Extrinsically controlling the intrinsic activity and stability of two-dimensional (2D) semiconducting materials by substitutional doping is crucial for energy-related applications. However, an in situ transition-metal doping strategy for uniform and large-area chemical vapor deposited 2D semiconductors remains a formidable challenge. Here, we successfully synthesize highly uniform niobium-substituted tungsten disulfide (Nb-WS2) monolayers, with a doping concentration of nearly 7% and sizes reaching 100 μm, through a metal dopant precursor route, using salt-catalyzed chemical vapor deposition (CVD). Our results reveal unusual effects in the structural, optical, electronic, and electrocatalysis characteristics of the Nb-WS2 monolayer. The Nb dopants readily induce a band restructuring effect, providing the most active site with a hydrogen adsorption energy of 0.175 eV and hence greatly improving its hydrogen evolution activity. The combined advantages of the unusual physics and chemistry by in situ CVD doping technique open the possibility in designing 2D-material-based electronics and catalysts of novel functionalities.
Keywords: Band structure; Chemical vapor deposition; Hydrogen evolution; Nb doping; Tungsten disulfides.