Creation of an air-stable surface electrene and its application to ammonia synthesis

Electrenes are unique materials characterized by a surface floating electron layer, which results in an ultra-low work function, making them ideal candidates for catalyzing chemical reactions via electron donation. However, these materials are extremely sensitive to air and moisture, thereby limiting their potential applications. Here, we demonstrate that oxygen-doped BaSiN₂ is an air-stable surface electrene. Its highly active surface, with an ultra-low WF of approximately 1.5 eV, can donate surface floating electrons to adsorbed N₂, forming an N₂-passivated surface, which can be constantly regenerated through hydrogenation of surface-activated N₂. This alternating pathway, particularly with the assistance of Ru loading, effectively produce ammonia: the Ru/BaSiN₂:O catalyst exhibits high ammonia synthesis rate of 43 mmol g_cat^-1 h^-1 at 300 °C and 0.9 MPa, and much superior air stability compared to the most active electrides and hydrides-based heterogeneous catalysts reported to date. This discovery opens a new way for electrene-driven heterogeneous catalysis.