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L. John Kennedy

Bio: L. John Kennedy is an academic researcher from VIT University. The author has contributed to research in topics: Diffuse reflectance infrared fourier transform & Crystallite. The author has an hindex of 48, co-authored 168 publications receiving 6401 citations. Previous affiliations of L. John Kennedy include Central Leather Research Institute.


Papers
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Journal ArticleDOI
TL;DR: Porous carbons prepared by carbonization of solid leather wastes were employed for supercapacitor applications using KOH electrolyte as discussed by the authors, and they exhibited high specific surface areas in a range of 613-716m2−g−1, as well as superior energy storage capacity as electrodes for super-capacitors.
Abstract: Porous carbons prepared by carbonization of solid leather wastes were employed for supercapacitor applications using KOH electrolyte Advanced instrumentation techniques were used to determine the physicochemical properties of the porous carbon samples Three-electrode configuration was used to investigate the electrochemical properties of porous carbon electrodes through cyclic voltammetry studies, galvanostatic charge–discharge tests, electrochemical impedance spectroscopy (EIS) techniques in 1 M KOH electrolyte Porous carbons exhibit high specific surface areas in a range of 613–716 m2 g−1, as well as superior energy storage capacity as electrodes for supercapacitors Porous carbon electrodes activated at 900 °C exhibited specific capacitance up to 1800 F/g in alkali medium All the solid leather waste carbons established stable cycle performance over 5000 cycles These desirable capacitive performances enable solid leather waste-derived carbons as a source of new materials for low-cost energy storage devices as well as supercapacitors This paper put forwards a new concept of ‘waste to value-added products’ that can be a helping hand for leather industries and its solid waste management disposal problems The highlights of this research work suggest that leather industries could implement and make it feasible for commercialization

16 citations

Journal ArticleDOI
TL;DR: In this article, the optical properties of Zr-AC, Ni-AC and Zn-AC composites were investigated using UV-Vis diffuse reflectance spectroscopy, and the photocatalytic efficiency was verified in the degradation of textile dyeing wastewater (TDW) in UV light irradiation.

16 citations

Journal ArticleDOI
TL;DR: The results indicated that the prepared photocatalysts shows a novel morphology, high crystallinity, uniform size distribution, and more defects.
Abstract: A novel self-assembled pure and Ce doped ZnO nano-particles (NPs) were successfully synthesized by a simple low temperature co-precipitation method. The prepared photocatalysts were characterized by X-ray diffraction (XRD), High resolution scanning electron microscopy (HR-SEM), High resolution transmission electron microscopy (HR-TEM), diffuse reflectance spectroscopy (DRS) and Photoluminescence (PL) spectroscopy. The results indicated that the prepared photocatalysts shows a novel morphology, high crystallinity, uniform size distribution, and more defects. Photocatalytic degradation (PCD) of nonylphenol, a potent endocrine disrupting chemical in aqueous medium was investigated. Higher amount of oxygen defects exhibits enhanced PCD of nonylphenol. In addition, the influence of the Ce contents on the structure, morphology, absorption, emission and photocatalytic activity of ZnO nanoparticles (NPs) were investigated systematically. The relative PCD efficiency of pure ZnO, Ce-doped ZnO NPs and commercial TiO2 (Degussa P-25) have also been discussed.

16 citations

Journal ArticleDOI
TL;DR: XRD patterns confirm the formation of single phase ZnAl2O4 without any impurities and the percentage porosity of zinc aluminate matrices decreased with increasing copper doping, indicating the quantum confinement phenomenon.
Abstract: Porous Zn(1-x)Cu(x)Al2O4 (x = 0, 0.1,0.2, 0.3, 0.4, 0.5) spinel nanostructures were synthesized by one-pot microwave combustion technique. All the samples were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and scanning electron microscopy (SEM). The XRD patterns confirm the formation of single phase ZnAl2O4 without any impurities. The results of XRD indicated the average crystallite size in the range of 12.44-22.86 nm. FT-IR spectra show the vibrational stretching frequencies corresponding to the zinc aluminate spinel structure. The estimated band gap of undoped ZnAl2O4 was 4.96 eV indicating the quantum confinement phenomenon. DRS spectra also indicated the band gap narrowing effect with increase in copper ion concentrations. The defect centers acting as trap levels were obtained from photoluminescence studies responsible for the emission spectra. SEM images showed the features of well created pore structures in all the matrices. The percentage porosity of zinc aluminate matrices decreased with increasing copper doping.

14 citations

Journal ArticleDOI
TL;DR: In order to reduce the band gap, transition metal dopants have been incorporated into ZnO so that it changes the photo electrochemical properties and the effect and variation of CBM and VBM in DSSC parameter are discussed.
Abstract: Pure ZnO and dZnO (doped ZnO) systems of type Zn1-xMxO (M = Co, Cu, Fe and Mn) synthesised by co-precipitation method were evaluated for DSSC studies. Tween-80, a non-ionic surfactant which was used during preparation process also acted as binder for coating the nanoparticles on the FTO glass plate. In order to reduce the band gap, transition metal dopants have been incorporated into ZnO so that it changes the photo electrochemical properties. The conduction band edge minimum (CBM) potentials and valence band edge maximum (VBM) potentials were calculated. The CBM and VBM potentials varied with different dopants. The band gap were engineered such that it shifts the conduction band minimum (CBM) to less negative potential than LUMO (Lower Unoccupied Molecular Orbital) of the dye (Rhodamine B). Pure ZnO showed highest open circuit voltage (Voc) of 631.7 mV and short-circuit current density (Jsc) of 3.5031 μA/cm². In case of dZnO, 5% doping showed highest short-circuit current density and highest power conversion efficiency for all dopants (Co, Cu, Fe and Mn). Nanoparticles with remarkable morphologies influence the efficiency of dye sensitized solar cell (DSSC). The DSSC parameters such as open circuit voltage (Voc), short-circuit current density (Jsc), Fill factor (FF) and photovoltaic efficiency (η) was calculated. The effect and variation of CBM and VBM in DSSC parameter are discussed.

14 citations


Cited by
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01 Nov 2000
TL;DR: In this paper, the authors compared the power density characteristics of ultracapacitors and batteries with respect to the same charge/discharge efficiency, and showed that the battery can achieve energy densities of 10 Wh/kg or higher with a power density of 1.2 kW/kg.
Abstract: The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

2,437 citations

Journal ArticleDOI
01 Oct 1971-Nature
TL;DR: Lipson and Steeple as mentioned in this paper interpreted X-ray powder diffraction patterns and found that powder-diffraction patterns can be represented by a set of 3-dimensional planes.
Abstract: Interpretation of X-ray Powder Diffraction Patterns . By H. Lipson and H. Steeple. Pp. viii + 335 + 3 plates. (Mac-millan: London; St Martins Press: New York, May 1970.) £4.

1,867 citations

Journal ArticleDOI
TL;DR: This paper presents a critical review of recent achievements in the modification of ZnO photocatalyst for organic contaminants degradation and recommends improvements in the heterogeneous photocatalysis under UV/visible/solar illumination.

1,646 citations

Journal ArticleDOI
TL;DR: In this paper, the photo-degradation mechanisms of persistent organic pollutants (POPs) and the recent progress in ZnO nanostructured fabrication methods including doping, heterojunction and modification techniques as well as improvements of ZnOs as a photocatalyst are reviewed.
Abstract: Persistent organic pollutants (POPs) are carbon-based chemical substances that are resistant to environmental degradation and may not be completely removed through treatment processes. Their persistence can contribute to adverse health impacts on wild-life and human beings. Thus, the solar photocatalysis process has received increasing attention due to its great potential as a green and eco-friendly process for the elimination of POPs to increase the security of clean water. In this context, ZnO nanostructures have been shown to be prominent photocatalyst candidates to be used in photodegradation owing to the facts that they are low-cost, non-toxic and more efficient in the absorption across a large fraction of the solar spectrum compared to TiO 2 . There are several aspects, however, need to be taken into consideration for further development. The purpose of this paper is to review the photo-degradation mechanisms of POPs and the recent progress in ZnO nanostructured fabrication methods including doping, heterojunction and modification techniques as well as improvements of ZnO as a photocatalyst. The second objective of this review is to evaluate the immobilization of photocatalyst and suspension systems while looking into their future challenges and prospects.

1,551 citations

Journal ArticleDOI
TL;DR: Recent progress in the applications of hierarchically structured porous materials from energy conversion and storage, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine is reviewed and could stimulate researchers to synthesize new advanced hierarchically porous solids.
Abstract: Over the last decade, significant effort has been devoted to the applications of hierarchically structured porous materials owing to their outstanding properties such as high surface area, excellent accessibility to active sites, and enhanced mass transport and diffusion. The hierarchy of porosity, structural, morphological and component levels in these materials is key for their high performance in all kinds of applications. The introduction of hierarchical porosity into materials has led to a significant improvement in the performance of materials. Herein, recent progress in the applications of hierarchically structured porous materials from energy conversion and storage, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine is reviewed. Their potential future applications are also highlighted. We particularly dwell on the relationship between hierarchically porous structures and properties, with examples of each type of hierarchically structured porous material according to its chemical composition and physical characteristics. The present review aims to open up a new avenue to guide the readers to quickly obtain in-depth knowledge of applications of hierarchically porous materials and to have a good idea about selecting and designing suitable hierarchically porous materials for a specific application. In addition to focusing on the applications of hierarchically porous materials, this comprehensive review could stimulate researchers to synthesize new advanced hierarchically porous solids.

1,052 citations