In situ 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 (Mo₂C@NC) were synthesized facilely via one-step high-temperature pyrolysis by adjusting the mass ratio of urea and ammonium molybdate. The Mo₂C@NC consisted of ultrasmall nanoparticles encapsulated by N-doped carbon, which had high specific surface area. They all exhibited efficient HER activity, and the Mo₂C@NC with a mass ratio of 160 (Mo₂C@NC-160) showed the best HER activity, with a low overpotential of 90 mV to reach 10 mA cm^-2 and a small Tafel slope of 50 mV dec^-1, which was one of the most active reported Mo₂C-based electrocatalysts. The excellent HER activity of Mo₂C@NC-160 was attributed to the following features: (1) the highly dispersed ultrasmall Mo₂C nanoparticles, which exhibited high electrochemically active surface areas; (2) the synergistic effect of the N-doped carbon shell/matrix, which facilitated the electron transport.