Large Dendritic Monolayer MoS Grown by Atmospheric Pressure Chemical Vapor Deposition for Electrocatalysis.

The edge sites of MoS are catalytically active for the hydrogen evolution reaction (HER), and growing monolayer structures that are edge-rich is desirable. Here, we show the production of large-area highly branched MoS dendrites on amorphous SiO/Si substrates using an atmospheric pressure chemical vapor deposition and explore their use in electrocatalysis. By tailoring the substrate construction, the monolayer MoS evolves from triangular to dendritic morphology because of the change of growth conditions. The rough edges endow dendritic MoS with a fractal dimension down to 1.54. The highly crystalline basal plane and the edge of the dendrites are visualized at atomic resolution using an annular dark field scanning transmission electron microscope. The monolayer dendrites exhibit strong photoluminescence, which is indicative of the direct band gap emission, which is preserved after being transferred. Post-transfer sulfur annealing restores the structural defects and decreases the n-type doping in MoS monolayers. The annealed MoS dendrites show good and highly durable HER performance on the glassy carbon with a large exchange current density of 32 μA cm, demonstrating its viability as an efficient HER catalyst.