High Entropy Oxynitride for Anti‐Poisoning Electrocatalytic Nitrogen Reduction

ABSTRACT Electrocatalytic nitrogen reduction reaction (eNRR) under ambient conditions is a promising route for sustainable ammonia synthesis, yet its progress is fundamentally limited by the inertness of N≡N bonds and the lack of robust, selective catalysts. Here, we report the first synthesis of a rutile‐structured high‐entropy oxynitride (HEON, CoFeTiVSnON). By leveraging the mixing entropy of five metal elements and dual anion regulation, HEON achieves dynamically regenerable nitrogen vacancies, and a tunable electronic structure. Operando spectroscopic investigations and density functional theory (DFT) calculations reveal that HEON uniquely activates N 2 via a stabilized vacancy‐mediated quasi Mars‐van Krevelen (MvK) mechanism, wherein nitrogen vacancies directly participate in the catalytic cycle, enabling continuous vacancy formation and healing. Correspondingly, the NH 3 poisoning and vacancy depletion issues that plague conventional binary nitrides have been circumvented whilst breaking linear scaling relationship of intermediate adsorption. The HEON catalyst delivers a high NH 3 yield rate of 159.2 µg h −1 mg cat. −1 and a Faradaic efficiency of 46.6% at −0.5 V vs. RHE, with good structural stability over extended operation. Our work establishes high‐entropy oxynitrides as a transformative platform for multi‐step electrocatalysis, and provides mechanistic insights for the rational design of catalysts stabilized by high entropy effects.