Azide-assisted hydrothermal synthesis of N-doped active carbon with high conductivity for supercapacitor
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ORIGINAL PAPER
Azide-assisted hydrothermal synthesis of N-doped active carbon with high conductivity for supercapacitor Qian Zhang 1 & Peng Zhao 1 & Sudong Yang 1 & Qiang Yan 1 & Maosong Sun 2 & Jie Zhu 1 Received: 16 July 2020 / Revised: 13 October 2020 / Accepted: 7 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In our investigation, the sodium azide–assisted hydrothermal method was employed to prepare the N-doped active carbon (NAC). The TEM image shows that the NAC demonstrated lattice fringes (0.398 nm) representing the graphitized area. The NAC has high adsorption surface (1903 m2 g−1). A variety of faradaic-active species (pyrrolic-N, pyridine-N, quaternary-N) provide many electrochemically active sites. The Rct of the NAC decreased by approximately 31.25% and the capacitances of the NAC increased by approximately 45.7% compared with the AC in a three-electrode configuration in 1 M Na2SO4 solution. Besides, it could retain 96.1% after 5000 cycles at 1 A g−1. The NAC device could achieve the high capacitance of 40 F g−1 in 1 M LiPF6/PC and high energy density of 50 Wh kg−1 at 0.762 kW kg−1. It provides a new way to improve the capacitances and conductivity of commercial active carbon. Keywords Sodium azide . N-doped active carbon . Electrochemical performance . High conductivity
Introduction With growing concerns on environmental problems and climate change, developing green energy-storage and technologies were urgent tasks [1, 2]. Carbon-based supercapacitors draw much attention due to their advantages including long cycle life and safety [3, 4]. Based on the formula of energy density (E): E = 0.5CV2, the high capacitance (C) will greatly enhance the energy density. However, there is still a challenge to improve the capacitance [5]. Excellent pore structure and high surface area which could improve the ion transport are two effective methods to enhance
Qian Zhang and Peng Zhao contributed equally to this work. * Jie Zhu [email protected] Qian Zhang [email protected] Peng Zhao [email protected] 1
Institute for Advanced Study, Chengdu University, No. 2025, Chengluo Avenue, Chengdu 610106, People’s Republic of China
2
Research Center for Optoelectronic Materials and Devices, School of Physical Science Technology, Guangxi University, Nanning 530004, China
the capacitance. Fine micropores will help the transport of ions and decrease diffusion distance. Besides, doping heteroatoms not only endows dense positive charge to accelerate ion transport but also yields the pseudocapacitance [6]. Given all of the above, the high capacitance of carbon materials should integrate the following two requirements: (1) fine pore structure to enhance the adsorption/desorption on the electrode surface and (2) doping heteroatom to provide additional pseudocapacitance [7, 8]. Consequently, preparing materials with heteroatom and fine architecture could solve the problem of low capacitance. Doping different atoms (N, P, B) could greatly improve the capacitance [9, 10]. It has be
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