Non-equilibrium fractal growth of MoS2 for electrocatalytic hydrogen evolution

Abstract

Non-equilibrium fractal growth of MoS₂ was induced by establishing an extremely Mo rich chemical vapor deposition (CVD) environment using a rapid heating rate in a confined reaction space. In addition, a detailed shape evolution mechanism was suggested based on the results of thermodynamics and kinetics studies. The extremely Mo rich CVD condition allowed various MoS₂ flakes to be synthesized with triangular, star-like, and dendrite-like shapes in series, owing to the thermodynamic preference to increase the number of growth directions. Moreover, numerous small triangular crystals led to the formation of MoS₂ flakes with jagged edges, probably as a result of the aggressive nucleation triggered by a fast and abundant supply of MoO_3−x vapors. Lastly, using the MoS₂ flakes with various fractal shapes, a systematic improvement of the hydrogen evolution reaction performance was demonstrated in accordance with the increase in the surrounding edge length.