Activated carbons prepared from rice husk by chemical activation with dual activation agents, KOH and NaOH, have been studied and characterized by BET, SEM, EDX, FTIR, Boehm titration, Raman, and TGA. It was found that the KOH/NaOH impregnation ratio plays an important role on textural properties of AC. At the same amount of total alkali hydroxide, the KOH/NaOH ratio higher than 1.33 resulted in larger specific surface area (2990∼3043 m2·g−1), microporous surface area (2747∼2831 m2·g−1), and higher micropore volume (1.4250∼1.4316 cm3·g−1). The as-prepared samples exist in the form of spherical-shaped particles with the size ranging from 20 to 60 nm and contain numerous surface functional groups. The as-prepared activated carbons were then assessed as an electrode material of supercapacitor operating in the 0.5 M K2SO4 electrolyte in potential windows of −1.0∼0.0 V. The highest capacitance obtained was 205 F·g−1 at the scan rate of 2 mV·s−1 and 225 F·g−1 at a current density of 0.2 A·g−1. At the scan rate as high as 50 mV·s−1, all the as-prepared activated carbons in this study have the specific capacitance greater than 100 F·g−1.
In the crystal structures of three 4-substituted-2,2′-bipyridines prepared using facile synthetic procedures, two novel 4-alkynyl-2,2-bipyridines via the Sonogashira cross-coupling reaction and one 4-aryl-2,2′-bipyridine via the Suzuki–Miyaura cross-coupling reaction, the planar 4-alkynyl-substituted derivatives are in contrast to the non-planar 4-aryl derivative.
In this study, the adsorption kinetics and equilibrium of methylene blue from aqueous solution onto activated carbon derived from coffee husk using one step ZnCl2 activation were investigated. The influence of initial methylene blue concentration and temperature were evaluated employing the batch experiment. To the experimental data, different kinetics and isotherm models were applied, finding that the best fitted is the pseudo-second-order equation and the Redlich-Peterson model, respectively. The mechanism of the adsorption was examined using the Weber and Morris model, and the obtained results suggested that the intra-particle diffusion was not the only rate-controlling step. The scale-up system was also designed for 50 - 90% methylene blue removal from an initial concentration of 100 mg L-1 at 30 oC.
NiS as an electrode material for electrochemical capacitors has been synthesized by chemical and hydrothermal methods. The results show that the synthesized NiS is in amorphous form, increasing the reaction temperature or hydrothermal time tends to reduce the porosity of the materials. NiS synthesized by hydrothermal method exhibits better electrochemical properties than those synthesized by chemical method. NiS synthesized at the optimal condition of a hydrothermal temperature of 140 oC in 5h has a specific capacitance of 1592 F\g (265 mAh\g) and 1567 F\g (261 mAh\g) at a scan rate of 5 mV\s and a current density of 5 A\g, respectively. This value is about 88% of the theoretical value of NiS and is maintained after 25 continuous charge-discharge cycles at different current densities ranging from 5 to 40 A\g.
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