A first-principles study of gas adsorption on germanene

The adsorption of common gas molecules (N2, CO, CO2, H2O, NH3, NO, NO2, and O2) on germanene is studied with density functional theory. The results show that N2, CO, CO2, and H2O are physisorbed on germanene via van der Waals interactions, while NH3, NO, NO2, and O2 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. O2 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.