Local Structure of Sulfur Vacancies on the Basal Plane of Monolayer MoS<sub>2</sub>
Angel T. Garcia‐Esparza, Sangwook Park, Hadi Abroshan, Oscar A. Paredes Mellone, John Vinson, Baxter Abraham, Taeho R. Kim, Dennis Nordlund, Alessandro Gallo, Roberto Alonso‐Mori, Xiaolin Zheng, Dimosthenis Sokaras
Abstract
The nature of the S-vacancy is central to controlling the electronic properties of monolayer MoS2. Understanding the geometric and electronic structures of the S-vacancy on the basal plane of monolayer MoS2 remains elusive. Here, operando S K-edge X-ray absorption spectroscopy shows the formation of clustered S-vacancies on the basal plane of monolayer MoS2 under reaction conditions (H2 atmosphere, 100–600 °C). First-principles calculations predict spectral fingerprints consistent with the experimental results. The Mo K-edge extended X-ray absorption fine structure shows the local structure as coordinatively unsaturated Mo with 4.1 ± 0.4 S atoms as nearest neighbors (above 400 °C in an H2 atmosphere). Conversely, the 6-fold Mo–Mo coordination in the crystal remains unchanged. Electrochemistry confirms similar active sites for hydrogen evolution. The identity of the S-vacancy defect on the basal plane of monolayer MoS2 is herein elucidated for applications in optoelectronics and catalysis.