Ravindra N. Bulakhe

Chemical synthesis of 3D copper sulfide with different morphologies for high performance supercapacitors application

3D copper sulfide (Cu2S) with different morphologies for high performance supercapacitors were synthesized via a simple, cost effective successive ionic layer adsorption and reaction (SILAR) method. Further, these Cu2S nanostructure demonstrate excellent surface properties like uniform surface morphology, large surface area of Cu2S samples. X-ray diffraction (XRD) X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy of these samples confirmed the crystallinity and crystal structure of Cu2S. The electrochemical studies of Cu2S samples have been investigated by cyclic voltammetry, charge–discharge and electrochemical impedance spectroscopy techniques. The maximum specific capacitance of flower-like and integrated nanotubes samples are found 761 and 470 F g−1, respectively, at a scan rate of 5 mV s−1. The electrodes are prepared using a simple four-beaker SILAR system at ambient conditions, thus providing an easy approach to fabricate high-power and high-energy supercapacitors. Further, EIS analysis shows a lower ESR value, high power performance, excellent rate as well as frequency response to flower-like Cu2S sample. The Ragone plot shows better power and energy densities of all Cu2S nanostructured samples. The long-term cycling performance of Cu2S is examined with excellent retention of 95%. The high surface area provided by the porous and more conductive 3D nickel foam have been utilized properly to enhance the electrochemical properties of copper sulfides with charge transport and storage.

Oxidative degradation of benzoic acid using spray deposited WO3/TiO2 thin films

Layered WO3/TiO2 thin films have been deposited onto glass and FTO coated glass substrates using spray pyrolysis method. The structural, morphological, compositional and photocatalytic properties of layered WO3/TiO2 thin films are studied. The photoelectrochemical (PEC) study shows that, both short circuit current (Isc) and open circuit voltage (Voc) are (Iscu2009=u20090.575xa0mA and Vocu2009=u20090.485xa0V) relatively high at 15xa0ml spraying quantity of TiO2 solution on pre-deposited WO3. SEM images show that the substrate surface is well covered with a uniform and round shaped TiO2 nanoparticles. The AFM images show the rough nature of the film. The specific surface area of the layered WO3/TiO2 thin film is found to be 62.14xa0m2xa0g−1. Photoelectrocatalytic degradation of benzoic acid (BA) in aqueous solutions is studied. The end result shows that the degradation percentage of BA using layered WO3/TiO2 photoelectrode has reached 46.56% under sunlight illumination after 320xa0min. The amount of degradation is confirmed by COD analysis.

Layer-structured nanohybrid MoS2@rGO on 3D nickel foam for high performance energy storage applications

This paper describes the synthesis of molybdenum sulfide (MoS2)@reduced graphene oxide (rGO) on 3D nickel foam via an inexpensive room-temperature two-step method composed of the layer-by-layer (LBL) method followed by solution-based successive ionic layer adsorption and reaction (SILAR). “Self-assembly” growth mechanisms are proposed to discuss the growth of MoS2 on the rGO to form nanohybrid layered structures. The prepared nanohybrid multilayered structure with a high specific surface area and good electrical conductivity provided a higher specific capacitance of 1071 F g−1 at a current density of 2 A g−1 than that of the bare MoS2 electrode (661 F g−1 at 2 A g−1), showing an approximately 60% increase in capacitance. The nanohybrid layered structure showed an excellent energy density of 47.6 W h kg−1 and a power density of 7.6 kW kg−1 with a good retention capacity of 95% after 2000 cycles. An asymmetric supercapacitor with MoS2@rGO as the positive electrode and reduced graphene oxide as the negative electrode delivered a high energy density of 72.8 W h kg−1 at a power density of 7.4 kW kg−1 under an operating voltage window of 1.6 V. This performance was maintained at 92% of the original level at a constant current density of 8 A g−1, even after 4000 cycles. This approach offers a versatile technique for the design and synthesis of metal sulfide nanohybrid structures for electrochemical energy storage devices.

Chemical synthesis of PANI–TiO2 composite thin film for supercapacitor application

A unique and cost effective chemical route has been carried out for the synthesis of a polyaniline–titanium oxide (PANI–TiO2) composite thin film at room temperature. Characterization techniques, such as Fourier transform infrared and FT-Raman spectroscopy; have shown the formation of the composite. The result of X-ray diffraction indicates the amorphous nature of the PANI–TiO2 composite thin film. The morphology of the PANI–TiO2 composite thin film observed using scanning electron microscopy shows the porous framework of the agglomerated nanofibers. The electrochemical characterization of the pseudocapacitive PANI–TiO2 composite in a 1 M H2SO4 electrolyte displayed the highest specific capacitance of 783 F g−1 at the scan rate of 5 mV s−1. The synergistic effect between PANI with its counterpart TiO2 caused an increased cycle stability of 78% over 5000 consecutive cycles, which is higher than the virgin PANI with 70% specific capacitance retention. The distinctive structure of the PANI–TiO2 composite and the cohabitation of conducting PANI with TiO2 have been found to be responsible for the superior electrochemical properties.

Amperometric CO 2 gas sensor based on interconnected web-like nanoparticles of La 2 O 3 synthesized by ultrasonic spray pyrolysis

AbstractThin films of La2O3 were deposited onto glass substrates by ultrasonic spray pyrolysis. Their structural and morphological properties were characterized by X-ray diffraction, Fourier transform Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photo-electron spectroscopy, Brunauer-Emmett-Teller and optical absorption techniques. The sensor displays superior CO2 gas sensing performance at a low operating temperature of 498xa0K. The signal change on exposure to 300xa0ppm of CO2 is about 75%, and the signal only drops to 91% after 30xa0days of operation.n Graphical abstractSchematic diagram ofxa0the CO2 gas sensing mechanism ofxa0an interconnected web-like La2O3 nanostructure in presence of 300xa0ppm of CO2 gas and atxa0an operating temperature of 498xa0K.

Highly Uniform Atomic Layer-Deposited MoS2@3D-Ni-Foam: A Novel Approach To Prepare an Electrode for Supercapacitors

This article takes an effort to establish the potential of atomic layer deposition (ALD) technique toward the field of supercapacitors by preparing molybdenum disulfide (MoS2) as its electrode. While molybdenum hexacarbonyl [Mo(CO)6] serves as a novel precursor toward the low-temperature synthesis of ALD-grown MoS2, H2S plasma helps to deposit its polycrystalline phase at 200 °C. Several ex situ characterizations such as X-ray diffractometry (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and so forth are performed in detail to study the as-grown MoS2 film on a Si/SiO2 substrate. While stoichiometric MoS2 with very negligible amount of C and O impurities was evident from XPS, the XRD and high-resolution transmission electron microscopy analyses confirmed the (002)-oriented polycrystalline h-MoS2 phase of the as-grown film. A comparative study of ALD-grown MoS2 as a supercapacitor electrode on 2-dimensional stainless steel and on 3-dimensional (3D) Ni-foam substrates clearly reflects the advantage and the potential of ALD for growing a uniform and conformal electrode material on a 3D-scaffold layer. Cyclic voltammetry measurements showed both double-layer capacitance and capacitance contributed by the faradic reaction at the MoS2 electrode surface. The optimum number of ALD cycles was also found out for achieving maximum capacitance for such a MoS2@3D-Ni-foam electrode. A record high areal capacitance of 3400 mF/cm2 was achieved for MoS2@3D-Ni-foam grown by 400 ALD cycles at a current density of 3 mA/cm2. Moreover, the ALD-grown MoS2@3D-Ni-foam composite also retains high areal capacitance, even up to a high current density of 50 mA/cm2. Finally, this directly grown MoS2 electrode on 3D-Ni-foam by ALD shows high cyclic stability (>80%) over 4500 charge-discharge cycles which must invoke the research community to further explore the potential of ALD for such applications.

Micro-structural analysis of NiFe2O4 nanoparticles synthesized by thermal plasma route and its suitability for BSA adsorption

The paper presents the experimental studies pertaining to the adsorption of bovine serum albumin (BSA) on the nanoparticles of nickel ferrite (NiFe2O4) with a view of correlating the adsorption properties to their microstructure and zeta potentials. Physical properties of two kinds of nickel ferrites, one synthesized by thermal plasma route and the other by chemical co-precipitation method, are compared. Maximum adsorption (231.57xa0μg/mg) of BSA onto nickel ferrite nanoparticles, at body temperature (37xa0°C) was observed at pH-value of 5.58 for the thermal plasma synthesized particles showing its higher adsorption capacity than those synthesized by wet chemical means (178.71xa0μg/mg). Under the same physical conditions the value of zeta potential, obtained for the former, was higher than that of the latter over a wide range of pH values (3.64–9.66). This is attributed to the differences in the specific surface energies of the two kinds of nanoparticles arising from the degree of crystallinity. The paper presents the experimental evidence for the single crystalline nature of the individual nanoparticles, with mean size of 32xa0nm, for the thermal plasma synthesized particles as evidenced from the high resolution transmission electron microscopy and electron diffraction analysis. The measurements also reveal the poor crystalline morphology in the chemically prepared particles (mean size of 28xa0nm) although the X-ray diffraction patterns are not much different. The atomic force microscopy images confirm that the surfaces of plasma synthesized nanoparticles possesses higher surface roughness than that of chemically synthesized one. Presence of adsorbed protein was confirmed by vibrational spectroscopy. The Langmuir adsorption model is found to fit into the experimental data better than the Freundlich adsorption model.

Cadmium indium selenide semiconducting nanofibers by single step electrochemical route

The growth of ternary semiconductor thin films of cadmium indium selenide nanofibers has been carried out from aqueous solution of cadmium sulphate, indium trichloride, and selenium dioxide by electrochemical route. These thin films have been further optimized using photoelectrochemical cell (PEC). Optimized thin film has been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Chemically synthesized 3D nanostructured polypyrrole electrode for high performance supercapacitor applications

Three-dimensional (3D) polypyrrole (Ppy) electrodes are directly grown on Ni foam using a solution-based cost effective chemical method and an in situ controlled precipitation route for supercapacitor application. The Ppy electrodes are characterized for their structural and morphological studies using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy. The XRD study revealed that Ppy electrodes are amorphous. SEM shows the formation of tiny spherical grains spread over the entire electrode surface. The FT-IR study confirms the formation of Ppy film on the electrode surface. The supercapacitive performance of the Ppy electrode using the cyclic voltammetry technique in a 3M KOH electrolyte shows a maximum specific capacitance of 931xa0F/g at a scan rate of 5xa0mV/s. Performance analysis of the supercapacitive electrode carried out using electrochemical impedance spectroscopy (EIS). A distorted semicircle in the high frequency region of EIS shows reduction in charge-transfer resistance.