One-pot synthesis of a Mn(MnO)/Mn5C2/carbon nanotube nanocomposite for supercapacitors

We report a one-pot synthesis of Mn(MnO)/Mn5C2/carbon nanotube (CNTs) nanocomposite for supercapacitors. The Mn(MnO)/Mn5C2/CNTs composed of Mn(MnO) nanoflakes bonded with CNTs through interfacial Mn5C2 carbides was prepared by heating a mixture of Mn powder and CNTs at 600 degrees C under vacuum. The carbides obtained by an in situ reaction provided strong interface bonding between the CNTs and Mn(MnO), and consequently enhanced stability of the nanocomposite as a supercapacitor electrode material. The capacitive properties of the Mn(MnO)/Mn5C2/CNTs electrodes were investigated by a cyclic voltammetry (CV) test in a 0.5 M Na2SO4 aqueous solution. The Mn(MnO)/ Mn5C2/CNTs prepared at 600 degrees C for 1 h displayed a maximum specific capacitance of 378.9 F g(-1) (based on total mass of active materials) at 2 mV s(-1). The long-term cycling stability of the Mn(MnO)/Mn5C2/ CNT electrode was investigated by repeating the CV test from 0.1 and 0.8 V (vs. SCE) at 100 mV s(-1). Contrary to a traditional MnO2/CNTs electrode, whose specific capacitance would decrease with cycle number, the Mn(MnO)/Mn5C2/CNTs had an increased specific capacitance at the initial 450 cycles. This phenomenon is because of an electrochemical conversion from Mn(MnO) to MnO2 in the initial CV test. Little decrease in the specific capacitance was found even after 1000 cycles, indicating an excellent cycling stability. These properties are attributed to the unique Mn(MnO)/Mn5C2/CNT structure.