Preparation of MnO2-rGO/bamboo cellulose based carbon aerogel and its application in supercapacitors
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摘要: 研究以竹浆纤维为原料,在氢氧化钠和尿素溶解体系中加入氧化石墨烯,经过凝胶、热解制备还原氧化石墨烯(rGO)/竹纤维素基炭气凝胶。以此作为导电基质,采用水热法负载δ-MnO2纳米片,研究了MnO2负载量对复合材料的电化学性能影响,探讨了复合材料的储能机制。结果显示,随着MnO2负载量的增加,复合材料的电化学性能呈先提高后降低的趋势。当初始参与反应的KMnO4含量为0.005 mol时,复合材料比电容可达330 F/g。将其作为正极材料组装的非对称超级电容器在0.5 A/g的电流密度下,比电容高达68.8 F/g;在功率密度为163 W/kg时,能量密度高达16.2 W•h/kg;在2 A/g电流密度下循环8000次后仍能保持94%的初始容量。Abstract: Reduced graphene oxide (rGO)/bamboo cellulose based carbon aerogel was prepared after gel and pyrolysis by adding GO in sodium hydroxide and urea solution system. Then, the δ-MnO2 nanosheets were deposited on this conductive substrate by hydrothermal method. The effect of MnO2 deposition content on the electrochemical properties of the composites and the energy storage mechanism of the composites were studied. The results show that the electrochemical properties of the composites are firstly improved and then decreased with increasing MnO2 deposition amount. When 0.005 mol KMnO4 is added, the specific capacitance of the composite material is 330 F/g. In addition, the asymmetric supercapacitor exhibits a high specific capacitance of 68.8 F/g at 0.5 A/g, and reveals a high energy density of 16.2 W•h/kg at a power density of 163 W/kg. It retains 94% of the initial specific capacitance after 8000 cycles at 2 A/g.
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Key words:
- bamboo pulp fiber /
- MnO2 /
- graphene /
- carbon aerogel /
- supercapacitor /
- electrochemical properties /
- energy storage mechanism
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图 3 不同MnO2负载量下炭气凝胶的扫描电镜图:rGO/BCCA (a)、MnO2-rGO/BCCA5 ((b)~(d))、MnO2-rGO/BCCA1 (e)、MnO2-rGO/BCCA10 (f)、KMnO4含量为0.005 mol时的低倍和高倍透射电镜 ((g), (h)) 及EDS能谱图 (i)
Figure 3. SEM images of the carbon aerogel under different MnO2 contents: rGO/BCCA (a), MnO2-rGO/BCCA5 ((b)-(d)), MnO2-rGO/BCCA1 (e), MnO2-rGO/BCCA10 (f); TEM and HRTEM images ((g), (h)) and EDS spectrum diagrams (i) of the carbon aerogel synthetized with 0.005 mol KMnO4
图 5 不同MnO2负载量下炭气凝胶的电化学性能:三个样品在5 mV/s (a)和50 mV/s (b)扫描速率下的循环伏安曲线、MnO2-rGO/BCCA5样品的循环伏安曲线(c)和恒流充放电曲线(d)、三个样品的质量比电容(e)和尼奎斯特图(f)
Figure 5. Electrochemical performance of the carbon aerogel under different MnO2 content: the CV curves at scan rate of 5 mV/s (a) and 50 mV/s (b) of three samples, the CV curves (c) and GCD curves (d) of MnO2-rGO/BCCA5, the capacitance retentions (e) and Nyquist plots (f) of three samples
图 6 MnO2-rGO/BCCA5//N/BCCA非对称超级电容器的电化学性能:在不同电压窗口(a)和不同扫描速率(b)下的循环伏安曲线、不同电流密度下的恒流充放电曲线(c)和电压降与电流密度关系图(d)
Figure 6. Electrochemical performance of MnO2-rGO/BCCA5//N/BCCA asymmetric supercapacitor: the CV curves at different voltage windows (a) and different scan rates (b), the GCD surves at different current densities (c) and dependence of the IR drop on current density (d)
表 1 不同MnO2负载量下炭气凝胶的元素含量
Table 1. Element contents of the carbon aerogel under different MnO2 contents
Sample Element contents/wt% C1s N1s O1s Mn2p rGO/BCCA 81.62 9.49 8.90 — MnO2-rGO/BCCA1 43.95 3.04 37.26 15.74 MnO2-rGO/BCCA5 37.19 2.08 42.38 18.35 MnO2-rGO/BCCA10 35.59 1.62 43.96 18.83 Notes: MnO2-rGO/BCCAx(x=1, 5, 10)—MnO2-reduced graphene oxide/bamboo cellulose carbon aerogel composites with the initial KMnO4 contents involved in the reaction are 0.001 mol, 0.005 mol, 0.01 mol, respectively. -
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