CVD-Grown MoSe₂ Nanoflowers with Dual Active Sites for Efficient Electrochemical Hydrogen Evolution Reaction

Due to its unique electronic band characteristics (presence of d-orbital in both Mo and Se atoms), MoSe₂ has potential to exhibit high electrical conductivity and superior hydrogen evolution reaction (HER) kinetics when compared to other transition-metal dichalcogenides. Though various strategies were employed earlier to obtain MoSe₂ structure with different shapes and morphologies, precise control on achieving both Mo- and Se-edge sites and understanding their interaction with reactants in HER remains to be challenging. Here, we successfully demonstrate the vapor diffusion method to grow highly crystalline MoSe₂ nanoflowers on carbon cloth in a vertical orientation. Uniformly dispersed nanoflowers with Mo- and Se-edge sites exhibited remarkable electrocatalytic activity on hydrogen reduction in terms of low Tafel slope and high exchange current density. The existence of a strong interaction between MoSe₂ and carbon cloth assists in long-term hydrogen production and confirms the exceptional durability of the catalyst. A comprehensive evidence for hydrogen adsorption on dual active sites, viz., Mo- and Se-edges of MoSe₂, is provided using X-ray photoelectron spectroscopy and in situ Raman spectroscopy containing a specially designed liquid immersion objective lens.