中文摘要：

采用第一性原理密度泛函理论和周期性平板模型研究了NO在O预吸附Ir（100）表面的吸附和解离,并考察了预吸附的O对可能产物N2,N2O和NO2的选择性的影响.优化得到反应过程中初态、过渡态和末态的吸附构型,并获得反应的势能面信息.计算结果表明,NO在O预吸附表面最稳定的吸附位是桥位,其次是顶位.桥位和顶位的NO在表面存在两条解离通道,即直接解离通道和由桥位和顶位扩散到平行空位,继而发生N—O键断裂生成N原子和O原子的解离通道.此分离机理与洁净表面上NO解离机理相同,但后一种解离方式优于前一种,是NO在表面上解离的主要通道.预吸附的O原子在不同程度上抑制了NO的解离,导致桥位和顶位NO解离互相竞争.在O预吸附Ir（100）表面,N2气是唯一的产物,不会有副产物N2O和NO2的生成,与实验结果一致.预吸附的O在N/O低覆盖度下几乎不影响N2气的生成,但在较高覆盖度下则促进了N2气的生成.

英文摘要：

Adsorption and dissociation of NO on O-predosed Ir（100） and the effect of co-adsorbed oxygen on the selectivity of possible products N2, N2O and NO2 were investigated via first-principles density functional theory（DFT） and periodic slab model. The adsorption structures of the initial, transition and final states in- volved in the NO dissociation process were optimized, and the potential energy profile for each step was ob- tained. The results show that the most stable site for NO adsorption on O-predosed Ir（100） is the bridge site, while the top site is less stable. There are two dissociation paths for NO adsorbed on the bridge and top sites, one is direct dissociation, and the other is that NO firstly diffuses from bridge site to horizontal hollow site, followed by dissociation into N and O atoms. Similar as the decomposition mechanism on clean Ir（100） , the latter is favored over the former and is the primary path for NO dissociation. The predosed O atoms inhibit the dissociation of NO at the bridge and top sites in different degrees, leading to the competition of NO dissociation on both sites. N2 is still the predominant product, and N2O and NO2 are unlikely to be produced on O- predosed It（ 100）, well consistent with the experimental observation. Compared with clean Ir（ 100）, the pre- dosed O atoms on the surface have almost no impact on the formation of N2 at low N/O coverage, while pro- mote the N2 formation at high N/O coverage.