College of Chemistry, Jilin University, Changchun 130012, China.
State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130012, China.
Nanoscale. 2016 Aug 18;8(33):15262-72. doi: 10.1039/c6nr04775k.
Although layered transition metal dichalcogenide (TMD) nanosheets have attracted great attention due to their unique properties, it still remains challenge to develop a facile strategy for the precise control of the lateral sizes and layer numbers of TMD nanosheets. In this study, we demonstrate a solution-phase synthetic protocol to prepare colloidal MS2 (M = Mo, W) nanosheets which possess extremely small lateral dimensions from 15 to 40 nm and well-controlled odd numbers of layers, such as 1, 3, and 5 layers, as characterized by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The size- and layer-dependence of the optical properties of colloidal MS2 (M = Mo, W) nanosheets are revealed by Raman and absorption spectra for the first time. These colloidal nanosheets, especially the single-layer ones, possess a large number of edge sites that serve as active sites for the hydrogen evolution reaction (HER). The catalysts exhibit a small HER overpotential and low Tafel slope of approximately 100 mV and 52 mV per decade for MoS2, and 80 mV and 46 mV per decade for WS2, respectively. Importantly, these products show enhanced stability after 500 potential cycles, and the current density remains almost unchanged during the test.
尽管层状过渡金属二卤化物（TMD）纳米片因其独特的性质而引起了极大的关注，但仍需要开发一种简便的策略来精确控制 TMD 纳米片的横向尺寸和层数。在这项研究中，我们展示了一种在溶液相中制备胶体 MS2（M = Mo，W）纳米片的方法，该方法可制备具有非常小的横向尺寸（15 至 40nm）和精确控制的奇数层（如 1、3 和 5 层）的胶体 MS2（M = Mo，W）纳米片，这可通过透射电子显微镜、X 射线衍射和 X 射线光电子能谱进行表征。通过拉曼和吸收光谱首次揭示了胶体 MS2（M = Mo，W）纳米片的尺寸和层依赖性的光学性质。这些胶体纳米片，特别是单层纳米片，具有大量的边缘位点，这些边缘位点可作为析氢反应（HER）的活性位点。催化剂表现出较小的 HER 过电位和低的塔菲尔斜率，对于 MoS2 约为 100 mV 和 52 mV/每 decade，对于 WS2 约为 80 mV 和 46 mV/每 decade。重要的是，这些产物在 500 个电位循环后表现出增强的稳定性，并且在测试过程中电流密度几乎保持不变。
