Activating MoS2 with Super-High Nitrogen-Doping Concentration as Efficient Catalyst for Hydrogen Evolution Reaction

The development of nonprecious electrocatalysts with high hydrogen evolution reaction (HER) activity for water splitting is highly desirable but remains a significant challenge. Molybdenum disulfide (MoS2) has been demonstrated as a good candidate; however, insufficient active sites along with poor conductivity significantly hinder the overall efficiency of MoS2. In this work, we present a method to activate commercial MoS2 by high concentration nitrogen doping via a facile high-temperature treatment routine. The dominant N-doping mechanism is demonstrated to be an appropriate one-to-one substitution of sulfur atoms, which is confirmed by the approximate constancy between the atomic ratio of Mo/(S + N) and stoichiometric number of original MoS2. By controlling the activation time and temperature, the concentration of the doped nitrogen atoms can be tuned up to 41 atom %. The HER activity of the as-prepared materials was evaluated as electrode materials, showing that the catalytic activity is strongly correlated with the doped nitrogen concentration, and the catalytic current density of N-doped MoS2 can reach 15 times higher than that of the pristine MoS2. The prominent improvement of HER performance for N–MoS2 can be attributed to rich active sites, higher electron concentration around active sites, and ameliorative conductivity induced by N incorporation. The facile and controllable approach to activate MoS2 for achieving high-level N-doping developed in this study can shed significant light on the preparation of heteroatoms-doped electrocatalytic materials.