Owing to the exceptional physical properties and potential in sensor application, transition metal dichalcogenides (TMDCs) have attracted much attention in recent years. When the thickness of TMDCs is reduced to only monolayer or few atomic layers, a bandgap enlargement and transition from indirect to direct happen. Recently, researchers focus on the creation of various interesting nanostructures by different synthesis processes. Here, we present a novel chemical vapor reaction (CVR) method for the one-step synthesis of TMDC nanowalls from the reduction of WO_x into WSe₂ and WS₂ through the rapid diffusion and segregation of chalcogenides. By the rapid heating and rapid cooling procedure, we can achieve the formation of nanowalls standing perpendicularly on top of both SiO₂/Si and cabin-fiber paper substrates. Compared to the conventional solid-vapor phase CVD process, our approach is able to provide TMDCs with vertical nanostructures and enhanced surface area. Furthermore, the stoichiometry of WS_2xSe_2(1-x) walls can be adjusted by controlling the concentration ratio of sulfur and selenium. We provide Raman spectrum and X-ray Photoelectron Spectroscopies results supported by SEM and TEM observations to confirm the successful synthesis of the nanowalls with atomic thickness and varied compositions. This approach can also be applied to the synthesis of other TMDC materials, giving a step forward on the 2D materials research development.

The atomically thin TMDC materials are known for their great potential in sensing, optoelectronic, energy harvesting and Li-ion battery applications. Here, we demonstrate the catalytic property enhancement by utilizing WS_2xSe_2(1-x) on carbon-fiber paper as the cathode of hydrogen evolution reaction. In addition, due to the exposed edge sites of the TMDC nanowall structure, the application of gas sensing and photodetector was also investigated.