Interfacial interaction of Ag nanoparticles with graphene oxide supports for improving NH3 and NO adsorption: a first-principles study.

We investigated the structural and electronic properties of Ag13 nanoparticles (NPs) deposited on graphene oxides (GOs) and the effect of the interfacial interaction on NH3 and NO adsorption using density functional theory calculations. The epoxy functional group and its neighboring sp(2) carbon atoms of GOs, rather than the hydroxyl group, are used as active sites to enhance the binding of Ag13 to graphene through the C-O-Ag and C-Ag chemical bonds. The stability of deposited Ag NPs depends on the chemical environment of active sites in GOs, including the atomic arrangement of epoxides and their concentration. The deposited Ag13 NPs are likely to be further oxidized to form Ag13O by neighboring oxygen irrespective of the oxidation level of GOs. The strong interfacial interaction of Ag13/GOs, which effectively tunes the position of the d-band center of NPs due to large charge transfer from Ag13 to GOs, has a significant impact on the adsorption of NH3. The NH3 is strongly adsorbed on deposited Ag13 through the formation of an N-Ag bond and an N···HO hydrogen bond between NH3 and O from C-O-Ag. The electronic structure calculations show that the hybridization of the HOMO of NH3 with the conduction bands of Ag13-GOs results in the strong donor doping by an NH3 molecule, and gives rise to larger charge transfers from NH3 to the hybrid, compared to NH3 adsorption on isolated Ag13 and GOs. The adsorption of NO on oxidized Ag13 on GOs is obviously improved due to the oxidation of NO to NO2 by its neighboring oxygen atoms. In contrast to NH3, the adsorbed NO acts as an acceptor. The calculated results show good agreement with experimental observations.