Phase engineering of monodispersed ternary Co/Mo2C/Co3Mo3N heterojunctions for efficient alkaline HER electrocatalysis

Intermetallic compounds (IMCs) are promising alternatives to Pt-based catalysts for hydrogen evolution reaction (HER). However, their applications are hindered by agglomeration and limited activity. Herein, we report a ternary heterostructured catalyst composed of Co/Mo2C/Co3Mo3N nanoparticles embedded in a porous nitrogen-doped carbon support (Co/Mo2C/Co3Mo3N@PNCS), synthesized via a sol–gel method and annealing. Interface engineering enabled strong interfacial coupling and spatial confinement. Density of states analysis revealed enhanced conductivity in the Co/Mo2C/Co3Mo3N heterostructure, while density functional theory calculations showed that the Co/Mo2C/Co3Mo3N interface provided near-optimal hydrogen adsorption energy, facilitating electron redistribution and boosting HER kinetics. Electrochemical measurements demonstrated excellent HER performance in 1 M KOH, achieving 10 mA cm−2 at a low overpotential of 83 mV, with robust long-term stability. This study highlights an innovative strategy for designing non-noble IMC catalysts through interfacial modulation, offering both mechanistic understanding and practical guidance for advanced water electrolysis applications.