Wang Yanbo, Chen Yiqing, Zhao Hongwei, Li Lixiang, Ju Dongying, Wang Cunjing, An Baigang
Key Laboratory of Energy Materials and Electrochemistry Research Liaoning Province, School of Chemical Engineering, University of Science and Technology Liaoning, Anshan 114051, China.
School of Chemistry and Materials Engineering, Xinxiang University, Xinxiang 453003, China.
Nanomaterials (Basel). 2022 Oct 28;12(21):3804. doi: 10.3390/nano12213804.
Porous carbon has been one desirable electrode material for supercapacitors, but it is still a challenge to balance the appropriate mesopore volume and a high specific surface area (SSA). Herein, a good balance between a high SSA and mesopore volume in biomass-derived porous carbon is realized by precarbonization of wheat husk under air atmosphere via a chloride salt sealing technique and successive KOH activation. Due to the role of molten salt generating mesopores in the precarbonized product, which can further serve as the active sites for the KOH activation to form micropores in the final carbon material, the mesopore-micropore structure of the porous carbon can be tuned by changing the precarbonization temperature. The appropriate amount of mesopores can provide more expressways for ion transfer to accelerate the transport kinetics of diffusion-controlled processes in the micropores. A high SSA can supply abundant sites for charge storage. Therefore, the porous carbon with a good balance between the SSA and mesopores exhibits a specific gravimetric capacitance of 402 F g at 1.0 A g in a three-electrode system. In a two-electrode symmetrical supercapacitor, the biomass-derived porous carbon also delivers a high specific gravimetric capacitance of 346 F g at 1.0 A g and a good cycling stability, retaining 98.59% of the initial capacitance after 30,000 cycles at 5.0 A. This work has fundamental merits for enhancing the electrochemical performance of the biomass-derived porous carbon by optimizing the SSA and pore structures.
多孔碳一直是超级电容器理想的电极材料之一，但要平衡合适的中孔体积和高比表面积（SSA）仍然是一个挑战。在此，通过在空气气氛下采用氯盐密封技术对麦麸进行预碳化并随后进行KOH活化，实现了生物质衍生多孔碳中高比表面积和中孔体积之间的良好平衡。由于熔盐在预碳化产物中产生中孔的作用，其可进一步作为KOH活化的活性位点以在最终碳材料中形成微孔，因此可以通过改变预碳化温度来调节多孔碳的中孔 - 微孔结构。适量的中孔可为离子转移提供更多通道，以加速微孔中扩散控制过程的传输动力学。高比表面积可为电荷存储提供丰富的位点。因此，在三电极系统中，比表面积和中孔之间具有良好平衡的多孔碳在1.0 A g时表现出402 F g的比电容。在两电极对称超级电容器中，生物质衍生的多孔碳在1.0 A g时也具有346 F g的高比电容和良好的循环稳定性，在5.0 A下30000次循环后保留了初始电容的98.59％。这项工作对于通过优化比表面积和孔结构来提高生物质衍生多孔碳的电化学性能具有重要意义。
