2025/11/14 by Sophia Gershman, Gershman, Sophia, Mikhail N. Shneider +3
Engineering · Materials Science · Medicine · #Diamond and Carbon-based Materials Research #FOS: Physical sciences #Plasma Applications and Diagnostics #Plasma Diagnostics and Applications #Plasma Physics (physics.plasm-ph)
paper · pdf · doi:10.48550/arxiv.2511.10937
openalex publication_date 2025/11/14 · openalex created_date 2025/11/18 · openalex updated_date 2026/07/28
Decomposition of methane using non-thermal plasmas is an attractive route for producing hydrogen-rich gases and valuable carbon nanomaterials. Understanding how plasma discharge modes influence methane decomposition in optimizing plasma-assisted chemical conversion remains unexplored. This study explores the coupling between the discharge structure and product selectivity in RF capacitively coupled discharges operating in methane/inert gas mixtures in the pressure range of 2 to 3 torr. The discharge exhibits mode transitions from uniform to striated in Ar and Kr and from diffuse to contracted in Ar and Kr with 5 percent or less CH4. The discharges in He and Ne remained uniform under our operating conditions, and their mixtures with CH4 remained diffuse. A 0-D model for Ar/CH4 discharge established a threshold for contraction while also asserting the importance of Ar metastable in the dissociation and ionization processes. The highest degree of methane decomposition, 99.7% with the main products of acetylene and graphitized solid carbon was achieved in the contracted discharge mode for both Kr or Ar with 5% or less CH4. We demonstrate that contraction can play a crucial role in the effective decomposition of methane with value-added products and that both the electronic and thermal properties of plasma gas are responsible for this effect.