Graphene synthesis via thermal plasma: a comprehensive review of key process parameters and outcomes

Thermal plasma provides several advantages for graphene synthesis, including high conversion efficiency and rapid, continuous production. Furthermore, it enables precise control over process parameters, resulting in the production of high-quality graphene with low defects, leading to its usage in diverse applications. Despite these advancements, the primary challenge remains the low production rate of graphene, which limits the scalability and commercial viability of the synthesis process. The gas-phase graphene synthesis process is significantly influenced by factors such as pressure, power, hydrocarbon feedstock type and flow rates, plasma gas composition, catalyst presence, quenching rate, and oxygen/hydrogen content. A wide range of carbon nanostructures (including graphene (Gr), graphite, carbon black (CB), carbon nanotubes (CNTs), and carbon nanohorns (CNHs)) can be produced by modulating these factors. This review systematically investigates the impact of the aforementioned parameters on graphene synthesis and the underlying reaction mechanisms. It demonstrates the critical role of carbon concentration, temperature, and residence time in influencing plasma chemistry, and consequently the graphene quality, with major implications for advancing graphene-based technologies. This review article contributes to the existing literature by providing a comprehensive overview of the state of the art in thermal plasma-based graphene synthesis.