Nitrogen-doped graphene microtubes with opened inner voids: Highly efficient metal-free electrocatalysts for alkaline hydrogen evolution reaction

A facile method was developed to fabricate nitrogen-doped graphene microtubes (N-GMT) with ultra-thin walls of 1–4 nm and large inner voids of 1–2 μm. The successful introduction of nitrogen dopants afforded N-GMT more active sites for significantly enhanced hydrogen evolution reaction (HER) activity, achieving a current density of 10 mA·cm^–2 at overpotentials of 0.464 and 0.426 V vs. RHE in 0.1 and 6 M KOH solution, respectively. This HER performance surpassed that of the best metal-free catalyst reported in basic solution, further illustrating the great potential of N-GMT as an efficient HER catalyst for real applications in water splitting and chlor-alkali processes.