Deep Phase Transition of MoS₂ for Excellent Hydrogen Evolution Reaction by a Facile C‑Doping Strategy

Metallic 1T-phase MoS₂ is considered to be the ideal electrocatalyst to carry out hydrogen evolution reaction (HER) because of favorable conductivity and sufficient active site compared with 2H-phase MoS₂. Nevertheless, 1T-phase MoS₂ is conventionally synthesized in a complicated process, with the production of an unstable product, which hinders their practical applications. Herein, we propose a facile approach through a carbon-doping-induced phase transition to obtain highly stable 1T–2H mixed MoS₂ nanosheets. The phase transition process is characterized by Raman and X-ray photoelectron spectroscopy, as well as high-resolution transmission electron microscopy images and delivers a high phase purity of ∼60% for 1T-MoS₂. According to density functional theory simulations and experimental results, C-doped 1T–2H mixed MoS₂ has the advantages of abundant active sites, facilitated charge transfer rate, and high activity toward HER. The obtained C-doped MoS₂ exhibits a superb HER electrocatalytic performance, with a current density of 10 mA cm^–2 and the overpotential as low as 40 mV in 1 M KOH solution, and brilliant stability.