Composite Nanofibers by Growing Polypyrrole on the Surface of Polyaniline Nanofibers Formed under Free Melting Condition
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ISSN 1229-9197 (print version) ISSN 1875-0052 (electronic version)
Composite Nanofibers by Growing Polypyrrole on the Surface of Polyaniline Nanofibers Formed under Free Melting Condition and Shell-Thickness-Dependent Capacitive Properties Banglei Liang*, Yaqi Zhao, Xinxin Guo, Zhenxin Zhao, Qiao Feng, Jingyi Guo, Xiaoyuan Zhang, and Jinyu Tian School of Materials and Chemical Engineering, Henan University of Urban Construction, Pingdingshan 467036, China (Received October 7, 2019; Revised December 12, 2019; Accepted December 13, 2019) Abstract: An efficient approach was presented to prepare polyaniline/polypyrrole (PANi/PPy) composite nanofibers by growing PPy layers on the surface of PANi nanofibrous seeds as electrode materials for supercapacitors in neutral electrolyte. Core layer of PANi nanofiber was firstly synthesized by the chemical oxidative polymerization of aniline monomers under free melting condition of reaction solutions in fully aqueous system without the assistance of any templates or organic solvents. Then the shell layer of PPy was fabricated by in-situ chemical oxidative polymerization of pyrrole monomers with the above-mentioned PANi nanofiber as a seed, and the PPy shell layer thicknesses were tuned by changing the molar ratio of aniline to pyrrole. The resulting PANi/PPy composites were investigated by field-emission scanning electron microscopy, ultraviolet-visible spectroscopy, Fourier transform infrared and Raman spectrometry. Furthermore, electrochemical behaviors in Na SO electrolyte were tested by cyclic voltammetry, galvanostatic charge-discharge techniques and electrochemical impedance spectroscopy. It turned out that low molar ratio of aniline to pyrrole is helpful to increase the PPy shell layer thicknesses, yield and conductivity of PANi/PPy composite nanofibers. A great improvement on the capacitive properties could be achieved by choosing appropriate PPy shell layer thickness. The results showed that benefiting from strong synergy effect and π-π interaction between PANi core and PPy shell layer as well as low electrochemical impedance, PANi/PPy composite nanofibers prepared with the molar ratio of 1:1 (PPy shell layer thickness of about 12.5 nm) displayed the highest specific capacitance of 1550.2 F g at scan rate of 5 mV s and 758.8 F g at the current density of 1 A g with the best cycling stability of 70.3 % after 500 cycles in 0.5 M Na SO electrolyte, which exhibited a great potential in the development of high-performance electrode materials operated in environmentally friendly electrolyte. 2
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Keywords: Polyaniline, Polypyrrole, Composite nanofiber, Capacitive property, Thickness
that the PANi/PPy composites can display high electrical conductivity, good structural mechanical stability and great enhancement on the capacitive properties [10,14]. Noteworthily, PPy has been proven far more recalcitrant to nanofiber formation through the solution-phase chemical method [10,14,20,23]. Generally, PPy with fibrillar morphology was chemically synthesized usi
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