Adsorption on Metallic Edges of Transition Metal Dichalcogenides

Abstract

2D semiconducting transition metal dichalcogenides (TMDs) have attracted interest for optoelectronics, catalysis, and energy applications. Control over TMD electronic and optical properties, which depend on dimensionality and are modified by nanostructuring and adsorbates, is important for the development and deployment of reliable nanoscale devices for such applications. Density functional theory calculation results for the atomic structure, energetics, and electronic structure of the metal edges of 2D (M = Mo, W and X = S, Se) with several coverages of adsorbed hydrogen, oxygen, hydroxyl radicals, and water are presented. Using zigzag nanoribbon models, it is found that compared with the basal planes of MX2, edges are more active and exhibit a rich adsorbent behavior. In general, the thermodynamically stable M‐edges, with two X adatoms, weakly bind hydrogen, oxygen, and water and strongly bind hydroxyl. However, adsorption energies depend on the adsorbate type and coverage and may be tuned for the catalysis of important chemical reactions such as water splitting and hydrogen evolution. The electronic band structure calculations show that, besides bandgap energy modifications and gap states, the well‐established robust metallic character of the edge states is preserved, albeit Fermi‐level shifts that depend both on adsorbates and adsorbents.