活性炭的微结构与超级电容器性能的构效关系

doi:10.11949/0438-1157.20211639

摘要/Abstract

摘要：

以生物质柞木为原料，采用不同活化法制备具有不同结构特征的柞木基活性炭，利用N₂吸附、FT-IR、XPS、XRD、Raman光谱等表征手段对活性炭的微结构特性进行解析，探究活化方式对活性炭微结构性能的影响；微结构与超级电容器性能的构效关系。研究表明： KOH和H₃PO₄-KOH法制备的活性炭微孔发达，炭结构表面缺陷位与杂原子丰富，在低电流密度下表现出更高的比电容；H₃PO₄-KOH法制备的活性炭具备更宽的微介孔分布与孔道连通性，使其具有更好的电容保持率；CO₂、H₃PO₄和H₃PO₄-CO₂法制备的活性炭介孔发达，微孔体积小，孔道连通性差，炭结构相对完整，裸露于炭结构表面的缺陷与杂原子相对较少，尽管电容保持率较高，但比电容较低。因此，高性能的超级电容器活性炭电极应具有发达的微孔结构、较宽的微介孔分布、通畅的微介孔连通结构，同时含有更多的裸露于炭结构表面的结构缺陷与杂原子基团，从而提高超级电容器的能量密度。

关键词: 活化方式, 结构特征, 电化学性能, 构效关系

Abstract:

Zuomu-based activated carbon was prepared by different activation methods. The structure of activated carbon was investigated by N₂ adsorption, FT-IR, XPS, XRD, and Raman spectra. And the structure-property relationship of activated carbon was discussed. The results show that activated carbons prepared by different activation methods have different microstructure and electrochemical performance. Activated carbons prepared by KOH and H₃PO₄-KOH have well-developed micropores, abundant content of defective sites and heteroatoms on the surface of carbon matrix, which provide more energy storage space and active sites to increase the specific capacitance at low current density. The activated carbon prepared by H₃PO₄-KOH has better capacitance retention due to its wider micro mesopore distribution and pore connectivity. Activated carbons prepared by CO₂, H₃PO₄ and H₃PO₄-CO₂ activation possess well-developed mesopores, small micropore volume, poor connectivity, relatively complete carbon matrix, and fewer defects and heteroatoms exposed on the surface of the carbon matrix, resulting in the higher capacitance retention rate and lower specific capacitance. The microstructure of activated carbon has a great influence on the performance of supercapacitors. The developed microporous will provide abundant energy storage sites. The good connectivity will provide channels for fast ion transport to improve the capacitance retention. More exposed defects and heteroatomic groups on the surface or edges of the carbon matrix will be beneficial to improve the pseudo capacitance. These enable the supercapacitor to exhibit high specific capacitance and good cycling stability. Therefore, high-performance activated carbon electrodes for supercapacitors should have a well-developed microporous structure, a wide distribution of micro-mesopores, a smooth micro-mesoporous connected structure. At the same time, it contains more structural defects and heteroatom groups exposed on the surface of the carbon structure, thereby improving the energy density of the supercapacitor.

Key words: activation methods, structure characteristic, electrochemical performance, structure-property relationship

中图分类号:

TQ 174

刘宇喆, 李成才, 李琳, 王少辉, 刘培慧, 王同华. 活性炭的微结构与超级电容器性能的构效关系[J]. 化工学报, 2022, 73(4): 1807-1816.

Yuzhe LIU, Chengcai LI, Lin LI, Shaohui WANG, Peihui LIU, Tonghua WANG. Structure-property relationship between microstructure of activated carbon and supercapacitor performance[J]. CIESC Journal, 2022, 73(4): 1807-1816.

图/表 8

图1 不同活化方式制备的活性炭N2吸脱附等温线(a)与孔径分布(插图为介孔分布)(b)以及不同孔径范围内孔体积(c)

Fig.1 Activated carbons prepared by different activation methods: N2 adsorption isotherms (a), micropore size distribution (the inset shows the distribution of mesopore) (b), and pore volume in different pore size range (c)

表1 不同方法制备活性炭的孔结构信息

Table 1 The pore structure of activated carbon prepared by different activation methods

Samples	S_BET/(m²·g^-1)	V_tot/(cm³·g^-1)	V_mic/(cm³·g^-1)	V_meso/(cm³·g^-1)	(V_mic/ V_tot)/%	(V_meso/V_tot)/%
ZM-C	905	0.720	0.153	0.378	21.24	52.48
ZM-P	1453	1.027	0.260	0.438	25.32	42.65
ZM-K	1702	0.827	0.576	0.153	69.62	18.49
ZM-P-K	2070	1.010	0.737	0.170	72.97	16.83
ZM-P-C	1478	1.088	0.233	0.501	21.42	46.05

图2 ZM-P-K的FESEM图像

Fig.2 FESEM image of ZM-P-K

图3 不同活化方式制备活性炭的XRD谱图(a)，Raman光谱(b)以及拉曼光谱拟合(c)

Fig.3 XRD pattern (a) and Raman spectra (b) of activated carbon prepared by different activation methods, and Raman fitting spectra (c)

表2 拉曼拟合D峰（ID1， ID2， ID3）与G峰（IG）强度比

Table 2 Intensity ratio of ID1， ID2， ID3， and IG of Raman fitting peaks

Samples	I_D1/ I_G	I_D2/ I_G	I_D3/ I_G
ZM-C	1.12	0.41	0.55
ZM-P	1.07	0.40	0.44
ZM-P-C	1.18	0.34	0.45
ZM-K	1.97	0.46	1.36
ZM-P-K	1.47	0.49	0.99

图4 不同活化方式制备活性炭的红外光谱(a)；ZM-P-C的O 1s,N 1s,P 2p的分峰拟合图(b)

Fig.4 FT-IR spectra of activated carbons(a); Peak fitting of ZM-P-C for O 1s, N 1s and P 2p(b)

表3 五种活化方式元素组成和各个样品中O 1s的存在形式

Table 3 The element composition and types of O functional groups of activated carbon by different activation methods

Samples	Elements content/%(atom)				O 1s distribution/%(atom)
Samples	C	N	O	P	O-Ⅰ	O-Ⅱ	O-Ⅲ	O-Ⅳ	O-Ⅴ
ZM-C	92.29	0.99	6.72	—	—	27.94	—	44.73	27.33
ZM-P	90.12	0.20	8.24	1.44	12.80	—	56.60	17.46	11.39
ZM-K	90.47	0.61	8.92	—	—	51.06	—	34.60	14.34
ZM-P-K	89.14	0.51	9.66	0.69	10.84	28.74	41.84	12.85	5.73
ZM-P-C	94.53	0.28	4.72	0.47	11.78	26.80	35.83	16.95	8.63

图5 ZM-P-K在50 mV·s-1不同电压窗口下的CV曲线(a)；在5 mV·s-1扫速下不同活化方式制备的活性炭CV曲线(b)；0.1 A·g-1下的GCD曲线(c)；在不同电流密度下的比电容与电容保持率(d)；循环稳定性(e)；Nyquist谱图(f)

Fig.5 CV curves of ZM-P-K at different voltage windows of 50 mV·s-1 (a); CV curves at 5 mV·s-1 (b); GCD curves at 0.1 A·g-1 (c); Specific capacitance and capacitance retention at different scanning speed (d); Cyclic stability of activated carbon by different activation method (e); Nyquist plots (f)

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