Ammonia dehydrogenation over platinum-group metal surfaces. structure, stability, and reactivity of adsorbed NHx species
Ammonia dehydrogenation over platinum-group metal surfaces. structure, stability, and reactivity of adsorbed NHx species
复制标题
DOI：
10.1021/jp064742b
复制
发表时间：
2007
影响因子：
3.7
通讯作者：
G. Novell-Leruth;A. Valcárcel;J. Pérez–Ramírez;J. Ricart
中科院分区：
文献类型：
--
作者：
G. Novell-Leruth;A. Valcárcel;J. Pérez–Ramírez;J. Ricart
用平面波周期密度泛函方法比较研究了氨在铂族金属(Pd，Rh，Pt)的(111)和(100)面上的吸附和分解。研究了NH3及其脱氢中间体(NHx，x=0，1，2)的不同吸附构型和吸附位置。在所考察的六种表面上，NH3优先吸附在顶位，NH2优先吸附在桥位，NH和N优先吸附在中空位。然而，NHx部分的吸附能从一个表面到另一个表面有很大的差异。所有物种在(100)面上的吸附比在(111)面上的吸附更强。RH(100)为各种中间体提供了最大的稳定性。确定了连续脱氢步骤(NHx、→、NHx-1+H)的反应能、过渡态结构和活化势垒，使计算不同温度下的速率系数成为可能。我们的计算证实了高贵金属上的氨分解。
Periodic DFT calculations using plane waves have been applied to comparatively study the adsorption and decomposition of ammonia on the (111) and (100) surfaces of platinum-group metals (Pd, Rh, Pt). Different adsorption geometries and positions have been studied for NH3 and its dehydrogenation intermediates (NHx, x = 0, 1, 2). On the six surfaces investigated, NH3 adsorbs preferentially on top sites, NH2 on bridge, and NH and N on hollow sites. However, the adsorption energies of the NHx moieties differ considerably from one surface to another. All of the species adsorb more strongly on the (100) than on the (111) planes. Rh(100) provides the maximum stability for the various intermediates. The reaction energies, the structure of the transition states, and the activation barriers of the successive dehydrogenation steps (NHx → NHx-1 + H) have been determined, making it possible to compute rate coefficients at different temperatures. Our calculations have confirmed that ammonia decomposition over noble met...