First-principles study of borophene-boride hetero-structures*

Borophene (two-dimensional boron) is unusual among synthesized two-dimensional (2D) materials in its lack of layered 3D bulk counterparts and the richness of 2D allotropes/polymorph. Borophene has also been found to play roles in several important environmental and energy applications, such as CO₂ reduction, hydrogen and oxygen evolution reactions, nitrogen fixation, etc. Up to now, borophene synthesis has been realized on metal substrates. Due to the strong interactions with the substrates, however, the removal of borophene from metals have been difficult. Very recently, it was reported that boride is formed through the reconstruction of the top metal layer mixed with boron during borophene synthesis on Al(111). Metal borides have the potential to be superior substrates for borophene synthesis and separation. However, the interactions between borophene and borides, and the properties of borophene-boride hetero-structures have been rarely explored. Here, we investigate the properties of borophene-boride hetero-structures. Density functional theory (DFT) calculations are performed to explore their structures, binding energies, charge transfer, and work functions. This work allows us to explore alternative routes of borophene synthesis.