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

Abstract Molybdenum carbide (Mo 2 C) 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 Mo 2 C‐based eletrocatalyst (Mo 2 C/G‐NCS) by a spray‐drying, and followed by annealing. As‐prepared Mo 2 C/G‐NCS electrocatalyst displays that ultrafine Mo 2 C 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 Mo 2 C 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 Mo 2 C/G‐NCS demonstrates superior HER activity with a very low overpotential of 70 or 66 mV to achieve current density of 10 mA cm −2 , small Tafel slope of 39 or 37 mV dec −1 , respectively, in acidic and alkaline media, and high stability, indicating that it is a great potential candidate as HER electrocatalyst.