Understanding Bonding Nature of α‐Keggin Polyoxometalates [XW12O40]n− (X = Al, Si, P, S): A Generalized Superatomic Perspective

Abstract

α‐Keggin polyoxometalates (POMs) [XW12O40]n− (X = Al, Si, P, S) are widely used in batteries owing to their remarkable redox activity. However, the mechanism underlying the applications appears inconsistent with the widely accepted covalent bonding nature. Here, first‐principles calculations show that XW12 are core–shell structures composed of a shell and an XO4n− core, both are stabilized by covalent interactions. Interestingly, owing to the presence of a substantial number of electrons in W12O36 shell, the frontier molecular orbitals of XW12 are not only strongly delocalized but also exhibit superatomic properties with high‐angular momentum electrons that do not conform to the Jellium model. Detailed analysis indicates that energetically high lying filled molecular orbitals (MOs) have reached unusually high‐angular momentum characterized by quantum number K or higher, allowing for the accommodation of numerous electrons. This attribute confers strong electron acceptor ability and redox activity to XW12. Moreover, electrons added to XW12 still occupy the K orbitals and will not cause rearrangement of the MOs, thereby maintaining the stability of these structures. Our findings highlight the structure–activity relationship and provide a direction for tailor‐made POMs with specific properties at atomic level.