Direct synthesis of porous carbon nanotubes and its performance as conducting material of supercapacitor electrode

Abstract

Abstract Porous carbon nanotubes (CNTs) were directly synthesized for the first time by arc discharge in the presence of CO 2. Supercapacitor was fabricated with the addition of CNTs synthesized in different medium to the polarizable activated carbon (AC) electrode as conducting material for comparison purpose. The electrical properties of the AC/CNTs composite are systematically investigated using cyclic voltammetric, discharge at constant current and electrochemical impedance spectroscopic (EIS) techniques. Transmission electron microscope (TEM) observation reveals that a few CNTs synthesized in the presence of CO 2 are porous ones. Specific capacitance ( C sp) of the AC/CNTs composite passes through a maximum with increasing discharge current while the average internal resistance ( R i) of supercapacitor decreases with increasing discharge current. The C sp of AC/CNTs He/C2H2/CO2 composite with CNTs synthesized in He, C 2H 2 and CO 2 medium is bigger than that of AC/CNTs N2/C2H2/CO2 or AC/CNTs N2/C2H2 composite. The R i of AC/CNTs He/C2H2/CO2 composite is the same as that of AC/CNTs N2/C2H2 composite, which is smaller than that of AC/CNTs N2/C2H2/CO2 composite. EIS results show that the AC/CNTs composite have the similar charge storage mechanism. The above results show that CNTs He/C2H2/CO2 is one of the suitable conducting materials to decrease the resistance of supercapacitor while maintaining its higher specific capacitance.