Micro–mesoporous carbons from rice husk as active

Authors: Marina V Lebedeva Petr M Yeletsky Artem B Ayupov Aleksey N Kuznetsov Vadim A Yakovlev Valentin N Parmon

Publish Date: 2015/10/06

Volume: 4, Issue: 4, Pages: 20-

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Abstract

Activated carbons were prepared from rice husk carbonized in the fluidized catalysts bed reactor Using the different activating agents samples with BET surface area in the range from 540 to 3060 m2/g were achieved Using sodium or potassium carbonates results in the BET surface area up to 1400 m2/g Hydroxides of sodium or potassium yield the samples with the higher BET surface area up to 3060 m2/g Textural peculiarities of the carbons were studied by the adsorption of nitrogen at 77 K and of carbon dioxide at 273 K As active materials for supercapacitors the porous carbon samples were examined by cyclic voltammetry and chronopotentiometry in galvanostatic mode in 1 M H2SO4 as the electrolyte using homemade threeelectrode electrochemical glass cell Gravimetric capacitance of the carbons is linearly proportional to the BET surface area and reaches 230 and 196 F/g at discharge current density of 02 and 1 A/g respectively for the samples with the highest surface areaAmong various devices for electric energy storage supercapacitors take an intermediate position between batteries and conventional capacitors They possess unique energetic characteristics showing higher power density than batteries and higher energy density than capacitors In addition supercapacitors demonstrate long life cycle good reversibility and low maintenance cost 1 2 3 All these benefits draw a lot of attention to research and development of the new active materials suitable for the supercapacitor constructionThe specific character of energy storage requires tailored textural characteristics of the practical materials used in supercapacitors extended surface area and open porous structure accessible for ions of the electrolyte Carbons presented in variety forms and modifications help prospectively to improve existing supercapacitors thanks to physicochemical properties sufficient conductivity good corrosion resistance temperature stability relatively low cost and possibility to vary textural properties 4 Micro 5 6 7 8 and mesoporous 9 10 11 12 carbon materials have been widely investigated as active electrode materials for the supercapacitorsNow economic reasons and environmental challenges make biomass attract significant attention as a source for production of the carbon materials Woods leaves beer lees rice husk and other biomass precursors have been reported as a raw material for such production 5 9 13 14 15 16 17 18 19 20Rice husk RH is a largescale agricultural waste without any relevant commercial applications High amount of amorphous silica makes rice husk conversion difficult However on the other hand the presence of silica allows to consider RH as templatecontaining precursor for the preparation of porous carbons with textural characteristics depending on the template phase properties In our previous publications 21 22 23 two methods of preparation of porous carbons from RH carbonized in the fluidized catalyst bed reactor have been described—with the use of alkalis and carbonates of Na and K

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