Anionic and Cationic Co-Substitutions of S into Vertically Aligned WTe₂ Nanosheets as Catalysis for Hydrogen Evolution under Alkaline Conditions

The design of transition metal dichalcogenides that satisfies the essential requirements of the hydrogen evolution reaction (HER) in alkaline solutions remains a challenge. The study gives a description of sulfur atoms into both anionic and cationic sites of WTe2, which is deliberately designed and has been rarely reported. Herein, we report 3D self-supported anionic and cationic S-substituted WTe2 nanosheet arrays constructed on a carbon cloth by a three-step synthesis method at elevated temperatures. Experimental and theoretical analysis are both executed to investigate S-WTe2/CC nanocomposites for efficient alkaline HER, and the results attest to its excellent electrocatalytic performance. The optimized S-WTe2/CC exhibits an enhanced HER activity with an overpotential of 195 mV at the current density of 10 mA cm–2, which is 2.3 and 1.7 times lower than that of WO3/CC (451 mV) and WTe2/CC (327 mV), respectively. According to density functional theory calculations, such improvement of alkaline HER is attributed to the optimized p-band electron configuration of Te atoms, higher H* intermediate adsorption, and lower H2O dissociation energy barrier by anionic and cationic co-substitution of S, which accelerate the Volmer–Heyrovsky process. The present study paves a way to the modification strategy of WTe2 electrocatalysts.