Activated carbons (ACs) were prepared by microwave−assisted heating of bituminous coal with KOH as activation agent in different gas media for supercapacitors. The pore structure parameters of ACs are obtained by using nitrogen adsorption technique. ACs prepared in static nitrogen, flowing nitrogen and carbon dioxide are denoted as ACStatic-N2, ACFlowing-N2, ACFlowing-CO2. The specific surface area of ACFlowing-N2 is the biggest among the three ACs, which reaches 1201 m2g-1 with total pore volume being at 0.64 cm3 g-1. The specific capacitance of ACFlowing-N2 electrode and energy density of ACFlowing-N2 capacitor is the biggest among the three AC samples with specific capacitance being at 302.6 F g-1 and energy density being at 10.1 Wh kg-1 after 400 cycles. The microwave−assisted KOH activation of coal is an efficient approach to the preparation of ACs for supercapacitors.
Activated carbons (ACs) from petroleum coke by microwave heating KOH activation are treated by microwave to investigate the effect of microwave−treatment power on AC properties. The electrochemical properties of AC electrodes for supercapacitors were investigated by cyclic voltammetry, constant current charge−discharge and electrochemical impedance spectroscopy. The results showed that specific surface area (SBET) and total pore volume of microwave−treated ACs, specific capacitance and energy density of microwave−treated AC electrodes decreased. The electrical conductivity and stability of AC electrodes for supercapacitors were improved. Fast microwave−treatment is an efficient method to obtain suitable ACs for supercapacitors.
Activated carbon (AC) was prepared from lignite by microwave heating ZnCl2. The pore structure parameters of AC are characterized by nitrogen adsorption technique. The AC and ruthenium oxide/AC composite are characterized by thermogravimetric analysis and transmission electron microscope. Electrochemical properties of ACs and ruthenium oxide/AC composite electrodes were investigated by cyclic voltammetry and constant current charge–discharge after AC was pre−oxidized by HNO3 solution. The results show that the specific surface area and total pore volume of AC from lignite reaches 1310 m2 g−1 and 0.80 cm3 g−1, respectively. The micropore volume of AC from lignite totals only 12.5%. AC and ruthenium oxide/AC composite electrodes with 5wt.% ruthenium oxide loading show high cycle stability. Compared to pristine AC electrode, specific capacitance of ruthenium/AC composite electrode and energy density of ruthenium/AC capacitor after 100 charge−discharge cycles increases 40.8% and 39.1%, respectively.
NiMgAlO catalysts were prepared by two methods: coprecipition and impregnation. They were used to simultaneously adsorb SO2and NO with O2in a fixed bed at atmospheric pressure. Typically the molar composition of the feed gas was 1% SO2, 0.2% NO and O2with ultra-high purity Ar as the diluent. The results showed the catalysts were excellent materials for the simultaneous oxidation adsorption of SO2and NOx. The two kinds of catalysts were compared for the SO2and NOx adsorption capacity. The NiMgAlO catalyst prepared by coprecipition had better adsorption than impregnation. When NiMgAlO catalysts with 10 wt-% Ni content were calcined at 550°C, adsorption capacity was the largest at 120°C adsorption temperature: 1.392 mmol SO2and 0.213 mmol NOx were adsorbed on 1 g catalyst prepared by the coprecipition method. The causes are seen by the XRD, surface area and porous size analysis.
Microporous carbons (MCs) for supercapacitors were prepared from coal tar pitch (CTP) with potassium hydroxide (KOH) as activating agent at different KOH/CTP mass ratio by different heating modes. The results show that the specific surface area (SBET), micropore surface area (Smic), total pore volume (Vt) and micropore volume ((Vmic) of MCs made by microwave heating at 30 min heating time increases with the KOH/CTP mass ratio, respectively. At 14/7 of the KOH/CTP mass ratio, the SBET of MCs made by microwave heating at 30 min heating time reaches 1786 m2/g while that of MCs made by conventional heating at 180 min heating time is 1769 m2/g. The specific capacitance and energy density of the former reaches 269 F/g and 9.2 Wh/kg in 6 M KOH aqueous electrolyte while that of the latter is up to 307 F/g and 10.5 Wh/kg, respectively. And yet, the former brings bigger MC yield and bigger retention of energy density. The effects of the pore size distribution and pore volume on the specific capacitance and energy density of MC samples with the similar SBET by different heating modes are addressed in this paper.
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