Nitrogen doped carbon nanotubes with embedded Ru and decorated Mo2C as hydrogen evolution reaction electrocatalysts in alkaline and acid electrolytes

We reported a novel approach to the synthesis of hierarchically structured nitrogen-doped carbon nanotubes (NCNTs) via chemical vapor deposition using anodic aluminum oxides as templates and the following annealing in ammonia. The ruthenium (Ru) nanoparticles with low content of 1.6 wt% were embedded in NCNTs, and the molybdenum carbide (Mo2C) nanoparticles were decorated on outer surfaces of NCNTs. Thanks to the combined contributions of doped N, Ru and Mo2C, the Ru@NCNT/Mo2C composites exhibited a low overpotential of 22 mV at a current density of 10 mA cm- 2 and a small Tafel slope of 26 mV dec- 1 for hydrogen evolution reaction (HER) in 1 M KOH. After further constructing anion exchange membrane electrolyzers using Ru@NCNT/Mo2C composites as electrocatalysts in cathodes, the electrolyzers delivered a low cell voltage of 1.86 V at industry-level current density of 1 A cm- 2 as well as superior durability. Moreover, Ru@NCNT/Mo2C composites also demonstrated a low overpotential of 38 mV at 10 mA cm- 2, a small Tafel slope of 36 mV dec- 1 and good stability for HER in 0.5 M H2SO4. This work may pave a new way for the synthesis of high performance HER electrocatalysts in both alkaline and acid electrolytes.