Mo-Terminated Edge Reconstructions in Nanoporous Molybdenum Disulfide Film

Abstract

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.

Direct Visualization of Electric-Field-Induced Structural Dynamics in Monolayer Transition Metal Dichalcogenides

“…In addition, based on these calculated energy barriers, it is expected that the migration of sulfur atoms from the edges of the void to the interior of the grain would occur more rapidly than a similar process for molybdenum atoms and thus leave behind a molybdenum-rich region near the void region. This DFT prediction is supported by the fact that molybdenum-terminated edges are almost exclusively observed bordering voids, 46 as is suggested by our results, as well ( Figure S6). Additionally, the representative low magnification TEM image in Figure 4c demonstrates the presence of numerous molybdenum-rich particles residing near the void region, which also supports this prediction ( Figure 4c).…”

Differentiating Polymorphs in Molybdenum Disulfide via Electron Microscopy

“…Although it is difficult to grow the 1T′ phase as a film directly due to its metastability, we find that it may exist as a 1D structure at edges or domain discontinuities. STEM revealed that the edges of nanoporous H‐phase MoS 2 films grown by MBE under Mo‐rich (high Mo flux) conditions are 1T′‐like ( Figure a) . The as‐grown 1T′‐edges remain stable at 900 °C as confirmed by in situ STEM experiments (Figure b,c).…”

Ion Beam Defect Engineering on ReS2/Si Photocathode with Significantly Enhanced Hydrogen Evolution Reaction

“…Extensive studies have suggested that the catalysis of 2D TMDs originates mainly from the unsaturated atoms at edge sites of the sulfide compounds . Recently, enormous efforts have been dedicated to a variety of nanostructured TMDs to expose more active edge sites for enhancing HER performances …”