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 (RuO 2 , TiO 2 , and Fe 3 O 4 ) 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), RuO 2 -f-HEG, TiO 2 -f-HEG, Fe 3 O 4 -f-HEG, and PANI-f-HEG (PANI = polyaniline) nanocomposites is examined using cyclic voltammetry and galvanostatic chargeÀdischarge techniques for supercapacitor applications. A maximum specific capacitance of 80, 125, 265, 60, 180, and 375 F/g for HEG, f-HEG, RuO 2 -f-HEG, TiO 2 -f-HEG, Fe 3 O 4 -f-HEG, and PANI-f-HEG nanocomposites, respectively, is obtained with 1 M H 2 SO 4 as the electrolyte at the voltage sweep rate of 10 mV/s. The specific capacitance for each nanocomposites sustains up to 85% even at higher voltage sweep rate of 100 mV/s. A simple and cost-effective preparation technique of graphene and its nanocomposites with good capacitive behavior encourages its commercial use.

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Control over the CO2 emission via automobiles and industrial exhaust in atmosphere, is one of the major concerns to render environmental friendly milieu. Adsorption can be considered to be one of the more promising methods, offering potential energy savings compared to absorbent systems. Different carbon nanostructures (activated carbon and carbon nanotubes) have attracted attention as CO2 adsorbents due to their unique surface morphology. In the present work, we have demonstrated the CO2 adsorption capacity of graphene, prepared via hydrogen induced exfoliation of graphitic oxide at moderate temperatures. The CO2 adsorption study was performed using high pressure Sieverts apparatus and capacity was calculated by gas equation using van der Waals corrections. Physical adsorption of CO2 molecules in graphene was confirmed by FTIR study. Synthesis of graphene sheets via hydrogen exfoliation is possible at large scale and lower cost and higher adsorption capacity of as prepared graphene compared to other carbon nanostructures suggests its possible use as CO2 adsorbent for industrial application. Maximum adsorption capacity of 21.6 mmole/g was observed at 11 bar pressure and room temperature (25 ºC)

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A new type of flexible carbon fabric supported magnetite multiwalled carbon nanotubes (Fe 3 O 4 -MWNTs) nanocomposite based supercapacitor was fabricated for the removal of high concentration of arsenic and desalination of seawater. MWNTs were synthesized by a chemical vapor deposition (CVD) technique, purified by air oxidation and acid treatment followed by further functionalization. Decoration of magnetite (Fe 3 O 4 ) nanoparticles over functionalized MWNTs surface was done by a chemical technique. Fe 3 O 4 -MWNTs nanocomposite was characterized using different characterization techniques. Electrochemical activity of the nanocomposite was analyzed for arsenite and arsenate ions containing water as well as for seawater by using cyclic voltametry (CV). Adsorption isotherms and kinetic characteristics of sodium, arsenate, and arsenite ion removal were studied. Performance of the filter made up of nanocomposite-based electrodes was examined by an inductive coupled plasma optical emission spectroscopy (ICP-OES) technique. The present study shows the novel nature of the nanocomposite, which can remove both types of arsenic ions (arsenate and arsenite) and salt from seawater. High desalination efficiency (removal of sodium, magnesium, and calcium) of seawater and repeatability for the simultaneous removal of arsenic (both arsenate and arsenite) and sodium have been demonstrated in the present work.

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Herein, we report a preparation method of a novel binary hybrid nanocomposite based on polyaniline (PANI) and a-MnO 2 nanotubes (MNTs) by in situ polymerization. The polymerization is carried out in acidic medium using a-MnO 2 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 H 2 SO 4 as electrolyte. The nanocomposite shows maximum specific capacitance of 626 F g À1 and corresponding energy density of 17.8 W h kg À1 , as calculated from the charge-discharge curve at a specific current density of 2 A g À1 in the potential range 0-0.7 V.

It has long been seen as a demanding task to counteract the raised levels of greenhouse gases including carbon dioxide (CO 2 ). Current worldwide research is focused on the investigation of materials which can capture large amounts of CO 2 through physical or chemical adsorption. The present work focuses on a high pressure CO 2 adsorption study of functionalized MWNTs (f-MWNTs) and a magnetite decorated MWNT nanocomposite. Multiwalled carbon nanotubes (MWNTs) were prepared by a catalytic chemical vapor deposition method followed by purification and functionalization. Magnetite (Fe 3 O 4 ) nanoparticles were decorated over the f-MWNT surface by a chemical method. The functionalized MWNTs and magnetite decorated MWNTs were characterized by electron microscopy, X-ray powder diffraction, Raman spectroscopy and FTIR spectroscopy. The CO 2 adsorption capacity was measured using high pressure Sieverts' apparatus. A large enhancement in the CO 2 adsorption capacity was achieved by decorating magnetite nanoparticles over the MWNT surface.