硝酸膨化改性对石油焦基活性炭超级电容器性能的影响

doi:10.3724/SP.J.1077.2014.13288

摘要/Abstract

摘要：

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。

关键词: 石油焦, 膨化, 超级电容器, 活性炭

Abstract:

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.

Key words: petroleum coke, expanding, supercapacitor, activated carbon

中图分类号:

O646

邓梅根, 王仁清, 冯义红. 硝酸膨化改性对石油焦基活性炭超级电容器性能的影响[J]. 无机材料学报, 2014, 29(3): 245-249.

DENG Mei-Gen, WANG Ren-Qing, Feng Yi-Hong. Effect of Petroleum Coke Expanding by HNO₃ on the Performance of Supercapacitor Based on the Activated Carbon[J]. Journal of Inorganic Materials, 2014, 29(3): 245-249.

图/表 6

图1 PC和OPC的TG/DTG曲线

Fig. 1 TG/DTG curves of PC and OPC

表1 PC和EPC的石墨微晶结构参数

Table 1 Graphitic microcrystalline structural parameters of PC and EPC

Sample	d₀₀₂/nm	L_c /nm	N
PC	0.344	2.34	8
EPC	0.359	1.61	5

表2 ACs和EACs的孔结构参数

Table 2 Pore structure parameters of ACs and EACs

Sample	I₂ / (mg·g^-1)	V_t / (cm³·g^-1)	V_micro / (cm³·g^-1)	(V_micro/V_t) / %	S_BET / (m²·g^-1)	S_micro / (m²·g^-1)	(S_micro/S_BET) / %	L_c / nm
AC-3	2270	1.17	0.97	82.91	2216	1978	89.26	1.92
AC-4	2604	1.44	1.17	81.25	2929	2598	88.69	1.94
AC-5	2910	1.71	1.23	71.93	3291	2766	84.05	2.08
EAC-3	2923	1.76	1.21	68.75	3325	2731	82.14	2.16
EAC-4	2747	1.87	0.96	51.43	3054	1951	63.88	2.39
EAC-5	2345	2.04	0.58	25.88	2632	868	32.99	2.67

图2 EAC-3和AC-5电极在不同扫描速度下的循环伏安曲线

Fig. 2 CV curves of EAC-3 and AC-5 electrodes at different scan rates

图3 EAC-3和AC-5电极的归一化比容与扫速的关系

Fig. 3 Relationship between Normalized specific capacitance and scan rate for EAC-3 and AC-5 electrodes

图4 EAC-3和AC-5电极的交流阻抗谱

Fig. 4 EIS spectra of EAC-3 and AC-5 electrodes

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