Department of Chemistry and Nanoscience, College of Natural Sciences, Ewha Womans University, Seoul 03760, Korea.
Nanoscale. 2017 Jan 5;9(2):792-801. doi: 10.1039/c6nr08614d.
The galvanic exchange reaction of an exfoliated 2D layered metal oxide nanosheet (NS) with excess substituent metal cations enables the synthesis of a mixed metal oxide 2D NS with controllable cation compositions and physicochemical properties. The reaction of the exfoliated MnO NS with Fe or Sn ions at 90 °C induces the uniform galvanic replacement of Mn ions with these substituent ions, whereas the same reaction at 25 °C results in the intercalative restacking of the negatively-charged MnO NS with Fe or Sn cations. Upon the galvanic exchange reaction, the highly anisotropic MnO 2D NS retains its original 2D morphology and layered structure, which is in stark contrast to 0D nanoparticles yielding hollow nanospheres via the galvanic exchange reaction. This observation is attributable to the thin thickness of the 2D NS allowing the simultaneous replacement of all the component surface-exposed metal ions. The resulting substitution of the MnO NS with Fe and Sn ions remarkably improves the electrode performance of the carbon-coated derivatives of the MnO NS for lithium ion batteries. The present study clearly demonstrates that the galvanic exchange reaction can provide an efficient method not only to tailor cation compositions but also to improve the functionalities of 2D metal oxide NSs and their carbon-coated derivatives.
剥离的二维层状金属氧化物纳米片（NS）与过量取代金属阳离子之间的电交换反应能够合成具有可控阳离子组成和物理化学性质的混合金属氧化物二维 NS。在 90°C 下，剥离的 MnO NS 与 Fe 或 Sn 离子的反应导致 Mn 离子与这些取代离子的均匀电取代，而在 25°C 下，相同的反应导致带负电荷的 MnO NS 与 Fe 或 Sn 阳离子的插层堆积。在电交换反应中，各向异性的 MnO 二维 NS 保留了其原始的二维形态和层状结构，这与通过电交换反应生成空心纳米球的 0D 纳米颗粒形成鲜明对比。这种观察结果归因于二维 NS 的薄厚度允许同时取代所有组件的表面暴露金属离子。用 Fe 和 Sn 离子取代 MnO NS 显著提高了 MnO NS 的碳涂层衍生物作为锂离子电池的电极性能。本研究清楚地表明，电交换反应不仅可以提供一种有效的方法来调整阳离子组成，还可以改善二维金属氧化物 NS 及其碳涂层衍生物的功能。
