利用核桃壳制备高比表面积活性炭电极材料的研究

Preparation of High Specific Surface Area Activated Carbon Electrode Materials from Walnut Shell

以核桃壳为原料，采用KOH活化法制备活性炭，并将其用作超级电容器电极材料。利用N2吸附和扫描电镜（SEM）表征活性炭的孔结构及表面形貌，系统研究碱炭比（KOH与核桃壳炭化料的质量比）对活性炭孔结构的影响，并采用恒流充放电及循环伏安等测定核桃壳活性炭电极材料在3mol／LKOH电解液中的电化学性能。结果表明，随着碱炭比的增大，活性炭的比表面积、总孔容及中孔比例先逐渐增大后稍有减小。当活化温度为800℃，活化时间为1h，碱炭比为4时，可制备出比表面积为2404m^2／g，总孔容为1．344cm^3／g，中孔比例为28．6％，孔径分布在0．7～3．0nm之间的高比表面积活性炭。该活性炭用作超级电容器电极材料具有良好的大电流放电特性和优异的循环性能，电流密度由50mA／g提高到5000mA／g时，其比电容由340F／g降低到288F／g，经1000次循环后，比电容保持率为93．4％。

Activated carbons used as electrode materials for supercapacitors were prepared from walnut shell by KOH activation. The pore structure and surface morphology of activated carbon was characterized by N2 adsorption and scanning electron microscope （SEM）. The effects of weight ratio of KOH to carbonized precursor from walnut shell （KOH/carbonized precursor ratio） on the pore structure of ACs were extensively investigated. The electrochemical performance of walnut shell-based activated carbon electrode materials were evaluated by galvanostatie charge/discharge and cyclic voltammetry in 3 mol/L KOH electrolyte. The results showed that specific surface area, total pore volume and mesopore percentage increased gradually and then decreased slightly with the rising KOH/carbonized precursor ratio. The high specific surface area activated carbon with a specific surface area of 2404 m^2/g, total pore volume of 1. 344 cm^3/g, mesopore percentage of 28. 6% and pore size distribution in 0. 7-3. 0 nm was obtained at KOH/carbonized precursor ratio of 4, activation temperature of 800℃ and activation time of 1 h. The corresponding electrode materials for supercapacitors exhibited excellent high current density charge/discharge characteristics and su- perior cycling performance. The specific capacitance decreased from 340 F/g to 288 F/g as the current density in- creased from 50 mA/g to 5000 mA/g, and the residual specific capacitance was 93.4% after 1000 cycles.