Tunable interstitial anionic electrons in layered MXenes

Electrides with spatial electrons serving as 'anions' in the cavities or channels exhibit intriguing properties which can be applied in electron injection/emission and high-speed devices. Here, we report a new group of layered electrides, M₂X (M = Ti, V, and Cr; X = C and N) with electrons distributed in the interlayer spacings. We find that the interstitial electrons tend to be delocalized from the Ti-based structures to the Cr-based ones. We show that the interstitial electrons originate from thed-electrons of transition metal atoms. Our findings prove the existence of tunable interstitial electrons with rich electronic properties in layered MXenes and provide valuable insights into the design and fabrication of new materials with multiple applications.