Monolayer TiS ₂ Nanosheets on Au(111)–Structural Characterization and Effect of Edge Stability for Shape Control

Abstract Transition metal dichalcogenides are promising alternatives to noble metal catalysts, e.g., for (photo‐)activation of greenhouse gases or hydrogenations. Herein, a direct synthetic route for 2D TiS ₂ nanosheets on Au(111) by titanium deposition in the presence of a mild, organic, non‐oxidizing sulfur source is presented. High‐resolution scanning tunneling microscopy (STM) is used to gain atomic‐level insights into the TiS ₂ nanosheet morphology. In contrast to the literature, this protocol gains mostly hexagonal and truncated triangular nanosheets with an increased edge contrast in STM, analog to metallic edge states in MoS ₂ . Synchrotron‐based photoelectron spectroscopy allows insights into compositional details, specifically to distinguish different S sites on the TiS ₂ sheets and other S species on the sample. Further, a minimum size is identified (9 S atoms side length), which underlines the importance of moiré reconstructions for stress relief. The TiS ₂ sheets coexist with [Au]Ti ₁ S ₃ clusters, in which a single gold atom is alloyed into the surface and capped by three S atoms. Together with the finding of a critical sheet size, this points toward on‐surface Ostwald ripening as a relevant process in the sheet formation. Ab‐initio calculations (density functional theory) underscore that the chemical potential of S is an essential descriptor to maintain shape control.