Exploring kinetic control for the growth of layered MoS_2(1-x)Se_2x alloy and its electrocatalytic activity in hydrogen evolution reaction

Although controlled growth of monolayer two-dimensional (2D) transition metal dichalcogenides (TMDs) alloys has recently been achieved, a comprehensive understanding of their growth mechanism remains a major challenge due to the complex nucleation kinetics. In this study, the synthesis of large-area ternary MoS_2(1-x)Se_2x alloys by atmospheric pressure chemical vapor deposition (CVD) is effectively and efficiently controlled. Both experimental and theoretical investigations are conducted to explore the influence of precursors on growth kinetics. The results suggest that the introduction of Se not only reduces nucleation sites but also lowers diffusion energy, thereby promoting lateral growth of the alloy, which is supported by density functional theory (DFT) calculations. Furthermore, the electrocatalytic performance of MoS₂ film with discretely distributed triangle sheets is further enhanced by the incorporation of Se atoms during the hydrogen evolution reaction (HER). The Gibbs free energy of adsorbed hydrogen atom (ΔG_H*) has been calculated by DFT, showing that the replacement of S with Se at the edge site compared with the in-plane site would significantly reduce the Gibbs free energy. This study is crucial for improving the comprehension of the growth dynamics of TMD alloys and promoting their utilization in electrocatalytic hydrogen generation.