A tunable hierarchical porous carbon from starch pretreated by calcium acetate for high performance supercapacitors

摘要

Hierarchical porous carbons (HPCs) with abundant mesopores have been prepared by a facile route from the starch that was pretreated by calcium acetate. The scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and N-2 adsorption-desorption tests show that hierarchical porous carbons with bimodal mesopores have been obtained. Moreover, the pore sizes are tunable by simply adjusting the reactants ratio and carbonization temperature. The as-synthesized hierarchical porous carbon materials (HPCs-2-800) possesses the highest Brunauer-Emmett-Teller (BET)-specific surface area of 464 m(2) g(-1) and mesoporous volume of 0.663 cm(3) g(-1) at the carbonization temperature of 800 degrees C and starch to calcium acetate mass ratio of 2. Electrochemical measurements also display that the HPCs-2-800 electrodes have a high reversible capacity of 244 F g(-1) at the current density of 0.1 A g(-1) and 182 F g(-1) at the current density of 10 A g(-1). When the current density is elevated from 0.1 to 10 A g(-1), the high capacitance retention of 74.6 % reveals a good rate performance. Long charge-discharge cycling measurements disclose good stabilities over 25,000 cycles at different current densities of 1-10 A g(-1) (5000 cycles at each current density) for HPCs-2800 electrode. The cycling results indicate a high capacitance retention of 99.6% over 5000 charge-discharge cycles even at the current density of 10 A g(-1). The excellent supercapacitive performances imply that HPCs-2-800 is a promising candidate for supercapacitors.