Coupling ZnN₄ Atomic Sites with Graphitic Nitrogen for Enhanced Ammonium Production via Electrocatalytic Nitrate Reduction

The electrocatalytic nitrate reduction reaction (NO₃RR) presents a promising alternative to the traditional Haber-Bosch process for synthesizing ammonium (NH₃) under mild conditions. Supported single atoms have emerged as active catalysts for this conversion; however, the efficiency of NH₃ production are limited by the modest activity and selectivity of these catalysts. In this study, it is demonstrated that zinc single atoms supported on nitrogen-doped carbon (ZnNCs), derived from zeolitic imidazolate framework-8 (ZIF-8), possess remarkable catalytic performance for this conversion, achieving an unprecedented selectivity (exceeding 90%) for NH₃ formation across a broad potential range (-0.4--0.8 V vs. RHE). Comprehensive analyses reveal that the incorporation of a graphitic nitrogen atom adjacent to the Zn-N₄ site precisely modulates the reaction pathway, enabling a unique dual-site adsorption and cascading reaction route for NH₃ formation. These findings not only uncover a novel reaction mechanism for the NO₃RR but also have the potential to inspire the development of more efficient NO₃RR catalysts.