硝酸膨化改性对石油焦基活性炭超级电容器性能的影响

以KMnO₄为氧化剂, HNO₃为插层剂, 对石油焦进行膨化改性。以KOH为活化剂, 在碱碳比为3:1、4:1和5:1时, 将膨化石油焦制备成活性炭(产物标记为EAC-3、EAC-4和EAC-5); 作为对比, 按照相同碱碳比, 将未改性石油焦制备成活性炭(产物标记为AC-3、AC-4和AC-5)。采用TG、XRD、I₂吸附、N₂吸附、循环伏安和交流阻抗谱对石油焦和活性炭进行了表征。研究表明, 膨化改性使石油焦石墨微晶的晶面层间距由0.344 nm增加到0.359 nm, 微晶厚度由2.34 nm降低到1.61 nm; EAC-3和AC-5的比表面积分别为3325和3291 m²/g; 在0.5 mV/s的扫描速度下, EAC-3和AC-5比电容分别为448和429 F/g; 基于EAC-3的超级电容器具有更低的内阻和更好的功率特性。

Effect of Petroleum Coke Expanding by HNO3 on the Performance of Supercapacitor Based on the Activated Carbon

Petroleum coke (PC) was expanded by using KMnO₄ as oxidant and HNO₃ as intercalator so as to decrease the amount of KOH needed for the successive activation. The expanded PC (EPC) was activated at KOH / coke mass ratio of 3:1, 4:1 and 5:1. The products were denoted as EAC-3, EAC-4 and EAC-5, respectively. As a comparison, PC was also activated at the same KOH / coke mass ratio. The products were denoted as AC-3, AC-4 and AC-5, respectively. Thermogravimetry (TG), XRD, I₂ adsorption, N₂ adsorption, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were used to investigate the influence of expanding treatment on the structure and performance of the PCs and ACs. The research revealed that expanding treatment increased the interplanar distance of PC microcrystalline from 0.344 nm to 0.359 nm and decreased the microcrystalline thickness from 2.34 nm to 1.61 nm. The specific surface areas of EAC-3 and AC-5 were 3325 and 3291 m²/g, respectively. The average pore size of EAC-3 was 2.16 nm, which was 0.08 nm larger than that of AC-5. At a scan rate of 0.5 mV/s, EAC-3 and AC-5 achieved a specific gravimetric capacitance of 448 and 429 F/g, respectively. Supercapacitor based on EAC-3 possessed lower resistance and better power performance.