On the transition of reaction pathway during microwave plasma gas‐phase synthesis of graphene nanosheets: From amorphous to highly crystalline structure

Toman, Jozef; Jašek, Ondřej; Šnírer, Miroslav; Pavliňák, David; Navrátil, Zdeněk; Jurmanová, Jana; Chudják, Stanislav; Krčma, František; Kudrle, Vít; Michalička, Jan

doi:10.1002/ppap.202100008

Cited by 17 publications

(9 citation statements)

References 59 publications

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“…The yield decrease could be understood in terms of the reverse hydrogenation process of C 2 H and C 2 molecules when more gasphase hydrocarbons are formed (figure 1) and the amount of solid-state product decreases. This result is in agreement with the yield decrease of FLG and the analysis of decomposition products of ethanol formed in our microwave plasma torch discharge [33]. Together with previously reported FLG synthesis from ethanol (C 2 H 5 OH) and its isomer, dimethyl ether (CH 3 OCH 3 ) by Dato et al [14], our results showed that the synthesis using alcohols with the same stoichiometry is independent of the precursor molecular arrangement.…”

Section: Synthesis Of Graphene Nanosheets From Higher Alcoholssupporting

confidence: 93%

“…Dato et al [32] used mass spectrometry to analyze hydrogen content of the FLG prepared by microwave plasma decomposition of ethanol and only 1 at% or less of hydrogen was detected in the investigated material. This value is not surprising as most of the hydrogen is contained in the volatile hydrocarbon species such as CH 4 , C 2 H 2 , C 2 H 4 [33], and H 2 formed during the synthesis and escapes the experimental reactor by exhaust line.…”

Section: Synthesis Of Graphene Nanosheets From Acetylenementioning

confidence: 94%

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Microwave plasma-based high temperature dehydrogenation of hydrocarbons and alcohols as a single route to highly efficient gas phase synthesis of freestanding graphene

et al. 2021

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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.

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Section: Synthesis Of Graphene Nanosheets From Higher Alcoholssupporting

confidence: 93%

Section: Synthesis Of Graphene Nanosheets From Acetylenementioning

confidence: 94%

Microwave plasma-based high temperature dehydrogenation of hydrocarbons and alcohols as a single route to highly efficient gas phase synthesis of freestanding graphene

et al. 2021

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“…While the hydrogen species could be generated by the dehydration reactions of ethanol in the plasma. [ 16,28 ] Further, the dissociation of ethanol could be observed from the detected CH and H α species and from OH, H β , and O species, which are likely present but not clearly observed in the spectra obtained. The H α emission at the bulk liquid (Point 2: L) shows to be relatively more prominent compared to the H α emission observed at the gas phase (Point 1: G) and the immersed substrate (Point 3: S).…”

Section: Resultsmentioning

confidence: 98%

Deposition of carbon‐based materials directly on copper foil and nickel foam as 2D‐ and 3D‐networked metal substrates by in‐liquid plasma

Vega

Nguyen

Kondo

et al. 2023

Plasma Processes & Polymers

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In‐liquid plasma (ILP) process has been an attractive route for nanomaterial synthesis due to its high‐yield production in low‐temperature atmospheric pressure conditions. In comparison with conventional ILP synthesis that produces free‐standing nanomaterials, this work brings a new perspective on the application of the ILP process through carbon formation directly on ethanol‐immersed two‐dimensional (foil) and three‐dimensional (3D) (foam) metal substrates. Three types of carbon, including graphene, graphitic carbon, and amorphous carbon, were simultaneously produced during plasma discharge. Graphitic and amorphous carbon formed radially and coexisted on the metal substrate surface, while free‐standing graphene was produced in ethanol. A conformal coating was achieved on the exterior surface of the 3D‐networked substrate. The proposed mechanism for carbon formation on metal substrates is presented here.

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“…The theoretical yield of carbon, that is, 46.9% was calculated in the tea tree oil (chemical formula C 28 H 60 O 4 P 2 S 4 Zn). The breakdown of tea tree oil in the microwave plasma generated various carbon species, such as CO, CO 2 , and CH, [ 39 ] which contributed to ≈23% of the total yield of graphene.…”

Section: Resultsmentioning

confidence: 99%

Plasma‐Based Synthesis of Freestanding Graphene from a Natural Resource for Sensing Application

Zafar

Liu

Hernández

et al. 2023

Adv Materials Inter

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The bottomup approach, that is, modified Hummers' method, is a well-established chemical synthesis technique to synthesize graphene. However, this technique, not only utilizes strong acids and oxidants [4,5] but also entails numerous steps of synthesis such as dilution, mixing, oxidation, reduction, washing, centrifuging, and intense stirring. [6] On the other hand, some of the bottom-up methods, in particular, chemical vapor deposition (CVD) and plasma-enhanced chemical vapor deposition (PE-CVD) are expensive and laborious methodologies comprising pre-synthesis and post-synthesis requirements, that is, high vacuum, pre-heating, and subsequent transfer of graphene to other substrates. [7][8][9] Recently, a new bottom-up approach, so-called atmospheric pressure microwave plasma (APMP) is gaining popularity as it synthesizes graphene without the hassles of pre-heating, high vacuuming, and the need for a substrate. Most importantly, the graphene obtained through this method happens to be freestanding and scalable. [10,11] The precursors used for producing graphene have a significant role in determining the sustainability of the synthesis process. Often graphene is produced from commercially available graphite, [12] graphene oxide (GO), [13] methane, or other unreplenishable hydrocarbons. [14] These resources Atmospheric pressure microwave plasma has the lead in synthesizing freestanding and scalable graphene within seconds without the need for high vacuum and temperature. However, the process is limited in utilizing chemical sources for synthesis, such as methane and ethanol. Herein, the usage of an extract of a sustainable precursor, that is, Melaleuca alternifolia, commonly known as tea tree, is for the first time reported to synthesize graphene nanosheets in atmospheric pressure microwave plasma. The synthesis is carried out in a single step at a remarkably low microwave power of 200 W. The morphology, structure, and electrochemical properties of graphene are studied using state-of-the-art characterization techniques such as Raman spectroscopy, X-ray diffraction, transmission electron microscopy (TEM) and electrochemical impedance spectroscopy. The TEM images reveal the presence of a combination of nanostructures such as nano-horns, nano-rods, or nano-onions consisting of multi-layer graphitic architectures. An excellent sensing capability of as-synthesized graphene is demonstrated through the detection of diuron herbicide. A commendable linear range of 20 µm to 1 mm and a limit of detection of 5 µm of diuron is recorded.

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On the transition of reaction pathway during microwave plasma gas‐phase synthesis of graphene nanosheets: From amorphous to highly crystalline structure

Cited by 17 publications

References 59 publications

Microwave plasma-based high temperature dehydrogenation of hydrocarbons and alcohols as a single route to highly efficient gas phase synthesis of freestanding graphene

Microwave plasma-based high temperature dehydrogenation of hydrocarbons and alcohols as a single route to highly efficient gas phase synthesis of freestanding graphene

Deposition of carbon‐based materials directly on copper foil and nickel foam as 2D‐ and 3D‐networked metal substrates by in‐liquid plasma

Plasma‐Based Synthesis of Freestanding Graphene from a Natural Resource for Sensing Application

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