Synthesis of multiwall carbon nanotubes via an inert atmosphere absent autogenetic-pressure method for supercapacitor

Abstract

Absrtact Carbon nanotubes has attracted much attentions due to its huge application potential in various high-tech fields. Exploition of the simple and cost-efficient synthesis method for carbon nanotubes is crucial for its practical application. Herein, multi-wall carbon nanotubes (MCNTs) was successfully synthesized by one-step pyrolysis of a mixture of benzene and ferrocene in a sealed autoclave under autogenetic-pressure. A pyrolysis temperature of 800 °C, pyrolysis time for 30 min and a ferrocene/benzene molar ratio of 1:2 is found to be the optimal conditions for synthesizing the MCNTs via the mentioned autogenetic-pressure method. The synthesized MCNTs exhibits a “bamboo joint”-like multi-wall structure with about 12 layers of highly graphited tube wall and uniform external diameter of ca 20 nm. The specific capacitance of the synthesized MCNTs reaches 64 F g-1, which value is about 3.0 times higher than that of the typical commercial MCNTs. The synthesized MCNTs also exhibits very excellent superior rate and cycle performance. More than 95.5% initial specific capacitance is retained even under a large current density of 20 A g-1, and no apparent specific capacitance decrement is observed after 10,000 times charge-discharge cycles. The energy density of the synthesized MCNTs-based supercapacitor arrives 2.27 Wh kg-1 at a power density of 157 W kg-1, and 2.07 Wh kg-1 of energy density is still retained at a power density of 5.3 kW kg -1, while an energy density of 0.72 Wh kg-1 is arrived at a power density of 2.6 kW kg-1 for the typical commercial MCNTs-based supercapacitor. The superior capacitance performance of the synthesized MCNTs than that of the typical commercial MCNTs is ascribed to the higher conductivity induced by the higher graphitization degree than that of the typical commercial MCNTs, good surface wettability due to the high content of oxygen-contained functional groups on surface, and the supplementary contribution of pseudo-capacitance.