H. S. Panda

Schottky barrier tuning in semiconducting ZnO and BaTiO3 hybrid heterostructures shows dielectric and electrical anisotropy

Polygonal nanosize BaTiO3 and modified BaTiO3 with carbon are prepared using a modified hydrothermal process and utilized as solutes to set up bimodal hollow zinc oxide (ZnO) heterostructures. Powder X-ray diffraction and Raman spectroscopy confirmed the formation of tetragonal and pseudo-cubic structures for BaTiO3 and modified BaTiO3, respectively. Pure ZnO and ZnO heterostructures were well characterized with the aid of various sophisticated techniques. The results suggested the formation of stable heterostructures with structural inhomogeneity and a considerable shift in the band gap compared to that of pure ZnO. The dielectric study of the developed ZnO heterostructures was carried out over a wide range of frequencies (100 to 106 Hz) and temperatures (−100 to 60 °C) and showed a significant improvement in dielectric properties. The frequency dependent maxima in the imaginary part of electric modulus of the ZnO heterostructures followed the Arrhenius law and the activation energy of the heterostructures were found to be ∼0.16 eV. Furthermore, the localized electrical properties of the ZnO heterostructures were investigated using conductive atomic force microscopy (C-AFM) by recording current maps while simultaneously acquiring topographic images. The deliberate analysis of local current–voltage (I–V) characteristics of ZnO heterostructures by C-AFM exposed the formation of Schottky diodes with divergence in the barrier heights between the metal and semiconductor interface.

Facile synthesis of amorphous Co/Ni hydroxide hierarchical films and the study of their morphology and electrochemical properties

Amorphous Co/Ni hydroxide films were prepared by using a successive ionic adsorption and reaction method (SILAR) on a stainless steel substrate and their electrochemical properties were examined for supercapacitor application. The amorphous nature of the film was confirmed by powder X-ray diffraction. The vertically aligned interconnected nano sheet array morphology with uniform distribution was observed using scanning electron microscopy and atomic force microscopy. Their electrochemical properties were measured by performing cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy studies in an aqueous electrolyte. The specific capacitance was calculated to be 720 F g−1 at 5 mV s−1 for Co/Ni hydroxide, which shows a substantial improvement in electrochemical capacitance as compared to the pure cobalt hydroxide. The result suggested that the template free deposition method is a promising method for achieving next generation electrode materials.

Tuning the electro-chemical properties by selectively substituting transition metals on carbon in Ni/Co oxide-carbon composite electrodes for supercapacitor devices

Carbon black (CB) decorated Ni/Co oxide composite electrodes are fabricated in situ with variable CB percentages by using the successive ionic layer adsorption and reaction (SILAR) method. This green process tuned the metal ion concentration on carbon and offered binder-free, facile and scalable features. The structure, morphology and electrochemical performances of the developed nanocomposites are characterized using various sophisticated techniques. An elemental study suggested the substitution of more Ni2+ in NixCo1−xO4 with varying carbon concentrations, which was correlated with the change in the relaxation rate of the composites. X-ray photoelectron spectroscopy confirmed the presence of Ni2+ and Ni3+ in the Ni/Co–carbon composites, which are additionally responsible for improving the conductivity of the developed electrodes. Also, conductive atomic force microscopy supported the improvement in the local conductivity of NC7 compared to NC0. NC7 electrodes demonstrated a specific capacitance of around 1811 F g−1 at a current density of 0.5 mA cm−2 with excellent cyclic retention (92% even after 8000 cycles) and energy density (91 W h Kg−1). Further, NC7 electrodes are used to fabricate an asymmetric solid state supercapacitor device (capacitance around 258 F g−1), and are connected to a commercial solar cell for storing energy, which is effective to light a commercial LED.

Enhanced tortuosity for electrolytes in microwave irradiated self-organized carbon-doped Ni/Co hydroxide nanocomposite electrodes with higher Ni/Co atomic ratio and rate capability for an asymmetric supercapacitor

We demonstrate a green, facile and rapid microwave-mediated process for fabricating carbon black (CB) incorporated Ni/Co hydroxide porous nanocomposites and study the effect of various mass loading of CB on supercapacitor performance. The structure and interactions between CB and Ni/Co hydroxide are characterized by using x-ray diffraction, Fourier-transform infrared spectroscopy and x-ray photoelectron spectroscopy, which suggest the miniaturization of the single-phase Ni/Co hydroxide formation time. A morphology study reveals that the addition of CB into Ni/Co hydroxide develops a loose network structure with well-defined architectural pores. In addition, the nanocomposites demonstrate noticeable improvements in porosity and atomic ratio of Ni/Co with an increasing percentage of carbon, which results in a higher diffusion of electrolytes, and hence electrical conduction. The developed electrode materials exhibit a maximum specific capacitance value of 1526 Fg-1 at current density 1 Ag-1 with excellent cyclic stability (92% retention at 5000 cycles), energy density (76 Wh Kg-1), power density (250 W Kg-1) and rate capability. A solid state asymmetric supercapacitor device is fabricated and utilized to brighten a commercial LED effectively for validating real usage.

Localize current burst in modified carbon nanotube/polyaniline composite fibers mat electrode miniaturized resistance and improved rate capability for solid-state supercapacitor

Polyaniline-modified carbon nanotube composite nanofibers are deposited on carbon paper substrate using two steps template-free chemical oxidative deposition process. Regular nanofibers mat was observed through microscopy, and suggested better dispersion and interfacial adhesion ability of modified CNT with PANI matrix, which provided distinct architectural pores. Surface roughness was estimated using AFM surface topography image and decrease in roughness was observed in MPCNT nanofibers mat than PCNT nanofibers mat. Also, decrease in surface roughness due to reduction in agglomeration increased current burst and conducting pathway, which is confirmed in localized current profile plot. In addition, XPS results confirmed the improvement of intrinsic oxidation state, doping degree and conductivity in MPCNT than PC0. Fabricated MPCNT electrode miniaturized resistance and demonstrated highest specific capacitanceu2009~u20091302xa0F g−1 at current density 0.5xa0mA cm−2 with good cyclic stability (82% retention even after 6000 cycles). Also, MPCNT electrode exhibited high energy density (250 Wh kg−1) and power density (148xa0W kg−1). Moreover, develop electrode materials are used to fabricate an asymmetric supercapacitor device for demonstrating the applicability.

Morphology-controlled ultrafine \(\hbox {BaTiO}_{3}\)-based PVDF–HFP nanocomposite: synergistic effect on dielectric and electro-mechanical properties

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Electric-Potential-Driven Pressure-Sensing Observation in New Hollow Radial ZnO and Their Heterostructure with Carbon

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Enriched Doping Level and Tuned Fiber Fractal Dimensions in Nonwoven Carbon‐Doped Polyaniline for Efficient Solid‐State Supercapacitors

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