Colloidal Synthesis of 1T-WS₂ and 2H-WS₂ Nanosheets: Applications for Photocatalytic Hydrogen Evolution

Abstract

In recent years, a lot of attention has been devoted to monolayer materials, in particular to transition-metal dichalcogenides (TMDCs). While their growth on a substrate and their exfoliation are well developed, the colloidal synthesis of monolayers in solution remains challenging. This paper describes the development of synthetic protocols for producing colloidal WS₂ monolayers, presenting not only the usual semiconducting prismatic 2H-WS₂ structure but also the less common distorted octahedral 1T-WS₂ structure, which exhibits metallic behavior. Modifications of the synthesis method allow for control over the crystal phase, enabling the formation of either 1T-WS₂ or 2H-WS₂ nanostructures. We study the factors influencing the formation of the two WS₂ nanostructures, using X-ray diffraction, microscopy, and spectroscopy analytical tools to characterize them. Finally, we investigate the integration of these two WS₂ nanostructured polymorphs into an efficient photocatalytic hydrogen evolution system to compare their behavior