Department of Chemistry and Centre for Advanced 2D Materials (CA2DM), National University of Singapore , 3 Science Drive 3, Singapore, 117543, Singapore.
NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore , 13 Centre for Life Sciences, #05-01, 28 Medical Drive, Singapore 117456, Singapore.
Nano Lett. 2018 Jan 10;18(1):482-490. doi: 10.1021/acs.nanolett.7b04426. Epub 2017 Dec 22.
The catalytic and magnetic properties of molybdenum disulfide (MoS) are significantly enhanced by the presence of edge sites. One way to obtain a high density of edge sites in a two-dimensional (2D) film is by introducing porosity. However, the large-scale bottom-up synthesis of a porous 2D MoS film remains challenging and the correlation of growth conditions to the atomic structures of the edges is not well understood. Here, using molecular beam epitaxy, we prepare wafer-scale nanoporous MoS films under conditions of high Mo flux and study their catalytic and magnetic properties. Atomic-resolution electron microscopy imaging of the pores reveals two new types of reconstructed Mo-terminated edges, namely, a distorted 1T (DT) edge and the Mo-Klein edge. Nanoporous MoS films are magnetic up to 400 K, which is attributed to the presence of Mo-terminated edges with unpaired electrons, as confirmed by density functional theory calculation. The small hydrogen adsorption free energy at these Mo-terminated edges leads to excellent activity for the hydrogen evolution reaction.
二硫化钼 (MoS) 的催化和磁性特性通过边缘位点的存在得到显著增强。在二维 (2D) 薄膜中获得高密度边缘位点的一种方法是引入孔隙率。然而，大规模的自下而上合成多孔 2D MoS 薄膜仍然具有挑战性，并且生长条件与边缘原子结构的相关性尚未得到很好的理解。在这里，我们使用分子束外延在高 Mo 通量的条件下制备了晶圆级纳米多孔 MoS 薄膜，并研究了它们的催化和磁性性质。对孔的原子分辨率电子显微镜成像揭示了两种新型重构的 Mo 终止边缘，即扭曲的 1T（DT）边缘和 Mo-Klein 边缘。纳米多孔 MoS 薄膜在 400 K 以下具有磁性，这归因于存在具有未配对电子的 Mo 终止边缘，这通过密度泛函理论计算得到了证实。这些 Mo 终止边缘处的小氢吸附自由能导致了对析氢反应的优异活性。
