Cobalt-doped molybdenum carbide nanoparticles embedded in nitrogen-doped carbon nanosheets for efficient pH-universal hydrogen evolution

Abstract

The development of non-noble electrocatalysts for efficient hydrogen evolution reaction (HER) provides a viable approach for making a contribution in alleviating energy crisis aspect. In this paper, the cobalt-doped molybdenum carbide nanoparticles embedded in nitrogen-doped carbon (Co-Mo₂C/NC) nanosheets were fabricated via the calcination of MoO₃ coated with cobalt-based metal-organic framework (ZIF-67) and melamine. The incorporation of cobalt dopant in Mo₂C weakens the Mo-H bonding strength, giving rise to the optimized desorption of intermediate adsorbed hydrogen (H_ads) and accelerating the reaction kinetics, which presents remarkable electrocatalytic HER performance in a wide pH range, especially in alkaline medium. Furthermore, the in-situ formed nitrogen-doped carbon has the favorable conductivity and large active surface area. It also facilitates the dispersibility of the active material, therefore boosting the electrocatalytic performance as well as durability. The as-prepared Co-Mo₂C/NC nanosheets exhibit low overpotentials of 94, 79 and 102 mV to achieve 10 mA cm⁻², small Tafel slopes of 57.9, 60.6 and 75.8 mV dec⁻¹ and high exchange current densities of 0.238, 0.497 and 0.465 mA cm⁻² under acidic, alkaline as well as neutral electrolytes, along with good stability. This study shows a novel thought to exploit the highly efficient and pH-universal electrocatalysts for efficient hydrogen generation.