Facile and continuous synthesis of graphene nanoflakes in RF thermal plasma

• Published in: Carbon (New York) 2022-06, Vol.193, p.51-67
• Main Authors: Fronczak, Maciej, Keszler, Anna Maria, Mohai, Miklós, Jezsó, Bálint, Farkas, Attila, Károly, Zoltán
• Format: Article
• Language: English
• Subjects: Acetaldehyde; Acetic acid; Alcohols; Butyric acid; Carboxylic acids; Catalyst-free synthesis; Chemical composition; Continuous synthesis; Ethanol; Ethyl acetate; Flakes; Formic acid; Graphene; Graphene nanoflakes; Graphitization; Organic chemicals; Organic compounds; Oxygen-containing organic compounds; Photoelectrons; Plasma jets; Plasma processing; Precursors; Propionic acid; Radio frequency; Radio frequency plasma; Radiofrequency thermal plasma; Raman spectroscopy; Spherical plasmas; Synthesis; Thermal plasmas; Thermal stability; Thermogravimetry
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2022.03.008

The aim of this work was to test the oxygen-containing organic compounds as prospective precursors of graphene flakes in a radiofrequency thermal plasma jet. The research covered the plasma processing of nine compounds, including alcohols, carboxylic acids, etc. Herein, the influence of the operating parameters, namely pressure, applied power, precursor feeding rate, and addition of hydrogen, on the efficiency of the product formation rate and yield was thoroughly studied. The morphology of the obtained materials was investigated by electron microscopy. The graphitization was evaluated via Raman spectroscopy. The thermal stability of products was studied utilizing thermogravimetry. Finally, the chemical composition was determined using X-ray photoelectron spectroscopy. Five compounds (ethanol, butyric acid, propionic acid, acetic anhydride, acetaldehyde) were found to be suitable precursors for continuous synthesis of graphene flakes, while ethyl acetate gave the mixture of graphene flakes and quasi-spherical byproduct. The plasma processing of methanol, formic acid, and acetic acid did not form any solid product. [Display omitted] •Plasma processing of oxygen-containing compounds yields graphene nanoflakes.•Graphene nanoflakes are selectively synthesized from various compounds studied.•Graphene nanoflakes are continuously produced without catalysts.•Compounds with an oxygen to carbon ratio of 0.5 are favorable precursors for graphene nanoflakes synthesis.