Preparation and modification of high performance porous carbons from petroleum coke for use as supercapacitor electrodes
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摘要: 以石油炼制副产品石油焦为原料,采用KOH活化法制备高比面积多孔炭,通过氨水水热处理对多孔炭进行表面渗氮改性。系统考察了KOH/石油焦比例(碱/炭比)对多孔炭孔结构及电化学性能的影响。结果表明多孔炭的比表面积、孔结构和电化学性能可以通过碱/炭比有效地调控。随着碱/炭比的增大,多孔炭的孔道逐渐增大,当碱炭比为3:1时最大比表面积达到2964 m2·g-1。当碱/炭比为5:1时,多孔炭的比表面积和中孔率分别高达2842 m2·g-1和67.0%,其在50 mA·g-1电流密度下的比电容达到350 F·g-1。氨水水热处理多孔炭,可以有效地在多孔炭表面引入氮原子,从而提高了多孔炭电极的电化学性能,尤其提高其在高电流密度下的比电容值。KOH活化以及氨水水热处理为制备高性能低成本石油焦基超级电容器电极材料提供了一种简单有效的方法。Abstract: As a byproduct of oil refining, petroleum coke with a high carbon content (about 90 wt%) has been shown to be a good raw material for porous carbons (PCs). PCs with high specific surface areas were derived from petroleum coke by KOH activation. The effect of KOH/coke mass ratio on the pore structure of the PCs and their electrochemical performance as electrodes of electric double layer capacitors were investigated. Results showed that the specific surface area and pore size distribution of the PCs could be efficiently controlled by the KOH/coke ratio. The pore sizes of the PCs increase with increasing KOH/coke ratio, and the largest specific surface area was as high as 2 964 m2·g-1. A PC-5 electrode prepared with a KOH/coke ratio of 5:1 has a high specific surface area of 2 842 m2·g-1 and mesoporosity of 67.0%, and has the largest specific capacitance at all investigated current densities among the PCs examined. This is ascribed to its high specific surface area and high mesoporosity. Hydrothermal modification of PC-3 (KOH/coke ratio at 3:1) in ammonia at 200℃ increases its specific capacitance, especially at high discharge current densities. This improved electrochemical performance can be attributed to nitrogen-doping that occurs during the process, and this can induce pseudo-capacitance and improve the hydrophilicity of the PC electrode to the electrolyte. KOH activation combined with ammonia hydrothermal modification is a simple yet efficient approach to prepare cost-effective PCs for supercapacitors with excellent electrochemical performance.
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Key words:
- Petroleum coke /
- Porous carbon /
- Supercapacitors /
- Ammonia hydrothermal modification /
- Nitrogen doping
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