Edge-Enriched 2D MoS₂ Thin Films Grown\nby Chemical Vapor Deposition for Enhanced Catalytic Performance

Abstract

Chemical vapor deposition (CVD) is\nused to grow thin films of 2D\nMoS₂ with nanostructure for catalytic applications in the\nhydrogen evolution reaction (HER). Tailoring of the CVD parameters\nresults in an optimized MoS₂ structure for the HER that\nconsists of large MoS₂ platelets with smaller layered MoS₂ sheets growing off it in a perpendicular direction, which\nincreases the total number of edge sites within a given geometric\narea. A surface area to geometric area ratio of up to ∼340\nis achieved, benefiting from the edge-exposed high-porosity network\nstructure. The optimized thickness of the MoS₂ film is\ndetermined for maximum performance, revealing that increasing thickness\nleads to increased impedance of the MoS₂ film and reduced\ncurrent density. The current density of the optimum sample reaches\nas high as 60 mA/cm²_geo (normalized by geometric\narea) at an overpotential of 0.64 V vs RHE (in 0.5 M H₂SO₄), with a corresponding Tafel slope of ∼90 mV/dec\nand exchange current density of 23 μA/cm²_geo. The lowered Tafel slope and large exchange current density demonstrate\nthat the high-porosity edge-exposed MoS₂ network structure\nis promising as a HER catalyst.