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.

Metallic 1T‐WS2 for Selective Impedimetric Vapor Sensing

“…[ 14 ] It has been observed that the components of the 1T phase in the high-resolution W4f spectrum appear at binding energies about 1 eV lower than those belonging to the 2H phase. [ 18 ] Figure 2 shows high-resolution XPS spectrum of W4f for WS 2 in the bulk state and after exfoliation. It is clear that the material experienced a signifi cant phase transition upon exfoliation presenting the components of the metallic 1T phase (at ≈32 and 34 eV) more prominent than those of the 2H phase (at ≈33 and 35 eV).…”

Z‐Scheme Photocatalytic Systems for Promoting Photocatalytic Performance: Recent Progress and Future Challenges

“…Semiconductor photocatalyst systems can be used to split water into H 2 and O 2 , to photo‐reduce CO 2 into renewable fuels such as CH 3 OH, CH 4 , and CO, and to decompose various organic contaminations to remedy the environment. These methods use solar energy as the source of photons to promote reactions 1, 2. Photocatalytic reaction processes primarily involve three main steps: (1) the photogeneration of electron–hole pairs through the absorption of solar light of the energy larger than the band gap of photocatalyst, (2) the charge separation and migration onto the surface without recombination, and (3) the reduction/oxidation reaction on the surface of photocatalyst 3, 4, 5.…”

Two-dimensional inorganic analogues of graphene: transition metal dichalcogenides

“…1 nm [11], (c) adapted with permission from Mahler et al [54] and (d-g) adapted with permission from Yoo et al [55].…”

“…2H-WS 2 forms instead of 1T-WS 2 when hexamethyldisilazane (HMDS) is added to oleylamine [54]. Figure 5c shows the low-and high-resolution TEM images of 1T-and 2H-WS 2 monolayers formed in the absence and presence of HMDS, respectively.…”