Preparation of Walnut Shell Activated Carbons via Combination of Hydrothermal Carbonization and KOH Activation
ZHANG Chuantao1,2, XING Baolin1,2, HUANG Guangxu1,2, ZHANG Shuangjie3, ZHANG Chuanxiang1,2, SHI Changliang1,2, ZHU Ahui1, YAO Youheng1, ZHANG Qingshan1
1 College of Chemistry and Chemical Engineering, Henan Polytechnic University, Jiaozuo 454000; 2 Collaborative Innovation Center of Coal Work Safety of Henan Province, Jiaozuo 454000; 3 Do-Fluoride Chemicals Co., Ltd., Jiaozuo 454191
Abstract: Activated carbons applied as electrode materials for supercapacitors were prepared from walnut shell via hydrothermal carbonization and KOH activation. The microstructure and surface chemical property of activated carbons were characterized by low temperature N2 adsorption, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The electroche-mical performances of activated carbon electrode materials were also investigated by galvanostatic charge/discharge and cyclic voltammetry in 3 mol/L KOH aqueous electrolyte. The results show that walnut shell activated carbon with a specific surface of 1 236 m2/g, total pore volume of 0.804 cm3/g, mesopore percentage of 38.3% was obtained at KOH/hydrothermal carbon ratio of 3, activation temperature of 800 ℃ and activation time of 1 h. The walnut shell activated carbon applied as electrode materials for supercapacitor exhibited an excellent electrochemical performance and superior cycling performance in KOH aqueous electrolyte. The gravimetric specific capacitance was as high as 251 F/g at a current density of 50 mA/g and still remained 205 F/g even at a current density of 5 000 mA/g, and 92.4% of the initial specific capacitance was retained after 1 000 cycles. The superior electrochemical performance of walnut shell activated carbons were strongly related to their interconnected hierarchical pore structure and unique oxygen-enriched surface.
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