A first-principles study of gas adsorption on germanene.

The adsorption of common gas molecules (N-2, CO, CO2, H2O, NH3, NO, NO2, and O-2) on germanene is studied with density functional theory. The results show that N-2, CO, CO2, and H2O are physisorbed on germanene via van der Waals interactions, while NH3, NO, NO2, and O-2 are chemisorbed on germanene via strong covalent (Ge-N or Ge-O) bonds. The chemisorption of gas molecules on germanene opens a band gap at the Dirac point of germanene. NO2 chemisorption on germanene shows strong hole doping in germanene. O-2 is easily dissociated on germanene at room temperature. Different adsorption behaviors of common gas molecules on germanene provide a feasible way to exploit chemically modified germanene.