Fluorination activates the basal plane HER activity of ReS2: a combined experimental and theoretical study

Abstract

Two-dimensional (2D) rhenium disulfide (ReS₂) has been attracting immense interest as a highly promising hydrogen evolution reaction (HER) electrocatalyst recently. However, the HER catalytic active sites of ReS₂ are still limited to the finite edges of the nanosheets and the basal-plane is catalytically inert. How to activate the in-plane catalytic activity of ReS₂ accordingly becomes the sticking point to further boost its H₂ evolution efficiency. Here, the fluorinated ReS₂ hierarchical structure assembled as ultrathin nanosheets is proved to exhibit excellent HER activity, where the optimal sample of ReS₂-F_5.93 shows a low overpotential of 142 mV vs. RHE at a current density of 10 mA cm⁻², a Tafel slope of 64 mV dec⁻¹, and significantly improved stability. The enhanced HER performance is mainly attributed to the synergistic effects of increased in-plane active sites and remarkably accelerated charge transfer kinetics. The density functional theory calculation results reveal that F doping can yield the optimal H* adsorption Gibbs free energy and meanwhile increase the electronic states near the Fermi level for accelerated electron transfer. This work can broaden the horizon for designing efficient HER electrocatalysts via activating the in-plane catalytic activity of transition metal dichalcogenides (TMDs).