Surface Hydrogenation Strategy for Constructing a 2D B12X2H8 (X = N, P, As) Family with Embedded Aromatic Icosahedral B12 Superatoms.

Surface hydrogenation is a key strategy for material modification. The icosahedral B12 superatom, featuring a closed-shell electronic structure and aromatic stability, serves as an ideal building block for 2D functional materials. Using first-principles calculations, we design highly stable 2D boron-based h-B12X2H8 (X = N, P, As) by hydrogenating the parent h-B12X2 phases proposed in our previous work. Hydrogenation widens the bandgap from ~1 eV to 5.19-6.00 eV, strengthens bonding, and improves mechanical properties (higher Young's modulus and lower Poisson's ratio). Modified deformation-potential theory reveals carrier-type-selective mobilities, with the electron mobility of h-B12P2H8 reaching 1755 cm2V-1s-1. Notably, when h-B12X2H8 forms a heterojunction with its parent phase, it acts as a protective layer that preserves the parent's electronic structure, facilitating applications in harsh environments. This work provides a rational pathway for designing B12-based 2D materials via surface passivation and offers a model for constructing self-passivating protective layers on 2D materials.