Pressure-dependent synthesis of graphene nanoflakes using Ar/H2/CH4 non-thermal plasma based on rotating arc discharge

Abstract

Non-thermal plasma can be used for the continuous synthesis of graphene nanoflakes. In this paper, the influence of pressure on graphene nanoflake synthesis was studied in an Ar/H2/CH4 non-thermal plasma based on rotating arc discharge. Graphene nanoflakes were fabricated by CH4 decomposition in a pressure range of 20–200 kPa, and their properties were analyzed multiple characterization methods. The results showed that pressure affected the product properties and yield. From 60 to 200 kPa, all products were graphene nanoflakes with sizes of 50–300 nm and 1–20 graphite layers. A relatively high pressure favored the formation of graphene nanoflakes in high yield, with good crystalline structures, low oxygen contents, and excellent thermal stability. A low pressure promoted the formation of graphene nanoflakes with fewer layers and larger specific surface areas. Also, at a lower pressure (20 kPa), small spherical particles (3–8 nm diameter), similar to carbon dots, emerged on the graphene nanoflakes. Correlations between process parameters and characterization results suggested that different concentrations of carbonaceous radicals in the plasma zone affected the product characteristics.