Molybdenum Carbide Nanoparticles Coated into the Graphene Wrapping N-Doped Porous Carbon Microspheres for Highly Efficient Electrocatalytic Hydrogen Evolution Both in Acidic and Alkaline Media.

Molybdenum carbide (MoC) is recognized as an alternative electrocatalyst to noble metal for the hydrogen evolution reaction (HER). Herein, a facile, low cost, and scalable method is provided for the fabrication of MoC-based eletrocatalyst (MoC/G-NCS) by a spray-drying, and followed by annealing. As-prepared MoC/G-NCS electrocatalyst displays that ultrafine MoC nanopartilces are uniformly embedded into graphene wrapping N-doped porous carbon microspheres derived from chitosan. Such designed structure offer several favorable features for hydrogen evolution application: 1) the ultrasmall size of MoC affords a large exposed active sites; 2) graphene-wrapping ensures great electrical conductivity; 3) porous structure increases the electrolyte-electrode contact points and lowers the charge transfer resistance; 4) N-dopant interacts with H better than C atoms and favorably modifies the electronic structures of adjacent Mo and C atoms. As a result, the MoC/G-NCS demonstrates superior HER activity with a very low overpotential of 70 or 66 mV to achieve current density of 10 mA cm, small Tafel slope of 39 or 37 mV dec, respectively, in acidic and alkaline media, and high stability, indicating that it is a great potential candidate as HER electrocatalyst.