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.

了解简单且易于扩展的石墨烯合成方法背后的潜在过程，使其能够在新兴的能量存储和可打印设备应用中进行大规模部署。有机前驱体的微波等离子体分解形成了高于 3000 K 的高温环境，其中无催化剂脱氢和随后形成 C ₂分子的过程导致高质量少层石墨烯 (FLG) 的成核和生长。在这项工作中，我们展示了具有 H ₂和乙炔、C ₂ H ₂的气体混合物的高温环境的实验证据，导致从无定形材料转变为高度结晶材料，证明了建议的脱氢机制。碳到 FLG 的整体转化效率高达 47%，是甲烷或乙醇的 3 倍，并且随着微波功率的增加（即高温区的大小）和烃流量的增加而增加。产量随着 C:H 比的降低而降低，而当 C:H 比为 1:3 时，可获得最佳质量的 FLG（低 D/G-0.5 和高 2D/G-1.5 拉曼谱带比）。该结构包含少于 1at% 的氧。从具有相同化学计量的高级醇、1-丙醇和异丙醇合成 FLG 不需要额外的氢，但产率较低，为 15%，并且取决于前体的原子排列。通过扫描电子显微镜、拉曼、X 射线光电子能谱和热重分析对制备的 FLG 纳米粉体进行分析。通过光发射光谱监测微波等离子体。