煤基石墨烯量子点在超级电容器中的应用

doi:10.16085/j.issn.1000-6613.2022-1791

摘要/Abstract

摘要：

针对目前制备煤基活性炭氢氧化钾（KOH）使用比例过高及孔结构分布不合理问题，以太西无烟煤为碳源，先采用高铁酸钾与过氧化氢分步氧化将其氧化为石墨烯量子点，再与KOH混合活化制备煤基石墨烯量子点活性炭。结果表明，这种方法可降低KOH使用量（使碱炭比小于1），且碱炭比对煤基石墨烯量子点的活化机制与对煤的活化机制类似：KOH用量较少时（碱炭比0.25）只有造孔作用；增加用量后（碱炭比0.5），KOH不但有造孔作用，还有扩孔作用；过量的KOH（碱炭比0.75）则以扩孔为主。随着碱炭比的增加，活性炭的比表面积与总孔容也随之增加，微孔率逐渐下降，中孔率和平均孔径都在增长。在碱炭比为0.75时，活化效果最好，GQDAC-0.75比表面积为1207.3m²/g，微孔率为39.5%，中孔率为51.8%；得益于其独特的“大孔-中孔-微孔”的层次孔结构，GQDAC-0.75表现出最优的电化学性能，在0.5A/g电流密度下比电容达243.6F/g，当电流密度增大到10A/g时，GQDAC-0.75的比电容保持在202.2F/g，继续增大电流密度到100A/g，比电容仍有179.5F/g，且在20A/g电流密度下循环10000次后比电容仍有191.6F/g，保持率为98.1%，具有优异的倍率性能和循环稳定性。

关键词: 煤, 石墨烯量子点, 活化, 微观结构, 活性炭, 超级电容器

Abstract:

In order to solve the problems of excessive use of potassium hydroxide (KOH) and unreasonable pore structure distribution in the preparation of coal-based activated carbon, Taxi anthracite was used as carbon source to oxidize graphene quantum dots by potassium ferrate and hydrogen peroxide, and then mixed with KOH to prepare coal-based graphene quantum dots activated carbon. The results showed that this method could reduce the amount of KOH (making the alkali-carbon ratio less than 1), and the activation mechanism of the alkali-carbon ratio to graphene quantum dots was similar to that of coal. When the amount of KOH was small (alkali-carbon ratio with 0.25), only pore-forming effect was observed. After increasing the dosage (alkali-carbon ratio with 0.5), KOH had not only the pore-forming effect, but also the pore-expanding effect. The excess KOH (alkali carbon ratio with 0.75) was mainly focus on pore-expanding effect. With the increase of alkali-carbon ratio, the specific surface area and total pore volume of activated carbon also increased, and the micropore rate gradually decreased, while the mesoporous rate and the average pore size increased. When the alkali-carbon ratio was 0.75, the activation effect was the best. The specific surface area of GQDAC-0.75 was 1207.3m²/g, the micropore rate was 39.5%, and the mesoporous rate was 51.8%. Thanks to its unique hierarchical pore structure of "macropore-mesopore-micropore", GQDAC-0.75 showed the optimal electrochemical performance with specific capacitance of 243.6F/g at 0.5A/g current density. When the current density increased to 10A/g, the specific capacitance of GQDAC-0.75 was maintained at 202.2F/g. Even the current density continued to increase to 100A/g, the specific capacitance was still 179.5F/g, and the specific capacitance could remain 191.6F/g at the current density of 20A/g after 10000 cycles with a 98.1% retention rate, which indicated the excellent rate performance and cycle performance.

Key words: coal, graphene quantum dots, activation, microstructure, activated carbon, supercapacitor

中图分类号:

TM242

张耀杰, 张传祥, 孙悦, 曾会会, 贾建波, 蒋振东. 煤基石墨烯量子点在超级电容器中的应用[J]. 化工进展, 2023, 42(8): 4340-4350.

ZHANG Yaojie, ZHANG Chuanxiang, SUN Yue, ZENG Huihui, JIA Jianbo, JIANG Zhendong. Application of coal-based graphene quantum dots in supercapacitors[J]. Chemical Industry and Engineering Progress, 2023, 42(8): 4340-4350.

图/表 13

表1 原料煤的工业分析及元素分析（质量分数）

样品	工业分析/%				元素分析/%
样品	水分	灰分	挥发分	固定碳	碳	氢	氧	氮	硫
太西无烟煤	1.55	2.32	6.94	93.06	94.08	3.61	1.42	0.76	0.13

图1 煤基石墨烯量子点的透射电镜（a）及高分辨图谱（b）

图2 煤基石墨烯量子点的荧光光谱

图3 不同活化比例的煤基石墨烯量子点活性炭的扫描电镜

图4 活性炭的等温吸附线（a）及孔径分步图（b）

表2 活性炭的比表面积及孔径参数

样品编号	比表面积/m²·g^-1	总孔容/cm³·g^-1	微孔孔容/cm³·g^-1	微孔率/%	中孔孔容/cm³·g^-1	中孔率/%	平均孔径/nm
GQDAC-0	268.8	0.204	0.156	76.6	0.029	13.9	2.24
GQDAC-0.25	654.1	0.476	0.421	88.4	0.049	10.3	1.84
GQDAC-0.5	1166.4	0.852	0.607	71.2	0.230	26.9	2.00
GQDAC-0.75	1207.3	1.346	0.531	39.5	0.697	51.8	3.59

图5 活性炭的XRD谱图（a）及拉曼谱图（b）

图6 活性炭的红外光谱

图7 活性炭的XPS全扫描谱图

图8 活性炭的C 1s高分辨谱图

表3 活性炭的元素含量及官能团含量

样品编号	C原子分数/%						氧原子分数（总含量）/%
样品编号	总含量	C—C/C $̿$ C	C—O	C—O—C	C $̿$ O	COOH	氧原子分数（总含量）/%
GQDAC-0	89.46	69.58	12.58	9.44	5.04	3.36	8.56
GQDAC-0.25	87.53	54.51	25.62	11.47	4.78	3.62	10.8
GQDAC-0.5	86.42	59.51	19.11	12.37	5.08	3.92	11.24
GQDAC-0.75	86.24	64.71	12.44	13.99	5.93	2.91	11.47

表3 活性炭的元素含量及官能团含量

样品编号	C原子分数/%						氧原子分数（总含量）/%
样品编号	总含量	C—C/C $̿$ C	C—O	C—O—C	C $̿$ O	COOH	氧原子分数（总含量）/%
GQDAC-0	89.46	69.58	12.58	9.44	5.04	3.36	8.56
GQDAC-0.25	87.53	54.51	25.62	11.47	4.78	3.62	10.8
GQDAC-0.5	86.42	59.51	19.11	12.37	5.08	3.92	11.24
GQDAC-0.75	86.24	64.71	12.44	13.99	5.93	2.91	11.47

图9 煤基石墨烯量子点活性炭在三电极体系下的电化学性能

表4 不同活性炭比电容对比总结表

前体	活化剂	测试体系	电解液	比电容 /F·g^-1（A·g^-1)	参考文献
褐煤	ZnCl₂	三电极	6mol/L KOH	140.0（10）	[14]
烟煤	PAN+DMF	三电极	6mol/L KOH	200.6（10）	[40]
无烟煤	CO₂+KOH	三电极	6mol/L KOH	190.0（5)	[41]
低阶煤	FeCl₂+CO₂	三电极	6mol/L KOH	180.0（10）	[29]
煤/半焦	PAN/PVP	三电极	6mol/L KOH	152.0（4）	[42]
煤沥青	KOH	三电极	6mol/L KOH	192.0（10）	[16]
褐煤	水蒸气	三电极	6mol/L KOH	122.0（10）	[43]
煤沥青/ 氧化石墨烯	1,6-二氨基乙烷	三电极	6mol/L KOH	163.0（30）	[44]
无烟煤	KOH	三电极	6mol/L KOH	202.2（10）	本文
				179.5（100）

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