Mo/Mo2C encapsulated in nitrogen-doped carbon nanofibers as efficiently integrated heterojunction electrocatalysts for hydrogen evolution reaction in wide pH range

It is extremely necessary to develop high-performance noble-metal-free hydrogen evolution reaction (HER) electrocatalysts applied over the whole pH values to replace expensive Pt-based catalysts. Herein, a typical metal-semiconductor heterostructure with metallic Mo and Mo2C nanoparticles encapsulated in nitrogen-doped carbon nanofibers (N-CNFs) is fabricated via the pyrolysis of electrospun polyacrylonitrile (PAN)/cellulose acetate (CA)/bis(acetylacetonato)dioxomolybdenum (MoO2(acac)2) nanofibers. The unique porous and channel-rich structure of Mo/Mo2C/N-CNFs can be manipulated by varying the mass ratio of polyacrylonitrile and cellulose acetate, leading to the exposure of abundant active centers and the acceleration of rapid mass transport. In addition, the synergetic effect among metal and semiconductor as well as the excellent conductivity of the N-CNFs result in excellent HER activity and stability over a wide pH range. To achieve the current density of 10 mA cm−2, the optimized Mo/Mo2C/N-CNFs exhibit overpotentials of 175, 162 and 294 mV in 0.5 M H2SO4, 1 M KOH and 0.1 M phosphate buffer solution (PBS), respectively. This work provides a feasible approach to synthesize high-performance and economical hydrogen evolution electrocatalysts at all pH values for renewable energy-related applications.