Regular Article ZnO-assisted synthesis of lignin-based ultra-fine microporous carbon nanofibers for supercapacitors Chang Ma a,b,⇑ , Liqiang Wu a , Mahmut Dirican b , Hui Cheng b , Junjing Li a , Yan Song c , Jingli Shi a , Xiangwu Zhang b,⇑ a Tianjin Municipal Key Lab of Advanced Fiber and Energy Storage Technology, Tiangong University, Tianjin 300387, China b Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science, Wilson College of Textiles, North Carolina State University, Raleigh, NC 27695-8301, United States c CAS Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, 030001, China graphical abstract article info Article history: Received 29 July 2020 Revised 22 October 2020 Accepted 24 October 2020 Available online xxxx Keywords: Lignin Ultra-fine Carbon nanofibers Supercapacitors Microporous carbons abstract Reducing the material size could be an effective approach to enhance the electrochemical performance of porous carbons for supercapacitors. In this work, ultra-fine porous carbon nanofibers are prepared by electrospinning using lignin/ polyvinylpyrrolidone as carbon precursor and zinc nitrate hexahydrate (ZNH) as an additive, followed by pre-oxidation, carbonization, and pickling processes. Assisted by the ZnO template, the pyrolytic product of ZNH, abundant micropores are yielded, leading to the formation of microporous carbon nanofibers with specific surface area (SSA) up to 1363 m 2 g À1 . The average diam- eter of the lignin-based ultra-fine porous carbon nanofibers (LUPCFs) is effectively controlled from 209 to 83 nm through adjusting the ZNH content. With good flexibility and self-standing nature, the LUPCFs could be directly cut into electrodes for use in supercapacitors. High accessible surface, enriched surface N/O groups, and reduced fiber diameters endow the LUPCFs-based electrodes with an excellent specific capacitance of 289 F g À1 . The reduction of fiber diameters remarkably improves the rate performance of the LUPCFs and leads to a low relaxation time constant of 0.37 s. The high specific capacitance of 162 F g À1 is maintained when the current density is increased from 0.1 to 20 A g À1 . Besides, the fabricated LUPCFs show exceptional cycling stability in symmetrical supercapacitors, manifesting a promising appli- cation prospect in the next generation of supercapacitors. Ó 2020 Elsevier Inc. All rights reserved. https://doi.org/10.1016/j.jcis.2020.10.105 0021-9797/Ó 2020 Elsevier Inc. All rights reserved. ⇑ Corresponding authors at: Tianjin Municipal Key Lab of Advanced Fiber and Energy Storage Technology, Tiangong University, Tianjin 300387, China (C. Ma). E-mail addresses: machang@tiangong.edu.cn (C. Ma), xiangwu_zhang@ncsu.edu (X. Zhang). Journal of Colloid and Interface Science xxx (xxxx) xxx Contents lists available at ScienceDirect Journal of Colloid and Interface Science journal homepage: www.elsevier.com/locate/jcis Please cite this article as: C. Ma, L. Wu, M. Dirican et al., ZnO-assisted synthesis of lignin-based ultra-fine microporous carbon nanofibers for supercapac- itors, Journal of Colloid and Interface Science, https://doi.org/10.1016/j.jcis.2020.10.105