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In this study, we successfully demonstrate the fabrication of a MoS2-graphene heterostructure (MGH) on a 4 inch wafer at 300 °C by depositing a thin Mo film seed layer on graphene followed by sulfurization using H2S plasma. By utilizing Raman spectroscopy and high-resolution transmission electron microscopy, we have confirmed that 5–6 MoS2 layers with a large density of sulfur vacancies are grown uniformly on the entire substrate. The chemical composition of MoS2 on graphene was evaluated by X-ray photoelectron spectroscopy, which confirmed the atomic ratio of Mo to S to be 1:1.78, which is much lower than the stoichiometric value of 2 from standard MoS2. To exploit the properties of the nanocrystalline and defective MGH film obtained in our process, we have utilized it as a catalyst for hydrodesulfurization and as an electrocatalyst for the hydrogen evolution reaction. Compared to MoS2 grown on an amorphous SiO2 substrate, the MGH has smaller onset potential and Tafel slope, indicating its enhanced catalytic performance. Our practical growth approach can be applied to other two-dimensional crystals, which are potentially used in a wide range of applications such as electronic devices and catalysis.

The metallic 1T phase of WS2 (1T-WS2 ), which boosts the charge transfer between the electron source and active edge sites, can be used as an efficient electrocatalyst for the hydrogen evolution reaction (HER). As the semiconductor 2H phase of WS2 (2H-WS2 ) is inherently stable, methods for synthesizing 1T-WS2 are limited and complicated. Herein, a uniform wafer-scale 1T-WS2 film is prepared using a plasma-enhanced chemical vapor deposition (PE-CVD) system. The growth temperature is maintained at 150 °C enabling the direct synthesis of 1T-WS2 films on both rigid dielectric and flexible polymer substrates. Both the crystallinity and number of layers of the as-grown 1T-WS2 are verified by various spectroscopic and microscopic analyses. A distorted 1T structure with a 2a0 × a0 superlattice is observed using scanning transmission electron microscopy. An electrochemical analysis of the 1T-WS2 film demonstrates its similar catalytic activity and high durability as compared to those of previously reported untreated and planar 1T-WS2 films synthesized with CVD and hydrothermal methods. The 1T-WS2 does not transform to stable 2H-WS2 , even after a 700 h exposure to harsh catalytic conditions and 1000 cycles of HERs. This synthetic strategy can provide a facile method to synthesize uniform 1T-phase 2D materials for electrocatalysis applications.