Crystalline/Amorphous Phosphide Heterostructures with Built‐in Electric Fields for Efficient and Long‐Term Industrial‐Scale Alkaline Water Electrolysis

Abstract Alkaline water electrolysis is a promising pathway for large‐scale hydrogen production, yet its efficiency is limited by the sluggish kinetics of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, a bifunctional CoFeP electrocatalyst is reported featuring a crystalline/amorphous heterostructure with engineered built‐in electric fields (BEFs). The integration of crystalline CoP and Fe 2 P domains with amorphous regions induces interfacial charge redistribution, driven by work function differences, which in turn generates BEFs that modulate the electronic structure and optimize the d‐band center. This tuning enhances the adsorption/desorption energetics of reaction intermediates, thereby boosting catalytic performance. As a result, CoFeP delivers low overpotentials of 199 mV for HER and 329 mV for OER at 1 A cm −2 in 1 m KOH. Remarkably, the catalyst exhibits outstanding durability over 1500 h under industrially relevant conditions (6 m KOH, 80 °C, 0.5 A cm −2 ). Technoeconomic analysis estimates a hydrogen production cost of $1.10 per gasoline gallon equivalent, significantly below the U.S. DOE's 2026 target. A rational design strategy is offered here for interface and electronic structure engineering and a viable platform is presented for next‐generation industrial water electrolysis.