A Phosphide Active‐Hydrogen Valve: Redirecting Interfacial Hydrogen from Hydrogen Evolution into C–N Coupling for Efficient Urea Electrosynthesis

ABSTRACT Electrocatalytic CO 2 /NO 3 − co‐reduction offers a sustainable route to urea synthesis but remains constrained by mismatched carbon/nitrogen intermediate supply and uncontrolled competition between substrate hydrogenation and the hydrogen evolution reaction (HER). Here, interfacial active‐hydrogen flux regulation is proposed as a design principle that matches *H generation with directional consumption within the C–N coupling network and is realized in Fe‐doped Ni 2 P nanosheet arrays. The metal‐phosphorus framework buffers and delivers *H, sustaining hydrogenation while suppressing futile recombination into H 2 . Fe incorporation simultaneously constructs electronically dichotomous microdomains: electron‐deficient Fe sites activate CO 2 and stabilize *CO, whereas the electron‐enriched Ni sites drive NO 3 − hydrogenation toward *NH 2 . Such synergistic regulation synchronizes *CO/*NH 2 supply with timely *H utilization, redirecting interfacial hydrogen from a competing HER precursor into a productive coupling resource. Operando spectroscopy and theoretical calculations corroborate enhanced precursor formation, a lowered C–N coupling barrier, and thermodynamic preference for substrate hydrogenation over HER. Fe‐Ni 2 P delivers a urea Faradaic efficiency of 65.84% and a yield rate of 1820.31 µg h −1 cm −2 at −0.4 V vs. RHE in an H‐cell, reaching 3688.91 µg h −1 cm −2 at 1.6 V in a membrane electrode assembly with a 50.69% Faradaic efficiency, offering a transferable design strategy for multi‐reactant C–N coupling electrocatalysis.