预活化时间对稻壳基活性炭结构和电化学性能的影响

以农业废料稻壳为碳源,氢氧化钠为活化剂,采用干法两步活化法制备活性炭。X射线衍射分析表明该法能有效去除稻壳中的灰分,提高活性炭的孔隙率。扫描电镜结果表明,活性炭具有发达的孔隙结构。以活性炭制备超级电容器的电极,并组装成扣式电容器。采用恒流充放电、循环伏安、交流阻抗等测定超级电容器的电化学性能,并着重探究了预活化时间对活性炭的结构及电化学性能的影响。结果表明,预活化时间为120 min的活性炭的比电容最大,在0.25 A/g电流密度下,可达219F/g,经过1 000次循环后,其电容保持率仍达85.4%。这表明活性炭电极具有较理想的电容特性,且循环性能稳定。

Effect of Pre-activation Time on Structure and Electrochemical Performance for Rice Husk-based Activated Carbon

In this paper, agricultural waste rice husk as carbon source, sodium hydroxide as activator, dry two-step activation was used to prepare activated carbon. The results of X-ray diffraction (XRD) showed that this activation method could effectively remove ash from rice husk and improve the porosity of activated carbon. Scanning electron microscopy (SEM) revealed that the activated carbon has a developed pore structure. And then the electrode of supercapacitor was prepared with activated carbon and assembled into a button capacitor. The electrochemical performance of supercapacitor was measured by constant current charging-discharging, cyclic voltammetry (CV) and alternating current (AC) impedance. In addition, the effect of pre-activation time on structure and electrochemical properties of activated carbon was investigated. The results showed that the activated carbon with the pre-activation time of 120 min possessed the largest specific capacitance of 219 F/g at 0.25 A/g for current density. And the capacitance retention rate was as high as 85.4% after 1 000 cycles, indicating that the activated carbon electrode had ideal capacitance characteristics and stable cycling performance.