Enhancement of the Conductivity in Nanosized Carbon Ball by Introducing Chlorinated Benzene Derivatives via Room Temperature Solution Plasma Process
O. L. Li1,2,3,4, H. Hayashi1, K. Urashima5, and N. Saito1,2,3,4,6
1Graduate School of Engineering, Nagoya University, Japan
2Department of Material Science and Engineering, Nagoya University, Japan
3Institution of Innovation for future society, Center of Innovation, COI stream, Japan
4Green Mobility Collaborative Research Center, Nagoya University, Japan
5National Institute of Advanced Industrial Science and Technology (AIST), Japan
6CREST, Japan Science and Technology Agency (JST), Japan
Abstract- A special type of liquid plasma, named solution plasma (SP), has been applied to produce nanosized carbon black for the electrode material in Li-air battery. However, heat-treatment around 800 degree is essential to reduce the hydrogen atom remained within the carbon and to increase carbon's conductivity. In order to eliminate the energy-intensive heating process, in this study, we proposed to remove hydrogen atom by introducing chemical with halogen atom under room temperature plasma operation. Carbon nanoparticles were prepared by solution plasma with pure benzene (C6H6), chlorobenzene (C6H5Cl), various types of dichlorobenzene (C6H5Cl2) including 1,2-chlorobenzene, 1,3-chlorobenzene and 1,4 chlorobenzene served as the carbon precursors. The applied pulse frequency, applied voltage and pulse width were strictly controlled to be 25 kHz, 1 kV and 2 μs. The energy per pulse E and average energy per second Eavg by this specific plasma condition were calculated to be approximately 200 μJ and 5 J. The morphology of the synthesized carbon nanoball from benzene and 1,4-chlorobenzene were indicated in Fig. 1. The layer structure has been developed clearly on the outer layer of the carbon synthesized by chlorobenzene, as shown in Fig. 1(b). The resistivity of synthesized carbon by benzene was found to be 820 Ωcm, and decreased to 1.8 Ωcm when chlorobenzene was applied as precursor. From elemental analysis, the mole percentage of hydrogen remained in the synthesized carbon matrix decreased from 20% to 8.8% when the precursor changed from benzene to 1,4-chlorobenzene. We proposed that the chlorine atom in chlorobenzene reacted with hydrogen atoms and formed HCl (g), and successfully subtracted the hydrogen atom from the carbon matrix. Thus, sp2 bonding within carbon atoms was preferred and the conductivity of the synthesized carbon was easily enhanced.
Keywords-Solution plasma process, chlorobenzene, carbon nanoparticles, conductivity