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 gcat−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. Air- and moisture-sensitive electrenes have shown promise for catalysis but remain challenging to apply in practice. Here, the authors report oxygen-doped BaSiN2 as the first air-stable surface electrene and demonstrate its application in ammonia synthesis.