Microwave plasma-based high temperature dehydrogenation of hydrocarbons and alcohols as a single route to highly efficient gas phase synthesis of freestanding graphene
- 8 September 2021
- journal article
- research article
- Published by IOP Publishing in Nanotechnology
- Vol. 32 (50), 505608
- https://doi.org/10.1088/1361-6528/ac24c3
Abstract
Understanding underlying processes behind the simple and easily scalable graphene synthesis methods enables their large-scale deployment in the emerging energy storage and printable device applications. Microwave plasma decomposition of organic precursors forms a high-temperature environment, above 3000 K, where the process of catalyst-free dehydrogenation and consequent formation of C2 molecules leads to nucleation and growth of high-quality few-layer graphene (FLG). In this work, we show experimental evidence that a high-temperature environment with a gas mixture of H2 and acetylene, C2H2, leads to a transition from amorphous to highly crystalline material proving the suggested dehydrogenation mechanism. The overall conversion efficiency of carbon to FLG reached up to 47 %, three times as much as for methane or ethanol, and increased with increasing microwave power (i.e. with the size of the high-temperature zone) and hydrocarbon flow rate. The yield decreased with decreasing C:H ratio while the best quality FLG (low D/G - 0.5 and high 2D/G - 1.5 Raman band ratio) was achieved for C:H ratio of 1:3. The structures contained less than 1 at% of oxygen. No additional hydrogen was necessary for the synthesis of FLG from higher alcohols having the same stoichiometry, 1-propanol and isopropanol, but the yield was lower, 15 %, and dependent on the atom arrangement of the precursor. The prepared FLG nanopowder was analyzed by scanning electron microscopy, Raman, X-ray photoelectron spectroscopy, and thermogravimetry. Microwave plasma was monitored by optical emission spectroscopy.Keywords
Funding Information
- Grantová Agentura České Republiky (18-08520S)
- Ministerstvo Školství, Mládeže a Tělovýchovy (LM2018097)
This publication has 37 references indexed in Scilit:
- Drastic reduction in the growth temperature of graphene on copper via enhanced London dispersion forceScientific Reports, 2013
- Substrate-free microwave synthesis of graphene: experimental conditions and hydrocarbon precursorsNew Journal of Physics, 2010
- Substrate-Free Gas-Phase Synthesis of Graphene SheetsNano Letters, 2008
- Raman Spectrum of Graphene and Graphene LayersPhysical Review Letters, 2006
- Formation of Shell‐Shaped Carbon Nanoparticles Above a Critical Laser Power in Irradiated AcetyleneAdvanced Materials, 2004
- The mechanism of the reversible reaction: 2C2H2 ⇌ vinyl acetylene and the pyrolysis of butadieneInternational Journal of Chemical Kinetics, 1989
- Chemical Kinetics of Soot Particle GrowthAnnual Review of Physical Chemistry, 1985
- Mechanism of the Pyrolysis of AcetyleneCanadian Journal of Chemistry, 1971
- The pyrolysis of isopropanolTransactions of the Faraday Society, 1960
- The pyrolysis of n-propanolTransactions of the Faraday Society, 1960