Hydrogen Bubble Engineering of Lewis Acid Sites in Phosphorene for Efficient Nitrogen Reduction

The electrochemical synthesis of ammonia through nitrogen reduction (ENRR) is hindered by N 2 inertness and competing hydrogen evolution reaction (HER). Phosphorene, despite its promise, inherently lacks the eletron‐backdonation capability for effective N 2 activation. Herein, we present a water‐free hydrogen bubble electroetching strategy to simultaneously exfoliate and engineer black phosphorus into defect‐rich porous phosphorene (D‐BP ene ) with abundant in‐plane phosphorus vacancies for ENRR catalysis. Four‐dimensional scanning transmission electron microscopy resolves distorted hexagonal rings where pairs of P atoms from the upper and lower sub‐layers show mutually perpendicular orientations. D‐BP ene exhibits superior electrocatalytic nitrogen reduction reaction performance, achieving a high NH 3 yield of 14.94 µg h −1 mg cat −1 at −0.05 V versus RHE and a Faradaic efficiency of 35.51% at 0 V versus RHE that corresponds to an ultralow overpotential of 92 mV, outperforming most metal‐free catalysts, while remaining stable for over 36 h. Density functional theory calculations reveal that phosphorus vacancies act as Lewis acid sites, reducing the energy barrier for the potential‐determining step from 2.012 to 1.387 eV via strengthened σ‐donation and π‐backdonation, while increasing the HER kinetic barrier by inhibiting *H desorption. This work presents an effective synthetic route to vacancy‐engineered two‐dimensional materials with potential applications extending beyond nitrogen fixation.