Unique three-dimensional Mo2C@MoS2 heterojunction nanostructure with S vacancies as outstanding all-pH range electrocatalyst for hydrogen evolution

Abstract It is essential but still a great challenge to improve the property of non-precious Hydrogen Evolution Reaction (HER) catalysts at all pH values to meet the vast energy demands even though much progress has been made in this field. Herein, an enhanced HER catalyst, non-noble-metal three-dimensional Mo2C@MoS2 heterojunction nanostructure with high concentration of sulphur vacancies (3D Mo2C@MoS2 NS) has been synthesized via multistep annealing in Ar atmosphere. The unique 3D Mo2C@MoS2 NS delivers excellent HER performances over a wide range of pH 0–14, with Tafel slopes of 37, 46, and 39 mV dec−1 and overpotentials of 67, 121, and 86 mV at −10 mA cm−2 in 0.5 M H2SO4, 1 M PBS and 1 M KOH as well as continuous durability above 120 h, which are better than that of partial reported carbide, phosphide and selenide electrocatalysts. The excellent performance is attributed to high specific surface area, strong electronic interaction and abundant active sites. Besides, the density functional theory further indicates that the 3D Mo2C@MoS2 NS could lower the Gibbs free energy of H adsorption (△GH*), leading to increased HER performance. Thus the 3D Mo2C@MoS2 NS as an all-pH HER catalyst makes a major breakthrough in hydrogen evolution.