Synthesis of vertical graphene nanowalls by cracking n-dodecane using RF inductively-coupled plasma-enhanced chemical vapor deposition

Abstract

A facile and controllable one-step method to treat liquid hydrocarbons and synthesize vertical graphene nanowalls has been developed by using the technique of inductively-coupled plasma-enhanced chemical vapor deposition for plasma cracking of n-dodecane. Herein, the morphology and microstructure of solid carbon material and graphene nanowalls are characterized in terms of different operating conditions, i.e. input power, H2/Ar ratio, injection rate and reaction temperature. The results reveal that the optimal operating conditions were 500 W, 5:10, 30 μl min−1 and 800 °C for the input power, H2/Ar ratio, injection rate and reaction temperature, respectively. In addition, the degree of graphitization and the gaseous product are analyzed by Raman spectroscopy and gas chromatography detection. It can be calculated from the Raman spectrum that the relative intensity of ID/IG is approximately 1.55, and I2D/IG is approximately 0.48, indicating that the graphene prepared from n-dodecane has a rich defect structure and a high degree of graphitization. By calculating the mass loading and detecting the outlet gas, we find that the cracking rate of n-dodecane is only 6%–7% and that the gaseous products below C2 mainly include CH4, C2H2, C2H4, C2H6 and H2. Among them, the proportion of hydrogen in the outlet gas of n-dodecane cracking ranges from 1.3%–15.1% under different hydrogen flows. Based on our research, we propose a brand new perspective for both liquid hydrocarbon treatment and other value-added product syntheses.