Ambient-Air Atmospheric-Pressure Plasma Jet Treatment of Graphite Towards Energy-Effective Synthesis of Multiwalled Carbon Nanotubes

We report the formation of multi-walled carbon nanotubes (MWCNTs) through the interaction of an atmospheric-pressure plasma jet, generated via a capillary discharge, with a graphite surface. This surface-modifying discharge was established in a brief air gap between the cathode and ignition electrode, manipulated across varying discharge power levels. Notably, the structural properties of MWCNTs on the graphite anodes demonstrated a clear dependence on discharge power. Utilizing scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy, we observed a progression toward disordering in the nanotubes alongside the emergence of graphitized clusters with increasing discharge energy. The formation of relatively defect-free MWCNTs at minimal discharge energy presents an opportunity for their synthesis with low energy consumption of 4.7 kJ/cm2. The suggested energy-efficient, rapid and straightforward technique for tailoring MWCNT formation significantly reduces the reliance on complex and expensive instrumentation, presenting a promising pathway for effective surface modification with potential applications in electronics, gas sensors, and water treatment.