Engineering carbon nanowall (CNW) nanostructures is a daunting task as the synthesis of vertical few-layer graphene (FLGs) nanostructures with precise control over the layers remains elusive. The underlying reason is that the CNW growth mechanism is not yet fully understood, and the huge feature space in the characterization datasets cannot be analyzed with conventional techniques. In the present work, we endeavor to engineer FLG nanostructures via plasma-enhanced chemical vapor deposition, where the number of graphene layers in the FLGs was especially controlled. The aim was to decipher the growth mechanism of the FLG and CNW nanostructures. Machine learning (ML) techniques were employed to decode the feature space of plasma optical spectra. ML techniques extract crucial information, identify the vital factors that govern the transition from CNWs to FLG nanostructures and provide invaluable insights into the growth mechanism. We report a new hybrid FLG/CNW nanostructure that does not exist thus far: FLGs at the bottom and CNWs on top. Furthermore, we develop an ultrafast and commercially viable carbon nano-coating technique that applies to a wide variety of specimens with CNWs. The efficacy of the process is demonstrated by fabricating a cathode for a Li–O₂ battery for nano-energy applications. The nano-carbon-coated electrode is composed of a 3D network of hierarchically interconnected porous graphene sheets (3D-HPG). We demonstrate that the specific capacity of 3D-HPG-based electrodes in Li–O₂ batteries (without any binder and catalyst) can be as high as 12 400 mA h g⁻¹. As it is an inexpensive, efficient, and highly reproducible process, we believe that the current approach opens up a new avenue for Li–air battery research.

中文翻译：

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垂直排列石墨烯片的合成和生长机制，精确控制锂氧电池的层数


设计碳纳米墙（CNW）纳米结构是一项艰巨的任务，因为合成垂直少层石墨烯（FLG）纳米结构并精确控制各层仍然难以实现。根本原因是CNW的增长机制尚未完全理解，并且表征数据集中巨大的特征空间无法用传统技术进行分析。在目前的工作中，我们致力于通过等离子体增强化学气相沉积来设计FLG纳米结构，其中FLG中石墨烯层的数量受到特别控制。目的是破译 FLG 和 CNW 纳米结构的生长机制。采用机器学习（ML）技术来解码等离子体光谱的特征空间。机器学习技术提取关键信息，识别控制从 CNW 到 FLG 纳米结构转变的重要因素，并为生长机制提供宝贵的见解。我们报告了一种迄今为止尚不存在的新型混合 FLG/CNW 纳米结构：FLG 位于底部，CNW 位于​​顶部。此外，我们还开发了一种超快且商业上可行的碳纳米涂层技术，适用于各种具有 CNW 的样本。通过制造用于纳米能源应用的锂氧 ₂ 电池的阴极，证明了该工艺的有效性。纳米碳涂层电极由分层互连的多孔石墨烯片 (3D-HPG) 的 3D 网络组成。我们证明，Li-O ₂ 电池（不含任何粘合剂和催化剂）中基于 3D-HPG 的电极的比容量可高达 12 400 mAh g ⁻¹ 。由于它是一种廉价、高效且高度可重复的过程，我们相信当前的方法为锂空气电池研究开辟了一条新途径。