Metallic Tungsten Nanoparticles That Exhibit an Electronic State Like Carbides during the Carbothermal Reduction of WCl6 by Hydrogen
Metallic Tungsten Nanoparticles That Exhibit an Electronic State Like Carbides during the Carbothermal Reduction of WCl6 by Hydrogen
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在氢气碳热还原 WCl6 过程中表现出类似碳化物电子态的金属钨纳米粒子
DOI：
10.1021/acs.inorgchem.0c01930
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发表时间：
2020
影响因子：
4.6
通讯作者：
Kimihisa Yamamoto
中科院分区：
文献类型：
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作者：
Masanori Wakizaka;Wang-Jae Chun;Takane Imaoka;Kimihisa Yamamoto
碳热氢还原（CHR）是一种独特的干法化学工艺，用于在碳载体上制造金属和碳化物。在这项研究中，首次证明了wcl6在石墨载体上的逐级CHR。粉末x射线衍射研究表明，在773 K时产生了金属钨纳米颗粒，而在1073 K时产生了亚稳W2C相，而不是热力学稳定的WC相。x射线光电子能谱和x射线吸收近边结构研究表明，W纳米粒子的化学状态同时表现为金属W（~ 0）和碳化物W（δ+）特征。结果表明，虽然金属钨原子与石墨载体之间存在电子相互作用，但金属钨的体心立方结构得到了扩展的x射线吸收精细结构的证实。此外，高分辨率扫描透射电子显微镜观察显示，W纳米颗粒在支架上呈现薄而扁平的形状。这些结果支持了这样一种观点，即在CHR过程中W纳米颗粒的形成机制受到W纳米颗粒与石墨载体之间电子相互作用的影响。因此，我们的工作表明，早期过渡金属原子和碳基支架的组合可以通过电子相互作用提供可调制的电子系统。
Carbothermal hydrogen reduction (CHR) is a unique dry chemical process used to fabricate metals and carbides on carbon supports. In this study, a stepwise CHR of WCl6on a graphite support is demonstrated for the first time. Powder X-ray diffraction studies revealed that, at 773 K, metallic tungsten nanoparticles are produced, whereas, at 1073 K, the metastable W2C phase is generated rather than the thermodynamically stable WC phase. X-ray photoelectron spectroscopy and X-ray absorption near edge structure studies showed that the chemical state of the W nanoparticles simultaneously exhibits metallic W(∼0) and carbide W(δ+) character. The obtained results suggest that, although electronic interactions exist between the metallic W atoms and the graphite support, the body-centered cubic structure of the metallic tungsten is maintained, confirmed by the extended X-ray absorption fine structure. In addition, high-resolution scanning transmission electron microscopy observations revealed that the W nanoparticles exhibit a thin flattened shape on the support. These results support the notion that the mechanism for the formation of the W nanoparticles during the CHR is influenced by the electronic interactions between the W nanoparticles and the graphite support. Our work thus suggests that the combination of early-transition-metal atoms and carbon-based supports would afford modulatable electronic systems though the electronic interactions.