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.