Energetics, Charge Transfer, and Magnetism of Small Molecules Physisorbed on Phosphorene

First-principles calculations are performed to investigate the interaction of physisorbed small molecules, including CO, H2, H2O, NH3, NO, NO2, and O2, with phosphorene, and their energetics, charge transfer, and magnetic moment are evaluated on the basis of dispersion-corrected density functional theory. Our calculations reveal that CO, H2, H2O, and NH3 molecules act as a weak donor, whereas O2 and NO2 act as a strong acceptor. While the NO molecule donates electrons to graphene, it receives electrons from phosphorene. Among all the investigated molecules, NO2 has the strongest interaction through hybridizing its frontier orbitals with the 3p orbital of phosphorene. The nontrivial and distinct charge transfer occurring between phosphorene and these physisorbed molecules not only renders phosphorene promising for application as a gas sensor but also provides an effective route for modulating the polarity and density of carriers in phosphorene. In addition, the intermediate binding energy of hydrogen molecules on phosphorene implies stable hydrogen storage at ambient conditions and subsequent facile release.