Shifts in valence states in bimetallic MXenes revealed by electron energy-loss spectroscopy (EELS)
Shifts in valence states in bimetallic MXenes revealed by electron energy-loss spectroscopy (EELS)
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DOI：
10.1088/2053-1583/ac4ba2
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发表时间：
2022-01
期刊：
影响因子：
5.5
通讯作者：
Alexandre C. Foucher;Meikang Han;C. Shuck;K. Maleski;Y. Gogotsi;E. Stach
中科院分区：
文献类型：
--
作者：
Alexandre C. Foucher;Meikang Han;C. Shuck;K. Maleski;Y. Gogotsi;E. Stach
MXenes是一类新兴的二维材料，具有非常广泛的应用前景。多种MXene的合成，特别是固溶体MXene，允许对其性质进行微调，扩大其应用范围，并提高性能。固溶体MXene的功能与其组分的价态密切相关：过渡金属，氧，碳和氮。然而，MXene中元素氧化态变化的影响尚未得到很好的理解。在这项工作中，三个相互关联的固溶体MXene系统（Ti 2 −y Nb y CT x，Nb 2 −y V y CT x和Ti 2 −y V y CT x）用扫描透射电子显微镜和电子能量损失谱进行了研究，以确定纳米尺度下金属的局部价态。分析表明，在修改整体组成和单个MXene薄片后，V的电子构型发生了变化。这些氧化态的变化可以解释固溶体MXene的非线性光学和电子特性。钒似乎是特别敏感的修改价态，而钛保持相同的氧化态在Ti-Nb和Ti-V MXene，无论化学计量。该研究还解释了Nb在Nb-V和Nb-Ti系统中先前观察到的电子性质中的影响作用。
MXenes are an emergent class of two-dimensional materials with a very wide spectrum of promising applications. The synthesis of multiple MXenes, specifically solid-solution MXenes, allows fine tuning of their properties, expands their range of applications, and leads to enhanced performance. The functionality of solid-solution MXenes is closely related to the valence state of their constituents: transition metals, oxygen, carbon, and nitrogen. However, the impact of changes in the oxidation state of elements in MXenes is not well understood. In this work, three interrelated solid-solution MXene systems (Ti2−y Nb y CT x , Nb2−y V y CT x , and Ti2−y V y CT x ) were investigated with scanning transmission electron microscopy and electron energy-loss spectroscopy to determine the localized valence states of metals at the nanoscale. The analysis demonstrates changes in the electronic configuration of V upon modification of the overall composition and within individual MXene flakes. These shifts of oxidation state can explain the nonlinear optical and electronic features of solid-solution MXenes. Vanadium appears to be particularly sensitive to modification of the valence state, while titanium maintains the same oxidation state in Ti–Nb and Ti–V MXenes, regardless of stoichiometry. The study also explains Nb’s influential role in the previously observed electronic properties in the Nb–V and Nb–Ti systems.