One-Dimensional Porous Hybrid Structure of Mo2C-CoP Encapsulated in N-Doped Carbon Derived from MOF: An Efficient Electrocatalyst for Hydrogen Evolution Reaction over the Entire pH Range

The development of outstanding noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER) has attracted broad interest. Herein, a novel one-dimensional (1D) HER hybrid catalyst consisted of cobalt phosphide (CoP) and molybdenum carbide (Mo2C) nanoparticles wrapped by nitrogen-doped graphitic carbon (called CoP/Mo2C-NC) was successfully fabricated by a facile continuous-flow method and a simple two-step annealing process. During these processes, the successful synthesis of the MoO3 nanorods coated with cobalt zeolitic imidazolate frameworks (Co-ZIF-67) (Co-ZIF-67@MoO3) through the continuous-flow method plays a key role. The as-synthesized CoP/Mo2C-NC hybrid electrocatalyst exhibits a significantly enhanced HER electrocatalytic activity over the entire pH range relative to that of the control materials CoP, Mo2C-NC, and physically mixed CoP and Mo2C-NC. The outstanding HER catalytic performance is mainly due to the fact that the electron cloud transfers from Co to Mo in CoP/Mo2C-NC through the Co-P-Mo bond, resulting in the formation of a high valence state for Co (Co3+) species and lower valence states for Mo (i.e., Mo2+, Mo3+) species, providing the abundant HER active sites. Moreover, the Gibbs free energy (Δ GH*) of CoP/Mo2C-NC obtained by the density function theory calculations indicates a good balance between the Volmer and Heyrovsky/Tafel steps in HER kinetics. Such a cobalt zeolitic imidazolate framework-mediated strategy depicted in this work offers an interesting perspective for developing highly efficient noble-metal-free electrocatalysts for hydrogen production.