State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China.
J Chem Phys. 2011 Nov 28;135(20):204707. doi: 10.1063/1.3663621.
Density functional theory (DFT) and periodic slab model have been used to systemically study the adsorption and dissociation of NO and the formation of N(2) on the Ir(100) surface. The results show that NO prefers the bridge site with the N-end down and NO bond-axis perpendicular to the Ir surface, and adsorption to the top site is only 0.05 eV less favorable, whereas the hollow adsorption is the least stable. Two dissociation pathways for the adsorbed NO on bridge or top site are located: One is a direct decomposition of NO and the other is diffusion of NO from the initial state to the hollow site followed by dissociation into N and O atoms. The latter pathway is more favorable than the former one due to the lower energy barrier and is the primary pathway for NO dissociation. Based on the DFT results, microkinetic analysis suggests that the recombination of two N adatoms on the di-bridge sites is the predominant pathway for N(2) formation, whereas the formation of N(2)O or NO(2) is unlikely to occur during NO reduction. The high selectivity of Ir(100) toward N(2) is in good agreement with the experimental observations.
密度泛函理论（DFT）和周期性平板模型已被用于系统地研究 NO 在 Ir(100)表面上的吸附和离解以及 N(2)的形成。结果表明，NO 更喜欢桥位，N 端朝下，NO 键轴垂直于 Ir 表面，而吸附到顶位仅稍微不利，而中空吸附是最不稳定的。在桥位或顶位吸附的 NO 有两种离解途径：一种是 NO 的直接分解，另一种是 NO 从初始状态扩散到中空位，然后解离成 N 和 O 原子。由于较低的能垒，后者途径比前者更有利，是 NO 离解的主要途径。基于 DFT 的结果，微观动力学分析表明，两个 N 原子在双桥位上的重组是 N(2)形成的主要途径，而在 NO 还原过程中形成 N(2)O 或 NO(2)的可能性不大。Ir(100)对 N(2)的高选择性与实验观察结果一致。
