Catalyst Activation by Microplasma for Carbon Nanofiber Synthesis in a Microreactor

A dielectric barrier discharge is generated by flowing helium and hydrogen through a microreactor capillary which contains a coating of Ni/alumina catalyst to activate carbon nanofiber (CNF) synthesis. Optical and electrical measurements have been done to characterize the discharge during catalyst treatment. A sinusoidal voltage of 6 kV (peak) with a frequency of 50 kHz has been applied to a high-voltage electrode, and a helium gas flow stabilizes the discharge to have a uniform and high-power-density surface treatment. Cold-plasma operation for 15 min is simple and audiovisual, increases the CNF yield significantly compared to nonactivated samples, and can compete with high-temperature treatment at 973 K for 2 h. Increasing the discharge treatment duration to 30 min results in sintering of catalyst particles and nonuniform growth of the nanofibers.