spectroscopy (EIS), which was used to investigate interface property, yielded a considerably higher power density of 172.41 KW/kg with an equivalent series resistance of 5 ?. © 2021 Informa UK Limited, trading as Taylor & Francis Group.
Electrochemical performance of activated carbon-supported vanadomolybdates electrodes for energy conversion
(Elsevier Ltd, 2021) Maity, S.; Anandan Vannathan, A.; Kella, T.; Shee, D.; Das, P.P.; Mal, S.
Reinforcing polyoxomolybdates (POMs) into the activated carbon (AC) template engenders a nanohybrid electrode material for high-performance supercapacitor applications. Herein, a first-time novel integration of two polyoxometalates ([PVMo11O40]4-, [PV2Mo10O40]5-) with AC has been demonstrated, and their structural and electrochemical performances were analyzed. AC-VMo11 composite displayed an enhanced capacitance of 450 Fg-1 with an improved energy density of 59.7 Whkg-1. Furthermore, the symmetric supercapacitor cell for AC-VMo11 and AC-V2Mo10 showed high cell capacitances of 38.8 and 20.01 mF, respectively, alongside 99.99% capacitance retention of over 5000 cycles. In addition, the influence of ionic liquid as an electrolyte on AC-V2Mo10 based supercapacitor cell was investigated in tetrabutylammonium bromide (TBAB) electrolyte solution. © 2021 Elsevier Ltd and Techna Group S.r.l.
Investigation of physico-chemical properties of native and gamma irradiated starches
(Elsevier Ltd, 2022) Govindaraju, I.; Sunder, M.; Chakraborty, I.; Mumbrekar, K.D.; Mal, S.; Mazumder, N.
Starch is one of the most abundantly found carbohydrates in cereals, roots, legumes and fruits located in amyloplasts of plants. Native starch comprises of amylose, a linear α-glucan with α-1,4-linkage and amylopectin, a branched polysaccharide with both α-1,4-linkage and α-1,6-linkage. In food industries, the native starch is modified to manufacture the desired quality of starchy foods by means of physical, chemical, and enzymatic modification techniques. Gamma irradiation technique is one among the physical modifications of starch which is extensively used for the modification of native starch as it is rapid, less toxic and cost-effective technique. When starch is radiated with gamma rays, it is observed to produce free radicals owing to cleavage of amylopectin branches and exhibit variation in their physicochemical properties. In this study, commercially available corn, rice, and potato starch were irradiated with 10 kGy dose of gamma radiation and changes in their physicochemical properties were investigated. Native and irradiated starch was subjected to enzymatic hydrolysis with bacterial α-amylase (150 U/mL). The highest starch hydrolysis was observed for irradiated rice starch (17.03%). Amylose content of irradiated starch decreased by 3–4 %. The optical microscopic images showed the surface erosions of the irradiated starch and differential scanning calorimeter (DSC) revealed the thermal transition temperatures. Overall, starch hydrolysis and amylose content showed inverse correlation between them. Further studies regarding the effect of storage on gamma irradiated starch can help to gain new insights into the usage of modified starches in the manufacture of processed foods. © 2022
Investigation of structural and physico-chemical properties of rice starch with varied amylose content: A combined microscopy, spectroscopy, and thermal study
(Elsevier B.V., 2022) Govindaraju, I.; Zhuo, G.-Y.; Chakraborty, I.; Melanthota, S.K.; Mal, S.; Sarmah, B.; Baruah, V.J.; Mahato, K.K.; Mazumder, N.
Starch from a given botanical source can vary considerably in terms of physicochemical properties in its native and hydrolyzed forms. The current study investigated the structural and functional characteristics of starch from ten indigenous rice varieties endemic to Northeast India. In vitro enzymatic hydrolysis was used to reveal the dextrose equivalent profile of each type of starch. Gezep Sali and Betguti Sali respectively exhibited the highest and lowest starch hydrolysis. Among the ten rice varieties, amylose content varied between 7.50 and 28.58%. Optical and scanning electron microscopy (SEM) revealed the polyhedral shape of the native starch granules and deformation of the shape upon enzymatic hydrolysis. Second harmonic generation (SHG) microscopy and X-ray diffraction (XRD) analysis confirmed the presence of and variations in starch crystallinity. XRD revealed spectral peaks characteristic of A-type starch crystals in the native form. The elevated intensity of XRD peaks in hydrolyzed starch granules confirmed the occurrence of amylose hydrolysis rather than hydrolysis in amylopectin regions. Fourier transform infrared (FTIR) spectra revealed the common stretching and bending of bonds in all native starches; however, changes were observed in the fingerprint region (1080, 1000, 926 cm−1) of hydrolyzed starch granules, which indicates the amylolysis of the amylose region and disturbances in the ordered arrangement in the crystalline part. Differential scanning calorimeter (DSC) endotherms revealed the highest and lowest gelatinization peak temperatures in Harfoni (78 °C) and Tulosi Sali (41 °C) rice cultivars, respectively. The findings in this study can help to optimize the usage of rice starch in food and non-food industries. Furthermore, understanding the control points of starch digestion and genetically tailoring rice grains with different digestibility could be beneficial for nutraceutical applications. © 2021 Elsevier Ltd
Investigations into the supercapacitor activity of bisphosphonate-polyoxovanadate compounds
(Academic Press Inc., 2021) Anandan Vannathan, A.; Thakre, D.; Ali, S.R.; De, M.; Banerjee, A.; Mal, S.
Electrochemical properties of two different bisphosphonate-polyoxovanadate derivatives have been studied. Both the compounds are oxovanadate polyanion derivatives having formula (NH4)4[H6(VIVO2)(VV2O5)2{O3P–C(O)(CH2-2-C5NH4)-PO3}2]•9H2O (1) and (NH4)4[H6(VIVO2)(VV2O5)2{O3P–C(O)(CH2-3-C5NH4)-PO3}2]•8H2O (2). Compounds 1 and 2 are isostructural mixed-valent polyoxovanadate structures containing 1-hydroxy-2-(2-pyridyl) ethylidene-1,1-bisphosphonate and 1-hydroxy-2-(3-pyridyl) ethylidene-1,1-bisphosphonate, respectively. Composites of these compounds have been prepared with activated carbon (AC), viz. AC-1 and AC-2 for compounds 1 and 2, respectively. In order to investigate the interaction between the parent compounds with activated carbon, the as prepared composites were further characterized using various analytical techniques, such as Infrared spectroscopy, thermal stability analysis, powder X-ray diffraction, FE-SEM, EDX, and surface adsorption studies. Electrodes from these composites have been prepared by deposition upon carbon cloth, and their electrochemical properties, with respect to the supercapacitance behavior, have been extensively studied. The electrochemical performance of both the composite materials have been tested in an aqueous 0.1 ?M ?H2SO4 electrolytic solution. AC-2 displays the highest specific capacitance of 313 ?F ?g?1 at a current density of 1 ?A ?g?1, along with incredible specific energy and power of 43.56 ?Wh kg?1 and 1999.72 ?W kg-1, respectively. Likewise, AC-1 exhibits a specific capacitance of 212 ?F ?g?1 also at the current density of 1 ?A ?g?1 with a specific energy of 29.45 ?Wh kg?1. The AC-2 electrode, therefore, shows more conducting and lower resistivity. As such, composite AC-2 was observed to light up red, green, and blue color LED bulbs for 71, 70, and 15 ?seconds, respectively, with only 42 ?mg of sample coated on carbon cloth, suggesting a remarkable specific power of that material. Comparatively, the composite AC-1 electrode could light up the red LED bulbs for about 190 ?seconds, albeit with 143 ?mg of sample coated on carbon cloth. As such, AC-2 was also observed to retain 98.71% of the electrode stability after 4500 cycles. © 2021 Elsevier Inc.
Organic cation linkers polyoxomolybdate-polypyrrole nanocomposite-based supercapacitors
(Springer Science and Business Media Deutschland GmbH, 2021) Muhammed Anees, P.K.; Anandan Vannathan, A.; Kella, T.; Shee, D.; Mal, S.
A few new hybrid electrode materials have been synthesized and immobilized for the next-generation energy storage device. The hybrid electrodes PVMo11-TBA, PVMo11-BTA, PVMo11-TBP, PVMo11-TBA-PPy, PVMo11-BTA-PPy, and PVMo11-TBP-PPy were well characterized by NMR, XRD, FTIR, FESEM, BET, and tested for electrochemical performance. Among these hybrid electrode materials, the PVMo11-TBA-PPy electrode shows a high specific capacitance of 144.37 F/g at a 1A/g current density and incredible power and energy density of 1100.16 W/kg and 15.28 Wh/kg, respectively. The high electrode’s capacitance was due to the synergistic effect between the PPy and TBA-PVMo11 and high ionic diffusion compared with other synthesized electrodes. It also exhibited high cycle stability of 72.78% after 4500 cycles at 1 M H2SO4 electrolyte. The EIS offers a lower ESR value of 0.72 ohms for the PVMo11-TBA-PPy than PVMo11-TBA, indicating the rapid charge/discharge rate. On the other hand, the PVMo11-BTA-PPy and PVMo11-TBP-PPy electrodes showed lower capacitance values of 26.98 and 19.53. F/g at 0.4 and 1 A/g current density, respectively. Lowering the capacitance could be the prevention of the interaction of organic cations with the counter polyanion. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Polyoxomolybdate-Polypyrrole-Graphene Oxide Nanohybrid Electrode for High-Power Symmetric Supercapacitors
(American Chemical Society, 2021) Maity, S.; Je, M.; Biradar, B.R.; Chandewar, P.R.; Shee, D.; Das, P.P.; Mal, S.
Supercapacitors have emerged as one of the most promising candidates for high-performance, safe, clean, and economical routes to store and release of nonfossil energy. Designing hybrid materials by integrating double-layer and pseudocapacitive materials is crucial to achieving high-power and high-energy storage devices simultaneously. Herein, we synthesized a polyoxomolybdate-polypyrrole-graphene oxide nanohybrid via a one-pot reaction. The inclusion of polypyrrole enables a uniform distribution of the polyoxomolybdate clusters; it also confines the restacking of graphene oxide nanosheets. The structural and morphological analysis to unveil the nanohybrid architecture implies excellent interfacial contact, enabling fast redox reaction of polyanions, and a quick transfer of charge to the interfaces. Electrochemical characteristics tested under a two-electrode system exhibit the highest capacitance of 354 F g-1 with significantly high specific energy and power of 49.16 Wh kg-1 and 999.86 W kg-1, respectively. In addition, the cell possesses a high-rate capability and long cycle life by maintaining 96% of its capacitance over 5000 sweeping cycles. The highest specific power of ?10 »000 W kg-1 was computed with Coulombic efficiency of 92.30% at 5 A g-1 current density. Electrochemical impedance spectroscopy additionally reveals enhanced redox charge transfer due to double hybridization. Furthermore, it also demonstrates the impedance and capacitive behavior of supercapacitor cells over a definite frequency regime. ©
Selective dehydration of 1-butanol to butenes over silica supported heteropolyacid catalysts: Mechanistic aspect
(Elsevier B.V., 2021) Kella, T.; Vennathan, A.A.; Dutta, S.; Mal, S.; Shee, D.
Butenes are considered as important olefinic building block to produce fuels/fuel additives and commodity chemicals. In the present investigation, selective dehydration of 1-butanol to butenes was studied in a continuous-flow fixed-bed reactor using various silica-supported heteropolyacid (HPA) catalysts such as phosphotungstic acid (PTA), silicotungstic acid (STA), phosphomolybdic acid (PMA), and silicomolybdic acid (SMA) as the solid acid catalysts. The physicochemical properties of these HPA were determined by BET, powder XRD, FTIR, NH3-TPD, and Py-FTIR. The acid strength and Brønsted/Lewis (B/L) acid ratio were increased with higher loading of HPA on silica. The nature of HPA (addenda and hetero atom) and loading of HPA are important factors for the dehydration of 1-butanol and selectivity towards butenes. PTA and STA showed superior catalytic activity than PMA and SMA. The reaction temperature and WHSV also strongly affected the butanol conversion and selectivity of butenes. The selectivity of di-n?butyl ether decreases with the rising temperature from 523 K to 623 K. The isomerization of 1-butene leading to the formation of other butene isomers depends on the HPA loading, temperature, and WHSV. The presence of molybdenum addendum atom in PMA and SMA promotes dehydrogenation and hydrogenation, leading to the formation of various light hydrocarbons. The 20PTA/SiO2 catalyst afforded 99.8% selectivity towards butenes at quantitative conversion of 1-butanol, whereas the 20STA/SiO2 catalyst gave nearly 97.0% conversion of 1-butanol and 99.9% butenes selectivity at 673 K, 37.4 h?1 of WHSV. © 2021