On The Transition Of Reaction Pathway During Microwave Plasma Gas-Phase Synthesis Of Graphene Nanosheets: From Amorphous To Highly Crystalline Structure

Fourier-transform infrared spectroscopy and proton-transfer-reaction-mass spectrometry are used in a complementary way to study gas-phase processes during decomposition of ethanol in a microwave plasma torch. Decomposition products (C, C-2 and simple hydrocarbons) reassemble into higher hydrocarbons and graphene nuclei and further grow into graphene nanosheets (GNS). Depending on microwave power, ethanol flow rate and molecular gas admixture, the material structure changes from amorphous to crystalline. The presence of C2n + 1Hy species was found to be responsible for the formation of defects in the GNS structure. O-2 and H-2 admixtures change the gas temperature axial profile and consequently modify reaction pathways influencing growth and production rate of GNS. Determination of reaction pathway selectivity enables us to predict whether high-quality or defective GNS are produced.