基于煤萃取物的类石墨状多孔炭的制备及其电容性能研究

doi:10.15541/jim20150329

摘要/Abstract

摘要：

以褐煤萃取物为炭前驱体, MgO为阻隔剂, KOH为活化剂, 在800℃惰性气氛下制备出类石墨状多孔炭材料。对该多孔炭材料进行了红外(FTIR)、X射线衍射(XRD)、透射电镜(TEM)和拉曼(Raman)表征。以活化前和活化后多孔炭为电极材料, 利用循环伏安、恒电流充放电、交流阻抗对其进行了电化学电容性能评价和比较。结果表明: 活化后炭材料呈现多孔的薄膜状, 比表面积高达1396 m²/g, 而活化前炭材料比表面积仅为138.4 m²/g。当电流密度为1 A/g和4 A/g时, 活化后炭材料比电容分别为533 F/g和390 F/g; 而活化前炭材料对应的比电容为366 F/g和198 F/g。在电流密度为5 A/g下循环8000圈后, 活化前后炭材料的电容保持率分别为72.5%和89.6%。可见, 经过KOH活化后的炭材料比电容和电化学稳定性有了显著提高。该研究证明阻隔剂和活化剂的使用, 能够获得高度柔性的高电容性能的类石墨状多孔炭。

关键词: 煤萃取物, 多孔炭, 电极材料, 电容性能

Abstract:

By using extracts of lignites as carbon precursors, MgO as isolation agent, and KOH as activator, porous graphene-like carbon materials were prepared at 800℃ under an inert atmosphere. Porous carbon materials were characterized by FTIR, XRD, TEM and Raman. Further, electrochemical capacitive properties of porous carbons before and after activation as the electrodes were evaluated by cyclic voltammetry, galvanostatic charge-discharge and impedance spectroscopic techniques. Results indicate that carbon materials after activation exhibit porous film-like shape. The specific surface areas of carbon materials before and after activation are 138.4 m²/g and 1396 m²/g, respectively. Specific capacitances of carbon materials after activation reach 533 F/g and 390 F/g at 1 A/g and 4 A/g, respectively, while those of carbon materials before activation at same conditions are 366 F/g and 198 F/g. After 8000 cycles at a current density of 5 A/g, the capacitance retentions of carbon materials before and after activation are 72.5% and 89.6%, respectively. Accordingly, after KOH activation, the specific capacitance and electrochemical stability of carbon materials are significantly improved. This study verifies that the use of the isolation agent and the activator can obtain highly flexible graphene-like porous carbon with high capacitance performance.

Key words: coal extracts, porous carbon, electrode material, capacitive performance

中图分类号:

TQ174

李金宏, 周岐雄, 米红宇, 李显, 李惠萍. 基于煤萃取物的类石墨状多孔炭的制备及其电容性能研究[J]. 无机材料学报, 2016, 31(1): 39-46.

LI Jin-Hong, ZHOU Qi-Xiong, MI Hong-Yu, LI Xian, LI Hui-Ping. Preparation and Capacitive Properties of Graphite-like Porous Carbon Based on Coal Extracts[J]. Journal of Inorganic Materials, 2016, 31(1): 39-46.

图/表 11

图1 萃取物的热重曲线

Fig. 1 TG-DTG curves of the extracts

表1 萃取物的工业分析和元素分析

Table 1 Proximate and ultimate analysis of extracts

Proximate analysis / wt%					Ultimate analysis /(wt%, daf)					H/C	O/C
M_ad	A_ad	V_daf	FC_ad		C	H	N	S	O^*	H/C	O/C
1.76	0.93	75.29	24.05		77.6	5.76	0.99	0.13	15.52	0.89	0.15

图2 萃取物和多孔炭(C2)的FTIR图谱

Fig. 2 FTIR spectra of the extracts and C2

图3 C2的XRD谱图(a) 和Raman谱图(b)

Fig. 3 XRD spectra (a) and Raman spectrum (b) of C2

图4 直接炭化物C3(a)、活化前多孔炭C1(b)和活化后多孔炭C2(c)的TEM照片

Fig. 4 TEM images of C3 (a), C1 (b) and C2 (c)

图5 77 K下C1(a)和C2(b)的N2吸脱附等温线及其孔径分布曲线

Fig. 5 N2 adsorption-desorption isotherms and pore size distribution of C1 (a) and C2 (b)

图6 C1(a)和C2(b)电极在不同扫速下的循环伏安曲线

Fig. 6 Cyclic voltammograms of C1 (a) and C2 (b) electrodes at different scanning rates

图7 C1(a)和C2(b)电极在不同电流密度下的充放电曲线

Fig. 7 Charge/discharge curves of C1 (a) and C2 (b) electrodes at different current densities

图8 C1和C2电极在不同电流密度下的比电容(a)和倍率特性(b)曲线

Fig. 8 Specific capacitance (a) and rate performance (b) for C1 and C2 electrodes at different current densities

图9 C1和C2电极在5 A/g电流密度下的循环寿命图和库伦效率图

Fig. 9 Cycling performance and coulombic efficiency of C1 and C2 electrodes at a current density of 5 A/g

图10 C1和C2电极循环8000圈前后的交流阻抗曲线

Fig. 10 Nyquist plots before and after 8000 cycles of C1 and C2 electrodes

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