Structural regulation of molybdenum carbide/nitride electrocatalyst for enhanced hydrogen evolution in acidic and alkaline media

Herein, the ultrafine molybdenum carbide/nitride (Mo 2 C/Mo 2 N) heterojunction loaded by nitrogen (N), phosphorus (P)-codoped carbon matrix with hierarchical porous (PNC) is prepared in-situ by fabricating the ternary complex of silica (SiO 2 ) nanoparticles, chitosan (CS) and phosphomolybdic acid (PMo 12 ) as precursor, followed by annealing and hydrofluoric acid (HF) etching. Due to the excellent structural characteristics of the optimized catalyst Mo 2 C/Mo 2 N@PNC-8-2, including the Mo 2 C/Mo 2 N heterojunction and its uniform dispersion in PNC, P-doping in Mo 2 C/Mo 2 N, Mo vacancies, the strong interface coupling between Mo 2 C/Mo 2 N heterojunctions and PNC, as well as the connected macroporous channels and hierarchical porous structure, etc., not only large numbers of active sites are exposed, but also the electron density distribution around Mo atoms is tuned. Therefore, the charge/mass transport is greatly improved, resulting in the more superior hydrogen evolution activity of Mo 2 C/Mo 2 N@PNC-8-2 than that of the single-phased Mo 2 C or Mo 2 N counterpart, with lower overpotentials of 62 or 97 mV to achieve10 mA cm −2 in alkaline or acidic solution, respectively. Moreover, Mo 2 C/Mo 2 N@PNC-8-2 still shows excellent long-term durability. This study opens up a new idea for designing highly efficient electrocatalysts via integrating heterojunction, defects, heteroatom doping, and hierarchical porous structure.