The low utilization of active sites and sluggish reaction kinetics of MoSe 2 severely impede its commercial application as electrocatalyst for hydrogen evolution reaction (HER). To address these two issues, the first example of introducing 1T MoSe 2 and N dopant into vertical 2H MoSe 2 /graphene shell/core nanoflake arrays that remarkably boost their HER activity is herein described. By means of the improved conductivity, rich catalytic active sites and highly accessible surface area as a result of the introduction of 1T MoSe 2 and N doping as well as the unique structural features, the N‐doped 1T‐2H MoSe 2 /graphene (N‐MoSe 2 /VG) shell/core nanoflake arrays show substantially enhanced HER activity. Remarkably, the N‐MoSe 2 /VG nanoflakes exhibit a relatively low onset potential of 45 mV and overpotential of 98 mV (vs RHE) at 10 mA cm −2 with excellent long‐term stability (no decay after 20 000 cycles), outperforming most of the recently reported Mo‐based electrocatalysts. The success of improving the electrochemical performance via the introduction of 1T phase and N dopant offers new opportunities in the development of high‐performance MoSe 2 ‐based electrodes for other energy‐related applications.

Directional Construction of Vertical Nitrogen‐Doped 1T‐2H MoSe<sub>2</sub>/Graphene Shell/Core Nanoflake Arrays for Efficient Hydrogen Evolution Reaction

Directional Construction of Vertical Nitrogen‐Doped 1T‐2H MoSe2/Graphene Shell/Core Nanoflake Arrays for Efficient Hydrogen Evolution Reaction