  Charge transfer from a metal substrate stabilizes honeycomb borophene, whose
electron deficit would otherwise spoil the hexagonal order of a $\pi$-bonded 2D
atomic network. However, the coupling between the substrate and the boron
overlayer may result in the formation of strong chemical bonds that would
compromise the electronic properties of the overlayer. In this paper we present
a theoretical study, based on state-of-the-art density-functional and
genetic-optimization techniques, of the electronic and structural properties of
borophene grown on Al(111), with emphasis on the impact of oxygen on the
strength of the coupling between substrate and overlayer. While our results
confirm the formation of Al-B bonds, they also predict that oxygen doping
reduces charge transfer between aluminum and borophene, thus allowing
modulation of their strength and paving the way to engineering the electronic
properties of 2D-supported borophene sheets for industrial applications. Our
study is completed by a thorough study of the thermodynamic stability of the
oxygenated borophene-Al(111) interface.
