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

Chemical vapor deposition (CVD) is used to grow thin films of 2D MoS 2 with nanostructure for catalytic applications in the hydrogen evolution reaction (HER). Tailoring of the CVD parameters results in an optimized MoS 2 structure for the HER that consists of large MoS 2 platelets with smaller layered MoS 2 sheets growing off it in a perpendicular direction, which increases the total number of edge sites within a given geometric area. A surface area to geometric area ratio of up to ∼340 is achieved, benefiting from the edge-exposed high-porosity network structure. The optimized thickness of the MoS 2 film is determined for maximum performance, revealing that increasing thickness leads to increased impedance of the MoS 2 film and reduced current density. The current density of the optimum sample reaches as high as 60 mA/cm 2 geo (normalized by geometric area) at an overpotential of 0.64 V vs RHE (in 0.5 M H 2 SO 4 ), with a corresponding Tafel slope of ∼90 mV/dec and exchange current density of 23 μA/cm 2 geo . The lowered Tafel slope and large exchange current density demonstrate that the high-porosity edge-exposed MoS 2 network structure is promising as a HER catalyst.