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Abstract: In this work, sugar-derived carbon microspheres (CMSs) with diameters in the range of 5–10μm and uniform nanopores were prepared using the subcritical water carbonization method, followed by microwave-assisted KOH activation. The carbonization was conducted at 3MPa and moderate temperatures (150–170°C) in subcritical water, which is a green dehydrating agent. The formation of the CMSs from a sugar solution under subcritical water conditions followed a radical-catalysed emulsion polymerization mechanism. The specific surface area and pore volume of the CMSs were found to increase with increasing the mass ratio of KOH over carbon up to 1:1. Electrocapacitive results showed that a sample prepared at a KOH to carbon ratio of 1:1 and microwave irradiation level of 70% possessed the highest specific capacitance (about 179.2F/g) at a current density of 1A/g and excellent cycling performance over 1000 charging/discharging cycles without significantly loss in capacitance. The specific capacitance and capacitive retention of this electrode are comparable to that of an electrode prepared from commercial YP-80F activated carbon. [Copyright &y& Elsevier]

Abstract: A facile and green preparation of high surface area activated carbons with mixed microporosity and mesoporosity from durian shell waste is reported in this work. The pore structure and surface chemistry of the parent carbon were modified by the combination of ultrasonication and microwave irradiation techniques. The effects of temperature and time in the ultrasonication treatment and power output and time in the microwave irradiation were studied. The electrochemical performance of carbon electrodes for supercapacitors was tested by cyclic voltammeter (CV) and galvanostatic charge–discharge. The results show that the capacitive energy storage of electrodes is critically dependent on the microporosity and surface chemistry of activated carbons. The highest electrode capacitance in this work was 103.6F/g that prepared from activated carbon modified at an ultrasonication temperature of 323.15K for 10min and microwave power output of 900W for 10min. [Copyright &y& Elsevier]