synthesis of molybdenum carbide/N-doped carbon hybrids as an efficient hydrogen-evolution electrocatalyst.

The development of non-precious metal based electrocatalysts for the hydrogen evolution reaction (HER) has received more and more attention over recent years owing to energy and environmental issues, and Mo based materials have been explored as a promising candidate. In this work, molybdenum carbide/N-doped carbon hybrids (MoC@NC) were synthesized facilely one-step high-temperature pyrolysis by adjusting the mass ratio of urea and ammonium molybdate. The MoC@NC consisted of ultrasmall nanoparticles encapsulated by N-doped carbon, which had high specific surface area. They all exhibited efficient HER activity, and the MoC@NC with a mass ratio of 160 (MoC@NC-160) showed the best HER activity, with a low overpotential of 90 mV to reach 10 mA cm and a small Tafel slope of 50 mV dec, which was one of the most active reported MoC-based electrocatalysts. The excellent HER activity of MoC@NC-160 was attributed to the following features: (1) the highly dispersed ultrasmall MoC nanoparticles, which exhibited high electrochemically active surface areas; (2) the synergistic effect of the N-doped carbon shell/matrix, which facilitated the electron transport.