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.

Optimization of biodiesel production from waste cooking oil by magnesium oxide nanocatalyst synthesized using coprecipitation method

Abstract: Nanostructured magnesium oxide (MgO) catalysts were prepared by the coprecipitation method and employed for the transesterification of waste cooking oil using methanol. The X-ray diffraction analysis showed that nanostructured MgO phase was formed at calcination temperature of 500 °C. The mean crystallite size of MgO nanoparticles is 7.86 nm. Fourier-transformed infrared spectroscopy studies confirmed the formation of MgO phase with the characteristic vibrational mode of Mg–O. UV–Vis diffuse reflectance spectroscopy reveals that the energy band gap is around 5.84 eV. The presence of magnesium and oxygen elements was determined from energy-dispersive X-ray analysis. The effect of various parameters such as catalyst loading, methanol-to-oil molar ratio, reaction temperature, reaction time and reusability was investigated. A maximum biodiesel yield of 93.3% was achieved with 2 wt% of MgO nanocatalyst (MO5 sample), methanol/oil molar ratio of 24:1, reaction temperature about 65 °C and reaction time 1 h. The nanocatalyst (MgO) was reused at least for 5 times and thereafter resulted in a decrease in the biodiesel yield. The kinetic study of the transesterification reaction followed pseudo-first-order rate kinetics. The composition of fatty acid methyl ester was determined using gas chromatography–mass spectroscopy.

Surface and porous characterization of activated carbon prepared from pyrolysis of biomass (rice straw) by two-stage procedure and its applications in supercapacitor electrodes

Abstract: In this study, we used a two-stage process and phosphoric acid to thermochemically transform waste biomass rice straw into porous carbon (PC) for the preparation of high-performance supercapacitor electrodes. The morphological and chemical characteristics of PC were investigated by X-ray diffraction, scanning electron microscopy, surface area, and porosity analyses by the BET (Brunauer, Emmett, and Teller) nitrogen adsorption method, Fourier transform infrared spectroscopy. The modification process leads to the increase in the specific surface area and pore size of PC. The dc conductivity of the samples determined at room temperature was found to increase from 16.1 × 10−5 to 10.16 × 10−3 Ω−1 cm−1. The samples showed good electrochemical property with specific capacitance possessing in the range of 56–112 F/g. It was found that the carbonization temperature plays a crucial role on the evolution of structural and electrochemical properties of porous carbons. These porous carbons which show a particular large reversible capacity are proved to be promising electrode materials for high-rate and high-performance supercapacitors.

Ultracapacitors: Why, How, and Where is the Technology

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.

X-Ray Diffraction

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.

A review of ZnO nanoparticles as solar photocatalysts: Synthesis, mechanisms and applications

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.

Applications of hierarchically structured porous materials from energy storage and conversion, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine

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.