2D Inorganic Electrides: Interstitial Electrons as Key Drivers of Multifunctional Properties and Applications

2D inorganic electrides have attracted extensive interdisciplinary interest due to their unique physicochemical properties, which arise from the presence of non-nuclear-bound interstitial anionic electrons (IAEs). Nevertheless, the stringent design criteria for realizing 2D IAEs have limited viable candidates to only a few categories, thereby constraining the expansion of the candidate pool and further exploration of related applications. Here, based on the electronegativity differences of elements and combined with the design principles of 2D inorganic electrides, we constructed eight negative-valence transition metal-based AB-type 2D inorganic electrides (A = Ca/Sr/Ba, B = Cu/Ag/Au). These materials exhibit a typical layered structure, forming an ordered alternating arrangement of atomic layers and IAE layers along the k_z direction. Interestingly, despite the absence of conventional magnetic atoms, their monolayer structures display distinct magnetic ordering-originating from surface-floating IAEs. Furthermore, these electrides exhibit diverse topological phases and ultralow work functions. Leveraging their ability to mitigate hydrogen poisoning, we demonstrate that Ru supported on these electrides can serve as an efficient catalyst for ammonia (NH₃) synthesis. These findings not only establish a new material platform for exploring 2D inorganic electrides but also open avenues for designing and modulating their multifunctional properties toward applications in spintronics, topological electronics, and energy conversion.