First Principles Studies On Adsorption And Co-adsorption Of N₂O And H On Ir Surfaces

Nitric oxide (N2O) is one of the main greenhouse gases since it damages the ozone layer and then enhances UV radiation on the earth. Transition metals are good catalyst for N2O decomposition. The interaction between and transition metals has therefore attracted more and more attention. However, up to now there is no theoretical investigation for the interaction of N2O with Ir(1111) surface and the co-adsorption of N2O and H on Ir surfaces.Based on density-function theory, we have performed the first principles calculations for the interaction between N2O and Ir(111) and co-adsorption of N2O and H on Ir suefaces in this work. For N2O/Ir(111) system, the conclusions we have got could be outlined as follows. There are three kinds of stable adsorption structures of N2O on the Ir(111) surface. For the case through one atom of N2O interacting with the surface, the stable situation is deduced that N2O is situated via the Nt on an atop site of Ir(111) with the linear N2O molecule nearly perpendicular to the surface. Other stable adsorption modes via the Nt and O atoms or the two N atoms have been identified. In the two configurations, the N2O molecule is bent greatly and N-O bond or N-N bond is weakened. Comparing DOS of N2O in gas phase with that of adsorbed N2O on Ir(111) surface, we found that N2O interacts with the substrate through 7σorbital for N2O adsorption on Ir (111) via Nt, while for other two adsorption structures, the 2πand 3πorbitals are mixed with substrate orbitals and the back donation to 3πorbital leads to N2O activated and its bonds enlarged. In addition, there is a situation in which N2O decomposition may occur, while N2O may not need to be activated.Our first principle calculations for co-adsorption of N2O and H on Ir(100) indicates that Ir(100) sueface become inert when coverage of H atoms is close to 0.5ML and N2O is no longer discomposed on Ir(100). For Ir(111), our rude study reveals that Ir(111) surface still keeps active with co-adsorbed H atoms on it and N2O can be dissociated into N and NO.In summary, our study reveals that the interaction of N2O with Ir(111) is strong.The Ir(111) surface is still active with co-adsorbed H atoms on it, while the Ir(100) surface becomes inert when the coverage of H atoms is close to 0.5ML...