Phase Modulation of (1T-2H)-MoSe2/TiC-C Shell/Core Arrays via Nitrogen Doping for Highly Efficient Hydrogen Evolution Reaction.

Tailoring molybdenum selenide electrocatalysts with tunable phase and morphology is of great importance for advancement of hydrogen evolution reaction (HER). In this work, phase- and morphology-modulated N-doped MoSe2 /TiC-C shell/core arrays through a facile hydrothermal and postannealing treatment strategy are reported. Highly conductive TiC-C nanorod arrays serve as the backbone for MoSe2 nanosheets to form high-quality MoSe2 /TiC-C shell/core arrays. Impressively, continuous phase modulation of MoSe2 is realized on the MoSe2 /TiC-C arrays. Except for the pure 1T-MoSe2 and 2H-MoSe2 , mixed (1T-2H)-MoSe2 nanosheets are achieved in the N-MoSe2 by N doping and demonstrated by spherical aberration electron microscope. Plausible mechanism of phase transformation and different doping sites of N atom are proposed via theoretical calculation. The much smaller energy barrier, longer HSe bond length, and diminished bandgap endow N-MoSe2 /TiC-C arrays with substantially superior HER performance compared to 1T and 2H phase counterparts. Impressively, the designed N-MoSe2 /TiC-C arrays exhibit a low overpotential of 137 mV at a large current density of 100 mA cm-2 , and a small Tafel slope of 32 mV dec-1 . Our results pave the way to unravel the enhancement mechanism of HER on 2D transition metal dichalcogenides by N doping.