Showing papers by "Bharat B. Kale published in 2017"

V 2 O 5 encapsulated MWCNTs in 2D surface architecture: Complete solid-state bendable highly stabilized energy efficient supercapacitor device

Abstract: A simple and scalable approach has been reported for V2O5 encapsulation over interconnected multi-walled carbon nanotubes (MWCNTs) network using chemical bath deposition method. Chemically synthesized V2O5/MWCNTs electrode exhibited excellent charge-discharge capability with extraordinary cycling retention of 93% over 4000 cycles in liquid-electrolyte. Electrochemical investigations have been performed to evaluate the origin of capacitive behavior from dual contribution of surface-controlled and diffusion-controlled charge components. Furthermore, a complete flexible solid-state, flexible symmetric supercapacitor (FSS-SSC) device was assembled with V2O5/MWCNTs electrodes which yield remarkable values of specific power and energy densities along with enhanced cyclic stability over liquid configuration. As a practical demonstration, the constructed device was used to lit the ‘VNIT’ acronym assembled using 21 LED’s.

Facile Synthesis of Unique Cellulose Triacetate Based Flexible and High Performance Gel Polymer Electrolyte for Lithium Ion Batteries.

Abstract: Lithium ion batteries (LIBs) with polymer based electrolytes have attracted huge attention due to the possibility of fabricating intrinsically safer and flexible devices. However, economical and eco-friendly sustainable technology is an oncoming challenge to fulfill the ever increasing demand. To circumvent this issue, we have developed gel polymer electrolyte (GPE) based on renewable polymers like cellulose triacetate (CTA) and poly (polyethylene glycol methacrylate) p(PEGMA) by using a photo polymerization technique. Cellulose triacetate offers good mechanical strength with improved ionic conductivity, owing to its ether and carbonyl functional groups. It is observed that the presence of open network has a critical impact on lithium ion transport. At room temperature, GPE PC exhibits optimal ionic conductivity of 1.8 × 10-3 Scm-1 and transference number of 0.7. Interestingly, it affords an excellent electrochemical stability window up to 5.0 V vs. Li/Li+. GPE PC shows a discharge capacity of 164 mAhg-1 ...

Nanostructured N-doped orthorhombic Nb2O5 as an efficient stable photocatalyst for hydrogen generation under visible light

Abstract: The synthesis of orthorhombic nitrogen-doped niobium oxide (Nb2O5-xNx) nanostructures was performed and a photocatalytic study carried out in their use in the conversion of toxic H2S and water into hydrogen under UV-Visible light. Nanostructured orthorhombic Nb2O5-xNx was synthesized by a simple solid-state combustion reaction (SSCR). The nanostructural features of Nb2O5-xNx were examined by FESEM and HRTEM, which showed they had a porous chain-like structure, with chains interlocked with each other and with nanoparticles sized less than 10 nm. Diffuse reflectance spectra depicted their extended absorbance in the visible region with a band gap of 2.4 eV. The substitution of nitrogen in place of oxygen atoms as well as Nb-N bond formation were confirmed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. A computational study (DFT) of Nb2O5-xNx was also performed for investigation and conformation of the crystal and electronic structure. N-Substitution clearly showed a narrowing of the band gap due to N 2p bands cascading above the O 2p band. Considering the band gap in the visible region, Nb2O5-xNx exhibited enhanced photocatalytic activity toward hydrogen evolution (3010 μmol h-1 g-1) for water splitting and (9358 μmol h-1 g-1) for H2S splitting under visible light. The enhanced photocatalytic activity of Nb2O5-xNx was attributed to its extended absorbance in the visible region due to its electronic structure being modified upon doping, which in turn generates more electron-hole pairs, which are responsible for higher H2 generation. More significantly, the mesoporous nanostructure accelerated the supression of electron and hole recombination, which also contributed to the enhancement of its activity.

Unique perforated graphene derived from Bougainvillea flowers for high-power supercapacitors: a green approach

Abstract: Herein, we demonstrated a green approach for the synthesis of high surface area (850 m2 g−1) mesoporous perforated graphene (PG) from Bougainvillea flower for the first time using a template free single-step method. The existence of PG was confirmed by XRD, Raman spectroscopy, FESEM, and FETEM. Surprisingly, FETEM clearly showed 5–10 nm perforation on the graphene sheets. More significantly, these mesoporous perforated graphene sheets can be produced in large scale using the present green approach. Considering high surface area and unique perforated graphene architecture, these PGs were studied for supercapacitor applications in detail without any chemical or physical activation. The nanoporosity and high conductivity of PG derived from Bougainvillea flower exhibited excellent supercapacitive performance. According to the supercapacitor study, the synthesized perforated graphene sheets conferred a very high specific capacitance of 458 F g−1 and an energy density of 63.7 Wh kg−1 at the power density of around 273.2 Wh kg−1 in aqueous 1 M Na2SO4. Significantly, the areal capacitance of PG was observed to be very high, i.e. 67.2 mF cm−2. The cyclability study results showed excellent stability of synthesized perforated graphene sheets up to 10000 cycles. Note that the specific and areal capacitance and the energy density of the synthesized PGs are much higher than the earlier reported values. The high supercapacitive performance may be due to high surface area and mesoporosity of PG. The present approach has a good potential to produce cheaper and high surface area PG. These PGs are good candidates as an anode material in the lithium-ion battery.

Growth study of hierarchical Ag3PO4/LaCO3OH heterostructures and their efficient photocatalytic activity for RhB degradation.

Abstract: We have demonstrated the synthesis of Ag3PO4/LaCO3OH (APO/LCO) heterostructured photocatalysts by an in situ wet chemical method. From pre-screening evaluations of photocatalysts with APO/(x wt% LCO) composites with mass ratios of x = 5, 10, 15, 20, 25 and 30 wt%, we found that the APO/LCO (20 wt%) exhibited a superior photocatalytic activity for organic pollutant remediation. Therefore, an optimised photocatalyst APO/LCO (20 wt%) is selected for the present study and we investigate the effect of a mixed solvent system (H2O:THF) on the morphology, which has a direct effect on the photocatalytic performance. Interestingly, a profound effect on the morphological features of APO/LCO20 heterostructures was observed with variation in the ratio of the solvent system. From the FESEM study it is observed that the LCO spherical nanoparticles are transformed into nanorods with the variation of THF into the solvent system. Moreover, these LCO nanorods make intimate contact with the APO microstructures which is helpful for the improvement of the photocatalytic activity. The photocatalytic activities of the APO/LCO composites with different solvent ratios were evaluated by the degradation of rhodamine B (RhB) under visible light irradiation. Excellent photocatalytic activity was observed for the APO/LCO-2 (H2O : THF = 60 : 40) sample. This might be due to uniform covering of the APO microstructures by fine LCO rod-like structures offering intimate contact between the APO and LCO and providing proper channels for the degradation reactions. Furthermore, with an increasing THF volume ratio in the reaction system there was an increase of the dimensions of the LCO rod-like structures and also a loose compactness of their uniform intimate contact between the APO/LCO heterostructures. All in all, the enhanced photocatalytic activity of the APO/LCO heterostructures is attributed to the collective co-catalytic effect of LCO, by providing accelerated charge separation through the heterojunction interface, and THF, by helping to tune the unique morphological features which eventually facilitate the photocatalysis process.

Green sol–gel route for selective growth of 1D rutile N–TiO2: a highly active photocatalyst for H2 generation and environmental remediation under natural sunlight

Abstract: We report selective growth of N–TiO2 1D nanorods using a green aqueous sol–gel method followed by hydrothermal treatment. Titanium tetraisopropoxide, diethanolamine, and H2O2 were used as precursors for preparing an aqueous gel. Trifluoroacetic acid (TFA) was used as a growth regulator for selective growth of desired structure and morphology. Effects of TFA on the structure and morphology of N–TiO2 were studied by varying concentration of TFA between 1–10% by volume. Structural characterization using XRD confirmed formation of a specific rutile phase with slight crystal disorder with N-doped TiO2 samples. FESEM and HRTEM analysis showed formation of 1D rice grain shaped N–TiO2 in the presence of 1% TFA solution. One directional growth along the (211) plane was confirmed by both HRTEM and XRD. Optical characterization using UV-visible revealed a red shift in the absorption edge which is marginally extended in the visible region. Subsequent Tauc plot analysis showed decrease in the band gap reflecting a decrease in the energy threshold of TiO2 from N-doping. A FTIR spectrum showed Ti–O and Ti–N vibrations confirming the presence of N in the TiO2 matrix. XPS analysis was used to examine electronic states of nitrogen incorporation; peaks at 397.1 and 399.5 eV were attributed to substitutional (Ti–N–O) and interstitial (Ti–O–N) site doping, respectively. Quantification of N content in 5% N-doped TiO2 showed nitrogen concentration of 4.5% which is very close to the doped concentration, suggesting no loss of N in the hydrothermal reaction. The applicability of both undoped and N–TiO2 was tested for photosplitting of H2O and degradation of methyl orange (MO) under artificial solar light (xenon lamp) and natural solar light. Results of hydrogen production in aqueous solution of methanol under natural solar light were compared with artificial sunlight; N–TiO2 showed excellent photocatalytic activity under natural sunlight for H2O splitting and MO degradation. The rice grain shaped N–TiO2 sample showed a H2 generation rate of 7990 μmol g−1 h−1 under natural sunlight but only 4740 μmol g−1 h−1 under a xenon lamp. The superior photoactivity under natural sunlight may be due to the presence of both UV and visible light.

Mesoporous Mn2O3/reduced graphene oxide (rGO) composite with enhanced electrochemical performance for Li-ion battery

Abstract: Transition metal oxides are the most promising candidates in low-cost and eco-friendly energy storage/conversion applications. Herein, bare Mn2O3 and a Mn2O3/reduced graphene oxide (rGO) composite have been synthesized by a facile chemical co-precipitation and subsequent annealing procedure. The synthesized Mn2O3/rGO composite exhibits a porous microcube structure formed with several interconnected particles. The porous Mn2O3/rGO composite, with high surface area and increased conductivity, facilited the charge transfer to enhance the overall electrochemical performance when applied as an anode material in Li-ion batteries. The porous Mn2O3/rGO composite exhibits a highly reversible lithium storage capacity of 1015 mA h g−1 at a rate of 0.5 C (230 mA g−1) during 130 cycles with excellent cycling stability and rate capability. The superior electrochemical performance results mainly due to the combined effect of rGO and Mn2O3, which offers high conductivity, faster Li+ ion transfer, and enhanced structural stability. The material synthesis strategy presented in this study is simple, cost-effective and scalable, which can open new avenues for large-scale applications of composites of graphene and other transition metal oxides.

Triangular CdS nanostructure: effect of Mn doping on photoluminescence, electron spin resonance, and magneto-optical properties

Abstract: In this paper, we report synthesis and study of magneto-optic Faraday effect for dilute magnetic semiconductor nanostructure. The colloidal CdS nanocrystals were prepared via hot injection method and successfully doped with Mn2+ cations. The synthesized nanoparticles were characterized by using UV–Vis spectroscopy, X-ray diffraction, photoluminescence spectroscopy, transmission electron microscopy, and electron spin resonance spectroscopy. Systematic studies on effect of Mn2+ doping on photoluminescence, electron spin resonance, and magneto-optical properties are carried out. UV–Vis spectral analysis confirms blue shift in bandgap of CdS nanoparticles due to quantum confinement effect. The X-ray diffraction study confirms hexagonal wurtzite phase formation of CdS nanoparticles without any impurity phases. TEM analysis confirms uniform particle size, having particle size distribution around 5 nm. As-synthesized undoped CdS shows triangular-shaped nanocrystals with hexagonal structure; however, triangular shape of CdS nanoparticles is not conserved after Mn2+ doping. The photoluminescence characteristic spectra of Mn2+-doped CdS nanocrystals showed emission band at 660 nm and its intensity was found to increase with increasing Mn2+ concentration. Electron spin resonance signal, with six-line hyperfine structure splitting, confirmed doping of Mn2+ ions in CdS lattice. Magneto-optic measurements showed linear variation of Faraday rotation with respect to applied magnetic field, indicating paramagnetic behavior of Mn-doped CdS. The highest Verdet constant 24.81 deg/T cm was observed for 2% Mn-doped CdS nanocrystals, which further decreases with increasing Mn2+ concentration.

Template Free Architecture of Hierarchical Nanostructured ZnIn2S4 Rose-Like Flowers for Solar Hydrogen Production

Abstract: We have demonstrated the controlled synthesis of hierarchical nanostructured ZnIn₂S₄ using a facile template free hydrothermal/solvothermal method. The effect of solvents on the morphology and microstructure of ZnIn₂S₄ has been studied by using water, methanol and ethylene glycol as a solvents. The hierarchical nanostructure, i.e., rose-like morphology composed of very thin (5–6 nm) nanoplates of length ˜1 μm which was obtained in aqueous mediated ZnIn₂S₄. The porous structure (distorted flowers) and agglomerated nanoparticles were obtained using methanol-and ethylene glycol-mediated ZnIn₂S₄. Considering the band gap in the visible region, ZnIn₂S₄ is used as a solar light driven photocatalyst. An ecofriendly photocatalytic process for the conversion of poisonous H₂S into H₂ which is a green unconventional energy source has been demonstrated. The nanostructured ZnIn₂S₄ is employed as a photocatalyst for hydrogen production from H₂S via a solar light-driven eco-friendly approach. The stable photocatalytic activity of hydrogen evolution, i.e., 3964 μmol ⁻¹ was obtained using 0.5 gm of such hierarchical nanostructured ZnIn₂S₄ under visible light irradiation. The unique hierarchical nanostructured ZnIn₂S₄ ternary semiconductor having hexagonal layer is expected to have potential applications in solar cells, LEDs, charge storage, electrochemical recording, thermoelectricity, other prospective electronic and optical devices.

Engendering 0-D to 1-D PbCrO4 nanostructures and their visible light enabled photocatalytic H2S splitting

Abstract: Developing stable semiconducting oxides that are active in the visible region for photocatalytic reactions is a major technological challenge. Herein, we report a facile co-precipitation based synthesis of PbCrO4 nanostructures with the aim to study their hitherto unreported hydrogen production potential. It has been observed that monoclinic PbCrO4 nanorods have been generated using a simple co-precipitation method in the presence of water and methanol as solvents while spherical nanostructures are produced using an ultrasonication assisted co-precipitation method. The nanorods synthesized by the aqueous co-precipitation method have yielded the highest rate of hydrogen production (3214 μmol h−1 0.5 g−1) by splitting hydrogen sulfide (H2S) gas.

Cr Doped TiO2 Catalystin Photocatalytic Degradation of Jakofix Red Dye (HE7B)

Abstract: Pigment / dye manufacturing industries are one of the highly polluting industries generating large volumes of high strength of waste water with disobedient properties. Different process covering anaerobic, aerobic as well as physico-chemical methods have been employed to treat this coloured effluent. The intense colour of the effluent leads to acute ecological problem when released untreated in to environment. Thedecolourisationor deterioration of effluent is known to be very challenging task. In this paper degradation of industrial dyein terms of colour, was studied by usingCr doped TiO2 photo catalyst. The Cr doped TiO2 nanoparticles were prepared by a using Chromium and titanium peroxide gel method with Titanium Isopropoxide as a precursor. The physico-chemical characteristics of the Chromium–titania catalysts of concentration range 0.5 to 5% (w/v) were determined using the methods of Brunauer-Emmett-Teller adsorption, X-ray diffraction, FE-SEM, FT-IR,and UV visible spectroscopy (DRS).The Cr-TiO2 catalystshowed a photo-degradation of dye for all concentration i.e. 0.5 to 5% (wt %).The maximum photocatalytic degradation (90%) ofwas observed for Jakofix red dye (HE 7B)at 0.5% Cr-TiO2sol gel catalyst, as compared to pure TiO2.