Engineering Self-Woven Hierarchical Bimetallic Nitride Electrode with Built-In Interfacial Electric Field for Enhanced Alkaline Hydrogen Evolution

Single-phase transition metal nitrides (TMNs) for alkaline hydrogen evolution reaction (HER) are limited by sluggish charge transfer kinetics, suboptimal adsorption, and restricted accessibility of active sites—intrinsic drawbacks of their electronic structure and conventional electrode architecture. Herein, we circumvent these obstacles by constructing a Ni4N/CoN heterostructure on nickel foam (Ni4N/CoN/NF) with two synergistic features: a built-in interfacial electric field (BIEF) and a hierarchical porous morphology. The work function difference between Ni4N and CoN generates a robust BIEF that drives directional electron transfer from Ni to Co, precisely tailoring the electronic configuration of Ni sites to optimize adsorption energy. Moreover, this hierarchical architecture, assembled from interconnected nanochains and nanosheets, simultaneously enhances active-site exposure, facilitates electron transport, and promotes efficient gas release. Benefiting from these synergistic advantages, the Ni4N/CoN electrode delivers an industrial-level current density of 1000 mA cm–2 at an overpotential of only 213 mV in alkaline media. Moreover, the combination of its robust interwoven nanochain architecture and strong interfacial electronic coupling endows the electrode with outstanding operational stability, sustaining continuous hydrogen evolution for over 500 h at the current density of 500 mA cm–2. This work presents a viable strategy for designing efficient and durable heterostructure electrocatalysts toward practical water electrolysis.