Modulating intrinsic electronic and geometric structures of bimetallic electrocatalysts has been regarded as a promising strategy to effectively solve the sluggish kinetics and large overpotential of OER (Oxygen evolution reaction) and HER (Hydrogen evolution reaction) involved in future large-scale electricity-to-hydrogen generation. Here, the bifunctional Co/Mo2C electrocatalysts encapsulated in 3D hierarchical nitrogen-doped carbon nanofibers synchronously rooted with abundant carbon nanotubes (Co/Mo2C-NCNTs) were successfully fabricated by a facile electrospinning method. Due to the unique heterostructures and strong synergetic effects between Co and Mo2C nanoparticles to improve OH- affinity, moderate Mo-H bonds, and expose more active sites, the Co/Mo2C-NCNTs displayed a tiny overpotential for OER (eta(10)=310 mV) and HER (eta(10)=170 mV) and stably operated for 24 h. Moreover, the results of a water electrolysis device demonstrated that the faradaic efficiency was close to 100 %, which further proved that this method was feasible and effective to fabricate high-efficiency bifunctional non-noble electrocatalysts for water splitting.