A First-principles Investigation of The Adsorption of CO and NO Molecules on Germanene

The adsorption of common pollutant gases on germanene is investigated using first-principles calculation by means of density functional theory. In this work, CO and NO molecules are used as pollutant gases. Our calculation results show that CO molecule is physisorbed on germanene, while NO molecule is chemisorbed since it opens band gap of germanene at the Dirac point. To investigate the mechanism of the adsorption process, we calculate the transfer of charges between germanene and gas molecules. In order to obtain understanding into the transformation of electron density upon the adsorption processes, Mulliken analysis is used to evaluate atomic charge of each atom. We found that electron charge of NO molecule obviously increased due to adsorption process, while CO molecule slightly increased.