Evidence for a core-shell structure of hydrothermal carbon
Evidence for a core-shell structure of hydrothermal carbon
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DOI：
10.1016/j.carbon.2020.01.060
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发表时间：
2020-05-01
期刊：
影响因子：
10.9
通讯作者：
Mishra, Bhoopesh
中科院分区：
文献类型：
--
作者：
Higgins, Luke J. R.;Brown, Andy P.;Mishra, Bhoopesh
水热碳化（HTC）已被证明是一种可持续的热化学过程，能够生产适用于广泛应用的功能化碳材料。为了更好地应用此类材料，必须了解控制热液碳生长的局部化学和反应途径。我们报告使用扫描透射 X 射线显微镜 (STXM) 来观察 HTC 界面和本体区域之间碳功能的化学变化。空间分辨、元素特异性 X 射线光吸收光谱显示，葡萄糖衍生的热液碳球的本体“核”和界面“壳”区域之间存在不同的局部碳化学。 STXM 提供了直接证据表明热液碳的核和壳之间的机制途径不同。在壳区域中，在水-碳界面处，更多的醛和/或羧基物质被怀疑提供了与局部呋喃基单体发生桥联反应的反应性界面。相反，缩合反应似乎在核心中占主导地位，去除了聚呋喃域之间的芳基连接单元。 STXM 在 HTC 中的应用为更全面地了解热液碳中碳物种的空间分布提供了机会，特别是在溶剂-碳界面处。 (C) 2020 作者。由爱思唯尔有限公司出版
Hydrothermal carbonisation (HTC) has been demonstrated to be a sustainable thermochemical process, capable of producing functionalised carbon materials for a wide range of applications. In order to better apply such materials, the local chemistry and reaction pathways governing hydrothermal carbon growth must be understood. We report the use of scanning transmission X-ray microscopy (STXM) to observe chemical changes in the functionality of carbon between the interface and bulk regions of HTC. Spatially-resolved, element-specific X-ray photo-absorption spectra show the presence of differing local carbon chemistry between bulk "core" and interface "shell" regions of a glucose-derived hydrothermal carbon spherule. STXM provides direct evidence to suggest that mechanistic pathways differ between the core and shell of the hydrothermal carbon. In the shell region, at the water-carbon interface, more aldehyde and/or carboxylic species are suspected to provide a reactive interface for bridging reactions to occur with local furan-based monomers. In contrast, condensation reactions appear to dominate in the core, removing aryl-linking units between polyfuranic domains. The application of STXM to HTC presents opportunities for a more comprehensive understanding of the spatial distribution of carbon species within hydrothermal carbon, especially at the solvent-carbon interface. (C) 2020 The Authors. Published by Elsevier Ltd.