Platinum-Group Metal Grown on Vertically Aligned MoS₂ as Electrocatalysts for Hydrogen Evolution Reaction

In the past few years, research on Pt substitutes has focused on the electrocatalytic properties of layered transition metal dichalcogenides (LTMDs). The decoration of LTMDs with platinum-group metal (PGM) demonstrates a synergetic effect with PGM deposited on the LTMD basal plane. We report on the hydrogen evolution reaction (HER) electrocatalysis by PGM grown on vertically aligned (VA) MoS₂. The VA-MoS₂ films were processed by chemical vapor deposition (CVD) and the PGM (Pt and Pd) were electrodeposited specifically on the edges of the MoS₂ flakes from a simple metallic foil. Electron microscopy shows the formation of nm-scale metallic clusters binding through the dangling bonds of the unsaturated sulfides. The VA-MoS₂ remains intact through the electrodeposition process, as demonstrated by Raman spectroscopy and high-resolution transmission electron microscopy. In acidic media, both electrocatalysts VA-MoS₂@Pt and VA-MoS₂@Pd show a very low overpotential (91 and 106 mV respectively at 10 mA cm⁻²) with high current density at 300 mV overpotential (318 and 174 mA cm⁻² respectively). Interestingly, the Tafel slope of VA-MoS₂@Pt is even lower than that of platinum foil (24 vs 33 mV dec⁻¹ respectively).