水热炭化-KOH活化制备核桃壳活性炭电极材料的研究

以核桃壳为原料,经水热炭化-KOH活化制备活性炭,并将其用作超级电容器电极材料。采用低温氮气吸附、扫描电镜(SEM)及X射线光电子能谱(XPS)等手段系统研究核桃壳活性炭的微观结构及表面化学性质,并利用恒流充放电、循环伏安等探讨其对应电极材料的电化学性能。研究表明,在碱碳比为3∶1、活化温度为800℃、活化时间为1h的条件下,核桃壳水热炭经KOH活化可制备出比表面积为1 236m2/g、总孔容为0.804cm3/g、中孔比例为38.3%的活性炭。该核桃壳活性炭用作电极材料在KOH电解液中具有优异的电化学特性,其在50mA/g电流密度下的比电容可达251F/g,5 000mA/g电流密度下的比电容为205F/g,且具有良好的循环稳定性,1 000次循环后比电容保持率达92.4%,是一种比较理想的超级电容器电极材料。核桃壳活性炭优异的电化学性能与其相互贯通的层次孔结构和独特的含氧表面密切相关。

Preparation of Walnut Shell Activated Carbons via Combination ofHydrothermal Carbonization and KOH Activation

Activated carbons applied as electrode materials for supercapacitors were prepared from walnut shell via hydrother-mal carbonization and KOH activation.The microstructure and surface chemical property of activated carbons were characterized by low temperature N2adsorption,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 voltam-metry 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,activa-tion temperature of 800 ℃ and activation time of 1 h.The walnut shell activated carbon applied as electrode materials for supercapaci-tor 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.