Electrospinning Hetero-Nanofibers of Fe₃ C-Mo₂ C/Nitrogen-Doped-Carbon as Efficient Electrocatalysts for Hydrogen...

Heterostructured electrocatalysts with multiple active components are expected to synchronously address the two elementary steps in the hydrogen evolution reaction (HER), which require varied hydrogen-binding strength on the catalyst surface. Herein, electrospinning followed by a pyrolysis is introduced to design Fe₃ C-Mo₂ C/nitrogen-doped carbon (Fe₃ C-Mo₂ C/NC) hetero-nanofibers (HNFs) with tunable composition, leading to abundant Fe₃ C-Mo₂ C hetero-interfaces for synergy in electrocatalysis. Owing to the strong hydrogen binding on Mo₂ C and the relatively weak one on Fe₃ C, the hetero-interfaces of Fe₃ C-Mo₂ C remarkably promote HER kinetics and intrinsic activity. Additionally, the loose and porous N-doped carbon matrix, as a result of Fe-catalyzed carbonization, ensures the fast transport of electrolytes and electrons, thus minimizing diffusion limitation. As expected, the optimized Fe₃ C-Mo₂ C/NC HNFs afforded a low overpotential of 116 mV at a current density of -10 mA cm^-2 and striking kinetics metrics (onset overpotential: 42 mV, Tafel slope: 43 mV dec^-1 ) in 0.5 m H₂ SO₄ , outperforming most recently reported noble-metal-free electrocatalysts.