Approaches, Derivatives and Applications Vasilios Georgakilas,† Michal Otyepka,‡ Athanasios B. Bourlinos,‡ Vimlesh Chandra, Namdong Kim, K. Christian Kemp, Pavel Hobza,‡,§,⊥ Radek Zboril,*,‡ and Kwang S. Kim* †Institute of Materials Science, NCSR “Demokritos”, Ag. Paraskevi Attikis, 15310 Athens, Greece ‡Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc, 17. listopadu 12, 771 46 Olomouc, Czech Republic Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang 790-784, Korea Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo naḿ. 2, 166 10 Prague 6, Czech Republic

Functionalization of Graphene: Covalent and Non-Covalent Approaches, Derivatives and Applications

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.

Ultracapacitors: Why, How, and Where is the Technology

This paper presents a review of the research progress in the carbon–metal oxide composites for supercapacitor electrodes. In the past decade, various carbon–metal oxide composite electrodes have been developed by integrating metal oxides into different carbon nanostructures including zero-dimensional carbon nanoparticles, one-dimensional nanostructures (carbon nanotubes and carbon nanofibers), two-dimensional nanosheets (graphene and reduced graphene oxides) as well as three-dimensional porous carbon nano-architectures. This paper has described the constituent, the structure and the properties of the carbon–metal oxide composites. An emphasis is placed on the synergistic effects of the composite on the performance of supercapacitors in terms of specific capacitance, energy density, power density, rate capability and cyclic stability. This paper has also discussed the physico-chemical processes such as charge transport, ion diffusion and redox reactions involved in supercapacitors.

Nanostructured carbon–metal oxide composite electrodes for supercapacitors: a review

Graphene/metal oxide composite electrode materials for energy storage

Securing our energy future is the most important problem that humanity faces in this century. Burning fossil fuels is not sustainable, and wide use of renewable energy sources will require a drastically increased ability to store electrical energy. In the move toward an electrical economy, chemical (batteries) and capacitive energy storage (electrochemical capacitors or supercapacitors) devices are expected to play an important role. This Account summarizes research in the field of electrochemical capacitors conducted over the past decade.Overall, the combination of the right electrode materials with a proper electrolyte can successfully increase both the energy stored by the device and its power, but no perfect active material exists and no electrolyte suits every material and every performance goal. However, today, many materials are available, including porous activated, carbide-derived, and templated carbons with high surface areas and porosities that range from subnanometer to just a few nanometers. ...

Capacitive Energy Storage in Nanostructured Carbon–Electrolyte Systems

A modern technological society demands the use and storage of energy on a large scale. In this regard, the development of high performance supercapacitors is the focus of current scientific research. Graphene, due to its excellent properties, has attracted attention for supercapacitor applications. In the present work, graphene is synthesized via hydrogen-induced exfoliation and is further functionalized to decorate with metal oxide (RuO2, TiO2, and Fe3O4) nanoparticles and polyaniline using the chemical route. Materials are characterized by electron microscopy, X-ray diffraction, Fourier transform infrared, and Raman spectroscopy techniques. Electrochemical performance of as-prepared graphene (HEG), functionalized graphene (f-HEG), RuO2-f-HEG, TiO2-f-HEG, Fe3O4-f-HEG, and PANI-f-HEG (PANI = polyaniline) nanocomposites is examined using cyclic voltammetry and galvanostatic charge–discharge techniques for supercapacitor applications. A maximum specific capacitance of 80, 125, 265, 60, 180, and 375 F/g for ...

Functionalized Graphene-Based Nanocomposites for Supercapacitor Application

Functionalized graphene sheets for arsenic removal and desalination of sea water

Endophytic actinomycetes from Azadirachta indica A. Juss. were screened and evaluated for their anti-microbial activity against an array of pathogenic fungi and bacteria. A total of 55 separate isolates were obtained from 20 plants, and 60% of these showed inhibitory activity against one or more pathogenic fungi and bacteria. Actinomycetes were most commonly recovered from roots (54.5% of all isolates), followed by stems (23.6%), and leaves (21.8%). The dominant genus was Streptomyces (49.09% of all isolates), while Streptosporangium (14.5%), Microbispora (10.9%), Streptoverticillium (5.5%), Sacchromonospora sp. (5.5%), and Nocardia (3.6%) were also recovered. Streptomyces isolates AzR 006, 011, and 031 (all from roots) had acute activity against Pseudomonas fluorescens, while AzR027, 032, and 051 (also all from roots) showed activity against Escherichia coli. Meanwhile, an isolate of Nocardia sp. from leaves (AzL025) showed antagonism against Bacillus subtilis. Overall, 32 of the 55 were found to have broad spectrum significant antimicrobial activity, while about 4% of them showed strong and acute inhibition to pathogenic fungi and bacteria. Isolates of Streptomyces AzR031, 008, and 047, Nocardia sp. AzL025, and Streptosporangium sp. AzR 021 and 048 are of particular interest because they showed significant antagonistic activity against root pathogens, including Pythium and Phytophthora sp. Thus, many of the isolates recovered from A. indica in this study may be used in developing potential bio-control agents against a range of pathogenic fungi and bacteria and in the production of novel natural antimicrobial compounds. These results not only further our understanding of plant–microbe interactions but also indicate that there is an untapped resource of endophytic microorganisms that could be exploited in the biotechnological, medicinal, and agricultural industries.

Endophytic Actinomycetes from Azadirachta indica A. Juss.: Isolation, Diversity, and Anti-microbial Activity

Study of removal of azo dye by functionalized multi walled carbon nanotubes

Herein, we report a preparation method of a novel binary hybrid nanocomposite based on polyaniline (PANI) and α-MnO2 nanotubes (MNTs) by in situpolymerization. The polymerization is carried out in acidic medium using α-MnO2 nanotubes as oxidant. A symmetrical supercapacitor is fabricated and the electrochemical performance of the supercapacitor is investigated by cyclic voltammetry (CV), chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS) techniques using 1.0 M H2SO4 as electrolyte. The nanocomposite shows maximum specific capacitance of 626 F g−1 and corresponding energy density of 17.8 W h kg−1, as calculated from the charge–discharge curve at a specific current density of 2 A g−1 in the potential range 0–0.7 V.

Ashish Kumar Mishra

Papers

Functionalized Graphene-Based Nanocomposites for Supercapacitor Application

Functionalized graphene sheets for arsenic removal and desalination of sea water

Endophytic Actinomycetes from Azadirachta indica A. Juss.: Isolation, Diversity, and Anti-microbial Activity

Study of removal of azo dye by functionalized multi walled carbon nanotubes

Polyaniline–MnO2 nanotube hybrid nanocomposite as supercapacitor electrode material in acidic electrolyte