Xanthoceras sorbifolia seed coats derived porous carbon with unique architecture for high rate performance supercapacitors

摘要

Here in this report, Xanthoceras sorbifolia seed coats are selected to prepare porous carbons. Biochar is first prepared by dry distillation of the seed coats, and then is transformed into porous carbon by KOH activation. The regulation of activation temperatures and ratios of activator is studied. The optimized condition is activation temperature of 750 degrees C, and the ratio of biochar to activator is 1:3. HRTEM, X-ray diffraction and the Brunauer-Emmett-Teller methods were used to characterize the samples. The porous carbon prepared under the optimum condition has a specific surface area of 2148 m(2) g(-1) with a large amount of micropores of about 0.5 nm-2 nm closely and orderly distributed, together with a certain number of mesporous (similar to 12% of the total specific surface area), such a unique structure provides both a large storage space for electrons and a channel for them to passage quickly. Due to this unique architecture, the specific capacitance of the porous carbon is as high as 421 F/g at a current density of 0.5 A/g, with a moderate rate capability (259 F/g at 10 A/g), and good cycle stability (90.7% capacitance retention after 5000 cycles at 10 A/g), suggesting it one of the ideal materials for the development of supercapacitors. Symmetrical supercapacitor based on this material has also been assembled and tested to further verify the actual capacitance properties. The specific capacitance of the symmetrical supercapacitor is 276 F/g at 0.5 A/g, and 50 F/g was achieved when the current density was raised up to 10 A/g. Under the current density of 10 A/g, the capacitance only decreased slightly after the circulation of 5000 cycles, and the retention rate reached 86%, illustrates the practical application potential of this material.